From d0f59d38429d945b3215890897eb2cfb90eacaa7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A9vin=20Dietrich?= <kevin.dietrich@mailoo.org>
Date: Fri, 29 Jan 2021 17:17:18 +0100
Subject: Fix T85144: Cycles crashes when editing render properties in viewport
 rendering

Issue was caused by the sample pattern LUT always being freed and not
rebuilt when properties driving its dimensions were modified.
---
 intern/cycles/render/integrator.cpp | 18 ++++++++++++++++--
 intern/cycles/render/integrator.h   |  1 +
 intern/cycles/render/light.cpp      |  4 ++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/intern/cycles/render/integrator.cpp b/intern/cycles/render/integrator.cpp
index c97a6549653..d93856ceb61 100644
--- a/intern/cycles/render/integrator.cpp
+++ b/intern/cycles/render/integrator.cpp
@@ -115,7 +115,15 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
     }
   });
 
-  if (sampling_pattern_is_modified()) {
+  const bool need_update_lut = ao_samples_is_modified() || diffuse_samples_is_modified() ||
+                               glossy_samples_is_modified() || max_bounce_is_modified() ||
+                               max_transmission_bounce_is_modified() ||
+                               mesh_light_samples_is_modified() || method_is_modified() ||
+                               sampling_pattern_is_modified() ||
+                               subsurface_samples_is_modified() ||
+                               transmission_samples_is_modified() || volume_samples_is_modified();
+
+  if (need_update_lut) {
     dscene->sample_pattern_lut.tag_realloc();
   }
 
@@ -248,7 +256,7 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
   int dimensions = PRNG_BASE_NUM + max_samples * PRNG_BOUNCE_NUM;
   dimensions = min(dimensions, SOBOL_MAX_DIMENSIONS);
 
-  if (sampling_pattern_is_modified()) {
+  if (need_update_lut) {
     if (sampling_pattern == SAMPLING_PATTERN_SOBOL) {
       uint *directions = dscene->sample_pattern_lut.alloc(SOBOL_BITS * dimensions);
 
@@ -272,6 +280,7 @@ void Integrator::device_update(Device *device, DeviceScene *dscene, Scene *scene
     }
   }
 
+  dscene->sample_pattern_lut.clear_modified();
   clear_modified();
 }
 
@@ -292,6 +301,11 @@ void Integrator::tag_update(Scene *scene, uint32_t flag)
     tag_ao_bounces_modified();
   }
 
+  if ((flag & LIGHT_SAMPLES_MODIFIED) && (method == BRANCHED_PATH)) {
+    /* the number of light samples may affect the size of the sample_pattern_lut */
+    tag_sampling_pattern_modified();
+  }
+
   if (filter_glossy_is_modified()) {
     foreach (Shader *shader, scene->shaders) {
       if (shader->has_integrator_dependency) {
diff --git a/intern/cycles/render/integrator.h b/intern/cycles/render/integrator.h
index 57dcaf95360..4eeeda92d41 100644
--- a/intern/cycles/render/integrator.h
+++ b/intern/cycles/render/integrator.h
@@ -92,6 +92,7 @@ class Integrator : public Node {
   enum : uint32_t {
     AO_PASS_MODIFIED = (1 << 0),
     BACKGROUND_AO_MODIFIED = (1 << 1),
+    LIGHT_SAMPLES_MODIFIED = (1 << 2),
 
     /* tag everything in the manager for an update */
     UPDATE_ALL = ~0u,
diff --git a/intern/cycles/render/light.cpp b/intern/cycles/render/light.cpp
index 6e9dea564c2..638ac376157 100644
--- a/intern/cycles/render/light.cpp
+++ b/intern/cycles/render/light.cpp
@@ -164,6 +164,10 @@ void Light::tag_update(Scene *scene)
 {
   if (is_modified()) {
     scene->light_manager->tag_update(scene, LightManager::LIGHT_MODIFIED);
+
+    if (samples_is_modified()) {
+      scene->integrator->tag_update(scene, Integrator::LIGHT_SAMPLES_MODIFIED);
+    }
   }
 }
 
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