Commit: a58814acf5567207478b030d1dafa6ad65b67496
Author: Brecht Van Lommel
Date: Wed Apr 2 15:41:45 2014 +0200
https://developer.blender.org/rBa58814acf5567207478b030d1dafa6ad65b67496
Fix T39525: cycles volume render difference between branched/non-branched path.
===================================================================
M intern/cycles/kernel/kernel_volume.h
===================================================================
diff --git a/intern/cycles/kernel/kernel_volume.h
b/intern/cycles/kernel/kernel_volume.h
index b035725..7928bdc 100644
--- a/intern/cycles/kernel/kernel_volume.h
+++ b/intern/cycles/kernel/kernel_volume.h
@@ -322,7 +322,6 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_homogeneous(KernelGloba
int closure_flag = sd->flag;
float t = ray->t;
float3 new_tp;
- float3 transmittance;
/* randomly scatter, and if we do t is shortened */
if(closure_flag & SD_SCATTER) {
@@ -344,6 +343,7 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_homogeneous(KernelGloba
if(xi >= sample_transmittance) {
/* scattering */
float3 pdf;
+ float3 transmittance;
float sample_t;
/* rescale random number so we can reuse it */
@@ -373,20 +373,22 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_homogeneous(KernelGloba
}
else {
/* no scattering */
- transmittance = volume_color_transmittance(sigma_t, t);
- float pdf = (transmittance.x + transmittance.y +
transmittance.z) * (1.0f/3.0f);
+ float3 transmittance =
volume_color_transmittance(sigma_t, t);
+ float pdf = average(transmittance);
new_tp = *throughput * transmittance / pdf;
}
}
else if(closure_flag & SD_ABSORPTION) {
/* absorption only, no sampling needed */
- transmittance = volume_color_transmittance(coeff.sigma_a, t);
+ float3 transmittance =
volume_color_transmittance(coeff.sigma_a, t);
new_tp = *throughput * transmittance;
}
/* integrate emission attenuated by extinction */
if(closure_flag & SD_EMISSION) {
- float3 emission = kernel_volume_emission_integrate(&coeff,
closure_flag, transmittance, t);
+ float3 sigma_t = coeff.sigma_a + coeff.sigma_s;
+ float3 transmittance = volume_color_transmittance(sigma_t,
ray->t);
+ float3 emission = kernel_volume_emission_integrate(&coeff,
closure_flag, transmittance, ray->t);
path_radiance_accum_emission(L, *throughput, emission,
state->bounce);
}
@@ -421,19 +423,12 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_heterogeneous(KernelGlo
/* compute coefficients at the start */
float t = 0.0f;
-
- /* accumulate these values so we can use a single stratified number to
sample */
float3 accum_transmittance = make_float3(1.0f, 1.0f, 1.0f);
- float3 accum_sigma_t = make_float3(0.0f, 0.0f, 0.0f);
- float3 accum_sigma_s = make_float3(0.0f, 0.0f, 0.0f);
/* cache some constant variables */
- float nlogxi;
+ float xi;
int channel = -1;
bool has_scatter = false;
-#if 0
- bool second_step = false;
-#endif
for(int i = 0; i < max_steps; i++) {
/* advance to new position */
@@ -441,12 +436,8 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_heterogeneous(KernelGlo
float dt = new_t - t;
/* use random position inside this segment to sample shader */
- if(new_t == ray->t) {
+ if(new_t == ray->t)
random_jitter_offset =
lcg_step_float(&state->rng_congruential) * dt;
-#if 0
- second_step = true;
-#endif
- }
float3 new_P = ray->P + ray->D * (t + random_jitter_offset);
VolumeShaderCoefficients coeff;
@@ -468,60 +459,48 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_heterogeneous(KernelGlo
/* lazily set up variables for sampling */
if(channel == -1) {
- float xi = path_state_rng_1D(kg, rng,
state, PRNG_SCATTER_DISTANCE);
- nlogxi = -logf(1.0f - xi);
+ /* pick random color channel, we use
the Veach one-sample
+ * model with balance heuristic for the
channels */
+ xi = path_state_rng_1D(kg, rng, state,
PRNG_SCATTER_DISTANCE);
float rphase = path_state_rng_1D(kg,
rng, state, PRNG_PHASE);
channel = (int)(rphase*3.0f);
sd->randb_closure = rphase*3.0f -
channel;
}
- /* pick random color channel, we use the Veach
one-sample
- * model with balance heuristic for the
channels */
- float sample_sigma_t =
kernel_volume_channel_get(accum_sigma_t + dt*sigma_t, channel);
-
- if(nlogxi < sample_sigma_t) {
- /* compute sampling distance */
- sample_sigma_t /= new_t;
- new_t = nlogxi/sample_sigma_t;
- dt = new_t - t; /* todo: apparently
negative dt can happen */
-
- transmittance =
