From 8cdce12d49cb655205143cbb9ff303e51c14424c Mon Sep 17 00:00:00 2001
From: Matt Pharr <matt@pharr.org>
Date: Fri, 11 May 2018 19:41:04 -0700
Subject: [PATCH] SPPM: don't trace rays with zero contributions

---
 src/integrators/sppm.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/integrators/sppm.cpp b/src/integrators/sppm.cpp
index b3bc648e33..a62b6cfeb9 100644
--- a/src/integrators/sppm.cpp
+++ b/src/integrators/sppm.cpp
@@ -158,6 +158,8 @@ void SPPMIntegrator::Render(const Scene &scene) {
                     RayDifferential ray;
                     Spectrum beta =
                         camera->GenerateRayDifferential(cameraSample, &ray);
+                    if (beta.IsBlack())
+                        continue;
                     ray.ScaleDifferentials(invSqrtSPP);
 
                     // Follow camera ray path until a visible point is created