SIM_RawField.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        SIM_RawField.h ( SIM Library, C++)
 *
 * COMMENTS:
 */

#ifndef __SIM_RawField__
#define __SIM_RawField__

#include "SIM_API.h"

#include <GEO/GEO_PointTree.h>
#include <UT/UT_VoxelArray.h>
#include <UT/UT_ThreadedAlgorithm.h>
#include <UT/UT_Vector.h>
#include <UT/UT_FloatArray.h>
#include <UT/UT_Wavelet.h>

class SIM_VectorField;
class SIM_RawField;
class SIM_RawIndexField;
class GEO_PrimVolume;
class GEO_PrimVDB;
class GEO_PrimVolumeXform;
class GU_Detail;
class CE_Grid;

class gu_sdf_qelem;

// The order of this enum is important.  It is a 3 bit array
// where each bit determines if the center value or corner value
// should be used on that axis.  0 means center, 1 means node.
// The least significant bit is x axis, then y, then z.
enum SIM_FieldSample
{
    SIM_SAMPLE_CENTER = 0,
    SIM_SAMPLE_FACEX = 1,
    SIM_SAMPLE_FACEY = 2,
    SIM_SAMPLE_EDGEXY = 3,
    SIM_SAMPLE_FACEZ = 4,
    SIM_SAMPLE_EDGEXZ = 5,
    SIM_SAMPLE_EDGEYZ = 6,
    SIM_SAMPLE_CORNER = 7
};

enum SIM_FieldBoundary
{
    SIM_BOUNDARY_NONE,  // Unchanged, free to change.
    SIM_BOUNDARY_SAME,  // Same as adjacent voxels.
    SIM_BOUNDARY_ZERO,  // Set to constant value, myBoundaryValue
    SIM_BOUNDARY_NEGATE,        // Opposite sign of adjacent voxels.
    SIM_BOUNDARY_FIXED, // Unaffected by enforcement, but should be treated
                        // as a fixed boundary by projection methods.
};

enum SIM_FieldAdvection
{
    SIM_ADVECT_SINGLE = 0,      // Take a single step
    SIM_ADVECT_TRACE = 1,       // Trace according to velocity field
    SIM_ADVECT_MIDPOINT = 2,    // Trace using midpoint updates
    SIM_ADVECT_HJWENO = 3,      // Don't trace, but use HJWENO update
    SIM_ADVECT_UPWIND = 4,      // First order upwind.
    SIM_ADVECT_RK3 = 5,         // Third order TVD-RK3
    SIM_ADVECT_RK4 = 6          // Fourth order TVD-RK4
};

//
// The boundary of the field can be set to be "open" above a
// line using the following struct. The height value specifies
// the dividing line between the open and closed boundary with 
// respect to the plane positioned at the origin and oriented with
// planeNormal. This is useful for letting liquid splash
// out of a closed boundary without the expense of explicitly
// creating a solid boundary.
//

struct SIM_BoundaryLine
{
    SIM_BoundaryLine()
        : activated(false)
        , height(0.)
        , planeNormal(UT_Vector3(0.))
        {}
    bool activated;
    fpreal height;
    UT_Vector3 planeNormal;
};


// Type definition for a velocity function
typedef UT_Vector3 (*sim_PointVelocityCB)(const UT_Vector3 &, int, void *);

struct SIM_API sim_PointVelocity
{
    sim_PointVelocity(sim_PointVelocityCB _cb, void *_data)
        : cb(_cb)
        , data(_data)
    {}

    sim_PointVelocityCB          cb;
    void                        *data;
};

class SIM_API SIM_RawField
{
public:
                SIM_RawField();
    virtual    ~SIM_RawField();

    /// Copy constructor:
                SIM_RawField(const SIM_RawField &src);

    /// Assigment operator:
    const SIM_RawField  &operator=(const SIM_RawField &src);            

    /// Initializes the field.
    /// The resolution given is in terms of voxels, the actual dimensions
    /// of this field may be slightly different due to the sampling
    /// choice.
    void        init(SIM_FieldSample sample, 
                     const UT_Vector3 &orig, const UT_Vector3 &size,
                     int xres, int yres, int zres);
    void        init(SIM_FieldSample sample, 
                     const UT_Vector3 &orig, const UT_Vector3 &size,
                     int xres, int yres, int zres, 
                     const UT_Vector3 &voxelsize);

    /// Initializes the field.
    /// Will gain ownership of the given voxel array.
    void        init(SIM_FieldSample sample,
                     const UT_Vector3 &orig, const UT_Vector3 &size,
                     UT_VoxelArrayF *voxels);
    void        init(SIM_FieldSample sample,
                     const UT_Vector3 &orig, const UT_Vector3 &size,
                     UT_VoxelArrayF *voxels,
                     const UT_Vector3 &voxelsize);

    /// Initializes the voxel iterator to only run over a subset
    /// of tiles that correspond to the appropriate range for
    /// the jobinfo.
    void        getPartialRange(UT_VoxelArrayIteratorF &vit,
                            const UT_JobInfo &info) const;

    /// Returns true if this should be multithreaded.
    bool        shouldMultiThread() const
                {
                    return field()->numTiles() > 1;
                }

    /// Initializes this to be the same dimensions, sampling pattern,
    /// etc, of the given field.
    /// The values of this may be reset to zero.
    void        match(const SIM_RawField &src);
    void        match(const SIM_RawIndexField &src);

    /// Initializes this field to a constant value.
    void        makeConstant(float cval);

    /// Initializes this to be the same as the given field.  The
    /// values of this will be found by resampling the other field
    /// with the new sampling pattern.
    void        resample(SIM_FieldSample sample, const SIM_RawField *src);

private:
    /// This helper function does the actual work for resample(...).
    THREADED_METHOD2(SIM_RawField, shouldMultiThread(), resampleHelper,
                     SIM_FieldSample, sample,
                     const SIM_RawField*, src);
    void resampleHelperPartial(SIM_FieldSample sample,
                               const SIM_RawField* src,
                               const UT_JobInfo& info);
public:

    /// Returns the set of samples in *this* field which correspond
    /// to the given location & sampling pattern.
    /// ix, iy, and iz should be size 8.
    /// If you want the deltas for the sampling pattern, call with
    /// x, y, z zero and clamp to false.
    void        getSamplePattern(SIM_FieldSample sample, int x, int y, int z,
                            int &numsample, int *ix, int *iy, int *iz,
                            bool clamp) const;

    /// Returns an offset, in voxel coords, to sample *this* field giving
    /// a voxel based address in a field with sampling pattern sample.
    /// The offset will be 0.5, 0, or -0.5 in each axis.
    UT_Vector3  getSampleVoxelOffset(SIM_FieldSample sample) const;

    /// Extrapolates the values of this field to all locations which are
    /// on the wrong side of the isocontour.  dir == 1 means greater than
    /// isocontour is wrong, dir == -1 is less than.
    /// maxdist, if not negative, represents the greatest *absolute*
    /// distance to extrapolate to.  Values outside of this are left
    /// unaffected, unless clamp is set, in which case they are set to
    /// clampval.
    void        extrapolate(const SIM_RawField *depths,
                            const SIM_RawField *valid,
                            fpreal isocontour, 
                            fpreal dir, fpreal maxdist,
                            bool clamp, fpreal clampval);

    struct sim_extrapolateFromIndexParms
    {
        const SIM_RawField *src;
        const SIM_RawField *depths;
        const SIM_RawField *valid;
        const SIM_RawField *collision;
        const SIM_RawIndexField *index;
        const GU_Detail *gdp;
        UT_DMatrix4 xform;
        fpreal isocontour;
        fpreal isotol;
        fpreal dir;
        fpreal maxdist;
        bool clamp;
        fpreal clampval;
    };

    struct sim_extrapolateCacheElem
    {
        sim_extrapolateCacheElem(fpreal v, fpreal w, const UT_Vector3 &p):
                            sampleval(v), samplew(w), ptpos(p) {}
        sim_extrapolateCacheElem() : sampleval(0), samplew(0) {}
        fpreal          sampleval;
        fpreal          samplew;
        UT_Vector3      ptpos;
    };

