43 lines
1.1 KiB
SourcePawn
43 lines
1.1 KiB
SourcePawn
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//
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const float M_PI = 3.141592653589793;
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vec4 SRGBtoLINEAR(vec4 srgbIn) {
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vec3 linOut = pow(srgbIn.xyz,vec3(2.2));
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return vec4(linOut, srgbIn.a);
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}
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// http://www.thetenthplanet.de/archives/1180
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// modified to fix handedness of the resulting cotangent frame
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mat3 cotangentFrame( vec3 N, vec3 p, vec2 uv ) {
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// get edge vectors of the pixel triangle
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vec3 dp1 = dFdx( p );
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vec3 dp2 = dFdy( p );
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vec2 duv1 = dFdx( uv );
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vec2 duv2 = dFdy( uv );
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// solve the linear system
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vec3 dp2perp = cross( dp2, N );
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vec3 dp1perp = cross( N, dp1 );
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vec3 T = dp2perp * duv1.x + dp1perp * duv2.x;
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vec3 B = dp2perp * duv1.y + dp1perp * duv2.y;
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// construct a scale-invariant frame
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float invmax = inversesqrt( max( dot(T,T), dot(B,B) ) );
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// calculate handedness of the resulting cotangent frame
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float w = (dot(cross(N, T), B) < 0.0) ? -1.0 : 1.0;
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// adjust tangent if needed
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T = T * w;
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return mat3( T * invmax, B * invmax, N );
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}
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vec3 perturbNormal(vec3 n, vec3 v, vec3 normalSample, vec2 uv) {
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vec3 map = normalize( 2.0 * normalSample - vec3(1.0) );
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mat3 TBN = cotangentFrame(n, v, uv);
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return normalize(TBN * map);
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}
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