void BVH4Intersector4Hybrid<PrimitiveIntersector4>::occluded(sseb* valid_i, BVH4* bvh, Ray4& ray)
    {
      /* load ray */
      const sseb valid = *valid_i;
      sseb terminated = !valid;
      sse3f ray_org = ray.org, ray_dir = ray.dir;
      ssef ray_tnear = ray.tnear, ray_tfar  = ray.tfar;
#if defined(__FIX_RAYS__)
      const ssef float_range = 0.1f*FLT_MAX;
      ray_org = clamp(ray_org,sse3f(-float_range),sse3f(+float_range));
      ray_dir = clamp(ray_dir,sse3f(-float_range),sse3f(+float_range));
      ray_tnear = max(ray_tnear,FLT_MIN); 
      ray_tfar  = min(ray_tfar,float(inf)); 
#endif
      const sse3f rdir = rcp_safe(ray_dir);
      const sse3f org(ray_org), org_rdir = org * rdir;
      ray_tnear = select(valid,ray_tnear,ssef(pos_inf));
      ray_tfar  = select(valid,ray_tfar ,ssef(neg_inf));
      const ssef inf = ssef(pos_inf);
      
      /* allocate stack and push root node */
      ssef    stack_near[stackSizeChunk];
      NodeRef stack_node[stackSizeChunk];
      stack_node[0] = BVH4::invalidNode;
      stack_near[0] = inf;
      stack_node[1] = bvh->root;
      stack_near[1] = ray_tnear; 
      NodeRef* stackEnd = stack_node+stackSizeChunk;
      NodeRef* __restrict__ sptr_node = stack_node + 2;
      ssef*    __restrict__ sptr_near = stack_near + 2;
      
      while (1)
      {
        /* pop next node from stack */
        assert(sptr_node > stack_node);
        sptr_node--;
        sptr_near--;
        NodeRef curNode = *sptr_node;
        if (unlikely(curNode == BVH4::invalidNode)) {
          assert(sptr_node == stack_node);
          break;
        }

        /* cull node if behind closest hit point */
        ssef curDist = *sptr_near;
        const sseb active = curDist < ray_tfar;
        if (unlikely(none(active))) 
          continue;
        
        /* switch to single ray traversal */
#if !defined(__WIN32__) || defined(__X86_64__)
        size_t bits = movemask(active);
        if (unlikely(__popcnt(bits) <= SWITCH_THRESHOLD)) {
          for (size_t i=__bsf(bits); bits!=0; bits=__btc(bits,i), i=__bsf(bits)) {
            if (occluded1(bvh,curNode,i,ray,ray_org,ray_dir,rdir,ray_tnear,ray_tfar))
              terminated[i] = -1;
          }
          if (all(terminated)) break;
          ray_tfar = select(terminated,ssef(neg_inf),ray_tfar);
          continue;
        }
#endif

        while (1)
        {
          /* test if this is a leaf node */
          if (unlikely(curNode.isLeaf()))
            break;
          
          const sseb valid_node = ray_tfar > curDist;
          STAT3(shadow.trav_nodes,1,popcnt(valid_node),4);
          const Node* __restrict__ const node = curNode.node();
          
          /* pop of next node */
          assert(sptr_node > stack_node);
          sptr_node--;
          sptr_near--;
          curNode = *sptr_node;
          curDist = *sptr_near;
          
#pragma unroll(4)
          for (unsigned i=0; i<4; i++)
          {
            const NodeRef child = node->children[i];
            if (unlikely(child == BVH4::emptyNode)) break;
            
