30 lines
1 KiB
GLSL
30 lines
1 KiB
GLSL
// http://www.thetenthplanet.de/archives/1180
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mat3 cotangentFrame(vec3 n, vec3 p, vec2 texCoord) {
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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(texCoord);
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vec2 duv2 = dFdy(texCoord);
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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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return mat3(t * invmax, b * invmax, n);
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}
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// vec3 perturbNormal(vec3 n, vec3 v, vec2 texCoord) {
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// Assume N, the interpolated vertex normal and V, the view vector (vertex to eye)
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// vec3 map = texture(snormal, texCoord).xyz * (255.0 / 127.0) - (128.0 / 127.0);
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// WITH_NORMALMAP_2CHANNEL
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// map.z = sqrt(1.0 - dot(map.xy, map.xy));
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// WITH_NORMALMAP_GREEN_UP
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// map.y = -map.y;
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// mat3 TBN = cotangentFrame(n, -v, texCoord);
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// return normalize(TBN * map);
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// }
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