1 files changed, 82 insertions, 27 deletions

diff --git a/intern/cycles/render/light.cpp b/intern/cycles/render/light.cpp
index cb7474017fa..225cedfef55 100644
--- a/intern/cycles/render/light.cpp
+++ b/intern/cycles/render/light.cpp
@@ -450,6 +450,7 @@ void LightManager::device_update_distribution(Device *,
 
   /* update device */
   KernelIntegrator *kintegrator = &dscene->data.integrator;
+  KernelBackground *kbackground = &dscene->data.background;
   KernelFilm *kfilm = &dscene->data.film;
   kintegrator->use_direct_light = (totarea > 0.0f);
 
@@ -493,15 +494,18 @@ void LightManager::device_update_distribution(Device *,
 
     /* Portals */
     if (num_portals > 0) {
-      kintegrator->portal_offset = light_index;
-      kintegrator->num_portals = num_portals;
-      kintegrator->portal_pdf = background_mis ? 0.5f : 1.0f;
+      kbackground->portal_offset = light_index;
+      kbackground->num_portals = num_portals;
+      kbackground->portal_weight = 1.0f;
     }
     else {
-      kintegrator->num_portals = 0;
-      kintegrator->portal_offset = 0;
-      kintegrator->portal_pdf = 0.0f;
+      kbackground->num_portals = 0;
+      kbackground->portal_offset = 0;
+      kbackground->portal_weight = 0.0f;
     }
+
+    /* Map */
+    kbackground->map_weight = background_mis ? 1.0f : 0.0f;
   }
   else {
     dscene->light_distribution.free();
@@ -511,9 +515,12 @@ void LightManager::device_update_distribution(Device *,
     kintegrator->pdf_triangles = 0.0f;
     kintegrator->pdf_lights = 0.0f;
     kintegrator->use_lamp_mis = false;
-    kintegrator->num_portals = 0;
-    kintegrator->portal_offset = 0;
-    kintegrator->portal_pdf = 0.0f;
+
+    kbackground->num_portals = 0;
+    kbackground->portal_offset = 0;
+    kbackground->portal_weight = 0.0f;
+    kbackground->sun_weight = 0.0f;
+    kbackground->map_weight = 0.0f;
 
     kfilm->pass_shadow_scale = 1.0f;
   }
@@ -562,7 +569,7 @@ void LightManager::device_update_background(Device *device,
                                             Scene *scene,
                                             Progress &progress)
 {
-  KernelIntegrator *kintegrator = &dscene->data.integrator;
+  KernelBackground *kbackground = &dscene->data.background;
   Light *background_light = NULL;
 
   /* find background light */
@@ -575,31 +582,79 @@ void LightManager::device_update_background(Device *device,
 
   /* no background light found, signal renderer to skip sampling */
   if (!background_light || !background_light->is_enabled) {
-    kintegrator->pdf_background_res_x = 0;
-    kintegrator->pdf_background_res_y = 0;
+    kbackground->map_res_x = 0;
+    kbackground->map_res_y = 0;
+    kbackground->map_weight = 0.0f;
+    kbackground->sun_weight = 0.0f;
+    kbackground->use_mis = (kbackground->portal_weight > 0.0f);
     return;
   }
 
   progress.set_status("Updating Lights", "Importance map");
 
-  assert(kintegrator->use_direct_light);
+  assert(dscene->data.integrator.use_direct_light);
+
+  int2 environment_res = make_int2(0, 0);
+  Shader *shader = scene->background->get_shader(scene);
+  int num_suns = 0;
+  foreach (ShaderNode *node, shader->graph->nodes) {
+    if (node->type == EnvironmentTextureNode::node_type) {
+      EnvironmentTextureNode *env = (EnvironmentTextureNode *)node;
+      ImageMetaData metadata;
+      if (!env->handle.empty()) {
+        ImageMetaData metadata = env->handle.metadata();
+        environment_res.x = max(environment_res.x, metadata.width);
+        environment_res.y = max(environment_res.y, metadata.height);
+      }
+    }
+    if (node->type == SkyTextureNode::node_type) {
+      SkyTextureNode *sky = (SkyTextureNode *)node;
+      if (sky->type == NODE_SKY_NISHITA && sky->sun_disc) {
+        /* Ensure that the input coordinates aren't transformed before they reach the node.
+         * If that is the case, the logic used for sampling the sun's location does not work
+         * and we have to fall back to map-based sampling. */
+        const ShaderInput *vec_in = sky->input("Vector");
+        if (vec_in && vec_in->link && vec_in->link->parent) {
+          ShaderNode *vec_src = vec_in->link->parent;
+          if ((vec_src->type != TextureCoordinateNode::node_type) ||
+              (vec_in->link != vec_src->output("Generated"))) {
+            environment_res.x = max(environment_res.x, 4096);
+            environment_res.y = max(environment_res.y, 2048);
+            continue;
+          }
+        }
+
+        float latitude = sky->sun_elevation;
+        float longitude = M_2PI_F - sky->sun_rotation + M_PI_2_F;
+        float half_angle = sky->sun_size * 0.5f;
+        kbackground->sun = make_float4(cosf(latitude) * cosf(longitude),
+                                       cosf(latitude) * sinf(longitude),
+                                       sinf(latitude),
+                                       half_angle);
+        kbackground->sun_weight = 4.0f;
+        environment_res.x = max(environment_res.x, 512);
+        environment_res.y = max(environment_res.y, 256);
+        num_suns++;
+      }
+    }
+  }
+
+  /* If there's more than one sun, fall back to map sampling instead. */
+  if (num_suns != 1) {
+    kbackground->sun_weight = 0.0f;
+    environment_res.x = max(environment_res.x, 4096);
+    environment_res.y = max(environment_res.y, 2048);
+  }
+
+  /* Enable MIS for background sampling if any strategy is active. */
+  kbackground->use_mis = (kbackground->portal_weight + kbackground->map_weight +
+                          kbackground->sun_weight) > 0.0f;
 
   /* get the resolution from the light's size (we stuff it in there) */
   int2 res = make_int2(background_light->map_resolution, background_light->map_resolution / 2);
   /* If the resolution isn't set manually, try to find an environment texture. */
   if (res.x == 0) {
-    Shader *shader = scene->background->get_shader(scene);
-    foreach (ShaderNode *node, shader->graph->nodes) {
-      if (node->type == EnvironmentTextureNode::node_type) {
-        EnvironmentTextureNode *env = (EnvironmentTextureNode *)node;
-        ImageMetaData metadata;
-        if (!env->handle.empty()) {
-          ImageMetaData metadata = env->handle.metadata();
-          res.x = max(res.x, metadata.width);
-          res.y = max(res.y, metadata.height);
-        }
-      }
-    }
+    res = environment_res;
     if (res.x > 0 && res.y > 0) {
       VLOG(2) << "Automatically set World MIS resolution to " << res.x << " by " << res.y << "\n";
     }
@@ -609,8 +664,8 @@ void LightManager::device_update_background(Device *device,
     res = make_int2(1024, 512);
     VLOG(2) << "Setting World MIS resolution to default\n";
   }
-  kintegrator->pdf_background_res_x = res.x;
-  kintegrator->pdf_background_res_y = res.y;
+  kbackground->map_res_x = res.x;
+  kbackground->map_res_y = res.y;
 
   vector<float3> pixels;
   shade_background_pixels(device, dscene, res.x, res.y, pixels, progress);