#if defined(__AVX2__)
            const ssef lclipMinX = msub(node->lower_x[i],rdir.x,org_rdir.x);
            const ssef lclipMinY = msub(node->lower_y[i],rdir.y,org_rdir.y);
            const ssef lclipMinZ = msub(node->lower_z[i],rdir.z,org_rdir.z);
            const ssef lclipMaxX = msub(node->upper_x[i],rdir.x,org_rdir.x);
            const ssef lclipMaxY = msub(node->upper_y[i],rdir.y,org_rdir.y);
            const ssef lclipMaxZ = msub(node->upper_z[i],rdir.z,org_rdir.z);
#else
            const ssef lclipMinX = (node->lower_x[i] - org.x) * rdir.x;
            const ssef lclipMinY = (node->lower_y[i] - org.y) * rdir.y;
            const ssef lclipMinZ = (node->lower_z[i] - org.z) * rdir.z;
            const ssef lclipMaxX = (node->upper_x[i] - org.x) * rdir.x;
            const ssef lclipMaxY = (node->upper_y[i] - org.y) * rdir.y;
            const ssef lclipMaxZ = (node->upper_z[i] - org.z) * rdir.z;
#endif
    
#if defined(__SSE4_1__)
            const ssef lnearP = maxi(maxi(mini(lclipMinX, lclipMaxX), mini(lclipMinY, lclipMaxY)), mini(lclipMinZ, lclipMaxZ));
            const ssef lfarP  = mini(mini(maxi(lclipMinX, lclipMaxX), maxi(lclipMinY, lclipMaxY)), maxi(lclipMinZ, lclipMaxZ));
            const sseb lhit   = maxi(lnearP,ray_tnear) <= mini(lfarP,ray_tfar);      
#else
            const ssef lnearP = max(max(min(lclipMinX, lclipMaxX), min(lclipMinY, lclipMaxY)), min(lclipMinZ, lclipMaxZ));
            const ssef lfarP  = min(min(max(lclipMinX, lclipMaxX), max(lclipMinY, lclipMaxY)), max(lclipMinZ, lclipMaxZ));
            const sseb lhit   = max(lnearP,ray_tnear) <= min(lfarP,ray_tfar);      
#endif
            
            /* if we hit the child we choose to continue with that child if it 
               is closer than the current next child, or we push it onto the stack */
            if (likely(any(lhit)))
            {
              assert(sptr_node < stackEnd);
              assert(child != BVH4::emptyNode);
              const ssef childDist = select(lhit,lnearP,inf);
              sptr_node++;
              sptr_near++;
              
              /* push cur node onto stack and continue with hit child */
              if (any(childDist < curDist))
              {
                *(sptr_node-1) = curNode;
                *(sptr_near-1) = curDist; 
                curDist = childDist;
                curNode = child;
              }
              
              /* push hit child onto stack */
              else {
                *(sptr_node-1) = child;
                *(sptr_near-1) = childDist; 
              }
            }	      
          }
        }
        
        /* return if stack is empty */
        if (unlikely(curNode == BVH4::invalidNode)) {
          assert(sptr_node == stack_node);
          break;
        }
        
        /* intersect leaf */
        const sseb valid_leaf = ray_tfar > curDist;
        STAT3(shadow.trav_leaves,1,popcnt(valid_leaf),4);
        size_t items; const Primitive* prim = (Primitive*) curNode.leaf(items);
        terminated |= PrimitiveIntersector4::occluded(!terminated,ray,prim,items,bvh->geometry);
        if (all(terminated)) break;
        ray_tfar = select(terminated,ssef(neg_inf),ray_tfar);
      }
      store4i(valid & terminated,&ray.geomID,0);
      AVX_ZERO_UPPER();
    }
    __forceinline bool BVH4Intersector4Hybrid<PrimitiveIntersector4>::occluded1(const BVH4* bvh, NodeRef root, size_t k, Ray4& ray, 
                                                                                const sse3f& ray_org, const sse3f& ray_dir, const sse3f& ray_rdir, 
                                                                                const ssef& ray_tnear, const ssef& ray_tfar)
    {
      /*! stack state */
      NodeRef stack[stackSizeSingle];  //!< stack of nodes that still need to get traversed
      NodeRef* stackPtr = stack+1;        //!< current stack pointer
      NodeRef* stackEnd = stack+stackSizeSingle;
      stack[0]  = root;
      
