Campbell Barton
9b89de2571
Also use doxy style function reference `#` prefix chars when referencing identifiers.
124 lines
3.2 KiB
GLSL
124 lines
3.2 KiB
GLSL
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/**
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* Sampling distribution routines for Monte-carlo integration.
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*/
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#pragma BLENDER_REQUIRE(common_math_geom_lib.glsl)
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#pragma BLENDER_REQUIRE(bsdf_common_lib.glsl)
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/* -------------------------------------------------------------------- */
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/** \name Microfacet GGX distribution
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* \{ */
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#define USE_VISIBLE_NORMAL 1
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float pdf_ggx_reflect(float NH, float NV, float VH, float alpha)
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{
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float a2 = sqr(alpha);
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#if USE_VISIBLE_NORMAL
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float D = a2 / D_ggx_opti(NH, a2);
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float G1 = NV * 2.0 / G1_Smith_GGX_opti(NV, a2);
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return G1 * VH * D / NV;
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#else
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return NH * a2 / D_ggx_opti(NH, a2);
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#endif
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}
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vec3 sample_ggx(vec3 rand, float alpha, vec3 Vt)
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{
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#if USE_VISIBLE_NORMAL
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/* From:
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* "A Simpler and Exact Sampling Routine for the GGXDistribution of Visible Normals"
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* by Eric Heitz.
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* http://jcgt.org/published/0007/04/01/slides.pdf
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* View vector is expected to be in tangent space. */
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/* Stretch view. */
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vec3 Th, Bh, Vh = normalize(vec3(alpha * Vt.xy, Vt.z));
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make_orthonormal_basis(Vh, Th, Bh);
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/* Sample point with polar coordinates (r, phi). */
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float r = sqrt(rand.x);
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float x = r * rand.y;
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float y = r * rand.z;
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float s = 0.5 * (1.0 + Vh.z);
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y = (1.0 - s) * sqrt(1.0 - x * x) + s * y;
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float z = sqrt(saturate(1.0 - x * x - y * y));
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/* Compute normal. */
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vec3 Hh = x * Th + y * Bh + z * Vh;
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/* Unstretch. */
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vec3 Ht = normalize(vec3(alpha * Hh.xy, saturate(Hh.z)));
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/* Microfacet Normal. */
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return Ht;
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#else
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/* Theta is the cone angle. */
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float z = sqrt((1.0 - rand.x) / (1.0 + sqr(alpha) * rand.x - rand.x)); /* cos theta */
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float r = sqrt(max(0.0, 1.0 - z * z)); /* sin theta */
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float x = r * rand.y;
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float y = r * rand.z;
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/* Microfacet Normal */
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return vec3(x, y, z);
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#endif
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}
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vec3 sample_ggx(vec3 rand, float alpha, vec3 V, vec3 N, vec3 T, vec3 B, out float pdf)
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{
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vec3 Vt = world_to_tangent(V, N, T, B);
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vec3 Ht = sample_ggx(rand, alpha, Vt);
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float NH = saturate(Ht.z);
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float NV = saturate(Vt.z);
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float VH = saturate(dot(Vt, Ht));
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pdf = pdf_ggx_reflect(NH, NV, VH, alpha);
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return tangent_to_world(Ht, N, T, B);
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}
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/** \} */
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/* -------------------------------------------------------------------- */
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/** \name Uniform Hemisphere
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* \{ */
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float pdf_uniform_hemisphere()
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{
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return 0.5 * M_1_PI;
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}
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vec3 sample_uniform_hemisphere(vec3 rand)
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{
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float z = rand.x; /* cos theta */
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float r = sqrt(max(0.0, 1.0 - z * z)); /* sin theta */
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float x = r * rand.y;
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float y = r * rand.z;
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return vec3(x, y, z);
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}
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vec3 sample_uniform_hemisphere(vec3 rand, vec3 N, vec3 T, vec3 B, out float pdf)
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{
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vec3 Ht = sample_uniform_hemisphere(rand);
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pdf = pdf_uniform_hemisphere();
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return tangent_to_world(Ht, N, T, B);
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}
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/** \} */
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/* -------------------------------------------------------------------- */
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/** \name Uniform Cone sampling
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* \{ */
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vec3 sample_uniform_cone(vec3 rand, float angle)
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{
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float z = cos(angle * rand.x); /* cos theta */
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float r = sqrt(max(0.0, 1.0 - z * z)); /* sin theta */
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float x = r * rand.y;
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float y = r * rand.z;
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return vec3(x, y, z);
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}
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vec3 sample_uniform_cone(vec3 rand, float angle, vec3 N, vec3 T, vec3 B)
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{
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vec3 Ht = sample_uniform_cone(rand, angle);
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/* TODO: pdf? */
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return tangent_to_world(Ht, N, T, B);
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}
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/** \} */
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