[Bf-blender-cvs] [8f5eb7a] soc-2014-cycles: Tweak for yesterdays volume shadow optimization.

[Thomas Dinges]

Commit: 8f5eb7a5638daa23ea0a132659c13972f80408cc
Author: Thomas Dinges
Date:   Fri Aug 1 00:26:03 2014 +0200
Branches: soc-2014-cycles
https://developer.blender.org/rB8f5eb7a5638daa23ea0a132659c13972f80408cc

Tweak for yesterdays volume shadow optimization.

* Avoid division and branching, suggested by Sergey.

===================================================================

M	intern/cycles/kernel/kernel_volume.h

===================================================================

diff --git a/intern/cycles/kernel/kernel_volume.h b/intern/cycles/kernel/kernel_volume.h
index 2f61eb7..6d5b1c2 100644
--- a/intern/cycles/kernel/kernel_volume.h
+++ b/intern/cycles/kernel/kernel_volume.h
@@ -177,7 +177,6 @@ ccl_device void kernel_volume_shadow_heterogeneous(KernelGlobals *kg, PathState
 	float t = 0.0f;
 
 	float3 sum = make_float3(0.0f, 0.0f, 0.0f);
-	bool tp_calculated = false;
 
 	for(int i = 0; i < max_steps; i++) {
 		/* advance to new position */
@@ -197,24 +196,20 @@ ccl_device void kernel_volume_shadow_heterogeneous(KernelGlobals *kg, PathState
 			 * because exp(a)*exp(b) = exp(a+b), also do a quick tp_eps check then. */
 
 			sum += (-sigma_t * (new_t - t));
-			if((i % 8) == 0) { /* ToDo: Other interval? */
-				tp_calculated = true;
+			if((i & 0x07) == 0) { /* ToDo: Other interval? */
 				tp = *throughput * make_float3(expf(sum.x), expf(sum.y), expf(sum.z));
 
 				/* stop if nearly all light blocked */
 				if(tp.x < tp_eps && tp.y < tp_eps && tp.z < tp_eps)
 					break;
 			}
-			else
-				tp_calculated = false;
 		}
 
 		/* stop if at the end of the volume */
 		t = new_t;
 		if(t == ray->t) {
-			if(!tp_calculated)
-				/* Update throughput in case we have't done it above */
-				tp = *throughput * make_float3(expf(sum.x), expf(sum.y), expf(sum.z));
+			/* Update throughput in case we have't done it above */
+			tp = *throughput * make_float3(expf(sum.x), expf(sum.y), expf(sum.z));
 			break;
 		}
 	}