From 90cd7675ea20251ced129ff05ad0ea22968be823 Mon Sep 17 00:00:00 2001
From: tatsy <tatsy.mail@gmail.com>
Date: Tue, 15 Mar 2016 14:38:43 +0900
Subject: [PATCH] Fix bug on QBVH.

---
 sources/accelerator/qbvh.cc | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/sources/accelerator/qbvh.cc b/sources/accelerator/qbvh.cc
index df4bff4..39d8d2b 100644
--- a/sources/accelerator/qbvh.cc
+++ b/sources/accelerator/qbvh.cc
@@ -238,12 +238,14 @@ bool QBVHAccel::intersect(Ray& ray, SurfaceInteraction* isect) const {
             }
         } else {
             // Leaf
-            const auto& prim = primitives_[item.node.index];
-            SurfaceInteraction temp;
-            if (primitives_[item.node.index]->intersect(ray, &temp)) {
-                *isect = temp;
-                isect->setPrimitive(prim.get());
-                hit = true;
+            if (item.node.index >= 0) {
+                const auto& prim = primitives_[item.node.index];
+                SurfaceInteraction temp;
+                if (primitives_[item.node.index]->intersect(ray, &temp)) {
+                    *isect = temp;
+                    isect->setPrimitive(prim.get());
+                    hit = true;
+                }
             }
         }
     }