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Cycles code refactor: move some more volume code into separate functions.

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This commit is contained in:
Brecht Van Lommel 2014-03-29 13:03:49 +01:00
parent b1615f0e0e
commit 676e1cbe40
1 changed files with 83 additions and 59 deletions
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142
intern/cycles/kernel/kernel_volume.h
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@ -193,7 +193,7 @@ ccl_device_noinline void kernel_volume_shadow(KernelGlobals *kg, PathState *stat
/* Equi-angular sampling as in:
* "Importance Sampling Techniques for Path Tracing in Participating Media" */
ccl_device float kernel_volume_equiangular_sample(Ray *ray, float3 light_P, float xi, float *pdf)
ccl_device float kernel_volume_equiangular_sample(Ray *ray, float3 sigma_t, float3 light_P, float xi, float3 *transmittance, float *pdf)
{
float t = ray->t;
@ -205,7 +205,10 @@ ccl_device float kernel_volume_equiangular_sample(Ray *ray, float3 light_P, floa
*pdf = D / ((theta_b - theta_a) * (D * D + t_ * t_));
return min(t, delta + t_); /* min is only for float precision errors */
float sample_t = min(t, delta + t_); /* min is only for float precision errors */
*transmittance = volume_color_attenuation(sigma_t, sample_t);
return sample_t;
}
ccl_device float kernel_volume_equiangular_pdf(Ray *ray, float3 light_P, float sample_t)
@ -224,6 +227,69 @@ ccl_device float kernel_volume_equiangular_pdf(Ray *ray, float3 light_P, float s
return pdf;
}
ccl_device bool kernel_volume_equiangular_light_position(KernelGlobals *kg, PathState *state, Ray *ray, RNG *rng, float3 *light_P)
{
/* light RNGs */
float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
/* light sample */
LightSample ls;
light_sample(kg, light_t, light_u, light_v, ray->time, ray->P, &ls);
if(ls.pdf == 0.0f)
return false;
*light_P = ls.P;
return true;
}
/* Distance sampling */
ccl_device bool kernel_volume_distance_sample(Ray *ray, float3 sigma_t, int channel, float xi, float *sample_t, float3 *transmittance, float *pdf)
{
/* xi is [0, 1[ so log(0) should never happen, division by zero is
* avoided because sample_sigma_t > 0 when SD_SCATTER is set */
float sample_sigma_t = kernel_volume_channel_get(sigma_t, channel);
*sample_t = min(ray->t, -logf(1.0f - xi)/sample_sigma_t);
*transmittance = volume_color_attenuation(sigma_t, *sample_t);
if(*sample_t < ray->t) {
/* hit */
*pdf = dot(sigma_t, *transmittance) * (1.0f/3.0f);
return true;
}
else {
/* miss */
*pdf = (transmittance->x + transmittance->y + transmittance->z) * (1.0f/3.0f);
return false;
}
}
/* Emission */
ccl_device float3 kernel_volume_emission_integrate(VolumeShaderCoefficients *coeff, int closure_flag, float3 transmittance, float t)
{
/* integral E * exp(-sigma_t * t) from 0 to t = E * (1 - exp(-sigma_t * t))/sigma_t
* this goes to E * t as sigma_t goes to zero
*
* todo: we should use an epsilon to avoid precision issues near zero sigma_t */
float3 emission = coeff->emission;
if(closure_flag & SD_ABSORPTION) {
float3 sigma_t = coeff->sigma_a + coeff->sigma_s;
emission.x *= (sigma_t.x > 0.0f)? (1.0f - transmittance.x)/sigma_t.x: t;
emission.y *= (sigma_t.y > 0.0f)? (1.0f - transmittance.y)/sigma_t.y: t;
emission.z *= (sigma_t.z > 0.0f)? (1.0f - transmittance.z)/sigma_t.z: t;
}
else
emission *= t;
return emission;
}
/* Volume Path */
/* homogeneous volume: assume shader evaluation at the start gives
@ -257,21 +323,17 @@ ccl_device VolumeIntegrateResult kernel_volume_integrate_homogeneous(KernelGloba
/* distance sampling */
if(kernel_data.integrator.volume_homogeneous_sampling == 0 || !kernel_data.integrator.num_all_lights) {
/* xi is [0, 1[ so log(0) should never happen, division by zero is
