Cycles Volume Render: scattering support.
This is done by adding a Volume Scatter node. In many cases you will want to add together a Volume Absorption and Volume Scatter node with the same color and density to get the expected results. This should work with branched path tracing, mixing closures, overlapping volumes, etc. However there's still various optimizations needed for sampling. The main missing thing from the volume branch is the equiangular sampling for homogeneous volumes. The heterogeneous scattering code was arranged such that we can use a single stratified random number for distance sampling, which gives less noise than pseudo random numbers for each step. For volumes where the color is textured there still seems to be something off, needs to be investigated.
This commit is contained in:
Brecht Van Lommel
@@ -48,6 +48,89 @@
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CCL_NAMESPACE_BEGIN
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#ifdef __VOLUME__
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ccl_device_inline bool kernel_path_integrate_scatter_lighting(KernelGlobals *kg, RNG *rng,
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ShaderData *sd, float3 *throughput, PathState *state, PathRadiance *L, Ray *ray,
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float num_samples_adjust)
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{
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#ifdef __EMISSION__
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if(kernel_data.integrator.use_direct_light) {
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/* sample illumination from lights to find path contribution */
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if(sd->flag & SD_BSDF_HAS_EVAL) {
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float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
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#ifdef __MULTI_CLOSURE__
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float light_o = 0.0f;
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#else
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float light_o = path_state_rng_1D(kg, rng, state, PRNG_LIGHT_F);
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#endif
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float light_u, light_v;
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path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
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Ray light_ray;
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BsdfEval L_light;
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bool is_lamp;
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#ifdef __OBJECT_MOTION__
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light_ray.time = sd->time;
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#endif
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if(direct_emission(kg, sd, -1, light_t, light_o, light_u, light_v, &light_ray, &L_light, &is_lamp, state->bounce)) {
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/* trace shadow ray */
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float3 shadow;
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if(!shadow_blocked(kg, state, &light_ray, &shadow)) {
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/* accumulate */
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path_radiance_accum_light(L, *throughput * num_samples_adjust, &L_light, shadow, 1.0f, state->bounce, is_lamp);
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}
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}
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}
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}
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#endif
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/* sample phase function */
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float phase_pdf;
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BsdfEval phase_eval;
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float3 phase_omega_in;
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differential3 phase_domega_in;
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float phase_u, phase_v;
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path_state_rng_2D(kg, rng, state, PRNG_PHASE_U, &phase_u, &phase_v);
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int label;
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label = shader_volume_phase_sample(kg, sd, phase_u, phase_v, &phase_eval,
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&phase_omega_in, &phase_domega_in, &phase_pdf);
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if(phase_pdf == 0.0f || bsdf_eval_is_zero(&phase_eval))
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return false;
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/* modify throughput */
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path_radiance_bsdf_bounce(L, throughput, &phase_eval, phase_pdf, state->bounce, label);
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/* set labels */
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state->ray_pdf = phase_pdf;
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#ifdef __LAMP_MIS__
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state->ray_t = 0.0f;
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#endif
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state->min_ray_pdf = fminf(phase_pdf, state->min_ray_pdf);
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/* update path state */
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path_state_next(kg, state, label);
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/* setup ray */
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ray->P = sd->P;
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ray->D = phase_omega_in;
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ray->t = FLT_MAX;
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#ifdef __RAY_DIFFERENTIALS__
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ray->dP = sd->dP;
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ray->dD = phase_domega_in;
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#endif
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return true;
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}
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#endif
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#if defined(__BRANCHED_PATH__) || defined(__SUBSURFACE__)
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ccl_device void kernel_path_indirect(KernelGlobals *kg, RNG *rng, Ray ray, ccl_global float *buffer,
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@@ -91,7 +174,17 @@ ccl_device void kernel_path_indirect(KernelGlobals *kg, RNG *rng, Ray ray, ccl_g
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if(state.volume_stack[0].shader != SHADER_NO_ID) {
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Ray volume_ray = ray;
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volume_ray.t = (hit)? isect.t: FLT_MAX;
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kernel_volume_integrate(kg, &state, &volume_ray, L, &throughput);
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ShaderData volume_sd;
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VolumeIntegrateResult result = kernel_volume_integrate(kg, &state,
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&volume_sd, &volume_ray, L, &throughput, rng);
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if(result == VOLUME_PATH_SCATTERED) {
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if(kernel_path_integrate_scatter_lighting(kg, rng, &volume_sd, &throughput, &state, L, &ray, 1.0f))
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continue;
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else
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break;
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}
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}
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#endif
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@@ -498,7 +591,17 @@ ccl_device float4 kernel_path_integrate(KernelGlobals *kg, RNG *rng, int sample,
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if(state.volume_stack[0].shader != SHADER_NO_ID) {
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Ray volume_ray = ray;
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volume_ray.t = (hit)? isect.t: FLT_MAX;
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kernel_volume_integrate(kg, &state, &volume_ray, &L, &throughput);
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ShaderData volume_sd;
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VolumeIntegrateResult result = kernel_volume_integrate(kg, &state,
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&volume_sd, &volume_ray, &L, &throughput, rng);
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if(result == VOLUME_PATH_SCATTERED) {
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if(kernel_path_integrate_scatter_lighting(kg, rng, &volume_sd, &throughput, &state, &L, &ray, 1.0f))
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continue;
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else
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break;
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}
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}
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#endif
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@@ -934,7 +1037,7 @@ ccl_device_noinline void kernel_branched_path_integrate_lighting(KernelGlobals *
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kernel_volume_stack_enter_exit(kg, sd, ps.volume_stack);
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#endif
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/* update RNG state */
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/* branch RNG state */
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path_state_branch(&ps, j, num_samples);
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/* set MIS state */
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@@ -996,7 +1099,42 @@ ccl_device float4 kernel_branched_path_integrate(KernelGlobals *kg, RNG *rng, in
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if(state.volume_stack[0].shader != SHADER_NO_ID) {
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Ray volume_ray = ray;
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volume_ray.t = (hit)? isect.t: FLT_MAX;
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kernel_volume_integrate(kg, &state, &volume_ray, &L, &throughput);
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int num_samples = kernel_data.integrator.volume_samples;
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float num_samples_inv = 1.0f/num_samples;
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float3 avg_tp = make_float3(0.0f, 0.0f, 0.0f);
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/* todo: we should cache the shader evaluations from stepping
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* through the volume, for now we redo them multiple times */
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for(int j = 0; j < num_samples; j++) {
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PathState ps = state;
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Ray pray = ray;
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ShaderData volume_sd;
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float3 tp = throughput;
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/* branch RNG state */
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path_state_branch(&ps, j, num_samples);
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VolumeIntegrateResult result = kernel_volume_integrate(kg, &ps,
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&volume_sd, &volume_ray, &L, &tp, rng);
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if(result == VOLUME_PATH_SCATTERED) {
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/* todo: use all-light sampling */
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if(kernel_path_integrate_scatter_lighting(kg, rng, &volume_sd, &tp, &ps, &L, &pray, num_samples_inv)) {
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kernel_path_indirect(kg, rng, pray, buffer, tp*num_samples_inv, num_samples, ps, &L);
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/* for render passes, sum and reset indirect light pass variables
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* for the next samples */
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path_radiance_sum_indirect(&L);
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path_radiance_reset_indirect(&L);
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}
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}
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else
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avg_tp += tp;
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}
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throughput = avg_tp * num_samples_inv;
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}
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#endif
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