text: //
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  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Copyright (c) 2008-2021 NVIDIA Corporation. All rights reserved.
  // Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
  // Copyright (c) 2001-2004 NovodeX AG. All rights reserved.  
  
  
  #include "foundation/PxMemory.h"
  #include "extensions/PxSmoothNormals.h"
  
  #include "PsMathUtils.h"
  #include "PsUserAllocated.h"
  #include "PsUtilities.h"
  #include "CmPhysXCommon.h"
  
  using namespace physx;
  
  static PxReal computeAngle(const PxVec3* verts, const PxU32* refs, PxU32 vref)
  {
  	PxU32 e0=0,e2=0;
  	if(vref==refs[0])
  	{
  		e0 = 2;
  		e2 = 1;
  	}
  	else if(vref==refs[1])
  	{
  		e0 = 2;
  		e2 = 0;
  	}
  	else if(vref==refs[2])
  	{
  		e0 = 0;
  		e2 = 1;
  	}
  	else
  	{
  		PX_ASSERT(0);
  	}
  	const PxVec3 edge0 = verts[refs[e0]] - verts[vref];
  	const PxVec3 edge1 = verts[refs[e2]] - verts[vref];
  
  	return Ps::angle(edge0, edge1);
  }
  
  bool PxBuildSmoothNormals(PxU32 nbTris, PxU32 nbVerts, const PxVec3* verts, const PxU32* dFaces, const PxU16* wFaces, PxVec3* normals, bool flip)
  {
  	if(!verts || !normals || !nbTris || !nbVerts)	
  		return false;
  
  	// Get correct destination buffers
  	// - if available, write directly to user-provided buffers
  	// - else get some ram and keep track of it
  	PxVec3* FNormals = reinterpret_cast<PxVec3*>(PX_ALLOC_TEMP(sizeof(PxVec3)*nbTris, "PxVec3"));
  	if(!FNormals) return false;
  
  	// Compute face normals
  	const PxU32 c = PxU32(flip!=0);
  	for(PxU32 i=0; i<nbTris; i++)
  	{
  		// compute indices outside of array index to workaround
  		// SNC bug which was generating incorrect addresses
  		const PxU32 i0 = i*3+0;
  		const PxU32 i1 = i*3+1+c;
  		const PxU32 i2 = i*3+2-c;
  
  		const PxU32 Ref0 = dFaces ? dFaces[i0] : wFaces ? wFaces[i0] : 0;
  		const PxU32 Ref1 = dFaces ? dFaces[i1] : wFaces ? wFaces[i1] : 1;
  		const PxU32 Ref2 = dFaces ? dFaces[i2] : wFaces ? wFaces[i2] : 2;
  
  		FNormals[i] = (verts[Ref2]-verts[Ref0]).cross(verts[Ref1] - verts[Ref0]);
  		PX_ASSERT(!FNormals[i].isZero());
  		FNormals[i].normalize();
  	}
  
  	// Compute vertex normals
  	PxMemSet(normals, 0, nbVerts*sizeof(PxVec3));
  
  	// TTP 3751
  	PxVec3* TmpNormals = reinterpret_cast<PxVec3*>(PX_ALLOC_TEMP(sizeof(PxVec3)*nbVerts, "PxVec3"));
  	PxMemSet(TmpNormals, 0, nbVerts*sizeof(PxVec3));
  	for(PxU32 i=0;i<nbTris;i++)
  	{
  		PxU32 Ref[3];
  		Ref[0] = dFaces ? dFaces[i*3+0] : wFaces ? wFaces[i*3+0] : 0;
  		Ref[1] = dFaces ? dFaces[i*3+1] : wFaces ? wFaces[i*3+1] : 1;
  		Ref[2] = dFaces ? dFaces[i*3+2] : wFaces ? wFaces[i*3+2] : 2;
  
  		for(PxU32 j=0;j<3;j++)
  		{
  			if(TmpNormals[Ref[j]].isZero())
  				TmpNormals[Ref[j]] = FNormals[i];
  		}
  	}
  	//~TTP 3751
  
  	for(PxU32 i=0;i<nbTris;i++)
  	{
  		PxU32 Ref[3];
  		Ref[0] = dFaces ? dFaces[i*3+0] : wFaces ? wFaces[i*3+0] : 0;
  		Ref[1] = dFaces ? dFaces[i*3+1] : wFaces ? wFaces[i*3+1] : 1;
  		Ref[2] = dFaces ? dFaces[i*3+2] : wFaces ? wFaces[i*3+2] : 2;
  
  		normals[Ref[0]] += FNormals[i] * computeAngle(verts, Ref, Ref[0]);
  		normals[Ref[1]] += FNormals[i] * computeAngle(verts, Ref, Ref[1]);
  		normals[Ref[2]] += FNormals[i] * computeAngle(verts, Ref, Ref[2]);
  	}
  
  	// Normalize vertex normals
  	for(PxU32 i=0;i<nbVerts;i++)
  	{
  		if(normals[i].isZero())
  			normals[i] = TmpNormals[i];
  //		PX_ASSERT(!normals[i].isZero());
  		normals[i].normalize();
  	}
  
  	PX_FREE_AND_RESET(TmpNormals);	// TTP 3751
  	PX_FREE_AND_RESET(FNormals);
  
  	return true;
  }
  
  