71 lines
2.2 KiB
HLSL
71 lines
2.2 KiB
HLSL
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#ifndef UNITY_REFRACTION_INCLUDED
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#define UNITY_REFRACTION_INCLUDED
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//-----------------------------------------------------------------------------
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// Util refraction
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//-----------------------------------------------------------------------------
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struct RefractionModelResult
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{
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real dist; // length of the transmission during refraction through the shape
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float3 positionWS; // out ray position
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real3 rayWS; // out ray direction
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};
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RefractionModelResult RefractionModelSphere(real3 V, float3 positionWS, real3 normalWS, real ior, real thickness)
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{
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// Sphere shape model:
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// We approximate locally the shape of the object as sphere, that is tangent to the shape.
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// The sphere has a diameter of {thickness}
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// The center of the sphere is at {positionWS} - {normalWS} * {thickness} * 0.5
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//
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// So the light is refracted twice: in and out of the tangent sphere
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// First refraction (tangent sphere in)
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// Refracted ray
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real3 R1 = refract(-V, normalWS, 1.0 / ior);
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// Center of the tangent sphere
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real3 C = positionWS - normalWS * thickness * 0.5;
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// Second refraction (tangent sphere out)
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real NoR1 = dot(normalWS, R1);
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// Optical depth within the sphere
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real dist = -NoR1 * thickness;
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// Out hit point in the tangent sphere
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real3 P1 = positionWS + R1 * dist;
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// Out normal
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real3 N1 = normalize(C - P1);
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// Out refracted ray
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real3 R2 = refract(R1, N1, ior);
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real N1oR2 = dot(N1, R2);
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real VoR1 = dot(V, R1);
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RefractionModelResult result;
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result.dist = dist;
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result.positionWS = P1;
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result.rayWS = R2;
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return result;
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}
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RefractionModelResult RefractionModelBox(real3 V, float3 positionWS, real3 normalWS, real ior, real thickness)
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{
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// Plane shape model:
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// We approximate locally the shape of the object as a plane with normal {normalWS} at {positionWS}
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// with a thickness {thickness}
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// Refracted ray
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real3 R = refract(-V, normalWS, 1.0 / ior);
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// Optical depth within the thin plane
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real dist = thickness / max(dot(R, -normalWS), 1e-5f);
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RefractionModelResult result;
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result.dist = dist;
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result.positionWS = positionWS + R * dist;
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result.rayWS = -V;
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return result;
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}
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#endif
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