    /// Extrapolates the values of this field to all locations which are
    /// on the wrong side of the isocontour.  dir == 1 means greater than
    /// isocontour is wrong, dir == -1 is less than.
    /// maxdist, if not negative, represents the greatest *absolute*
    /// distance to extrapolate to.  Values outside of this are left
    /// unaffected, unless clamp is set, in which case they are set to
    /// clampval.  The extrpolated values are found by interpolating at the
    /// position of the closest points in the provided GU_Detail, as stored
    /// in the index field by point index.
    void extrapolateFromIndex(const SIM_RawField *depths,
                              const SIM_RawIndexField *index,
                              const SIM_RawField *collision,
                              const SIM_RawField *valid,
                              const GU_Detail *gdp,
                              const UT_DMatrix4 &xform,
                              fpreal isocontour,
                              fpreal isotol,
                              fpreal dir,
                              fpreal maxdist,
                              bool clamp,
                              fpreal clampval);

    THREADED_METHOD1(SIM_RawField, shouldMultiThread(),
                     extrapolateFromIndexInternal,
                     sim_extrapolateFromIndexParms &,parms);

    void extrapolateFromIndexInternalPartial(sim_extrapolateFromIndexParms &p,
                                             const UT_JobInfo &info);

    /// Advances source field along the field's curvature.
    /// Takes a given b to act as the movement coefficient.
    /// Does a single euler step.
    /// this is filled in with the resulting field.  this cannot be source.
    /// This solves:
    ///  dphi/dt = b * K * |grad(phi)|
    THREADED_METHOD3(SIM_RawField, shouldMultiThread(), moveAlongCurvature,
                    fpreal, b_val,
                    const SIM_RawField &, source,
                    fpreal, timestep)
    void         moveAlongCurvaturePartial(fpreal b_val, 
                            const SIM_RawField &source,
                            fpreal timestep,
                            const UT_JobInfo &jobinfo);

    /// Advances this field along the field's curvature.
    /// Is given a total amount to move and will calculate the appropriate
    /// timestep according to the given cfl condition & min/max iterations.
    void         moveAlongCurvature(fpreal amount,
                            fpreal cflcond,
                            int miniter, int maxiter);

    /// Advances source field along the field's normal direction.
    /// Takes a matching field which defines the speed to move in the
    /// normal direction on a per cell basis.
    /// Past the bandwidth assumes a valid SDF and skips gradient estimates.
    /// Does a single euler step.
    /// this is filled in with the resulting field.  this cannot
    /// be source.
    /// This solves:
    ///  dphi/dt + speed * |grad(phi)| = 0
    THREADED_METHOD4(SIM_RawField, shouldMultiThread(), moveAlongNormal,
                     const SIM_RawField &, speed,
                     const SIM_RawField &, source,
                     fpreal, timestep,
                     fpreal, bandwidth)
    void        moveAlongNormalPartial(const SIM_RawField &speed, 
                                const SIM_RawField &source, 
                                fpreal timestep, fpreal bandwidth,
                                const UT_JobInfo &info);

    /// Uses the midpoint method to do a second order temporal
    /// update of the moveAlongNormal algorithm.
    void        moveAlongNormalMidpoint(const SIM_RawField &speed,
                                const SIM_RawField &source,
                                fpreal timestep, fpreal bandwidth);

    /// Performs the reinitialization equation.
    /// This solves for:
    ///  dphi/dt + S(phi0) * (|grad(phi)| - 1) = 0
    /// at steady state.
    ///  S(phi0) = phi0 / sqrt(phi0^2 + dx^2), a smeared sign function.
    /// It is held constant for the reinitialization.
    /// Usemidpoint indicates using midpoint integration vs. Euler.
    /// Any parts of the SDF past the bandwidth are assumed to already
    /// be a valid SDF and not require reinitialization.
    void        reinitializeSignedDistance(int maxiter,
                                           bool usemidpoint,
                                           fpreal bandwidth);

    /// Negates all values in this field
    THREADED_METHOD(SIM_RawField, shouldMultiThread(), negate)
    void        negatePartial(const UT_JobInfo &info);

    /// Scales all values in this field
    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), scale,
                    fpreal, scale)
    void        scalePartial(fpreal scale, const UT_JobInfo &info);

    /// Makes this field the minimum or maximum 
    /// of this field and the other field.  The other field
    /// is not assumed to be matching.
    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), maximum,
                        const SIM_RawField *, other)
    void        maximumPartial(const SIM_RawField *other, const UT_JobInfo &info);

    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), minimum, 
                    const SIM_RawField *, other)
    void        minimumPartial(const SIM_RawField *other, const UT_JobInfo &jobinfo);

    /// Averages this with the other field.  Result in this.  Assumes
    /// fields match.
    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), average,
                    const SIM_RawField &, other)
    void        averagePartial(const SIM_RawField &other, const UT_JobInfo &jobinfo);   

    /// Sums the field into separate summation lists, one per component
    /// of the comp index field.  Negative components ignored, the given
    /// arrays should already be sized to fit the maxindex.
    THREADED_METHOD3_CONST(SIM_RawField, shouldMultiThread(), sumPerComponent,
                    UT_DoubleArray &, result,
                    UT_Int64Array &, activevoxels,
                    const SIM_RawIndexField *, comp)
    void        sumPerComponentPartial(UT_DoubleArray &result,
                    UT_Int64Array &activevoxels,
                    const SIM_RawIndexField *comp,
                    const UT_JobInfo &info) const;

    THREADED_METHOD5_CONST(SIM_RawField, shouldMultiThread(), sumComponent,
                    double &, result,
                    int64 &, activevoxels,
                    int, compnum,
                    const SIM_RawIndexField *, comp,
                    const SIM_RawField *, pressureboundary)
    void        sumComponentPartial(double &result,
                    int64 &activevoxels,
                    int compnum,
                    const SIM_RawIndexField *comp,
                    const SIM_RawField *pressureboundary,
                    const UT_JobInfo &info) const;

    /// Adds to this field the value given per component.  Negative components
    /// neglected.
    THREADED_METHOD2(SIM_RawField, shouldMultiThread(), addValuePerComponent,
                const UT_DoubleArray &, valuelist,
                const SIM_RawIndexField *, comp)
    void        addValuePerComponentPartial(const UT_DoubleArray &valuelist,
                    const SIM_RawIndexField *comp,
                    const UT_JobInfo &info);

    THREADED_METHOD4(SIM_RawField, shouldMultiThread(), addValueToComponent,
                double, value,
                int, compnum,
                const SIM_RawIndexField *, comp,
                const SIM_RawField *, pressureboundary)
    void        addValueToComponentPartial(double value,
                    int compnum,
                    const SIM_RawIndexField *comp,
                    const SIM_RawField *pressureboundary,
                    const UT_JobInfo &info);

    /// Sets this to A + s*B.  A & B match this.  This can be either
    /// A or B, or neither.
    THREADED_METHOD3(SIM_RawField, shouldMultiThread(), setScaleAdd, 
                    const SIM_RawField &, A,
                    fpreal, scale,
                    const SIM_RawField &, B)
    void        setScaleAddPartial(const SIM_RawField &A,
                            fpreal scale,
                            const SIM_RawField &B, const UT_JobInfo &jobinfo);

