Cycles: Use proper node counter to allocate QBVH nodes

Before all the nodes were counted and allocated, leading to situations when
bunch of allocated memory is not used because reasonable amount of nodes are
simply ignored.

intern/cycles/bvh/bvh.cpp

@@ -794,7 +794,7 @@ void QBVH::pack_inner(const BVHStackEntry& e, const BVHStackEntry *en, int num)
 
 void QBVH::pack_nodes(const array<int>& prims, const BVHNode *root)
 {
-	size_t node_size = root->getSubtreeSize(BVH_STAT_NODE_COUNT);
+	size_t node_size = root->getSubtreeSize(BVH_STAT_QNODE_COUNT);
 
 	/* resize arrays */
 	pack.nodes.clear();

intern/cycles/bvh/bvh_node.cpp

@@ -47,6 +47,20 @@ int BVHNode::getSubtreeSize(BVH_STAT stat) const
 		case BVH_STAT_CHILDNODE_COUNT:
 			cnt = num_children();
 			break;
+		case BVH_STAT_QNODE_COUNT:
+			cnt = 1;
+			for(int i = 0; i < num_children(); i++) {
+				BVHNode *node = get_child(i);
+				if(node->is_leaf()) {
+					cnt += 1;
+				}
+				else {
+					for(int j = 0; j < node->num_children(); j++) {
+						cnt += node->get_child(j)->getSubtreeSize(stat);
+					}
+				}
+			}
+			return cnt;
 		default:
 			assert(0); /* unknown mode */
 	}

intern/cycles/bvh/bvh_node.h

@@ -30,7 +30,8 @@ enum BVH_STAT
 	BVH_STAT_INNER_COUNT,
 	BVH_STAT_LEAF_COUNT,
 	BVH_STAT_TRIANGLE_COUNT,
-	BVH_STAT_CHILDNODE_COUNT
+	BVH_STAT_CHILDNODE_COUNT,
+	BVH_STAT_QNODE_COUNT,
 };
 
 class BVHParams;