Cycles: Add "Max Bounce" control for lamps

With this setting, we can limit the influence of a lamp to a certain amount of bounces.
0 = Only direct light contribution
1 = 1 light bounce
...

Differential revision: https://developer.blender.org/D860

You can find an example render in the release logs: http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.73/Cycles

1 files changed, 13 insertions, 1 deletions

diff --git a/intern/cycles/kernel/kernel_light.h b/intern/cycles/kernel/kernel_light.h
index 659c4a113ca..f9ac86e49d6 100644
--- a/intern/cycles/kernel/kernel_light.h
+++ b/intern/cycles/kernel/kernel_light.h
@@ -648,7 +648,13 @@ ccl_device int light_distribution_sample(KernelGlobals *kg, float randt)
 
 /* Generic Light */
 
-ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float randv, float time, float3 P, LightSample *ls)
+ccl_device bool light_select_reached_max_bounces(KernelGlobals *kg, int index, int bounce)
+{
+	float4 data4 = kernel_tex_fetch(__light_data, index*LIGHT_SIZE + 4);
+	return (bounce > __float_as_int(data4.x));
+}
+
+ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float randv, float time, float3 P, int bounce, LightSample *ls)
 {
 	/* sample index */
 	int index = light_distribution_sample(kg, randt);
@@ -670,6 +676,12 @@ ccl_device void light_sample(KernelGlobals *kg, float randt, float randu, float
 	}
 	else {
 		int lamp = -prim-1;
+
+		if(UNLIKELY(light_select_reached_max_bounces(kg, lamp, bounce))) {
+			ls->pdf = 0.0f;
+			return;
+		}
+
 		lamp_light_sample(kg, lamp, randu, randv, P, ls);
 	}
 }