    /// Sets this to the smeared sign function of the given sdf.
    ///  this = sdf / sqrt(sdf*sdf + bandwidth*bandwidth)
    /// this must already match sdf.
    THREADED_METHOD2(SIM_RawField, shouldMultiThread(), smearedSign,
                        const SIM_RawField &, sdf,
                        fpreal, bandwidth)
    void        smearedSignPartial(const SIM_RawField &sdf,
                                    fpreal bandwidth,
                                    const UT_JobInfo &info);

    /// Sets this to the heaviside function of itself.
    /// this = clamp(-this/diam+0.5, 0, 1)
    THREADED_METHOD(SIM_RawField, shouldMultiThread(), convertToHeaviside)
    void        convertToHeavisidePartial(const UT_JobInfo &info);

    /// Perform heaviside & inverse heaviside in a consistent fashion.
    static fpreal       toHeaviside(fpreal val, fpreal diam);
    static fpreal       fromHeaviside(fpreal val, fpreal diam);
    /// Defines width as maxcomponent of our voxels.
    fpreal              toHeaviside(fpreal val) const;
    fpreal              fromHeaviside(fpreal val) const;

    /// Types of reductions supported by reduceOp.
    enum REDUCE_NAMES
    {
        REDUCE_MAX,
        REDUCE_MIN,
        REDUCE_AVERAGE,
        REDUCE_SUM,
        REDUCE_SUMABS,
        REDUCE_SUMSQUARE,
        REDUCE_RMS,
        REDUCE_MEDIAN,
        REDUCE_MAXABS,
        REDUCE_MINABS
    };
    
    /// Perform reduction on the field using the given method
    /// The internal methods are helpers to deal with the threading
    /// collating.
    fpreal      reduceOp(REDUCE_NAMES op) const;

    /// Prebuilt versions.
    fpreal      average() const { return reduceOp(REDUCE_AVERAGE); }

    /// Performs a localized reduction on the field.
    /// Stores in this the result of the reduction.
    /// Radius is in world coordinates.
    void        localReduceOp(REDUCE_NAMES op, const UT_Vector3 &radius);

    /// Inplace box blur.
    /// Radius is in world coordinates.
    void        boxBlur(float radius) 
                { 
                    UT_Vector3          r(radius, radius, radius);
                    localReduceOp(REDUCE_AVERAGE, r); 
                }

    /// Performs the reduction only including parts of the field
    /// that match the given mask.  If mask is null, falls through
    /// to normal reduction.
    fpreal      reduceMaskedOp(REDUCE_NAMES op, 
                        const SIM_RawField *mask, bool maskissdf) const;

    /// Sorts the valid voxels (as defined by optional mask) and returns
    /// the given percentile voxel.  0.5 means median. 0.25 first quartile,
    /// etc.
    fpreal      findProportionalValue(fpreal position, 
                        const SIM_RawField *mask, bool maskissdf) const;

    /// Returns true if the given field and this one match in terms
    /// of number of voxels and bounding box size.
    /// This means the voxel cells match - not necessarily the sample
    /// points!
    bool        isMatching(const SIM_RawField *field) const;
    bool        isMatching(const SIM_RawIndexField *field) const;

    /// Returns true if the two fields are precisely aligned.  This
    /// means that samples are matched so a given integer index
    /// into either field would give the same result.
    bool        isAligned(const SIM_RawField *field) const;
    bool        isAligned(const SIM_RawIndexField *field) const;
    bool        isAligned(const GEO_PrimVolume *vold) const;

    /// Returns true if two fields have voxels aligned.
    /// They do not have to be of the same resolution or share origin.
    /// However, using the `offset` allows to access this field with index
    /// of the other field.
    /// i.e. field->indexToPos(index) == this->indexToPos(index + offset)
    bool        isColocated(const SIM_RawField *field, UT_Vector3I &offset) const;
    bool        isColocated(const SIM_RawIndexField *field, UT_Vector3I &offset) const;

    /// Returns true if our field has any NANs
    bool        hasNan() const { return field()->hasNan(); }

    /// Tests for nans, outputs text and asserts if has any
    /// Only runs if the test environment variable is set.
    void        testForNan() const;

    /// Fetches the raw field.
    const UT_VoxelArrayF        *field() const { if (myFieldOutOfDate) { updateFieldFromGrid(); } return myField; }
    UT_VoxelArrayF              *fieldNC() const { if (myGrid) { clearGrid(); } return myField; }

    /// Fetches the compute grid, returns 0 if not present.
    CE_Grid                     *grid() const;

    /// Fetches the compute grid but throws cl::Error() on failure.
    CE_Grid                     *requireGrid() const;

    /// Mark the field as out of date, but only if we have a valid grid.
    void                         markGridAsChanged() {if (myGrid) myFieldOutOfDate = true;}
    void                         clearGrid() const;

    /// Returns true if the OpenCL grid has more up-to-date data than the voxel array.
    bool         gridIsAuthoritative() const { return myGrid && myFieldOutOfDate; }

    /// Copies our field into the grid.
    void         updateGridFromField() const;

    /// Copies our grid into our field.
    void         updateFieldFromGrid() const;

    /// Steals the voxel array, leaving this pointing to a 0 constant
    /// array
    UT_VoxelArrayF              *steal();
    /// Adopts the heap-allocated voxel array. If the new voxel array is not
    /// of the right size, this field is left untouched, and the new voxel array
    /// is deleted.
    void adopt(UT_VoxelArrayF* newf);

    const UT_Vector3            &getOrig() const { return myOrig; }
    const UT_Vector3            &getSize() const { return mySize; }
    const UT_Vector3            &getBBoxOrig() const { return myBBoxOrig; }
    const UT_Vector3            &getBBoxSize() const { return myBBoxSize; }
    const UT_Vector3            &getVoxelSize() const { return myVoxelSize; }
    void                         setVoxelSize(const UT_Vector3 &voxelsize)
                                 { myVoxelSize = voxelsize; myVoxelDiameter = voxelsize.length(); }
    fpreal                       getVoxelDiameter() const { return myVoxelDiameter; }
    fpreal                       getVoxelVolume() const
                                 { return myVoxelSize.x() 
                                        * myVoxelSize.y() 
                                        * myVoxelSize.z(); }

    SIM_FieldSample              getSample() const { return mySample; }

    int64                        getMemoryUsage() const;

    /// Returns the resolution of the voxel grid that we are sampling.
    /// This is a count of voxels, so may differ for our different
    /// sampling methods.
    void                 getVoxelRes(int &xres, int &yres, int &zres) const;
    UT_Vector3I         getVoxelRes() const;

    /// Returns the actual number of samples in each resolution.
    /// Preferred over field()->getXRes() as it doesn't require a
    /// copy of the CE fields.
    exint                getXRes() const { return myField->getXRes(); }
    exint                getYRes() const { return myField->getYRes(); }
    exint                getZRes() const { return myField->getZRes(); }

    /// Functions to resolve quantities about the field.

