forked from bartvdbraak/blender
226 lines
6.5 KiB
C
226 lines
6.5 KiB
C
/*
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* Copyright 2013, Blender Foundation.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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CCL_NAMESPACE_BEGIN
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#define BSSRDF_MULTI_EVAL
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#define BSSRDF_SKIP_NO_HIT
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__device float bssrdf_sample_distance(KernelGlobals *kg, float radius, float refl, float u)
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{
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int table_offset = kernel_data.bssrdf.table_offset;
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float r = lookup_table_read_2D(kg, u, refl, table_offset, BSSRDF_RADIUS_TABLE_SIZE, BSSRDF_REFL_TABLE_SIZE);
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return r*radius;
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}
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#ifdef BSSRDF_MULTI_EVAL
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__device float bssrdf_pdf(KernelGlobals *kg, float radius, float refl, float r)
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{
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if(r >= radius)
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return 0.0f;
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/* todo: when we use the real BSSRDF this will need to be divided by the maximum
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* radius instead of the average radius */
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float t = r/radius;
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int table_offset = kernel_data.bssrdf.table_offset + BSSRDF_PDF_TABLE_OFFSET;
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float pdf = lookup_table_read_2D(kg, t, refl, table_offset, BSSRDF_RADIUS_TABLE_SIZE, BSSRDF_REFL_TABLE_SIZE);
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pdf /= radius;
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return pdf;
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}
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#endif
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__device ShaderClosure *subsurface_scatter_pick_closure(KernelGlobals *kg, ShaderData *sd, float *probability)
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{
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/* sum sample weights of bssrdf and bsdf */
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float bsdf_sum = 0.0f;
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float bssrdf_sum = 0.0f;
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for(int i = 0; i < sd->num_closure; i++) {
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ShaderClosure *sc = &sd->closure[i];
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if(CLOSURE_IS_BSDF(sc->type))
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bsdf_sum += sc->sample_weight;
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else if(CLOSURE_IS_BSSRDF(sc->type))
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bssrdf_sum += sc->sample_weight;
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}
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/* pick a random bsdf or bssrdf */
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float r = sd->randb_closure*(bsdf_sum + bssrdf_sum);
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float sum = 0.0f;
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int sampled;
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for(sampled = 0; sampled < sd->num_closure; sampled++) {
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ShaderClosure *sc = &sd->closure[sampled];
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if(CLOSURE_IS_BSDF(sc->type) || CLOSURE_IS_BSSRDF(sc->type)) {
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sum += sc->sample_weight;
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if(r <= sum) {
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/* if we picked a bssrdf, return the closure. also return probability
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* to adjust throughput depending if we picked a bsdf or bssrdf */
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if(CLOSURE_IS_BSSRDF(sc->type)) {
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sd->randb_closure = 0.0f; /* not needed anymore */
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#ifdef BSSRDF_MULTI_EVAL
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*probability = (bssrdf_sum > 0.0f)? (bsdf_sum + bssrdf_sum)/bssrdf_sum: 1.0f;
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#else
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*probability = (bssrdf_sum > 0.0f)? (bsdf_sum + bssrdf_sum)/sc->sample_weight: 1.0f;
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#endif
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return sc;
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}
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else {
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/* reuse randb for picking a bsdf */
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sd->randb_closure = (sd->randb_closure - sum - sc->sample_weight)/sc->sample_weight;
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*probability = (bsdf_sum > 0.0f)? (bsdf_sum + bssrdf_sum)/bsdf_sum: 1.0f;
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return NULL;
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}
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}
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}
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}
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*probability = 1.0f;
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return NULL;
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}
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#ifdef BSSRDF_MULTI_EVAL
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__device float3 subsurface_scatter_multi_eval(KernelGlobals *kg, ShaderData *sd, bool hit, float refl, float *r, int num_r)
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{
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/* compute pdf */
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float3 eval_sum = make_float3(0.0f, 0.0f, 0.0f);
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float pdf_sum = 0.0f;
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float sample_weight_sum = 0.0f;
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for(int i = 0; i < sd->num_closure; i++) {
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ShaderClosure *sc = &sd->closure[i];
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if(CLOSURE_IS_BSSRDF(sc->type)) {
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float pdf = 1.0f;
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for(int i = 0; i < num_r; i++)
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pdf *= bssrdf_pdf(kg, sc->data0, refl, r[i]);
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//float pdf = bssrdf_pdf(kg, sc->data0, refl, r[num_r-1]);
