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Cysles: Avoid having ShaderData on the stack

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This commit introduces a SSS-oriented intersection structure which is replacing
old logic of having separate arrays for just intersections and shader data and
encapsulates all the data needed for SSS evaluation.

This giver a huge stack memory saving on GPU. In own experiments it gave 25%
memory usage reduction on GTX560Ti (722MB vs. 946MB).

Unfortunately, this gave some performance loss of 20% which only happens on GPU.
This is perhaps due to different memory access pattern. Will be solved in the
future, hopefully.

Famous saying: won in memory - lost in time (which is also valid in other way
around).
This commit is contained in:
Sergey Sharybin
2015-11-22 15:00:29 +05:00
parent e6fff424db
commit 8bca34fe32
9 changed files with 290 additions and 109 deletions
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27
intern/cycles/kernel/kernel_path.h
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@@ -338,10 +338,16 @@ ccl_device bool kernel_path_subsurface_scatter(KernelGlobals *kg, ShaderData *sd
if(sc) {
uint lcg_state = lcg_state_init(rng, state, 0x68bc21eb);
ShaderData bssrdf_sd[BSSRDF_MAX_HITS];
SubsurfaceIntersection ss_isect;
float bssrdf_u, bssrdf_v;
path_state_rng_2D(kg, rng, state, PRNG_BSDF_U, &bssrdf_u, &bssrdf_v);
int num_hits = subsurface_scatter_multi_step(kg, sd, bssrdf_sd, state->flag, sc, &lcg_state, bssrdf_u, bssrdf_v, false);
int num_hits = subsurface_scatter_multi_intersect(kg,
&ss_isect,
sd,
sc,
&lcg_state,
bssrdf_u, bssrdf_v,
false);
#ifdef __VOLUME__
Ray volume_ray = *ray;
bool need_update_volume_stack = kernel_data.integrator.use_volumes &&
@@ -350,15 +356,26 @@ ccl_device bool kernel_path_subsurface_scatter(KernelGlobals *kg, ShaderData *sd
/* compute lighting with the BSDF closure */
for(int hit = 0; hit < num_hits; hit++) {
/* NOTE: We reuse the existing ShaderData, we assume the path
* integration loop stops when this function returns true.
*/
subsurface_scatter_multi_setup(kg,
&ss_isect,
hit,
sd,
state->flag,
sc,
false);
float3 tp = *throughput;
PathState hit_state = *state;
Ray hit_ray = *ray;
hit_state.rng_offset += PRNG_BOUNCE_NUM;
kernel_path_surface_connect_light(kg, rng, &bssrdf_sd[hit], tp, state, L);
if(kernel_path_surface_bounce(kg, rng, &bssrdf_sd[hit], &tp, &hit_state, L, &hit_ray)) {
kernel_path_surface_connect_light(kg, rng, sd, tp, state, L);
if(kernel_path_surface_bounce(kg, rng, sd, &tp, &hit_state, L, &hit_ray)) {
#ifdef __LAMP_MIS__
hit_state.ray_t = 0.0f;
#endif