SNOW_Solver.h

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/*
 * Copyright (c) 2025
 *      Side Effects Software Inc.  All rights reserved.
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 * Redistribution and use of Houdini Development Kit samples in source and
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 * following conditions are met:
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 *    this list of conditions and the following disclaimer.
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/*
 * The simplest network to see something working with this...
 *
 *  Empty Object     SnowVisualize
 *         \           /
 *         Snow VoxelArray
 *             |
 *        Snow Solver  (Birth rate .1)
 */

#ifndef __SNOW_Solver_h__
#define __SNOW_Solver_h__

#include <UT/UT_IStream.h>
#include <UT/UT_Map.h>
#include <UT/UT_VoxelArray.h>
#include <GA/GA_Types.h>
#include <GU/GU_DetailHandle.h>
#include <SIM/SIM_OptionsUser.h>
#include <SIM/SIM_SingleSolver.h>
#include <SIM/SIM_Geometry.h>

#define SIM_NAME_BIRTHRATE      "birthrate"
#define SIM_NAME_ORIGINALDEPTH  "originaldepth"

class SIM_Object;
class SIM_Random;

typedef unsigned char           u8;

namespace HDK_Sample {

class SNOW_VoxelArray;

// This class implemented a computational fluid dynamics solver.
class SNOW_Solver : public SIM_SingleSolver,
                       public SIM_OptionsUser
{
public:
    // Access methods for our configuration data.
    GETSET_DATA_FUNCS_F(SIM_NAME_BIRTHRATE, BirthRate);
    GETSET_DATA_FUNCS_I(SIM_NAME_ORIGINALDEPTH, OriginalDepth);
    
protected:
    explicit             SNOW_Solver(const SIM_DataFactory *factory);
                        ~SNOW_Solver() override;

    SIM_Random          *createRandomData(SIM_Object *obj) const;

    SIM_Result           solveSingleObjectSubclass(SIM_Engine &engine,
                                        SIM_Object &object,
                                        SIM_ObjectArray &feedbacktoobjects,
                                        const SIM_Time &timestep,
                                        bool newobject) override;

    int                  rand_choice(int numchoice, SIM_Random *rand) const;
    bool                 brownianize(int &v, int dv, int max,
                                     SIM_Random *rand) const;
    int                  clearInDirection(const SNOW_VoxelArray &snow,
                                int sx, int sy, int sz,
                                int dx, int dy, int dz,
                                int &rx, int &ry, int &rz,
                                int maxdist,
                                SIM_Random *rand) const;
    void                 clearSnow(SNOW_VoxelArray &snow,
                                int x, int y, int z,
                                SIM_Random *rand) const;

    void                 fillRow(SNOW_VoxelArray &snow,
                                fpreal startx, fpreal endx,
                                int y, int z,
                                u8 voxeltype,
                                SIM_Random *rand) const;
    void                 applyGeometry(SNOW_VoxelArray &snow,
                                const GU_ConstDetailHandle &gdh,
                                const UT_DMatrix4 &xform,
                                u8 voxletype,
                                SIM_Random *rand) const;

private:
    static const SIM_DopDescription     *getSolverSNOWDopDescription();

    void                 solveForObject(SIM_Object &object,
                                        SNOW_VoxelArray &snow,
                                        const SIM_Time &timestep) const;
    void                 setVoxelArrayAttributes(
                                        SNOW_VoxelArray *voxelarray) const;

    DECLARE_STANDARD_GETCASTTOTYPE();
    DECLARE_DATAFACTORY(SNOW_Solver,
                        SIM_SingleSolver,
                        "SNOW Solver",
                        getSolverSNOWDopDescription());
};

// Standard defines for voxel elements:
#define VOXEL_EMPTY             0
#define VOXEL_SNOW              1
#define VOXEL_COMPRESSED        2
#define VOXEL_WALL              3
#define VOXEL_OBJECT            4

#define SNOW_NAME_DIVISIONS     "div"
#define SNOW_NAME_CENTER        "t"
#define SNOW_NAME_SIZE          "size"

// This class hold an oriented bounding box tree.
class SNOW_VoxelArray : public SIM_Geometry
                        // SIM_Geometry already mixes this in.
                        // public SIM_OptionsUser
{
public:
    GETSET_DATA_FUNCS_V3(SNOW_NAME_DIVISIONS, Divisions);
    GETSET_DATA_FUNCS_V3(SNOW_NAME_SIZE, Size);
    GETSET_DATA_FUNCS_V3(SNOW_NAME_CENTER, Center);

