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GT_CurveEval.h File Reference
#include "GT_API.h"
#include "GT_Types.h"
#include "GT_Handles.h"
#include <UT/UT_Array.h>
+ Include dependency graph for GT_CurveEval.h:

Go to the source code of this file.


void allocateNumericArrays (UT_Array< GT_DataArrayHandle > &arrays, const GT_AttributeListHandle &hull, GT_Size total_points) const
bool refineToNumeric (int order, UT_Array< GT_DataArrayHandle > &arrays, GT_Offset dest_offset, GT_Size dest_count, const GT_AttributeListHandle &hull, GT_Offset hull_offset, GT_Size hull_count, const GT_DataArrayHandle &knots, GT_Offset knot_offset, int segment=0) const
bool copyToAttributes (GT_AttributeListHandle &dest, UT_Array< GT_DataArrayHandle > &arrays, int segment=0) const
void preCompute (int order, EvalBuffer &ebuf, int span, fpreal t, const Knots &knots) const
 When computing with knots, there need to be Order*2+1 knots for a span. More...


GT_Basis myBasis
int myOrder
int myStep
bool myPeriodic

Function Documentation

void allocateNumericArrays ( UT_Array< GT_DataArrayHandle > &  arrays,
const GT_AttributeListHandle hull,
GT_Size  total_points 
) const

Class to perform evaluation of the curve spline types.

This is similar to UT_Spline but supports higher order curves and a different set of basis functions.

To evaluate a curve, you do something like:

const GT_CurveEval eval(...);
int nspans = eval.spanCount(nvertices);
type result[nspans*points_per_span];
Note: There only dependency on GT is the basis type. This can likely be
moved to a lower library (i.e. UT).
class GT_API GT_CurveEval
static int maximumBezierOrder();
static void orderRange(GT_Basis basis, int &min_order, int &max_order);
GT_CurveEval(GT_Basis basis, bool periodic);
GT_CurveEval(const GT_CurveEval &eval);
void setOrder(int order)
if (order != myOrder)
Class to hold non-uniform knot vector.
class Knots
: myKnots(0)
, mySize(0)
The knots passed in are not owned by this class, so they must stay
in existence while the Knots object is in existence.
Knots(const fpreal *knots, int length)
: myKnots(knots)
, mySize(length)
Test validity
bool valid() const { return myKnots && mySize > 1; }
Return the full knot vector
const fpreal *knots() const { return myKnots; }
Return the knots for the given span
const fpreal *knots(int span) const { return myKnots + span; }
For a given @c span, and interpolant @c t (between 0 and 1), return
the proper knot value for interpolation.
fpreal getU(int span, int order, fpreal t) const
int n = span + order - 1;
UT_ASSERT(n >= 0 && n+1 < mySize);
return SYSlerp(myKnots[n], myKnots[n+1], t);
Return the length of the knot vector
int size() const { return mySize; }
Lookup a knot
fpreal operator()(int i) const
UT_ASSERT(i >= 0 && i < mySize);
return myKnots[i];
Lookup a knot
fpreal operator[](int i) const
UT_ASSERT(i >= 0 && i < mySize);
return myKnots[i];
Set up knot vector
void setKnots(const fpreal *knots, int size)
myKnots = knots;
mySize = size;
bool save(UT_JSONWriter &w);
void dump(const char *msg="");
const fpreal *myKnots;
int mySize;
Test if there's a valid count for the given curve type (of the given
bool validCount(int nvertices, int order) const;
Access member data
GT_Basis basis() const { return myBasis; }
bool periodic() const { return myPeriodic; }
Return the step size for iterating through spans
int step() const { return myStep; }
Return the number of spans for a given hull
int spanCount(int nvtx, int order) const
{ return GTbasisSpans(myBasis, nvtx, myPeriodic, order); }
The EvalBuffer class is used to store state for evaluation
class EvalBuffer
EvalBuffer() {}
~EvalBuffer() {}
// This size is tied to constants in GT_Binomial.h
Weights for each element in the span
const fpreal *w() const { return myW; }
fpreal *w() { return myW; }
Which element in the span contributes the most
int conditional() const { return myConditional; }
void setConditional(int c) { myConditional = c; }
Find the element which contributes the most in the span
void computeConditional(int nvals)
myConditional = 0;
for (int i = 1; i < nvals; ++i)
if (myW[i] > myW[myConditional])
myConditional = i;
fpreal myW[EVAL_BUF_SIZE];
int myConditional;
Evaluate a the hull of a curve at a given parametric coordinate.
There should be @c order elements in the hull.
The default template implementation performs conditional copying.
template <typename DATA_T>
inline DATA_T eval(int order, const EvalBuffer &ebuf,
const DATA_T *hull, int stride=1) const
{ return hull[ebuf.conditional()*stride]; }
Evaluate a the hull of a curve at a given parametric coordinate and an
indirection array. The elements in the indirection array are used to
perform the lookup.
There should be @c order elements in the index array.
template <typename DATA_T>
inline DATA_T evalIndex(int order, const EvalBuffer &ebuf,
const DATA_T *hull, const int *index) const
{ return hull[index[ebuf.conditional()]]; }
Precompute the evaluation buffer for a span
void preCompute(int order, EvalBuffer &ebuf, fpreal t) const;
Refine to numeric arrays
- @c dest must be an array of GT_DANumeric sub-classes
- @c dest_offset into the dest arrays to begin writing the evaluated
- @c dest_count the number of evaluations
- @c hull The attributes to be evaluated
- @c hull_offset the offset into the hull arrays
- @c hull_count is the number of elements in the array for the hull
For example, given a GT_PrimCurveMesh with a two curves: @code
// Refine 1st curve to 10 points and the second to 32
int dpts[] = { 10, 32 }
UT_Array<GT_DataArrayHandle> arrays;
const GT_AttributeListHandle &vertex = curve->getcVertexAttributes();
eval.allocateNumericArrays(arrays, vertex, 42);
refineToNumeric(arrays, 0, 10, vertex,
refineToNumeric(arrays, 10, 32, vertex,
// Create a destination attribute list
GT_AttributeListHandle dest(new GT_AttributeListHandle(*vertex));
// And copy the array data into the attribute list
copyToAttributes(dest, arrays);
You must ensure that setOrder() has been called
bool copyToAttributes ( GT_AttributeListHandle dest,
UT_Array< GT_DataArrayHandle > &  arrays,
int  segment = 0 
) const
void preCompute ( int  order,
EvalBuffer &  ebuf,
int  span,
fpreal  t,
const Knots &  knots 
) const

When computing with knots, there need to be Order*2+1 knots for a span.

bool refineToNumeric ( int  order,
UT_Array< GT_DataArrayHandle > &  arrays,
GT_Offset  dest_offset,
GT_Size  dest_count,
const GT_AttributeListHandle hull,
GT_Offset  hull_offset,
GT_Size  hull_count,
const GT_DataArrayHandle knots,
GT_Offset  knot_offset,
int  segment = 0 
) const

Variable Documentation

GT_Basis myBasis

Definition at line 262 of file GT_CurveEval.h.

int myOrder

Definition at line 263 of file GT_CurveEval.h.

bool myPeriodic

Definition at line 265 of file GT_CurveEval.h.

int myStep

Definition at line 264 of file GT_CurveEval.h.