Cycles: remove old Sobol pattern, simplify sampling dimensions

The multi-dimensional Sobol pattern required us to carefully use as low
dimensions as possible, as quality goes down in higher dimensions. Now that we
have two sampling patterns that are at least as good, there is no need to keep
it around and the implementation can be simplified.

Differential Revision: https://developer.blender.org/D15788

1 files changed, 18 insertions, 50 deletions

diff --git a/intern/cycles/scene/integrator.cpp b/intern/cycles/scene/integrator.cpp
index 58daf417ab0..86a2c9571c6 100644
--- a/intern/cycles/scene/integrator.cpp
+++ b/intern/cycles/scene/integrator.cpp
@@ -13,7 +13,6 @@
 #include "scene/object.h"
 #include "scene/scene.h"
 #include "scene/shader.h"
-#include "scene/sobol.h"
 #include "scene/stats.h"
 
 #include "kernel/types.h"
@@ -87,10 +86,9 @@ NODE_DEFINE(Integrator)
   SOCKET_FLOAT(light_sampling_threshold, "Light Sampling Threshold", 0.01f);
 
   static NodeEnum sampling_pattern_enum;
-  sampling_pattern_enum.insert("sobol", SAMPLING_PATTERN_SOBOL);
-  sampling_pattern_enum.insert("pmj", SAMPLING_PATTERN_PMJ);
   sampling_pattern_enum.insert("sobol_burley", SAMPLING_PATTERN_SOBOL_BURLEY);
-  SOCKET_ENUM(sampling_pattern, "Sampling Pattern", sampling_pattern_enum, SAMPLING_PATTERN_SOBOL);
+  sampling_pattern_enum.insert("pmj", SAMPLING_PATTERN_PMJ);
+  SOCKET_ENUM(sampling_pattern, "Sampling Pattern", sampling_pattern_enum, SAMPLING_PATTERN_PMJ);
   SOCKET_FLOAT(scrambling_distance, "Scrambling Distance", 1.0f);
 
   static NodeEnum denoiser_type_enum;
@@ -139,23 +137,6 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
 
   KernelIntegrator *kintegrator = &dscene->data.integrator;
 
-  /* Adaptive sampling requires PMJ samples.
-   *
-   * This also makes detection of sampling pattern a bit more involved: can not rely on the changed
-   * state of socket, since its value might be different from the effective value used here. So
-   * instead compare with previous value in the KernelIntegrator. Only do it if the device was
-   * updated once (in which case the `sample_pattern_lut` will be allocated to a non-zero size). */
-  const SamplingPattern new_sampling_pattern = (use_adaptive_sampling) ? SAMPLING_PATTERN_PMJ :
-                                                                         sampling_pattern;
-
-  const bool need_update_lut = max_bounce_is_modified() || max_transmission_bounce_is_modified() ||
-                               dscene->sample_pattern_lut.size() == 0 ||
-                               kintegrator->sampling_pattern != new_sampling_pattern;
-
-  if (need_update_lut) {
-    dscene->sample_pattern_lut.tag_realloc();
-  }
-
   device_free(device, dscene);
 
   /* integrator parameters */
@@ -236,7 +217,9 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
                                            FLT_MAX :
                                            sample_clamp_indirect * 3.0f;
 
-  kintegrator->sampling_pattern = new_sampling_pattern;
+  /* Adaptive sampling requires PMJ, see sample_is_even. */
+  kintegrator->sampling_pattern = (use_adaptive_sampling) ? SAMPLING_PATTERN_PMJ :
+                                                            sampling_pattern;
   kintegrator->scrambling_distance = scrambling_distance;
 
   if (light_sampling_threshold > 0.0f) {
@@ -246,36 +229,21 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
     kintegrator->light_inv_rr_threshold = 0.0f;
   }
 
-  /* sobol directions table */
-  int max_samples = max_bounce + transparent_max_bounce + 3 + VOLUME_BOUNDS_MAX +
-                    max(BSSRDF_MAX_HITS, BSSRDF_MAX_BOUNCES);
-
-  int dimensions = PRNG_BASE_NUM + max_samples * PRNG_BOUNCE_NUM;
-  dimensions = min(dimensions, SOBOL_MAX_DIMENSIONS);
-
-  if (need_update_lut) {
-    if (kintegrator->sampling_pattern == SAMPLING_PATTERN_SOBOL) {
-      uint *directions = (uint *)dscene->sample_pattern_lut.alloc(SOBOL_BITS * dimensions);
-
-      sobol_generate_direction_vectors((uint(*)[SOBOL_BITS])directions, dimensions);
-
-      dscene->sample_pattern_lut.copy_to_device();
+  if (kintegrator->sampling_pattern == SAMPLING_PATTERN_PMJ &&
+      dscene->sample_pattern_lut.size() == 0) {
+    constexpr int sequence_size = NUM_PMJ_SAMPLES;
+    constexpr int num_sequences = NUM_PMJ_PATTERNS;
+    float2 *directions = (float2 *)dscene->sample_pattern_lut.alloc(sequence_size * num_sequences *
+                                                                    2);
+    TaskPool pool;
+    for (int j = 0; j < num_sequences; ++j) {
+      float2 *sequence = directions + j * sequence_size;
+      pool.push(
+          function_bind(&progressive_multi_jitter_02_generate_2D, sequence, sequence_size, j));
     }
-    else if (kintegrator->sampling_pattern == SAMPLING_PATTERN_PMJ) {
-      constexpr int sequence_size = NUM_PMJ_SAMPLES;
-      constexpr int num_sequences = NUM_PMJ_PATTERNS;
-      float2 *directions = (float2 *)dscene->sample_pattern_lut.alloc(sequence_size *
-                                                                      num_sequences * 2);
-      TaskPool pool;
-      for (int j = 0; j < num_sequences; ++j) {
-        float2 *sequence = directions + j * sequence_size;
-        pool.push(
-            function_bind(&progressive_multi_jitter_02_generate_2D, sequence, sequence_size, j));
-      }
-      pool.wait_work();
+    pool.wait_work();
 
-      dscene->sample_pattern_lut.copy_to_device();
-    }
+    dscene->sample_pattern_lut.copy_to_device();
   }
 
   kintegrator->has_shadow_catcher = scene->has_shadow_catcher();