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Cycles: Fix two numerical issues in the volume code 

This hopefully fixes T48383 by avoiding two numerical problems that I found in the volume code.

Reviewers: sergey, dingto, brecht

Reviewed By: sergey, dingto, brecht

Maniphest Tasks: T48383

Differential Revision: https://developer.blender.org/D2051
This commit is contained in:
Lukas Stockner 2016-06-08 03:17:19 +02:00
parent a506f4c74e
commit 654019fa01
Notes: blender-bot 2023-02-14 08:38:11 +01:00 
Referenced by issue #48383, Cycles Smoke/Fire render procudes NAN pixels
1 changed files with 6 additions and 4 deletions
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10
intern/cycles/kernel/kernel_volume.h
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@ -276,7 +276,7 @@ ccl_device float kernel_volume_distance_sample(float max_t, float3 sigma_t, int
float sample_t = min(max_t, -logf(1.0f - xi*(1.0f - sample_transmittance))/sample_sigma_t);
*transmittance = volume_color_transmittance(sigma_t, sample_t);
*pdf = (sigma_t * *transmittance)/(make_float3(1.0f, 1.0f, 1.0f) - full_transmittance);
*pdf = safe_divide_color(sigma_t * *transmittance, make_float3(1.0f, 1.0f, 1.0f) - full_transmittance);
/* todo: optimization: when taken together with hit/miss decision,
* the full_transmittance cancels out drops out and xi does not
@ -290,7 +290,7 @@ ccl_device float3 kernel_volume_distance_pdf(float max_t, float3 sigma_t, float
float3 full_transmittance = volume_color_transmittance(sigma_t, max_t);
float3 transmittance = volume_color_transmittance(sigma_t, sample_t);
return (sigma_t * transmittance)/(make_float3(1.0f, 1.0f, 1.0f) - full_transmittance);
return safe_divide_color(sigma_t * transmittance, make_float3(1.0f, 1.0f, 1.0f) - full_transmittance);
}
/* Emission */
@ -625,11 +625,13 @@ ccl_device void kernel_volume_decoupled_record(KernelGlobals *kg, PathState *sta
const int global_max_steps = kernel_data.integrator.volume_max_steps;
step_size = kernel_data.integrator.volume_step_size;
/* compute exact steps in advance for malloc */
max_steps = max((int)ceilf(ray->t/step_size), 1);
if(max_steps > global_max_steps) {
if(ray->t > global_max_steps*step_size) {
max_steps = global_max_steps;
step_size = ray->t / (float)max_steps;
}
else {
max_steps = max((int)ceilf(ray->t/step_size), 1);
}
#ifdef __KERNEL_CPU__
/* NOTE: For the branched path tracing it's possible to have direct
* and indirect light integration both having volume segments allocated.