Cycles: take into account IES texture node strength input for light tree

To better estimate light contribution. Note that estimating the texture
from the IES file is still missing.

Contributed by Alaska.

Differential Revision: https://developer.blender.org/D16901

intern/cycles/scene/shader.cpp

@@ -263,8 +263,9 @@ static float3 output_estimate_emission(ShaderOutput *output, bool &is_constant)
 
     return estimate;
   }
-  else if (node->type == LightFalloffNode::get_node_type()) {
-    /* Light Falloff node. */
+  else if (node->type == LightFalloffNode::get_node_type() ||
+           node->type == IESLightNode::get_node_type()) {
+    /* Get strength from Light Falloff and IES texture node. */
     ShaderInput *strength_in = node->input("Strength");
     is_constant = false;