Cycles: Only use first lamp in indirect_lamp_emission

Produces different results when lamps overlap from POV of a ray, but allows
for this function to be split. The differences probably wont be noticeable
in most scenes. Old behavior could be reattained by placing lamps
into the BVH.

2 files changed, 24 insertions, 13 deletions

diff --git a/intern/cycles/kernel/kernel_emission.h b/intern/cycles/kernel/kernel_emission.h
index fa54a7d756a..295fa978e15 100644
--- a/intern/cycles/kernel/kernel_emission.h
+++ b/intern/cycles/kernel/kernel_emission.h
@@ -287,10 +287,11 @@ ccl_device_noinline bool indirect_lamp_emission(KernelGlobals *kg,
 
 	*emission = make_float3(0.0f, 0.0f, 0.0f);
 
-	for(int lamp = 0; lamp < kernel_data.integrator.num_all_lights; lamp++) {
-		LightSample ls;
+	LightSample ls;
+	ls.t = ray->t;
 
-		if(!lamp_light_eval(kg, lamp, ray->P, ray->D, ray->t, &ls))
+	for(int lamp = 0; lamp < kernel_data.integrator.num_all_lights; lamp++) {
+		if(!lamp_light_eval(kg, lamp, ray->P, ray->D, ls.t, &ls))
 			continue;
 
 #ifdef __PASSES__
@@ -305,6 +306,10 @@ ccl_device_noinline bool indirect_lamp_emission(KernelGlobals *kg,
 		}
 #endif
 
+		hit_lamp = true;
+	}
+
+	if(hit_lamp) {
 		float3 L = direct_emissive_eval(kg,
 		                                emission_sd,
 		                                &ls,
@@ -333,7 +338,6 @@ ccl_device_noinline bool indirect_lamp_emission(KernelGlobals *kg,
 		}
 
 		*emission += L;
-		hit_lamp = true;
 	}
 
 	return hit_lamp;
diff --git a/intern/cycles/kernel/kernel_light.h b/intern/cycles/kernel/kernel_light.h
index 1a3ae4c1f32..6defef13d1e 100644
--- a/intern/cycles/kernel/kernel_light.h
+++ b/intern/cycles/kernel/kernel_light.h
@@ -617,16 +617,9 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
 	float4 data1 = kernel_tex_fetch(__light_data, lamp*LIGHT_SIZE + 1);
 
 	LightType type = (LightType)__float_as_int(data0.x);
-	ls->type = type;
-	ls->shader = __float_as_int(data1.x);
-	ls->object = PRIM_NONE;
-	ls->prim = PRIM_NONE;
-	ls->lamp = lamp;
-	/* todo: missing texture coordinates */
-	ls->u = 0.0f;
-	ls->v = 0.0f;
+	int shader = __float_as_int(data1.x);
 
-	if(!(ls->shader & SHADER_USE_MIS))
+	if(!(shader & SHADER_USE_MIS))
 		return false;
 
 	if(type == LIGHT_DISTANT) {
@@ -665,6 +658,10 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
 		ls->D = D;
 		ls->t = FLT_MAX;
 
+		/* todo: missing texture coordinates */
+		ls->u = 0.0f;
+		ls->v = 0.0f;
+
 		/* compute pdf */
 		float invarea = data1.w;
 		ls->pdf = invarea/(costheta*costheta*costheta);
@@ -734,6 +731,10 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
 			return false;
 		}
 
+		/* todo: missing texture coordinates */
+		ls->u = 0.0f;
+		ls->v = 0.0f;
+
 		ls->D = D;
 		ls->Ng = Ng;
 		ls->pdf = area_light_sample(P, &light_P, axisu, axisv, 0, 0, false);
@@ -743,6 +744,12 @@ ccl_device bool lamp_light_eval(KernelGlobals *kg, int lamp, float3 P, float3 D,
 		return false;
 	}
 
+	ls->type = type;
+	ls->shader = shader;
+	ls->object = PRIM_NONE;
+	ls->prim = PRIM_NONE;
+	ls->lamp = lamp;
+
 	ls->pdf *= kernel_data.integrator.pdf_lights;
 
 	return true;