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#ifndef GU_TRIANGLE_REFINEMENT_H
#define GU_TRIANGLE_REFINEMENT_H

// Indexing scheme for sub-triangles in recursive triangle subdivision scheme
// Each subdivision step creates 4 triangles out of the previous one:
// - First triangle is the "a corner"
// - Second triangle is the "b corner"
// - Third triangle is the "c corner"
// - Fourth triangle is the center

#include "foundation/PxVec3.h"

namespace physx {
	namespace Gu {
		PX_FORCE_INLINE PX_CUDA_CALLABLE void getSubTriangle4(int id, PxVec3& baryA, PxVec3& baryB, PxVec3& baryC)
		{

			PxVec3 ab = 0.5f * (baryA + baryB);
			PxVec3 bc = 0.5f * (baryB + baryC);
			PxVec3 ca = 0.5f * (baryC + baryA);

			switch (id)
			{
				case 0:
					baryB = ab;
					baryC = ca;
					break;
				case 1:
					baryA = ab;
					baryC = bc;
					break;
				case 2:
					baryA = ca;
					baryB = bc;
					break;
				case 3:
					baryA = ab;
					baryB = bc;
					baryC = ca;
					break;
				default:
					PX_ASSERT(false);
			}
		}

		PX_FORCE_INLINE PX_CUDA_CALLABLE void getSubTriangle(PxVec3& a, PxVec3& b, PxVec3& c, PxU32 id, PxU32 numSubdivisionSteps)
		{
			for (PxU32 i = 0; i < numSubdivisionSteps; ++i)
			{
				PxU32 j = numSubdivisionSteps - i - 1;
				PxU32 local = id >> (2 * j);
				local = local & 3;
				getSubTriangle4(local, a, b, c);
			}
		}

		PX_FORCE_INLINE PX_CUDA_CALLABLE PxU32 encodeSubdivisionId(PxU32 subdivisionLevel, PxU32 subTriangleIndex)
		{
			//4 bits for subdivision level, the rest for the index
			const PxU32 shift = 30 - 4;
			return (subdivisionLevel << shift) | subTriangleIndex;
		}

		PX_FORCE_INLINE PX_CUDA_CALLABLE void decodeSubdivisionId(PxU32 encodedId, PxU32& subdivisionLevel, PxU32& subTriangleIndex)
		{
			const PxU32 shift = 30 - 4;
			subdivisionLevel = encodedId >> shift;
			subTriangleIndex = encodedId & ((1 << shift) - 1);
		}

		//Increases the subdivision level by one and sets the index to the specified sub triangle that got created out of the previous triangle due to one additional level of subdivision
		PX_FORCE_INLINE PX_CUDA_CALLABLE PxU32 elevateSubdivisionId(PxU32 encodedId, PxU32 subTriangle = 0)
		{
			PX_ASSERT(subTriangle >= 0 && subTriangle < 4);

			PxU32 subdivisionLevel;
			PxU32 subTriangleIndex;
			decodeSubdivisionId(encodedId, subdivisionLevel, subTriangleIndex);

			return encodeSubdivisionId(subdivisionLevel + 1, 4 * subTriangleIndex + subTriangle);
		}

		PX_FORCE_INLINE PX_CUDA_CALLABLE void getSubTriangleEncoded(PxVec3& a, PxVec3& b, PxVec3& c, PxU32 encodedSubIndex)
		{
			PxU32 subdivisionLevel;
			PxU32 subTriangleIndex;
			decodeSubdivisionId(encodedSubIndex, subdivisionLevel, subTriangleIndex);
			getSubTriangle(a, b, c, subTriangleIndex, subdivisionLevel);
		}

	} // namespace Gu
} // namespace physx
#endif // GU_TRIANGLE_REFINEMENT_H