66 lines
2.0 KiB
GLSL
66 lines
2.0 KiB
GLSL
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#pragma BLENDER_REQUIRE(bsdf_common_lib.glsl)
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/* ---------------------------------------------------------------------- */
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/** \name Utiltex
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*
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* Utiltex is a sampler2DArray that stores a number of useful small utilitary textures and lookup
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* tables.
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* \{ */
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uniform sampler2DArray utilTex;
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#define LUT_SIZE 64
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#define texelfetch_noise_tex(coord) texelFetch(utilTex, ivec3(ivec2(coord) % LUT_SIZE, 2.0), 0)
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/* Return texture coordinates to sample Surface LUT */
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vec2 lut_coords(float cosTheta, float roughness)
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{
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float theta = acos(cosTheta);
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vec2 coords = vec2(roughness, theta / M_PI_2);
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/* scale and bias coordinates, for correct filtered lookup */
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return coords * (LUT_SIZE - 1.0) / LUT_SIZE + 0.5 / LUT_SIZE;
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}
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vec2 lut_coords_ltc(float cosTheta, float roughness)
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{
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vec2 coords = vec2(roughness, sqrt(1.0 - cosTheta));
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/* scale and bias coordinates, for correct filtered lookup */
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return coords * (LUT_SIZE - 1.0) / LUT_SIZE + 0.5 / LUT_SIZE;
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}
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float get_btdf_lut(float NV, float roughness, float ior)
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{
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const vec3 lut_scale_bias_texel_size = vec3((LUT_SIZE - 1.0), 0.5, 1.5) / LUT_SIZE;
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vec3 coords;
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/* Try to compensate for the low resolution and interpolation error. */
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coords.x = (ior > 1.0) ? (0.9 + lut_scale_bias_texel_size.z) +
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(0.1 - lut_scale_bias_texel_size.z) * f0_from_ior(ior) :
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(0.9 + lut_scale_bias_texel_size.z) * ior * ior;
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coords.y = 1.0 - saturate(NV);
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coords.xy *= lut_scale_bias_texel_size.x;
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coords.xy += lut_scale_bias_texel_size.y;
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const float lut_lvl_ofs = 4.0; /* First texture lvl of roughness. */
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const float lut_lvl_scale = 16.0; /* How many lvl of roughness in the lut. */
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float mip = roughness * lut_lvl_scale;
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float mip_floor = floor(mip);
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coords.z = lut_lvl_ofs + mip_floor + 1.0;
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float btdf_high = textureLod(utilTex, coords, 0.0).r;
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coords.z -= 1.0;
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float btdf_low = textureLod(utilTex, coords, 0.0).r;
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float btdf = (ior == 1.0) ? 1.0 : mix(btdf_low, btdf_high, mip - coords.z);
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return btdf;
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}
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/** \} */
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