Cycles/Eevee: unify light strength and color

Cycles lights now use strength and color properties of the light outside
of the shading nodes, just like Eevee. The shading nodes then act as a
multiplier on this, and become optional unless textures, fallof or other
effects are desired.

Backwards compatibility is not exact, as we can't be sure which renderer
the .blend was designed for or even if it was designed for a single one.

If the render engine in the active scene is set to Cycles, lights are
converted to ensure overall light strength remains the same, and removing
unnecessary shader node setups that only included a single emission node.

If the engine is set to Eevee, we increase strength to remove the automatic
100x multiplier that was there to match Cycles.

Differential Revision: https://developer.blender.org/D4588

1 files changed, 97 insertions, 0 deletions

diff --git a/source/blender/blenloader/intern/versioning_cycles.c b/source/blender/blenloader/intern/versioning_cycles.c
index 2bd379c6f19..7616e62af9f 100644
--- a/source/blender/blenloader/intern/versioning_cycles.c
+++ b/source/blender/blenloader/intern/versioning_cycles.c
@@ -49,6 +49,12 @@ static float *cycles_node_socket_float_value(bNodeSocket *socket)
   return &socket_data->value;
 }
 
+static float *cycles_node_socket_rgba_value(bNodeSocket *socket)
+{
+  bNodeSocketValueRGBA *socket_data = socket->default_value;
+  return socket_data->value;
+}
+
 static IDProperty *cycles_properties_from_ID(ID *id)
 {
   IDProperty *idprop = IDP_GetProperties(id, false);
@@ -291,6 +297,87 @@ static void image_node_colorspace(bNode *node)
   }
 }
 
+static void light_emission_node_to_energy(Light *light, float *energy, float color[3])
+{
+  *energy = 1.0;
+  copy_v3_fl(color, 1.0f);
+
+  /* If nodetree has animation or drivers, don't try to convert. */
+  bNodeTree *ntree = light->nodetree;
+  if (ntree == NULL || ntree->adt) {
+    return;
+  }
+
+  /* Find emission node */
+  bNode *output_node = ntreeShaderOutputNode(ntree, SHD_OUTPUT_CYCLES);
+  if (output_node == NULL) {
+    return;
+  }
+
+  bNode *emission_node = NULL;
+  for (bNodeLink *link = ntree->links.first; link; link = link->next) {
+    if (link->tonode == output_node && link->fromnode->type == SH_NODE_EMISSION) {
+      emission_node = link->fromnode;
+      break;
+    }
+  }
+
+  if (emission_node == NULL) {
+    return;
+  }
+
+  /* Don't convert if anything is linked */
+  bNodeSocket *strength_socket = nodeFindSocket(emission_node, SOCK_IN, "Strength");
+  bNodeSocket *color_socket = nodeFindSocket(emission_node, SOCK_IN, "Color");
+
+  if ((strength_socket->flag & SOCK_IN_USE) || (color_socket->flag & SOCK_IN_USE)) {
+    return;
+  }
+
+  float *strength_value = cycles_node_socket_float_value(strength_socket);
+  float *color_value = cycles_node_socket_rgba_value(color_socket);
+
+  *energy = *strength_value;
+  copy_v3_v3(color, color_value);
+
+  *strength_value = 1.0f;
+  copy_v4_fl(color_value, 1.0f);
+  light->use_nodes = false;
+}
+
+static void light_emission_unify(Light *light, const char *engine)
+{
+  if (light->type != LA_SUN) {
+    light->energy *= 100.0f;
+  }
+
+  /* Attempt to extract constant energy and color from nodes. */
+  bool use_nodes = light->use_nodes;
+  float energy, color[3];
+  light_emission_node_to_energy(light, &energy, color);
+
+  if (STREQ(engine, "CYCLES")) {
+    if (use_nodes) {
+      /* Energy extracted from nodes */
+      light->energy = energy;
+      copy_v3_v3(&light->r, color);
+    }
+    else {
+      /* Default cycles multipliers if there are no nodes */
+      if (light->type == LA_SUN) {
+        light->energy = 1.0f;
+      }
+      else {
+        light->energy = 100.0f;
+      }
+    }
+  }
+  else {
+    /* Disable nodes if scene was configured for Eevee */
+    light->use_nodes = false;
+  }
+}
+
 void blo_do_versions_cycles(FileData *UNUSED(fd), Library *UNUSED(lib), Main *bmain)
 {
   /* Particle shape shared with Eevee. */
@@ -364,4 +451,14 @@ void do_versions_after_linking_cycles(Main *bmain)
     }
     FOREACH_NODETREE_END;
   }
+
+  if (!MAIN_VERSION_ATLEAST(bmain, 280, 64)) {
+    /* Unfiy Cycles and Eevee settings. */
+    Scene *scene = bmain->scenes.first;
+    const char *engine = (scene) ? scene->r.engine : "CYCLES";
+
+    for (Light *light = bmain->lights.first; light; light = light->id.next) {
+      light_emission_unify(light, engine);
+    }
+  }
 }