    /// Sample the field at the given world space location.
    fpreal               getValue(UT_Vector3 pos) const;

    /// Returns the field value at the given voxel.
    fpreal               getValueIndex(UT_Vector3I index) const;

    /// Returns an averaged value for the center of the given voxel.
    fpreal               getCellValue(int x, int y, int z) const;

    /// Adds the value to the given voxel cell, averaging out among
    /// adjacent samples if we aren't sampled evenly.
    void                 addToCell(int x, int y, int z, fpreal v);

    /// Ensures the given voxel cell has the given value.  This
    /// will set all of the adjacent samples if we aren't sampled
    /// evenly.
    void                 setCellValue(int x, int y, int z, fpreal v);

    /// Return the gradient of the field at the given world space location.
    /// Uses central differencing with a sample spacing of the voxelsize.
    UT_Vector3           getGradient(UT_Vector3 pos) const;

    /// Returns the gradient at the given voxel index.
    /// Uses central differencing.
    UT_Vector3           getGradientAtIndex(int x, int y, int z) const;

    /// Computes the laplacian of the field at the world space
    /// coordinate using interpolation of getLaplacianAtIndex
    fpreal64             getLaplacian(UT_Vector3 pos) const;

    /// Computes the laplacian of the field at the specific voxel index
    /// specified
    fpreal64             getLaplacianAtIndex(int x, int y, int z) const;

    /// Returns the curvature of the field at a given world space location.
    /// Uses interpolation of index based getCurvatureAtIndex.
    fpreal64             getCurvature(UT_Vector3 pos) const;

    /// Computes the curvature at the given voxel index.
    /// Uses central differencing.
    /// The resulting curvature is clamped according to the resolution
    /// of the field to avoid abnormally large values in noisy data.
    fpreal64             getCurvatureAtIndex(int x, int y, int z) const;

    /// Computes the curvature according to a 3^3 voxel probe
    static fpreal64      getCurvatureAtProbe(UT_VoxelROProbeCubeF &probe, const UT_Vector3 &invvoxelsize);

    /// Computes K |grad(phi|), the curvature times the length of the
    /// gradient.  By folding the two operations, we can return a non-zero
    /// value where grad goes to zero (but curvature doesn't) using
    /// L'Hospital's rule.  This also does not clamp the curvature.
    fpreal64             getCurvatureTimesGradAtIndex(int x, int y, int z) const;

    /// Giving the relevent divided differences, compute the HJWENO
    /// approxmiation of the derivative.
    fpreal64             calculateHJWENO(fpreal64 v1, fpreal64 v2, fpreal64 v3, fpreal64 v4, fpreal64 v5) const;

    /// Calculate the derivitive along the specified axis using
    /// an HJ WENO method at the given index.  The boolean
    /// determines whether the derivitive in the positive or negative
    /// direction is computed.
    fpreal64             calculateDerivative(int x, int y, int z,
                                    int axis, bool positivegradient) const;

    /// Converts the boundary line information from world space to local index space.
    /// This applies an inverse transform to the plane normal and regular transform
    /// to the height value to put both into index space.
    SIM_BoundaryLine    boundaryLineToIndex(const SIM_BoundaryLine &worldbline) const;

    /// Convert indices to world coordinates and vice-versa.  Note this uses
    /// this field's indices which change depending on sampling.
    bool                 indexToPos(int x, int y, int z, UT_Vector3 &pos) const;
    bool                 indexToPos(exint x, exint y, exint z, UT_Vector3D &pos) const;
    bool                 indexToPos(UT_Vector3I index, UT_Vector3 &pos) const;
    UT_Vector3           indexToPos(UT_Vector3I index) const;


    /// Converts a worldspace position into an integer index.
    bool                 posToIndex(UT_Vector3 pos, int &x, int &y, int &z) const;

    bool                posToIndex(UT_Vector3 wpos, UT_Vector3 &ipos) const;
    UT_Vector3I         posToIndex(UT_Vector3 pos) const;

    /// Converts worldspace position into an integer index + the lerp values
    /// required to interpolate.
    /// Lerp with (1-dx) * (x,y,z) + dx * (x+1,y,z)
    bool                 posToIndex(UT_Vector3 pos, int &x, int &y, int &z,
                                    fpreal &dx, fpreal &dy, fpreal &dz) const;
    /// Convert voxel cell indices to world coordinates and vice-versa.
    /// Returns values at cell centers.  Is equivalent to the indexToPos
    /// style functions only when sampling is CENTER.
    bool                 cellIndexToPos(int x, int y, int z, UT_Vector3 &pos) const;
    bool                 posToCellIndex(UT_Vector3 pos, int &x, int &y, int &z) const;

    /// Verbs that can be performed on these fields.

    /// Advect a point in space according to an array of velocity
    /// fields.
    static void          advect(UT_Vector3 &pos, 
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, float time,
                                const SIM_RawField *collision = 0, 
                                float cfl = 1.0F);
    static void          advect(UT_Vector3 &pos,
                                sim_PointVelocity getVelocity,
                                float time, float voxelsize,
                                int jobnum = 0,
                                const SIM_RawField *collision = 0,
                                float cfl = 1.0F);

    /// Advect a point with the midpoint method.
    static void         advectMidpoint(UT_Vector3 &pos,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, float time,
                                const SIM_RawField *collision = 0,
                                float cfl = 1.0F);
    static void         advectMidpoint(UT_Vector3 &pos,
                                sim_PointVelocity getVelocity,
                                float time, float voxelsize,
                                int jobnum = 0,
                                const SIM_RawField *collision = 0,
                                float cfl = 1.0F);

    /// Advect a point with TVD-RK3 method.
    static void         advectRK3(UT_Vector3 &pos,
                                const SIM_RawField *velx,
                                const SIM_RawField *vely,
                                const SIM_RawField *velz, float time,
                                const SIM_RawField *collision = 0,
                                float cfl = 1.0F);

    /// Advect a point with TVD-RK4 method.
    static void         advectRK4(UT_Vector3 &pos,
                                const SIM_RawField *velx,
                                const SIM_RawField *vely,
                                const SIM_RawField *velz, float time,
                                const SIM_RawField *collision = 0,
                                float cfl = 1.0F);

    /// Move a point to the given isooffset.
    /// Returns false if fails to complete the move in the given time.
    bool                movePtToIso(UT_Vector3 &pos,
                                    fpreal goaliso,
                                    fpreal maxtime,
                                    fpreal tol = 1e-4) const;

    /// Advect the source field by the given set of velocity fields,
    /// setting this to the result.  Source cannot be this.
    /// this and source are assumed to match.
    void                 advect(const SIM_RawField *source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                SIM_FieldAdvection advectmethod,
                                float cfl);

    void                advectMinMax(const SIM_RawField *source,
                                SIM_RawField *minf, SIM_RawField *maxf,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                SIM_FieldAdvection advectmethod,
                                float cfl);

    struct sim_advectParms
    {
        const SIM_RawField *source;
        const SIM_RawField *velx, *vely, *velz;
        float               time;
        const SIM_RawField *collision;
        float               cfl;
        SIM_RawField       *minf, *maxf;
        SIM_FieldAdvection advectmethod;
    };

    THREADED_METHOD7(SIM_RawField, shouldMultiThread(), advectSingle,
                    const SIM_RawField *, source,
                    const SIM_RawField *, velx,
                    const SIM_RawField *, vely,
                    const SIM_RawField *, velz,
                    float, time,
                    const SIM_RawField *, collision,
                    float, cfl
                    )
    void                 advectSinglePartial(const SIM_RawField *source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                float cfl,
                                const UT_JobInfo &info);

    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), advectSingleMinMax,
                    const sim_advectParms &, parms)
    void                 advectSingleMinMaxPartial(const sim_advectParms &parms,
                                const UT_JobInfo &info);

    THREADED_METHOD7(SIM_RawField, shouldMultiThread(), advectTrace,
                    const SIM_RawField *, source,
                    const SIM_RawField *, velx,
                    const SIM_RawField *, vely,
                    const SIM_RawField *, velz,
                    float, time,
                    const SIM_RawField *, collision,
                    float, cfl
                    )
    void                 advectTracePartial(const SIM_RawField *source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                float cfl,
                                const UT_JobInfo &info);

    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), advectTraceMinMax,
                    const sim_advectParms &, parms)
    void                 advectTraceMinMaxPartial(const sim_advectParms &parms,
                                const UT_JobInfo &info);

    THREADED_METHOD8(SIM_RawField, shouldMultiThread(), advectMultistep,
                    const SIM_RawField *, source,
                    const SIM_RawField *, velx,
                    const SIM_RawField *, vely,
                    const SIM_RawField *, velz,
                    float, time,
                    const SIM_RawField *, collision,
                    float, cfl,
                    SIM_FieldAdvection, advectmethod
                    )
    void                 advectMultistepPartial(const SIM_RawField *source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                float cfl,
                                SIM_FieldAdvection advectmethod,
                                const UT_JobInfo &info);