    // Read an element:  This will return 0 for out of bound x/y/z values.
    u8                   getVoxel(int x, int y, int z) const;
    void                 setVoxel(u8 voxel, int x, int y, int z);

    void                 collapseAllTiles();

    void                 pubHandleModification()
                         { handleModification(); }

protected:
    explicit             SNOW_VoxelArray(const SIM_DataFactory *factory);
                        ~SNOW_VoxelArray() override;

    // Overrides to properly implement this class as a SIM_Data.
    void                 initializeSubclass() override;
    void                 makeEqualSubclass(const SIM_Data *source) override;
    // Normally you could override saveSubclass and loadSubclass
    // and the IO variants would chain to it, but because SIM_Geometry
    // has implemented the new IO path we need to as well.
    void                 saveIOSubclass(std::ostream &os,
                                        SIM_DataThreadedIO *io) const override;
    bool                 loadIOSubclass(UT_IStream &is,
                                        SIM_DataThreadedIO *io) override;
    void                 handleModificationSubclass(int code) override;

    int64                getMemorySizeSubclass() const override;

    /// Invoked when our parameters are changed, we use it to
    /// invalidate our array.
    void                 optionChangedSubclass(const char *name) override;

    // Override the getGeometrySubclass function to construct our geometric
    // representation in a just-in-time fashion.
    GU_ConstDetailHandle getGeometrySubclass() const override;

private:
    static const SIM_DopDescription     *getVoxelArrayDopDescription();

    GA_Offset            createOrFindPoint(GU_Detail *gdp, int x, int y, int z);
    void                 buildFace(GU_Detail *gdp,
                                   int x0, int y0, int z0,
                                   int x1, int y1, int z1,
                                   int x2, int y2, int z2,
                                   int x3, int y3, int z3);
    void                 buildGeometryFromArray();
    void                 freeArray() const;
    void                 allocateArray() const;

    mutable GU_DetailHandle              myDetailHandle;
    mutable UT_VoxelArray<u8>           *myVoxelArray;

    UT_Map<exint, GA_Offset>             myPointHash;

    DECLARE_STANDARD_GETCASTTOTYPE();
    DECLARE_DATAFACTORY(SNOW_VoxelArray,        // Our Classname
                        SIM_Geometry,           // Base type
                        "hdk_VoxelArray",       // DOP Data Type
                        getVoxelArrayDopDescription() // PRM list.
                        );
};

// This class hold an oriented bounding box tree.
class SNOW_Visualize : public SIM_Data,
                        public SIM_OptionsUser
{
public:
    GET_GUIDE_FUNC_B(SIM_NAME_SHOWGUIDE, ShowGuide, true);
    GET_GUIDE_FUNC_V3(SIM_NAME_COLOR, Color, (1, 1, 1));
    GET_GUIDE_FUNC_B("usebox", UseBox, false);

protected:
    explicit             SNOW_Visualize(const SIM_DataFactory *factory);
                        ~SNOW_Visualize() override;

    // Overrides to properly implement this class as a SIM_Data.
    void                 initializeSubclass() override;

    bool                 getIsAlternateRepresentationSubclass() const override;
    void                 initAlternateRepresentationSubclass(
                                const SIM_Data &) override;
    SIM_Guide           *createGuideObjectSubclass() const override;
    void                 buildGuideGeometrySubclass(const SIM_RootData &root,
                                                    const SIM_Options &options,
                                                    const GU_DetailHandle &gdh,
                                                    UT_DMatrix4 *xform,
                                                    const SIM_Time &t
                                                    ) const override;

    static void                  createBoundingBoxGuide(GU_Detail *gdp,
                                    const UT_BoundingBox &bbox,
                                    const UT_Vector3 &color);

private:
    static const SIM_DopDescription     *getVisualizeDopDescription();

    const SNOW_VoxelArray       *myArray;

    DECLARE_STANDARD_GETCASTTOTYPE();
    DECLARE_DATAFACTORY(SNOW_Visualize, // Our Classname
                        SIM_Data,               // Base type
                        "hdk_SnowVisualize",    // DOP Data Type
                        getVisualizeDopDescription() // PRM list.
                        );
};

} // End the HDK_Sample namespace

#endif