volume_color_transmittance(sigma_t, dt);
-
- accum_transmittance *= transmittance;
- accum_sigma_t = (accum_sigma_t +
dt*sigma_t)/new_t;
- accum_sigma_s = (accum_sigma_s +
dt*sigma_s)/new_t;
+ /* compute transmittance over full step */
+ transmittance =
volume_color_transmittance(sigma_t, dt);
- /* todo: it's not clear to me that this
is correct if we move
- * through a color volume, needs
verification */
- float pdf = dot(accum_sigma_t,
accum_transmittance);
- new_tp = tp * accum_sigma_s *
transmittance * (3.0f / pdf);
+ /* decide if we will scatter or continue */
+ float sample_transmittance =
kernel_volume_channel_get(transmittance, channel);
+ if(1.0f - xi >= sample_transmittance) {
+ /* compute sampling distance */
+ float sample_sigma_t =
kernel_volume_channel_get(sigma_t, channel);
+ float new_dt = -logf(1.0f -
xi)/sample_sigma_t;
+ new_t = t + new_dt;
+
+ /* transmittance, throughput */
+ float3 new_transmittance =
volume_color_transmittance(sigma_t, new_dt);
+ float pdf = average(sigma_t *
new_transmittance);
+ new_tp = tp * sigma_s *
new_transmittance / pdf;
scatter = true;
}
else {
- transmittance =
volume_color_transmittance(sigma_t, dt);
+ /* throughput */
+ float pdf = average(transmittance);
+ new_tp = tp * transmittance / pdf;
- accum_transmittance *= transmittance;
- accum_sigma_t += dt*sigma_t;
- accum_sigma_s += dt*sigma_s;
-
- new_tp = tp * transmittance;
+ /* remap xi so we can reuse it and keep
thing stratified */
+ xi = 1.0f - (1.0f -
xi)/sample_transmittance;
}
}
else if(closure_flag & SD_ABSORPTION) {
/* absorption only, no sampling needed */
float3 sigma_a = coeff.sigma_a;
- transmittance =
volume_color_transmittance(sigma_a, dt);
-
- accum_transmittance *= transmittance;
- accum_sigma_t += dt*sigma_a;
+ transmittance =
volume_color_transmittance(sigma_a, dt);
new_tp = tp * transmittance;
-
- /* todo: we could avoid computing expf() for
each step by summing,
- * because exp(a)*exp(b) = exp(a+b), but we
still want a quick
- * tp_eps check too */
}
/* integrate emission attenuated by absorption */
@@ -546,15 +525,12 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_heterogeneous(KernelGlo
sd->P = ray->P + new_t*ray->D;
*throughput = tp;
-#if 0
- /* debugging code to get exact same RNG
samples to compare
- * homogeneous and heterogeneous
sampling results */
- if(!second_step)
-
lcg_step_float(&state->rng_congruential);
-#endif
-
return VOLUME_PATH_SCATTERED;
}
+ else {
+ /* accumulate transmittance */
+ accum_transmittance *= transmittance;
+ }
}
}
@@ -564,13 +540,6 @@ ccl_device VolumeIntegrateResult
kernel_volume_integrate_heterogeneous(KernelGlo
break;
}
- /* include pdf for volumes with scattering */
- if(has_scatter) {
- float pdf = (accum_transmittance.x + accum_transmittance.y +
accum_transmittance.z);
- if(pdf > 0.0f)
- tp *= (3.0f/pdf);
- }
-
*throughput = tp;
return VOLUME_PATH_ATTENUATED;
@@ -662,6 +631,13 @@ ccl_device void
kernel_volume_decoupled_record(KernelGlobals *kg, PathState *sta
/* compute accumulated transmittance */
float3 transmittance =
volume_color_transmittance(sigma_t, dt);
+
+ /* compute emission attenuated by absorption */
+ if(closure_flag & SD_EMISSION) {
+ float3 emission =
kernel_volume_emission_integrate(&coeff, closure_flag, transmittance, dt);
+ accum_emission += accum_transmittance *
emission;
+ }
+
accum_transmittance *= transmittance;
/* compute pdf for distance sampling */
@@ -674,12 +650,6 @@ ccl_device void
kernel_volume_decoupled_record(KernelGlobals *kg, PathState *sta
step->closure_flag = closure_flag;
segment->closure_flag |= closure_flag;
-
- /* compute emission attenuated by absorption */
- if(closure_flag & SD_EMISSION) {
- float3 emission =
kernel_volume_emission_integrate(&coeff, closure_flag, transmittance, dt);
- accum_emission += accum_transmittance *
emission;
- }
}
else {
/* store empty step (todo: skip consecutive empty
steps) */
@@ -788,7 +758,7 @@ ccl_device VolumeIntegrateResult
kernel_volume_decoupled_scatter(
/* sample distance and compute transmittance */
float3 distance_pdf;
sample_t = prev_t + kernel_volume_distance_sample(step_t,
step->sigma_t, channel, xi, &transmittance, &distance_pdf);
- pdf = dot(distance_pdf, step_pdf) * (1.0f/3.0f);
+ pdf = average(distance_pdf * step_pdf);
}
/* equi-angular sampling */
else {
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