    THREADED_METHOD1(SIM_RawField, shouldMultiThread(), advectMultistepMinMax,
                    const sim_advectParms &, parms)
    void                 advectMultistepMinMaxPartial(const sim_advectParms &parms,
                                const UT_JobInfo &info);

    /// Advects the field using HJWENO
    THREADED_METHOD5(SIM_RawField, shouldMultiThread(), advectHJWENO,
                        const SIM_RawField &, source,
                        const SIM_RawField *, velx,
                        const SIM_RawField *, vely,
                        const SIM_RawField *, velz,
                        fpreal, timestep
                        )
    void                advectHJWENOPartial(const SIM_RawField &source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                fpreal timestep,
                                const UT_JobInfo &info);

    /// Advects the field using upwind
    THREADED_METHOD5(SIM_RawField, shouldMultiThread(), advectUpwind,
                        const SIM_RawField &, source,
                        const SIM_RawField *, velx,
                        const SIM_RawField *, vely,
                        const SIM_RawField *, velz,
                        fpreal, timestep
                        )
    void                advectUpwindPartial(const SIM_RawField &source,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                fpreal timestep,
                                const UT_JobInfo &info);


    THREADED_METHOD5(SIM_RawField, shouldMultiThread(), 
                        buoyancy,
            const SIM_RawField *, stencil,
                        const SIM_RawField *, temperature,
                        fpreal, up, 
                        fpreal, Tamb,
                        fpreal, buoyancy)
    void                 buoyancyPartial(const SIM_RawField *stencil,
                  const SIM_RawField *temperature,
                                  fpreal up, fpreal Tamb,
                                  fpreal buoyancy,
                                  const UT_JobInfo &info);

    enum MIX_NAMES {
        MIX_COPY,
        MIX_ADD,
        MIX_SUB,
        MIX_MUL,
        MIX_DIV,
        MIX_MAX,
        MIX_MIN,
        MIX_AVERAGE,
        NUM_MIX
    };

    /// Performs the requires mixing.
    static fpreal        mixValues(MIX_NAMES mixtype,
                               fpreal d, fpreal s)
    {
        switch (mixtype)
        {
        case MIX_COPY:
            d = s;
            break;
        case MIX_ADD:
            d += s;
            break;
        case MIX_SUB:
            d -= s;
            break;
        case MIX_MUL:
            d *= s;
            break;
        case MIX_DIV:
            d = SYSsafediv(d, s);
            break;
        case MIX_MAX:
            d = SYSmax(d, s);
            break;
        case MIX_MIN:
            d = SYSmin(d, s);
            break;
        case MIX_AVERAGE:
            d = d + s;
            d *= 0.5f;
            break;
        case NUM_MIX:
            UT_ASSERT(!"Invalid mix value");
            break;
        }

        return d;
    }

    struct sim_particleToFieldParms
    {
        float           threshold, bandwidth;
        bool            extrapolate, usemaxextrapolate;
        float           maxextrapolatedist;
        float           d_preadd, d_premul;
        float           s_preadd, s_premul;
        float           postadd, postmul;
        float           uniformrad;
        MIX_NAMES       calctype;

        bool            useattrib;
        const char      *attribname;
        int             offset;
        UT_DMatrix4     xform;
        GEO_PrimVolumeXform     *fieldxform;
        bool            useaffine;
        const char      *affinename;
    };

    static fpreal applyParticleToFieldParms(fpreal srcval, fpreal dstval,
                                    const sim_particleToFieldParms &parms)
    {
        // srcval is our source value from the particle-defined field.
        // dstval is original value from destination field.
        // Apply our calculation method, and return.
        srcval *= parms.s_premul;
        srcval += parms.s_preadd;
        dstval *= parms.d_premul;
        dstval += parms.d_preadd;
        dstval = mixValues(parms.calctype, dstval, srcval);

        dstval *= parms.postmul;
        dstval += parms.postadd;
        return dstval;

    }

    THREADED_METHOD3(SIM_RawField, shouldMultiThread(),
                            applyParticles,
                            const GU_Detail *, particles,
                            GEO_PointTreeGAOffset *, pttree,
                            sim_particleToFieldParms &, parms)
    void                 applyParticlesPartial(
                                    const GU_Detail *particles,
                                    GEO_PointTreeGAOffset *pttree,
                                    sim_particleToFieldParms &parms,
                                    const UT_JobInfo &info);

    void                 accumulateParticles(const GU_Detail *particles,
                                            sim_particleToFieldParms &parms,
                                            const GA_PointGroup *ptgrp = NULL);

    THREADED_METHOD6(SIM_RawField, shouldMultiThread(), advect2,
                    const SIM_RawField *, source,
                    sim_PointVelocity, getVelocity,
                    float, time, float, voxelsize,
                    const SIM_RawField *, collision,
                    float, cfl)
    void                advect2Partial(const SIM_RawField *source,
                                sim_PointVelocity getVelocity,
                                float time, float voxelsize,
                                const SIM_RawField *collision,
                                float cfl,
                                const UT_JobInfo &info);

    /// Advect this field by the given velocity fields.  Invokes
    /// advect but handles the creation of the intermediate field.
    void                 advectSelf(const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                SIM_FieldAdvection advectmethod,
                                float cfl);
    void                 advectSelf(sim_PointVelocity getVelocity,
                                float time, float voxelsize,
                                const SIM_RawField *collision,
                                float cfl);

    /// Like advectSelf, but also generates min/max fields.
    void                 advectMinMaxSelf(SIM_RawField *minfield,
                                SIM_RawField *maxfield,
                                const SIM_RawField *velx, 
                                const SIM_RawField *vely, 
                                const SIM_RawField *velz, 
                                float time,
                                const SIM_RawField *collision,
                                SIM_FieldAdvection advectmethod,
                                float cfl);
    /// Solve the diffusion equation over this field according to
    /// the given diffusion rate.  One likely wants to roll the
    /// desired timestep into the diffusion rate.
    void                 diffuse(fpreal diffrate,
                                int numiter,
                                const SIM_RawField *collision=0);

    /// Raw diffuse algorithm, exposed only for external performance tests
    static void          diffuse(float *dstdata, const float *srcdata[3][3][3],
                                 float b, float ivsx, float ivsy, float ivsz,
                                 int tx, int ty,
                                 int max_xtile, int max_ytile,
                                 int max_xvox, int max_yvox);

    /// Determine all components connected according to < 0 semantic
    void                 computeConnectedComponents(UT_VoxelArray<int64> &comp, int &numcomponent) const;

    /// Computes the divergence of the face-centered velocity field
    /// and stores the result in this.  this must match the velocity field.
    /// If stencil is provided (and surface is not), the divergence is only
    /// calculated in the areas where stencil value is greater than 0.5 (with
    /// the remaining regions left untouched). stencil field must be aligned
    /// with this.
    THREADED_METHOD3(SIM_RawField, shouldMultiThread(), buildDivergenceFace,
                        const SIM_VectorField *, vel,
                        const SIM_RawField *, surface,
            const SIM_RawField *, stencil)
    void                 buildDivergenceFacePartial(const SIM_VectorField *vel,
                                    const SIM_RawField *surface,
                    const SIM_RawField *stencil,
                                    const UT_JobInfo &info);

    enum PCG_METHOD
    {
        PCG_NONE,
        PCG_JACOBI,
        PCG_CHOLESKY,
        PCG_MIC
    };

