Fix T76897: Lamp Power Not Updating from Driver

Lamps were not tagged with `ID_RECALC_SHADING` when they were updated
from drivers. As a result, Cycles considered the lamp as unchanged. This
is resolved by having a (seemingly non-functional) callback in a new
`LIGHT_UPDATE` depsgraph node.

This patch unconditionally adds the `LIGHT_UPDATE` node + the relation
from the lamp's PARAMETERS node.

Differential Revision: https://developer.blender.org/D7822

Reviewed by: brecht

2 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_light.h b/source/blender/blenkernel/BKE_light.h
index a6f0fdbc8a3..2764233bc68 100644
--- a/source/blender/blenkernel/BKE_light.h
+++ b/source/blender/blenkernel/BKE_light.h
@@ -30,6 +30,7 @@ extern "C" {
 
 #include "BLI_compiler_attrs.h"
 
+struct Depsgraph;
 struct Light;
 struct Main;
 
@@ -37,6 +38,8 @@ struct Light *BKE_light_add(struct Main *bmain, const char *name) ATTR_WARN_UNUS
 struct Light *BKE_light_copy(struct Main *bmain, const struct Light *la) ATTR_WARN_UNUSED_RESULT;
 struct Light *BKE_light_localize(struct Light *la) ATTR_WARN_UNUSED_RESULT;
 
+void BKE_light_eval(struct Depsgraph *depsgraph, struct Light *la);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/blender/blenkernel/intern/light.c b/source/blender/blenkernel/intern/light.c
index 3d0503b2e70..58d50787c9f 100644
--- a/source/blender/blenkernel/intern/light.c
+++ b/source/blender/blenkernel/intern/light.c
@@ -47,6 +47,8 @@
 
 #include "BLT_translation.h"
 
+#include "DEG_depsgraph.h"
+
 static void light_init_data(ID *id)
 {
   Light *la = (Light *)id;
@@ -167,3 +169,8 @@ Light *BKE_light_localize(Light *la)
 
   return lan;
 }
+
+void BKE_light_eval(struct Depsgraph *depsgraph, Light *la)
+{
+  DEG_debug_print_eval(depsgraph, __func__, la->id.name, la);
+}