From 8e36089e411391243617808413d4d2b550aeb3b3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Cl=C3=A9ment=20Foucault?= Date: Fri, 4 Aug 2017 18:43:02 +0200 Subject: Eevee: LUT generation. We generate a 3D lut to precompute the btdf intensity. I decided to use a 64*64*16 (N dot V, ior, roughness) because the btdf varies less with roughness than with IOR. We also remap the ior to better use the space in the LUT. --- .../draw/engines/eevee/shaders/btdf_lut_frag.glsl | 59 ++++++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 source/blender/draw/engines/eevee/shaders/btdf_lut_frag.glsl (limited to 'source/blender/draw/engines/eevee/shaders/btdf_lut_frag.glsl') diff --git a/source/blender/draw/engines/eevee/shaders/btdf_lut_frag.glsl b/source/blender/draw/engines/eevee/shaders/btdf_lut_frag.glsl new file mode 100644 index 00000000000..2c604d69641 --- /dev/null +++ b/source/blender/draw/engines/eevee/shaders/btdf_lut_frag.glsl @@ -0,0 +1,59 @@ + +uniform float a2; + +out vec4 FragColor; + +void main() { + vec3 N, T, B, V; + + float x = gl_FragCoord.x / BRDF_LUT_SIZE; + float y = gl_FragCoord.y / BRDF_LUT_SIZE; + /* There is little variation if ior > 1.0 so we + * maximize LUT precision for ior < 1.0 */ + x = x * 1.1; + float ior = (x > 1.0) ? ior_from_f0((x-1.0) * 10.0) : sqrt(x); + float NV = (1.0 - (clamp(y, 1e-4, 0.9999))); + + N = vec3(0.0, 0.0, 1.0); + T = vec3(1.0, 0.0, 0.0); + B = vec3(0.0, 1.0, 0.0); + V = vec3(sqrt(1.0 - NV * NV), 0.0, NV); + + setup_noise(); + + /* Integrating BTDF */ + float btdf_accum = 0.0; + for (float i = 0.0; i < sampleCount; i++) { + vec3 H = sample_ggx(i, a2, N, T, B); /* Microfacet normal */ + + float VH = dot(V, H); + + /* Check if there is total internal reflections. */ + float c = abs(VH); + float g = ior * ior - 1.0 + c * c; + + float eta = 1.0/ior; + if (dot(H, V) < 0.0) { + H = -H; + eta = ior; + } + + vec3 L = refract(-V, H, eta); + float NL = -dot(N, L); + + if ((NL > 0.0) && (g > 0.0)) { + float LH = dot(L, H); + + float G1_l = NL * 2.0 / G1_Smith_GGX(NL, a2); /* Balancing the adjustments made in G1_Smith */ + + /* btdf = abs(VH*LH) * (ior*ior) * D * G(V) * G(L) / (Ht2 * NV) + * pdf = (VH * abs(LH)) * (ior*ior) * D * G(V) / (Ht2 * NV) */ + float btdf = G1_l * abs(VH*LH) / (VH * abs(LH)); + + btdf_accum += btdf; + } + } + btdf_accum /= sampleCount; + + FragColor = vec4(btdf_accum, 0.0, 0.0, 1.0); +} \ No newline at end of file -- cgit v1.2.3