    /// Solves the pressure field that would eliminate the given
    /// divergence field.
    void                 solvePressure(const SIM_RawField *divergence,
                                        const SIM_RawField *collision,
                                        int numiter = 20);
    void                 solvePressurePCG(const SIM_RawField &divergence,
                                        SIM_RawIndexField &index,
                                        SIM_VectorField *vel,
                                        const SIM_RawIndexField *comp = 0,
                                        const UT_IntArray *expandable = 0,
                                        const SIM_RawField *surface = 0,
                                        bool variational = true,
                                        bool ghostfluid = true,
                                        PCG_METHOD pcgmethod = PCG_MIC);

    // For each voxel v in *this and corresponding voxel b in *B
    // sv = sum of 6-way neighbours of v
    // v' = (sv * sumweight + b) * weight
    // This is only applied to the voxels whose parity (x^y^z) matches
    // parity, so should be called twice to complete a single iteration.
    THREADED_METHOD4(SIM_RawField, shouldMultiThread(),
            gaussSeidelIteration,
            const SIM_RawField *, B,
            fpreal32,  weight,
            fpreal32,  sumweight,
            int,  parity)
    void gaussSeidelIterationPartial(
            const SIM_RawField * B,
            fpreal32  weight,
            fpreal32  sumweight,
            int  parity,
            const UT_JobInfo &info);

    // Note that in the flat case the destination field is passed
    // parameter, as opposed to the previous function where it is
    // the B field that is a parameter.
    THREADED_METHOD4_CONST(SIM_RawField, shouldMultiThread(),
            gaussSeidelIterationFlat,
            fpreal32 *, A,
            fpreal32,  weight,
            fpreal32,  sumweight,
            int,  parity)
    void gaussSeidelIterationFlatPartial(
            fpreal32 * A,
            fpreal32  weight,
            fpreal32  sumweight,
            int  parity,
            const UT_JobInfo &info) const;

    // Note that in the flat case the destination field is passed
    // parameter, as opposed to the previous function where it is
    // the B field that is a parameter.
    // This does a 4-way neighbours.
    THREADED_METHOD4_CONST(SIM_RawField, shouldMultiThread(),
            gaussSeidelIterationFlat2D,
            fpreal32 *, A,
            fpreal32,  weight,
            fpreal32,  sumweight,
            int,  parity)
    void gaussSeidelIterationFlat2DPartial(
            fpreal32 * A,
            fpreal32  weight,
            fpreal32  sumweight,
            int  parity,
            const UT_JobInfo &info) const;

    /// Enforces the boundary conditions on this field.
    /// Each axis can have its own conditions
    /// The boundary line is expected to be in index space
    void                 enforceBoundary(SIM_FieldBoundary collisionboundary = SIM_BOUNDARY_NONE, 
                                        const SIM_RawField *collision=0,
                                        const SIM_RawField *cvalue = 0,
                                        const SIM_RawField *boundary = 0,
                                        const SIM_BoundaryLine &indexbline = SIM_BoundaryLine());
    void                 enforceCollisionBoundary(SIM_FieldBoundary boundary,
                                        const SIM_RawField *collision,
                                        const SIM_RawField *cvalue = 0);
    void                 enforceSideBoundary(int axis, int side,
                                        SIM_FieldBoundary bound,
                                        fpreal boundaryvalue,
                                        const SIM_BoundaryLine &indexbline = SIM_BoundaryLine(),
                                        const SIM_RawField *boundaryfield = 0);

    THREADED_METHOD3(SIM_RawField, shouldMultiThread(),
                        enforceCollisionBoundaryInternal,
                        SIM_FieldBoundary, boundary,
                        const SIM_RawField *, collision,
                        const SIM_RawField *, cvalue)
    void                 enforceCollisionBoundaryInternalPartial(
                                SIM_FieldBoundary boundary,
                                const SIM_RawField *collision,
                                const SIM_RawField *cvalue,
                                const UT_JobInfo &info);

    /// Enforces the boundary conditions onto a flat array
    /// using the dimensions of this.
    /// Does SAME boundaries for collision objects.
    /// Index field is where to copy from for each collision voxel.
    void                enforceBoundaryFlat(fpreal32 *values,
                                const SIM_RawIndexField *collision_lookup);
    THREADED_METHOD2(SIM_RawField, shouldMultiThread(), 
                        enforceCollisionBoundaryFlat,
                        fpreal32 *, values,
                        const SIM_RawIndexField *, collision_lookup)

    void                enforceCollisionBoundaryFlatPartial(fpreal32 *values,
                                const SIM_RawIndexField *collision_lookup,
                                const UT_JobInfo &info);
    void                enforceSideBoundaryFlat(fpreal32 *values,
                                int axis, int side,
                                SIM_FieldBoundary bound,
                                fpreal boundval);

    /// These boundary conditions do *not* apply to reading outside
    /// of the valid field range.  The native UT_VoxelArray boundary
    /// condition is used for that.
    /// Instead, they are used for the behaviour of enforceBoundary
    /// and by various places where we want to distinguish open 
    /// velocity fields from closed.

    void                 setBoundary(int axis, int side, SIM_FieldBoundary bound)
                                    { myBoundary[axis][side] = bound; }
    SIM_FieldBoundary    getBoundary(int axis, int side) const 
                                    { return myBoundary[axis][side]; }
    void                 setBoundaryValue(int axis, int side, fpreal v)
                                    { myBoundaryValue[axis][side] = v; }
    fpreal               getBoundaryValue(int axis, int side) const
                                    { return myBoundaryValue[axis][side]; }

    /// Mark this field as being an extrapolated field.  Out of bound
    /// voxels will read the clamped value.  The difference between
    /// the clamped position and the real position is then dot producted
    /// with the given scale factor and added to the resulting value.
    /// This allows you to have rest fields that extrapolate meaningfully.
    void                 setAsExtrapolatedField(UT_Vector3 scale);

    /// These adjust the native UT_VoxelArray border values that *are*
    /// used for reading outside the valid range.
    UT_VoxelBorderType   getBorder() const;
    float                getBorderValue() const;
    void                 setBorder(UT_VoxelBorderType border, float bval);

    /// These adjust the native UT_VoxelArray comrpression options.
    void         setCompressionOptions(const UT_VoxelCompressOptions &options);
    const UT_VoxelCompressOptions &getCompressionOptions() const;

    /// These adjust the native UT_VoxelArray comrpression tolerance..
    void         setCompressionTolerance(fpreal tol);
    fpreal       getCompressionTolerance() const;

    /// Transform turns this into a packed set of wavelet coeffecients
    /// from the scalar data in field.  Inverse unpacks and generates
    /// a scalar field into this.
    ///
    /// Using a smooth edge conditon we assume that
    /// in case of an odd sized field, the ultimate row has
    /// zero diff coefficients.   We thus store the extra
    /// column in the averages side of the matrix, for
    /// ceil(n/2) in the averages and floor(n/2) in the diffs.
    /// Note this causes 3d fields that are actually 2d
    /// to properly decompose.
    void                 waveletTransform(UT_Wavelet::WAVELET_NAMES wavelettype,
                                        const SIM_RawField *field,
                                        int maxpasses = -1);
    void                 waveletInverseTransform(
                                        UT_Wavelet::WAVELET_NAMES wavelettype,
                                        const SIM_RawField *wavelet,
                                        int maxpasses = -1);

    /// Computes the sum of squares of the given level's detail vector.
    void                 waveletComputePSD(const SIM_RawField *wavelet,
                                            int level);

    /// Extracts the given component from a packed wavelet array.
    void                 waveletExtractComponent(const SIM_RawField *wavelet,
                                            int level,
                                            int component);

    /// Builds from either a GEO_PrimVolume or a GEO_PrimVDB.
    /// The provided volidx is the index inside of a vector volume
    /// to use for the building.
    void                 buildFromPrim(const GEO_Primitive *vol,
                                      int volidx,
                                      const UT_DMatrix4 &xform,
                                      fpreal scale);

