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68 行
1.8 KiB
68 行
1.8 KiB
#ifndef __SPHERICALPOLYGON_HLSL__
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#define __SPHERICALPOLYGON_HLSL__
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#ifndef SPHERICALPOLYGON_MAX_VERTS
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#define SPHERICALPOLYGON_MAX_VERTS 3
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#endif
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#ifndef SPHERICALPOLYGON_NUM_VERTS
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#define SPHERICALPOLYGON_NUM_VERTS 3
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#endif
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void SphericalPolygon_CalcInteriorAngles(in float3 P[SPHERICALPOLYGON_MAX_VERTS], out float A[SPHERICALPOLYGON_MAX_VERTS])
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{
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const int LAST_VERT = (SPHERICALPOLYGON_NUM_VERTS - 1);
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float3 N[SPHERICALPOLYGON_MAX_VERTS];
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// calc plane normals
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// where N[i] = normal of incident plane
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// eg. N[i+0] = cross(C, A);
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// N[i+1] = cross(A, B);
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{
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N[0] = -normalize(cross(P[LAST_VERT], P[0]));
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for (int i = 1; i != SPHERICALPOLYGON_NUM_VERTS; i++)
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{
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N[i] = -normalize(cross(P[i - 1], P[i]));
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}
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}
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// calc interior angles
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{
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for (int i = 0; i != LAST_VERT; i++)
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{
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A[i] = PI - sign(dot(N[i], P[i + 1])) * acos(clamp(dot(N[i], N[i + 1]), -1.0, 1.0));
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}
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A[LAST_VERT] = PI - sign(dot(N[LAST_VERT], P[0])) * acos(clamp(dot(N[LAST_VERT], N[0]), -1.0, 1.0));
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}
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/*
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float3 nCA = cross(C, A);// plane normals
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float3 nAB = cross(A, B);
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float3 nBC = cross(B, C);
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float wA = PI - sign(dot(nCA, B)) * acos(dot(nCA, nAB));
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float wB = PI - sign(dot(nAB, C)) * acos(dot(nAB, nBC));
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float wC = PI - sign(dot(nBC, A)) * acos(dot(nBC, nCA));
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return float3(wA, wB, wC);
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*/
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}
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void SphericalPolygon_CalcAreaFromInteriorAngles(in float A[SPHERICALPOLYGON_MAX_VERTS], out float area)
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{
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float E = 0.0;
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for (int i = 0; i != SPHERICALPOLYGON_NUM_VERTS; i++)
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{
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E += A[i];
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}
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area = E - (SPHERICALPOLYGON_NUM_VERTS - 2.0) * PI;
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}
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void SphericalPolygon_CalcAreaFromProjectedPositions(in float3 P[SPHERICALPOLYGON_MAX_VERTS], out float area)
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{
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float A[SPHERICALPOLYGON_MAX_VERTS];
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SphericalPolygon_CalcInteriorAngles(P, A);
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SphericalPolygon_CalcAreaFromInteriorAngles(A, area);
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}
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#endif//__SPHERICALPOLYGON_HLSL__
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