Brecht Van Lommel
7d5ef64bfb
Contributed by luzpaz. Differential Revision: https://developer.blender.org/D13264
109 lines
3.3 KiB
GLSL
109 lines
3.3 KiB
GLSL
|
|
#pragma BLENDER_REQUIRE(bsdf_common_lib.glsl)
|
|
|
|
/* ---------------------------------------------------------------------- */
|
|
/** \name Utiltex
|
|
*
|
|
* Utiltex is a sampler2DArray that stores a number of useful small utilitary textures and lookup
|
|
* tables.
|
|
* \{ */
|
|
|
|
uniform sampler2DArray utilTex;
|
|
|
|
#define LUT_SIZE 64
|
|
|
|
#define LTC_MAT_LAYER 0
|
|
#define LTC_BRDF_LAYER 1
|
|
#define BRDF_LUT_LAYER 1
|
|
#define NOISE_LAYER 2
|
|
#define LTC_DISK_LAYER 3 /* UNUSED */
|
|
|
|
/* Layers 4 to 20 are for BTDF Lut. */
|
|
const float lut_btdf_layer_first = 4.0;
|
|
const float lut_btdf_layer_count = 16.0;
|
|
|
|
/**
|
|
* Reminder: The 4 noise values are based of 3 uncorrelated blue noises:
|
|
* x : Uniformly distributed value [0..1] (noise 1).
|
|
* y : Uniformly distributed value [0..1] (noise 2).
|
|
* z,w : Uniformly distributed point on the unit circle [-1..1] (noise 3).
|
|
*/
|
|
#define texelfetch_noise_tex(coord) texelFetch(utilTex, ivec3(ivec2(coord) % LUT_SIZE, 2.0), 0)
|
|
|
|
/* Return texture coordinates to sample Surface LUT. */
|
|
vec2 lut_coords(float cos_theta, float roughness)
|
|
{
|
|
vec2 coords = vec2(roughness, sqrt(1.0 - cos_theta));
|
|
/* scale and bias coordinates, for correct filtered lookup */
|
|
return coords * (LUT_SIZE - 1.0) / LUT_SIZE + 0.5 / LUT_SIZE;
|
|
}
|
|
|
|
/* Returns the GGX split-sum precomputed in LUT. */
|
|
vec2 brdf_lut(float cos_theta, float roughness)
|
|
{
|
|
return textureLod(utilTex, vec3(lut_coords(cos_theta, roughness), BRDF_LUT_LAYER), 0.0).rg;
|
|
}
|
|
|
|
/* Return texture coordinates to sample Surface LUT. */
|
|
vec3 lut_coords_btdf(float cos_theta, float roughness, float ior)
|
|
{
|
|
/* ior is sin of critical angle. */
|
|
float critical_cos = sqrt(1.0 - ior * ior);
|
|
|
|
vec3 coords;
|
|
coords.x = sqr(ior);
|
|
coords.y = cos_theta;
|
|
coords.y -= critical_cos;
|
|
coords.y /= (coords.y > 0.0) ? (1.0 - critical_cos) : critical_cos;
|
|
coords.y = coords.y * 0.5 + 0.5;
|
|
coords.z = roughness;
|
|
|
|
coords = saturate(coords);
|
|
|
|
/* scale and bias coordinates, for correct filtered lookup */
|
|
coords.xy = coords.xy * (LUT_SIZE - 1.0) / LUT_SIZE + 0.5 / LUT_SIZE;
|
|
|
|
return coords;
|
|
}
|
|
|
|
/* Returns GGX BTDF in first component and fresnel in second. */
|
|
vec2 btdf_lut(float cos_theta, float roughness, float ior)
|
|
{
|
|
if (ior <= 1e-5) {
|
|
return vec2(0.0);
|
|
}
|
|
|
|
if (ior >= 1.0) {
|
|
vec2 split_sum = brdf_lut(cos_theta, roughness);
|
|
float f0 = f0_from_ior(ior);
|
|
/* Baked IOR for GGX BRDF. */
|
|
const float specular = 1.0;
|
|
const float eta_brdf = (2.0 / (1.0 - sqrt(0.08 * specular))) - 1.0;
|
|
/* Avoid harsh transition coming from ior == 1. */
|
|
float f90 = fast_sqrt(saturate(f0 / (f0_from_ior(eta_brdf) * 0.25)));
|
|
float fresnel = F_brdf_single_scatter(vec3(f0), vec3(f90), split_sum).r;
|
|
/* Setting the BTDF to one is not really important since it is only used for multiscatter
|
|
* and it's already quite close to ground truth. */
|
|
float btdf = 1.0;
|
|
return vec2(btdf, fresnel);
|
|
}
|
|
|
|
vec3 coords = lut_coords_btdf(cos_theta, roughness, ior);
|
|
|
|
float layer = coords.z * lut_btdf_layer_count;
|
|
float layer_floored = floor(layer);
|
|
|
|
coords.z = lut_btdf_layer_first + layer_floored;
|
|
vec2 btdf_low = textureLod(utilTex, coords, 0.0).rg;
|
|
|
|
coords.z += 1.0;
|
|
vec2 btdf_high = textureLod(utilTex, coords, 0.0).rg;
|
|
|
|
/* Manual trilinear interpolation. */
|
|
vec2 btdf = mix(btdf_low, btdf_high, layer - layer_floored);
|
|
|
|
return btdf;
|
|
}
|
|
|
|
/** \} */
|