    /// Builds from a GEO_PrimVolume
    void                 buildFromGeo(const GEO_PrimVolume *vol,
                                      const UT_DMatrix4 &xform,
                                      fpreal scale);

    /// Compute fractional volume weights representing the amount the voxel
    /// surrounding each sample point is inside the provided SDF.  This method
    /// just subsamples the voxel space according to the samplesperaxis
    /// parameter.


    void computeSDFWeightsSampled(const SIM_RawField *sdf,
                                         int samplesperaxis,
                                         bool invert,
                                         fpreal minweight,
                                         fpreal dilatedist = 0)
    { 
        computeSDFWeightsSampledInternal(sdf,samplesperaxis,invert,
                                            minweight, dilatedist);
    }

private:    
    THREADED_METHOD5(SIM_RawField, shouldMultiThread(),
                     computeSDFWeightsSampledInternal,
                     const SIM_RawField *, sdf,
                     int, samplesperaxis,
                     bool, invert,
                     fpreal, dilatedist,
                     fpreal, minweight);

    void computeSDFWeightsSampledInternalPartial(const SIM_RawField *sdf,
                                         int samplesperaxis,
                                         bool invert,
                                         fpreal minweight,
                                         fpreal dilatedist,
                                         const UT_JobInfo &info);
public:
    /// Compute fractional volume weights representing the amount the voxel
    /// surrounding each sample point is inside the provided SDF.  This method
    /// uses the normalized area of the square that is in the plane given by
    /// the axis parameter as an approximation.
    THREADED_METHOD4(SIM_RawField, shouldMultiThread(),
                     computeSDFWeightsFace,
                     const SIM_RawField *, sdf,
                     int, axis,
                     bool, invert,
                     fpreal, minweight);

    void computeSDFWeightsFacePartial(const SIM_RawField *sdf,
                                      int axis,
                                      bool invert,
                                      fpreal minweight,
                                      const UT_JobInfo &info);

    /// Compute fractional volume weights representing the amount the voxel
    /// surrounding each sample point is inside the provided SDF.  This method
    /// uses accurate volume fractions.
    THREADED_METHOD3(SIM_RawField, shouldMultiThread(),
                     computeSDFWeightsVolumeFraction,
                     const SIM_RawField *, sdf,
                     bool, invert,
                     fpreal, minweight);

    void computeSDFWeightsVolumeFractionPartial(const SIM_RawField *sdf,
                                      bool invert,
                                      fpreal minweight,
                                      const UT_JobInfo &info);


    /// Compute fractional volume weights for the voxel specified by x, y, z.
    /// This method uses the normalized area of the square that is in the
    /// plane given by the axis parameter as an approximation.
    fpreal computeVoxelSDFWeightFace(int x, int y, int z,
                                     const SIM_RawField *sdf,
                                     int axis) const;

    /// Scale this field by s * B / C or set to zero if scaled value is lower than
    /// given threshold
    THREADED_METHOD4(SIM_RawField, shouldMultiThread(),
                     setScaleDivideThreshold,
                     fpreal, scale,
                     const SIM_RawField *, B,
                     const SIM_RawField *, C,
                     fpreal, threshold)
    void    setScaleDivideThresholdPartial(fpreal scale,
                                     const SIM_RawField *B,
                                     const SIM_RawField *C,
                                     fpreal threshold,
                                     const UT_JobInfo &jobinfo);

protected:
    void                 waveletRebuildFromVoxelArray(
                                UT_VoxelArrayF *array,
                                float scale);


    static fpreal        applyBoundary(SIM_FieldBoundary bound, fpreal v,
                                        fpreal boundval);

    THREADED_METHOD2_CONST(SIM_RawField, shouldMultiThread(), reduceOpInternal,
                    fpreal64 *, sum,
                    REDUCE_NAMES, op)
    void        reduceOpInternalPartial(fpreal64 *sum, REDUCE_NAMES op, const UT_JobInfo &info) const;

    THREADED_METHOD5_CONST(SIM_RawField, shouldMultiThread(), reduceMaskedOpInternal,
                    fpreal64 *, sum,
                    fpreal64 *, masktotal,
                    REDUCE_NAMES, op,
                    const SIM_RawField *, mask,
                    bool, maskissdf)
    void        reduceMaskedOpInternalPartial(fpreal64 *sum, fpreal64 *masktotal, REDUCE_NAMES op, const SIM_RawField *maskfield, bool maskissdf, const UT_JobInfo &info) const;

    void                sortAllVoxels(UT_FloatArray &voxelvalues) const;
    void                sortAllVoxelsMasked(UT_FloatArray &voxelvalues, 
                                            const SIM_RawField *maskfield, 
                                            bool maskissdf) const;

    /// Methods for extrapolation
    THREADED_METHOD8(SIM_RawField, shouldMultiThread(), buildExtrapList,
                        UT_Array<UT_ValArray<gu_sdf_qelem *> > &, lists,
                        const SIM_RawField *, depths,
                        const SIM_RawField *, valid,
                        fpreal, isocontour,
                        fpreal, dir,
                        fpreal, maxdist,
                        bool, clamp,
                        fpreal, clampval)
    void                 buildExtrapListPartial(
                                UT_Array<UT_ValArray<gu_sdf_qelem *> > &lists,
                                const SIM_RawField *depths,
                                const SIM_RawField *valid,
                                fpreal isocontour,
                                fpreal dir, fpreal maxdist,
                                bool clamp, fpreal clampval,
                                const UT_JobInfo &info);

    /// Reduction by reducing each axis in turn.
    /// This *will* change field and dst != field is required.
    void                 localReduceByAxis(REDUCE_NAMES op,
                                            UT_VoxelArrayF &dst,
                                            UT_VoxelArrayF &field,
                                            UT_Vector3 radius) const;

    /// Reduce along a given axis by the specified radius in voxels.
    template <int AXIS, REDUCE_NAMES OP>
    void                 localReduceAxis(UT_VoxelArrayF &dstfield,
                                            const UT_VoxelArrayF &field,
                                            float radius,
                                            const UT_JobInfo &info) const;
    template <int AXIS, REDUCE_NAMES OP>
    void                 localMinMaxAxis(UT_VoxelArrayF &dstfield,
                                            const UT_VoxelArrayF &field,
                                            float radius,
                                            const UT_JobInfo &info) const;

    template <int AXIS>
    void                 localReduceAxisOp(REDUCE_NAMES op,
                                            UT_VoxelArrayF &dstfield,
                                            UT_VoxelArrayF &field,
                                            float radius,
                                            const UT_JobInfo &info) const;
    /// Again a triple specialization to engage threading.
    THREADED_METHOD4_CONST(SIM_RawField,
                    field.getTileRes(1)*field.getTileRes(2) > 1,
                    localReduceAxisX,
                    REDUCE_NAMES, op,
                    UT_VoxelArrayF &, dst,
                    UT_VoxelArrayF &, field,
                    float, radius)
    void                localReduceAxisXPartial(
                                REDUCE_NAMES op,
                                UT_VoxelArrayF &dst,
                                UT_VoxelArrayF &field,
                                float radius,
                                const UT_JobInfo &info) const
    { localReduceAxisOp<0>(op, dst, field, radius, info); }

    THREADED_METHOD4_CONST(SIM_RawField,
                    field.getTileRes(0)*field.getTileRes(2) > 1,
                    localReduceAxisY,
                    REDUCE_NAMES, op,
                    UT_VoxelArrayF &, dst,
                    UT_VoxelArrayF &, field,
                    float, radius)
    void                localReduceAxisYPartial(
                                REDUCE_NAMES op,
                                UT_VoxelArrayF &dst,
                                UT_VoxelArrayF &field,
                                float radius,
                                const UT_JobInfo &info) const
    { localReduceAxisOp<1>(op, dst, field, radius, info); }

