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Fix lightmapper rng

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In our previous attempts to fix the lightmapper we may have
inadvertently introduced the same issue we were trying to fix. It
appears that rand() will on some platforms introduce a mutex making it
slower and on others may have a per-thread state that would need to be
initialized with srand() on each thread. This slows down the lightbaking
further.

This sets up a separate rng state for each OpenMP thread by calling
rand() only in the single-threaded part of the code. We then keep a
vector of states.

I believe this solves our problems.
This commit is contained in:
Hein-Pieter van Braam 2017-12-20 12:04:52 +01:00
parent b08735f209
commit ccbb5923ac
2 changed files with 36 additions and 17 deletions
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51
scene/3d/voxel_light_baker.cpp
View file

@ -32,6 +32,10 @@
#include "os/os.h"
#include <stdlib.h>
#ifdef _OPENMP
#include <omp.h>
#endif
#define FINDMINMAX(x0, x1, x2, min, max) \
min = max = x0; \
if (x1 < min) min = x1; \
@ -1675,19 +1679,17 @@ Vector3 VoxelLightBaker::_compute_pixel_light_at_pos(const Vector3 &p_pos, const
return accum;
}
uint32_t xorshiftstate[] = { 123 }; // anything non-zero will do here
_ALWAYS_INLINE_ uint32_t xorshift32(uint32_t *seed) {
_ALWAYS_INLINE_ uint32_t xorshift32(uint32_t *state) {
/* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
uint32_t x = *seed;
uint32_t x = *state;
x ^= x << 13;
x ^= x >> 17;
x ^= x << 5;
*seed = x;
*state = x;
return x;
}
Vector3 VoxelLightBaker::_compute_ray_trace_at_pos(const Vector3 &p_pos, const Vector3 &p_normal) {
Vector3 VoxelLightBaker::_compute_ray_trace_at_pos(const Vector3 &p_pos, const Vector3 &p_normal, uint32_t *rng_state) {
int samples_per_quality[3] = { 48, 128, 512 };
@ -1709,16 +1711,11 @@ Vector3 VoxelLightBaker::_compute_ray_trace_at_pos(const Vector3 &p_pos, const V
const Light *light = bake_light.ptr();
const Cell *cells = bake_cells.ptr();
uint32_t seed = 0;
while (seed == 0) {
seed = rand(); //system rand is thread safe, do not replace by Math:: random.
}
for (int i = 0; i < samples; i++) {
float random_angle1 = (((xorshift32(&seed) % 65535) / 65535.0) * 2.0 - 1.0) * spread;
float random_angle1 = (((xorshift32(rng_state) % 65535) / 65535.0) * 2.0 - 1.0) * spread;
Vector3 axis(0, sin(random_angle1), cos(random_angle1));
float random_angle2 = ((xorshift32(&seed) % 65535) / 65535.0) * Math_PI * 2.0;
float random_angle2 = ((xorshift32(rng_state) % 65535) / 65535.0) * Math_PI * 2.0;
Basis rot(Vector3(0, 0, 1), random_angle2);
axis = rot.xform(axis);
@ -1852,21 +1849,43 @@ Error VoxelLightBaker::make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh
_plot_triangle(uv, vertex, normal, lightmap.ptrw(), width, height);
}
}
//step 3 perform voxel cone trace on lightmap pixels
//step 3 perform voxel cone trace on lightmap pixels
{
LightMap *lightmap_ptr = lightmap.ptrw();
uint64_t begin_time = OS::get_singleton()->get_ticks_usec();
volatile int lines = 0;
// make sure our OS-level rng is seeded
srand(OS::get_singleton()->get_ticks_usec());
// setup an RNG state for each OpenMP thread
uint32_t threadcount = 1;
uint32_t threadnum = 0;
#ifdef _OPENMP
threadcount = omp_get_max_threads();
#endif
Vector<uint32_t> rng_states;
rng_states.resize(threadcount);
for (uint32_t i = 0; i < threadcount; i++) {
do {
rng_states[i] = rand();
} while (rng_states[i] == 0);
}
uint32_t *rng_states_p = rng_states.ptrw();
for (int i = 0; i < height; i++) {
//print_line("bake line " + itos(i) + " / " + itos(height));
#ifdef _OPENMP
#pragma omp parallel for schedule(dynamic, 1)
#pragma omp parallel for schedule(dynamic, 1) private(threadnum)
#endif
for (int j = 0; j < width; j++) {
#ifdef _OPENMP
threadnum = omp_get_thread_num();
#endif
//if (i == 125 && j == 280) {
LightMap *pixel = &lightmap_ptr[i * width + j];
@ -1879,7 +1898,7 @@ Error VoxelLightBaker::make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh
pixel->light = _compute_pixel_light_at_pos(pixel->pos, pixel->normal) * energy;
} break;
case BAKE_MODE_RAY_TRACE: {
pixel->light = _compute_ray_trace_at_pos(pixel->pos, pixel->normal) * energy;
pixel->light = _compute_ray_trace_at_pos(pixel->pos, pixel->normal, &rng_states_p[threadnum]) * energy;
} break;
// pixel->light = Vector3(1, 1, 1);
//}

2
scene/3d/voxel_light_baker.h
View file

@ -148,7 +148,7 @@ private:
_FORCE_INLINE_ void _sample_baked_octree_filtered_and_anisotropic(const Vector3 &p_posf, const Vector3 &p_direction, float p_level, Vector3 &r_color, float &r_alpha);
_FORCE_INLINE_ Vector3 _voxel_cone_trace(const Vector3 &p_pos, const Vector3 &p_normal, float p_aperture);
_FORCE_INLINE_ Vector3 _compute_pixel_light_at_pos(const Vector3 &p_pos, const Vector3 &p_normal);
_FORCE_INLINE_ Vector3 _compute_ray_trace_at_pos(const Vector3 &p_pos, const Vector3 &p_normal);
_FORCE_INLINE_ Vector3 _compute_ray_trace_at_pos(const Vector3 &p_pos, const Vector3 &p_normal, uint32_t *rng_state);
public:
void begin_bake(int p_subdiv, const AABB &p_bounds);