* avoided because sample_sigma_t > 0 when SD_SCATTER is set */
float xi = path_state_rng_1D(kg, rng, state, PRNG_SCATTER_DISTANCE);
float sample_t = min(t, -logf(1.0f - xi)/sample_sigma_t);
float pdf, sample_t;
transmittance = volume_color_attenuation(sigma_t, sample_t);
if(sample_t < t) {
float pdf = dot(sigma_t, transmittance);
new_tp = *throughput * coeff.sigma_s * transmittance * (3.0f / pdf);
if(kernel_volume_distance_sample(ray, sigma_t, channel, xi, &sample_t, &transmittance, &pdf)) {
/* hit */
new_tp = *throughput * coeff.sigma_s * transmittance / pdf;
t = sample_t;
}
else {
float pdf = (transmittance.x + transmittance.y + transmittance.z);
new_tp = *throughput * transmittance * (3.0f / pdf);
/* miss */
new_tp = *throughput * transmittance / pdf;
}
}
/* equi-angular sampling */
@ -292,22 +354,14 @@ ccl_device VolumeIntegrateResult kernel_volume_integrate_homogeneous(KernelGloba
/* rescale random number so we can reuse it */
xi = (xi - sample_transmittance)/(1.0f - sample_transmittance);
/* light RNGs */
float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
float light_u, light_v;
path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);
/* light sample */
LightSample ls;
light_sample(kg, light_t, light_u, light_v, ray->time, ray->P, &ls);
if(ls.pdf == 0.0f)
/* sample position on light */
float3 light_P;
if(!kernel_volume_equiangular_light_position(kg, state, ray, rng, &light_P))
return VOLUME_PATH_MISSED;
/* sampling */
float sample_t, pdf;
sample_t = kernel_volume_equiangular_sample(ray, ls.P, xi, &pdf);
transmittance = volume_color_attenuation(sigma_t, sample_t);
float pdf;
float sample_t = kernel_volume_equiangular_sample(ray, sigma_t, light_P, xi, &transmittance, &pdf);
new_tp = *throughput * coeff.sigma_s * transmittance / ((1.0f - sample_transmittance) * pdf);
t = sample_t;
@ -320,24 +374,9 @@ ccl_device VolumeIntegrateResult kernel_volume_integrate_homogeneous(KernelGloba
new_tp = *throughput * transmittance;
}
/* integrate emission attenuated by extinction
* integral E * exp(-sigma_t * t) from 0 to t = E * (1 - exp(-sigma_t * t))/sigma_t
* this goes to E * t as sigma_t goes to zero
*
* todo: we should use an epsilon to avoid precision issues near zero sigma_t */
/* integrate emission attenuated by extinction */
if(closure_flag & SD_EMISSION) {
float3 emission = coeff.emission;
if(closure_flag & SD_ABSORPTION) {
float3 sigma_t = coeff.sigma_a + coeff.sigma_s;
emission.x *= (sigma_t.x > 0.0f)? (1.0f - transmittance.x)/sigma_t.x: t;
emission.y *= (sigma_t.y > 0.0f)? (1.0f - transmittance.y)/sigma_t.y: t;
emission.z *= (sigma_t.z > 0.0f)? (1.0f - transmittance.z)/sigma_t.z: t;
}
else
emission *= t;
float3 emission = kernel_volume_emission_integrate(&coeff, closure_flag, transmittance, t);
path_radiance_accum_emission(L, *throughput, emission, state->bounce);
}
@ -468,24 +507,9 @@ ccl_device VolumeIntegrateResult kernel_volume_integrate_heterogeneous(KernelGlo
* tp_eps check too */
}
/* integrate emission attenuated by absorption
* integral E * exp(-sigma_t * t) from 0 to t = E * (1 - exp(-sigma_t * t))/sigma_t
* this goes to E * t as sigma_t goes to zero
*
* todo: we should use an epsilon to avoid precision issues near zero sigma_t */
/* integrate emission attenuated by absorption */
if(closure_flag & SD_EMISSION) {
float3 emission = coeff.emission;
if(closure_flag & SD_ABSORPTION) {
float3 sigma_t = coeff.sigma_a + coeff.sigma_s;
emission.x *= (sigma_t.x > 0.0f)? (1.0f - transmittance.x)/sigma_t.x: dt;
emission.y *= (sigma_t.y > 0.0f)? (1.0f - transmittance.y)/sigma_t.y: dt;
emission.z *= (sigma_t.z > 0.0f)? (1.0f - transmittance.z)/sigma_t.z: dt;
}
else
emission *= dt;
float3 emission = kernel_volume_emission_integrate(&coeff, closure_flag, transmittance, dt);
path_radiance_accum_emission(L, tp, emission, state->bounce);
}