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eval_sum += sc->weight*pdf;
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pdf_sum += sc->sample_weight*pdf;
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sample_weight_sum += sc->sample_weight;
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}
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}
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float inv_pdf_sum = (pdf_sum > 0.0f)? sample_weight_sum/pdf_sum: 0.0f;
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float3 weight = eval_sum * inv_pdf_sum;
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return weight;
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}
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#endif
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/* replace closures with a single diffuse bsdf closure after scatter step */
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__device void subsurface_scatter_setup_diffuse_bsdf(ShaderData *sd, float3 weight)
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{
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ShaderClosure *sc = &sd->closure[0];
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sd->num_closure = 1;
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sc->weight = weight;
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sc->sample_weight = 1.0f;
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sc->data0 = 0.0f;
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sc->data1 = 0.0f;
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sc->N = sd->N;
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sd->flag &= ~SD_CLOSURE_FLAGS;
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sd->flag |= bsdf_diffuse_setup(sc);
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sd->randb_closure = 0.0f;
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/* todo: evaluate shading to get blurred textures and bump mapping */
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/* shader_eval_surface(kg, sd, 0.0f, state_flag, SHADER_CONTEXT_SSS); */
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}
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/* subsurface scattering step, from a point on the surface to another nearby point on the same object */
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__device void subsurface_scatter_step(KernelGlobals *kg, ShaderData *sd, int state_flag, ShaderClosure *sc, uint *lcg_state)
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{
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float radius = sc->data0;
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float refl = max(average(sc->weight)*3.0f, 0.0f);
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float r = 0.0f;
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bool hit = false;
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float3 weight = make_float3(1.0f, 1.0f, 1.0f);
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#ifdef BSSRDF_MULTI_EVAL
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float r_attempts[BSSRDF_MAX_ATTEMPTS];
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#endif
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int num_attempts;
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/* attempt to find a hit a given number of times before giving up */
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for(num_attempts = 0; num_attempts < kernel_data.bssrdf.num_attempts; num_attempts++) {
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/* random numbers for sampling */
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float u1 = lcg_step(lcg_state);
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float u2 = lcg_step(lcg_state);
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float u3 = lcg_step(lcg_state);
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float u4 = lcg_step(lcg_state);
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float u5 = lcg_step(lcg_state);
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float u6 = lcg_step(lcg_state);
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r = bssrdf_sample_distance(kg, radius, refl, u5);
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#ifdef BSSRDF_MULTI_EVAL
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r_attempts[num_attempts] = r;
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#endif
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float3 p1 = sd->P + sample_uniform_sphere(u1, u2)*r;
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float3 p2 = sd->P + sample_uniform_sphere(u3, u4)*r;
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/* create ray */
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Ray ray;
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ray.P = p1;
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ray.D = normalize_len(p2 - p1, &ray.t);
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ray.dP = sd->dP;
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ray.dD.dx = make_float3(0.0f, 0.0f, 0.0f);
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ray.dD.dy = make_float3(0.0f, 0.0f, 0.0f);
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ray.time = sd->time;
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/* intersect with the same object. if multiple intersections are
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* found it will randomly pick one of them */
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Intersection isect;
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if(scene_intersect_subsurface(kg, &ray, &isect, sd->object, u6) == 0)
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continue;
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/* setup new shading point */
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shader_setup_from_subsurface(kg, sd, &isect, &ray);
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hit = true;
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num_attempts++;
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break;
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}
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/* evaluate subsurface scattering closures */
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#ifdef BSSRDF_MULTI_EVAL
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weight *= subsurface_scatter_multi_eval(kg, sd, hit, refl, r_attempts, num_attempts);
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#else
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weight *= sc->weight;
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#endif
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#ifdef BSSRDF_SKIP_NO_HIT
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if(!hit)
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weight = make_float3(0.0f, 0.0f, 0.0f);
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#endif
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/* replace closures with a single diffuse BSDF */
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subsurface_scatter_setup_diffuse_bsdf(sd, weight);
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}
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CCL_NAMESPACE_END
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