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

intern/cycles/blender/addon/ui.py

@@ -1341,6 +1341,10 @@ class CYCLES_LIGHT_PT_light(CyclesButtonsPanel, Panel):
 
         col = layout.column()
 
+        col.prop(light, "color")
+        col.prop(light, "energy")
+        col.separator()
+
         if light.type in {'POINT', 'SUN', 'SPOT'}:
             col.prop(light, "shadow_soft_size", text="Size")
         elif light.type == 'AREA':
@@ -1384,8 +1388,7 @@ class CYCLES_LIGHT_PT_nodes(CyclesButtonsPanel, Panel):
         layout = self.layout
 
         light = context.light
-        if not panel_node_draw(layout, light, 'OUTPUT_LIGHT', 'Surface'):
-            layout.prop(light, "color")
+        panel_node_draw(layout, light, 'OUTPUT_LIGHT', 'Surface')
 
 
 class CYCLES_LIGHT_PT_spot(CyclesButtonsPanel, Panel):

intern/cycles/blender/blender_object.cpp

@@ -182,6 +182,10 @@ void BlenderSync::sync_light(BL::Object &b_parent,
     }
   }
 
+  /* strength */
+  light->strength = get_float3(b_light.color());
+  light->strength *= BL::PointLight(b_light).energy();
+
   /* location and (inverted!) direction */
   light->co = transform_get_column(&tfm, 3);
   light->dir = -transform_get_column(&tfm, 2);

intern/cycles/blender/blender_shader.cpp

@@ -1409,16 +1409,9 @@ void BlenderSync::sync_lights(BL::Depsgraph &b_depsgraph, bool update_all)
         add_nodes(scene, b_engine, b_data, b_depsgraph, b_scene, graph, b_ntree);
       }
       else {
-        float strength = 1.0f;
-
-        if (b_light.type() == BL::Light::type_POINT || b_light.type() == BL::Light::type_SPOT ||
-            b_light.type() == BL::Light::type_AREA) {
-          strength = 100.0f;
-        }
-
         EmissionNode *emission = new EmissionNode();
-        emission->color = get_float3(b_light.color());
-        emission->strength = strength;
+        emission->color = make_float3(1.0f, 1.0f, 1.0f);
+        emission->strength = 1.0f;
         graph->add(emission);
 
         ShaderNode *out = graph->output();

intern/cycles/kernel/kernel_emission.h

@@ -90,6 +90,11 @@ ccl_device_noinline float3 direct_emissive_eval(KernelGlobals *kg,
 
   eval *= ls->eval_fac;
 
+  if (ls->lamp != LAMP_NONE) {
+    const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, ls->lamp);
+    eval *= make_float3(klight->strength[0], klight->strength[1], klight->strength[2]);
+  }
+
   return eval;
 }
 

intern/cycles/kernel/kernel_types.h

@@ -1455,6 +1455,8 @@ typedef struct KernelLight {
   int samples;
   float max_bounces;
   float random;
+  float strength[3];
+  float pad1;
   Transform tfm;
   Transform itfm;
   union {

intern/cycles/render/light.cpp

@@ -114,6 +114,8 @@ NODE_DEFINE(Light)
   type_enum.insert("spot", LIGHT_SPOT);
   SOCKET_ENUM(type, "Type", type_enum, LIGHT_POINT);
 
+  SOCKET_COLOR(strength, "Strength", make_float3(1.0f, 1.0f, 1.0f));
+
   SOCKET_POINT(co, "Co", make_float3(0.0f, 0.0f, 0.0f));
 
   SOCKET_VECTOR(dir, "Dir", make_float3(0.0f, 0.0f, 0.0f));
@@ -162,6 +164,9 @@ void Light::tag_update(Scene *scene)
 
 bool Light::has_contribution(Scene *scene)
 {
+  if (strength == make_float3(0.0f, 0.0f, 0.0f)) {
+    return false;
+  }
   if (is_portal) {
     return false;
   }
@@ -672,7 +677,6 @@ void LightManager::device_update_points(Device *, DeviceScene *dscene, Scene *sc
     float3 co = light->co;
     Shader *shader = (light->shader) ? light->shader : scene->default_light;
     int shader_id = scene->shader_manager->get_shader_id(shader);
-    int samples = light->samples;
     int max_bounces = light->max_bounces;
     float random = (float)light->random_id * (1.0f / (float)0xFFFFFFFF);
 