    THREADED_METHOD4_CONST(SIM_RawField,
                    field.getTileRes(0)*field.getTileRes(1) > 1,
                    localReduceAxisZ,
                    REDUCE_NAMES, op,
                    UT_VoxelArrayF &, dst,
                    UT_VoxelArrayF &, field,
                    float, radius)
    void                localReduceAxisZPartial(
                                REDUCE_NAMES op,
                                UT_VoxelArrayF &dst,
                                UT_VoxelArrayF &field,
                                float radius,
                                const UT_JobInfo &info) const
    { localReduceAxisOp<2>(op, dst, field, radius, info); }

    THREADED_METHOD3(SIM_RawField, shouldMultiThread(), buildFromGeoSampled,
                    const GEO_PrimVolume *, vol,
                    const UT_DMatrix4 &, xform,
                    fpreal, scale)
    void                 buildFromGeoSampledPartial(const GEO_PrimVolume *vol,
                                                    const UT_DMatrix4 &xform,
                                                    fpreal scale,
                                                    const UT_JobInfo &info);

    THREADED_METHOD4(SIM_RawField, shouldMultiThread(), buildFromVDBSampled,
                    const GEO_PrimVDB *, vdb,
                    int, vdbidx,
                    const UT_DMatrix4 &, xform,
                    fpreal, scale)
    void                 buildFromVDBSampledPartial(const GEO_PrimVDB *vdb,
                                                    int vdbidx,
                                                    const UT_DMatrix4 &xform,
                                                    fpreal scale,
                                                    const UT_JobInfo &info);
    
    SIM_FieldSample              mySample;

    /// We always have myField at our current resolution.
    /// myGrid only exists if it matches myField.  If myField
    /// changes, myGrid will be destroyed.
    /// If something updates the grid the field is out of date
    /// so is flagged.
    UT_VoxelArrayF              *myField;
    mutable CE_Grid             *myGrid;
    mutable bool                 myFieldOutOfDate;

    // This is the size and offset which converts our UT_VoxelArray into
    // world coordinates.
    UT_Vector3                   myOrig, mySize;
    
    // This is our actual official size.
    UT_Vector3                   myBBoxOrig, myBBoxSize;

    UT_Vector3                   myVoxelSize;
    fpreal                       myVoxelDiameter;

    SIM_FieldBoundary            myBoundary[3][2];
    fpreal                       myBoundaryValue[3][2];
};


///
/// Allows you to iterate over the voxel cells of a RawField.  This
/// is different than iterating over the voxel samples!
/// The idea of getting or setting the raw value doesn't apply
/// here as we are not necessarily alligned with the sample grid.
///
class SIM_API SIM_RawFieldCellIterator
{
public:
             SIM_RawFieldCellIterator() 
             { 
                 myRes[0] = myRes[1] = myRes[2] = 0;
                 rewind(); 
             }
    virtual ~SIM_RawFieldCellIterator()
             {
             }
    
    void        setArray(const SIM_RawField *field)
                {
                    field->getVoxelRes(myRes[0], myRes[1], myRes[2]);
                    rewind();
                }

    void        rewind() 
                { 
                    myIdx[0] = 0; 
                    myIdx[1] = 0; 
                    myIdx[2] = 0; 
                }

    bool        atEnd() const 
                { 
                    return myIdx[2] >= myRes[2];
                }

    void        advance() 
                { 
                    myIdx[0]++;
                    if (myIdx[0] >= myRes[0])
                    {
                        myIdx[0] = 0;
                        myIdx[1]++;
                        if (myIdx[1] >= myRes[1])
                        {
                            myIdx[1] = 0;
                            myIdx[2]++;
                            if (myIdx[2] >= myRes[2])
                            {
                                // All done!
                                myIdx[2] = myRes[2];
                            }
                        }
                    }
                }

    int         x() const { return myIdx[0]; }
    int         y() const { return myIdx[1]; }
    int         z() const { return myIdx[2]; }
    int         idx(int axis) const { return myIdx[axis]; }
    
    /// Returns true if we are at the start of a new tile.
    /// Since we don't work on tile basis, we define a single
    /// x pass to be a tile.
    bool        isStartOfTile() const
                {
                    return myIdx[0] == 0;
                }

protected:
    int                                  myIdx[3];
    int                                  myRes[3];
};

//
// These macros create the CALL_VOXELPROBE macro
//
// CALL_VOXELPROBE(const SIM_RawField *src, 
//                 SIM_RawField *dst, 
//                 float defaultvalue,
//                 callFunc(dst, theprobe))
//
// callFunc should be
//
// template <typename P>
// void
// callFunc(SIM_RawField *dst, P &probe)
//
// dst->isMatching(src) must be true.
//
// The callFunc will receive in the parameter "theprobe" a
// UT_VoxelProbeAverage properly templated against the difference
// between the source and dest fields.
// theprobe.setIndex(x, y, z);
// will cause theprobe.getValue() to return the interpolated value
// in source of the destination's voxel sample (x, y, z).  This takes
// into account the different sampling patterns.
//
#define CALL_PROBEXY(XSTEP, YSTEP, src, dst, command)   \
{                                                       \
    if ((dstsample ^ srcsample) & 4)                    \
    {                                                   \
        if (dstsample & 4)      /* ZStep -1 */          \
        {                                               \
            UT_VoxelProbeAverage<fpreal32, XSTEP, YSTEP, -1> theprobe;  \
            theprobe.setArray(src->field());            \
            command;                                    \
        }                                               \
        else                    /* ZStep 1 */           \
        {                                               \
            UT_VoxelProbeAverage<fpreal32, XSTEP, YSTEP, 1> theprobe;   \
            theprobe.setArray(src->field());            \
            command;                                    \
        }                                               \
    }                                                   \
    else                        /* ZStep 0 */           \
    {                                                   \
        UT_VoxelProbeAverage<fpreal32, XSTEP, YSTEP, 0> theprobe;       \
        theprobe.setArray(src->field());                \
        command;                                        \
    }                                                   \
}

#define CALL_PROBEX(XSTEP, src, dst, command)           \
{                                                       \
    if ((dstsample ^ srcsample) & 2)                    \
    {                                                   \
        if (dstsample & 2)      /* YStep -1 */          \
        {                                               \
            CALL_PROBEXY(XSTEP, -1, src, dst, command); \
        }                                               \
        else                    /* YStep 1 */           \
        {                                               \
            CALL_PROBEXY(XSTEP, 1, src, dst, command);  \
        }                                               \
    }                                                   \
    else                        /* YStep 0 */           \
    {                                                   \
        CALL_PROBEXY(XSTEP, 0, src, dst, command);      \
    }                                                   \
}

#define CALL_VOXELPROBE(src, dst, defval, command)      \
{                                                       \
    if (!src)                                           \
    {                                                   \
        UT_VoxelProbeConstant<fpreal32> theprobe;       \
        theprobe.setValue(defval);                      \
        command;                                        \
    }                                                   \
    else                                                \
  {                                                     \
    int         dstsample, srcsample;                   \
    dstsample = dst->getSample();                       \
    srcsample = src->getSample();                       \
    if ((dstsample ^ srcsample) & 1)                    \
    {                                                   \
        if (dstsample & 1)      /* XStep -1 */          \
        {                                               \
            CALL_PROBEX(-1, src, dst, command);         \
        }                                               \
        else                    /* XStep 1 */           \
        {                                               \
            CALL_PROBEX(1, src, dst, command);          \
        }                                               \
    }                                                   \
    else                        /* XStep 0 */           \
    {                                                   \
        CALL_PROBEX(0, src, dst, command);              \
    }                                                   \
  }                                                     \
}

#endif