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Cycles: Make Background MIS building threaded 

Use multiple threads for building the MIS table, if the
resolution is higher than 512.
Also replace division by cdf_total, with a inverse multiplication by
cdf_total_inv. This gives further speedup.

On my Macbook (8 CPU threads) this improves the time to build the table:
Resolution 4096: From 0.16s to 0.03s
Resolution 8096: From 0.61s to 0.11s

This especially helps to reduce the scene update time, when tweaking world
shader while viewport rendering is running.

Patch by Sergey and myself.

Differential Revision: https://developer.blender.org/D1159
This commit is contained in:
Thomas Dinges 2015-03-12 11:58:43 +01:00
parent 583466fccf
commit cdb47b9dfc
1 changed files with 63 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

90
intern/cycles/render/light.cpp
View File

@ -26,6 +26,7 @@
#include "util_foreach.h"
#include "util_progress.h"
#include "util_logging.h"
CCL_NAMESPACE_BEGIN
@ -377,6 +378,45 @@ void LightManager::device_update_distribution(Device *device, DeviceScene *dscen
}
}
static void background_cdf(int start,
int end,
int res,
int cdf_count,
const vector<float3> *pixels,
float2 *cond_cdf)
{
/* Conditional CDFs (rows, U direction). */
for(int i = start; i < end; i++) {
float sin_theta = sinf(M_PI_F * (i + 0.5f) / res);
float3 env_color = (*pixels)[i * res];
float ave_luminamce = average(env_color);
cond_cdf[i * cdf_count].x = ave_luminamce * sin_theta;
cond_cdf[i * cdf_count].y = 0.0f;
for(int j = 1; j < res; j++) {
env_color = (*pixels)[i * res + j];
ave_luminamce = average(env_color);
cond_cdf[i * cdf_count + j].x = ave_luminamce * sin_theta;
cond_cdf[i * cdf_count + j].y = cond_cdf[i * cdf_count + j - 1].y + cond_cdf[i * cdf_count + j - 1].x / res;
}
float cdf_total = cond_cdf[i * cdf_count + res - 1].y + cond_cdf[i * cdf_count + res - 1].x / res;
float cdf_total_inv = 1.0f / cdf_total;
/* stuff the total into the brightness value for the last entry, because
* we are going to normalize the CDFs to 0.0 to 1.0 afterwards */
cond_cdf[i * cdf_count + res].x = cdf_total;
if(cdf_total > 0.0f)
for(int j = 1; j < res; j++)
cond_cdf[i * cdf_count + j].y *= cdf_total_inv;
cond_cdf[i * cdf_count + res].y = 1.0f;
}
}
void LightManager::device_update_background(Device *device, DeviceScene *dscene, Scene *scene, Progress& progress)
{
KernelIntegrator *kintegrator = &dscene->data.integrator;
@ -417,34 +457,28 @@ void LightManager::device_update_background(Device *device, DeviceScene *dscene,
float2 *marg_cdf = dscene->light_background_marginal_cdf.resize(cdf_count);
float2 *cond_cdf = dscene->light_background_conditional_cdf.resize(cdf_count * cdf_count);
/* conditional CDFs (rows, U direction) */
for(int i = 0; i < res; i++) {
float sin_theta = sinf(M_PI_F * (i + 0.5f) / res);
float3 env_color = pixels[i * res];
float ave_luminamce = average(env_color);
cond_cdf[i * cdf_count].x = ave_luminamce * sin_theta;
cond_cdf[i * cdf_count].y = 0.0f;
for(int j = 1; j < res; j++) {
env_color = pixels[i * res + j];
ave_luminamce = average(env_color);
cond_cdf[i * cdf_count + j].x = ave_luminamce * sin_theta;
cond_cdf[i * cdf_count + j].y = cond_cdf[i * cdf_count + j - 1].y + cond_cdf[i * cdf_count + j - 1].x / res;
double time_start = time_dt();
if(res < 512) {
/* Small enough resolution, faster to do single-threaded. */
background_cdf(0, res, res, cdf_count, &pixels, cond_cdf);
}
else {
/* Threaded evaluation for large resolution. */
const int num_blocks = TaskScheduler::num_threads();
const int chunk_size = res / num_blocks;
TaskPool pool;
for(int i = 0; i < num_blocks; ++i) {
const int current_chunk_size =
(i != num_blocks - 1) ? chunk_size
: (res - i * chunk_size);
pool.push(function_bind(&background_cdf,
i, i + current_chunk_size,
res,
cdf_count,
&pixels,
cond_cdf));
}
float cdf_total = cond_cdf[i * cdf_count + res - 1].y + cond_cdf[i * cdf_count + res - 1].x / res;
/* stuff the total into the brightness value for the last entry, because
* we are going to normalize the CDFs to 0.0 to 1.0 afterwards */
cond_cdf[i * cdf_count + res].x = cdf_total;
if(cdf_total > 0.0f)
for(int j = 1; j < res; j++)
cond_cdf[i * cdf_count + j].y /= cdf_total;
cond_cdf[i * cdf_count + res].y = 1.0f;
pool.wait_work();
}
/* marginal CDFs (column, V direction, sum of rows) */
@ -465,6 +499,8 @@ void LightManager::device_update_background(Device *device, DeviceScene *dscene,
marg_cdf[res].y = 1.0f;
VLOG(2) << "Background MIS build time " << time_dt() - time_start << "\n";
/* update device */
device->tex_alloc("__light_background_marginal_cdf", dscene->light_background_marginal_cdf);
device->tex_alloc("__light_background_conditional_cdf", dscene->light_background_conditional_cdf);