@@ -697,7 +701,10 @@ void LightManager::device_update_points(Device *, DeviceScene *dscene, Scene *sc
     }
 
     klights[light_index].type = light->type;
-    klights[light_index].samples = samples;
+    klights[light_index].samples = light->samples;
+    klights[light_index].strength[0] = light->strength.x;
+    klights[light_index].strength[1] = light->strength.y;
+    klights[light_index].strength[2] = light->strength.z;
 
     if (light->type == LIGHT_POINT) {
       shader_id &= ~SHADER_AREA_LIGHT;

intern/cycles/render/light.h

@@ -42,6 +42,7 @@ class Light : public Node {
   Light();
 
   LightType type;
+  float3 strength;
   float3 co;
 
   float3 dir;

source/blender/blenkernel/BKE_blender_version.h

@@ -27,7 +27,7 @@
  * \note Use #STRINGIFY() rather than defining with quotes.
  */
 #define BLENDER_VERSION 280
-#define BLENDER_SUBVERSION 63
+#define BLENDER_SUBVERSION 64
 /** Several breakages with 280, e.g. collections vs layers. */
 #define BLENDER_MINVERSION 280
 #define BLENDER_MINSUBVERSION 0

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);
+    }
+  }
 }

source/blender/draw/engines/eevee/eevee_lights.c

@@ -645,7 +645,7 @@ float light_attenuation_radius_get(Light *la, float light_threshold)
 
   /* Compute max light power. */
   float power = max_fff(la->r, la->g, la->b);
-  power *= fabsf(la->energy);
+  power *= fabsf(la->energy / 100.0f);
   power *= max_ff(1.0f, la->spec_fac);
   /* Compute the distance (using the inverse square law)
    * at which the light power reaches the light_threshold. */
@@ -683,7 +683,7 @@ static float light_shape_power_get(const Light *la, const EEVEE_Light *evli)
   /* Make illumination power constant */
   if (la->type == LA_AREA) {
     power = 1.0f / (evli->sizex * evli->sizey * 4.0f * M_PI) * /* 1/(w*h*Pi) */
-            80.0f; /* XXX : Empirical, Fit cycles power */
+            0.8f; /* XXX : Empirical, Fit cycles power */
     if (ELEM(la->area_shape, LA_AREA_DISK, LA_AREA_ELLIPSE)) {
       /* Scale power to account for the lower area of the ellipse compared to the surrounding
        * rectangle. */
@@ -691,8 +691,7 @@ static float light_shape_power_get(const Light *la, const EEVEE_Light *evli)
     }
   }
   else if (la->type == LA_SPOT || la->type == LA_LOCAL) {
-    power = 1.0f / (4.0f * evli->radius * evli->radius * M_PI * M_PI) * /* 1/(4*r²*Pi²) */
-            M_PI * M_PI * 10.0; /* XXX : Empirical, Fit cycles power */
+    power = 1.0f / (4.0f * evli->radius * evli->radius * M_PI * M_PI); /* 1/(4*r²*Pi²) */
 
     /* for point lights (a.k.a radius == 0.0) */
     // power = M_PI * M_PI * 0.78; /* XXX : Empirical, Fit cycles power */

source/blender/editors/object/object_add.c

@@ -1176,7 +1176,6 @@ static const char *get_light_defname(int type)
 
 static int object_light_add_exec(bContext *C, wmOperator *op)
 {
-  Scene *scene = CTX_data_scene(C);
   Object *ob;
   Light *la;
   int type = RNA_enum_get(op->ptr, "type");
@@ -1207,11 +1206,6 @@ static int object_light_add_exec(bContext *C, wmOperator *op)
   la = (Light *)ob->data;
   la->type = type;
 
-  if (BKE_scene_uses_cycles(scene)) {
-    ED_node_shader_default(C, &la->id);
-    la->use_nodes = true;
-  }
-
   return OPERATOR_FINISHED;
 }
 

source/blender/editors/space_node/node_edit.c

@@ -453,13 +453,8 @@ void ED_node_shader_default(const bContext *C, ID *id)
       output_type = SH_NODE_OUTPUT_LIGHT;
       shader_type = SH_NODE_EMISSION;
 
-      copy_v3_v3(color, &la->r);
-      if (la->type == LA_LOCAL || la->type == LA_SPOT || la->type == LA_AREA) {
-        strength = 100.0f;
-      }
-      else {
-        strength = 1.0f;
-      }
+      copy_v3_fl3(color, 1.0f, 1.0f, 1.0f);
+      strength = 1.0f;
       break;
     }
     default: