Rasagar/Library/PackageCache/com.unity.render-pipelines.core/ShaderLibrary/MostRepresentativePoint.hlsl
2024-08-26 23:07:20 +03:00

77 lines
2.4 KiB
HLSL

#ifndef UNITY_AREA_MRP_INCLUDED
#define UNITY_AREA_MRP_INCLUDED
// Ref: Moving Frostbite to PBR (Listing 11).
// Returns the solid angle of a rectangle at the point.
float SolidAngleRectangle(float3 positionWS, float4x3 lightVerts)
{
float3 v0 = lightVerts[0] - positionWS;
float3 v1 = lightVerts[1] - positionWS;
float3 v2 = lightVerts[2] - positionWS;
float3 v3 = lightVerts[3] - positionWS;
float3 n0 = normalize(cross(v0, v1));
float3 n1 = normalize(cross(v1, v2));
float3 n2 = normalize(cross(v2, v3));
float3 n3 = normalize(cross(v3, v0));
float g0 = FastACos(dot(-n0, n1));
float g1 = FastACos(dot(-n1, n2));
float g2 = FastACos(dot(-n2, n3));
float g3 = FastACos(dot(-n3, n0));
return g0 + g1 + g2 + g3 - TWO_PI;
}
// Optimized (and approximate) solid angle routine. Doesn't handle the horizon.
float SolidAngleRightPyramid(float positionWS, float lightPositionWS, float halfWidth, float halfHeight)
{
const float a = halfWidth;
const float b = halfHeight;
const float h = length(positionWS - lightPositionWS);
return 4.0 * FastASin(a * b / sqrt (( a * a + h * h) * (b * b + h * h) ));
}
float FlatAngleSegment(float3 positionWS, float3 lightP1, float3 lightP2)
{
float3 v0 = normalize(lightP1 - positionWS);
float3 v1 = normalize(lightP2 - positionWS);
return FastACos(dot(v0,v1));
}
// Ref: Moving Frostbite to PBR (Appendix E, Listing E.2)
// Returns the closest point to a rectangular shape defined by right and up (and the rect extents).
float3 ClosestPointRectangle(float3 positionWS, float3 planeOrigin, float3 left, float3 up, float halfWidth, float halfHeight)
{
float3 dir = positionWS - planeOrigin;
// Project into the 2D light plane.
float2 dist2D = float2(dot(dir, left), dot(dir, up));
// Clamp within the rectangle.
const float2 halfSize = float2(halfWidth, halfHeight);
dist2D = clamp(dist2D, -halfSize, halfSize);
// Compute the new world position.
return planeOrigin + dist2D.x * left + dist2D.y * up;
}
// Ref: Moving Frostbite to PBR (Listing 13)
float3 ClosestPointLine(float3 a, float3 b, float3 c)
{
float3 ab = b - a;
float t = dot(c - a, ab) / dot(ab, ab);
return a + t * ab;
}
float3 ClosestPointSegment(float3 a, float3 b, float3 c)
{
float3 ab = b - a;
float t = dot(c - a, ab) / dot(ab, ab);
return a + saturate(t) * ab;
}
#endif // UNITY_AREA_MRP_INCLUDED