      /*! offsets to select the side that becomes the lower or upper bound */
      const size_t nearX = ray_dir.x[k] >= 0.0f ? 0*sizeof(ssef) : 1*sizeof(ssef);
      const size_t nearY = ray_dir.y[k] >= 0.0f ? 2*sizeof(ssef) : 3*sizeof(ssef);
      const size_t nearZ = ray_dir.z[k] >= 0.0f ? 4*sizeof(ssef) : 5*sizeof(ssef);
      
      /*! load the ray into SIMD registers */
      const sse3f org (ray_org .x[k],ray_org .y[k],ray_org .z[k]);
      const sse3f rdir(ray_rdir.x[k],ray_rdir.y[k],ray_rdir.z[k]);
      const sse3f norg = -org, org_rdir(org*rdir);
      const ssef rayNear(ray_tnear[k]), rayFar(ray_tfar[k]); 
      
      /* pop loop */
      while (true) pop:
      {
        /*! pop next node */
        if (unlikely(stackPtr == stack)) break;
        stackPtr--;
        NodeRef cur = (NodeRef) *stackPtr;
        
        /* downtraversal loop */
        while (true)
        {
          /*! stop if we found a leaf */
          if (unlikely(cur.isLeaf())) break;
          STAT3(shadow.trav_nodes,1,1,1);
          
          /*! single ray intersection with 4 boxes */
          const Node* node = cur.node();
          const size_t farX  = nearX ^ 16, farY  = nearY ^ 16, farZ  = nearZ ^ 16;
#if defined (__AVX2__)
          const ssef tNearX = msub(load4f((const char*)node+nearX), rdir.x, org_rdir.x);
          const ssef tNearY = msub(load4f((const char*)node+nearY), rdir.y, org_rdir.y);
          const ssef tNearZ = msub(load4f((const char*)node+nearZ), rdir.z, org_rdir.z);
          const ssef tFarX  = msub(load4f((const char*)node+farX ), rdir.x, org_rdir.x);
          const ssef tFarY  = msub(load4f((const char*)node+farY ), rdir.y, org_rdir.y);
          const ssef tFarZ  = msub(load4f((const char*)node+farZ ), rdir.z, org_rdir.z);
#else
          const ssef tNearX = (norg.x + load4f((const char*)node+nearX)) * rdir.x;
          const ssef tNearY = (norg.y + load4f((const char*)node+nearY)) * rdir.y;
          const ssef tNearZ = (norg.z + load4f((const char*)node+nearZ)) * rdir.z;
          const ssef tFarX  = (norg.x + load4f((const char*)node+farX )) * rdir.x;
          const ssef tFarY  = (norg.y + load4f((const char*)node+farY )) * rdir.y;
          const ssef tFarZ  = (norg.z + load4f((const char*)node+farZ )) * rdir.z;
#endif
          
#if defined(__SSE4_1__)
          const ssef tNear = maxi(maxi(tNearX,tNearY),maxi(tNearZ,rayNear));
          const ssef tFar  = mini(mini(tFarX ,tFarY ),mini(tFarZ ,rayFar ));
          const sseb vmask = cast(tNear) > cast(tFar);
          size_t mask = movemask(vmask)^0xf;
#else
          const ssef tNear = max(tNearX,tNearY,tNearZ,rayNear);
          const ssef tFar  = min(tFarX ,tFarY ,tFarZ ,rayFar);
          const sseb vmask = tNear <= tFar;
          size_t mask = movemask(vmask);
#endif
          
          /*! if no child is hit, pop next node */
          if (unlikely(mask == 0))
            goto pop;
          
          /*! one child is hit, continue with that child */
          size_t r = bitscan(mask); mask = __btc(mask,r);
          if (likely(mask == 0)) {
            cur = node->child(r);
            assert(cur != BVH4::emptyNode);
            continue;
          }
          
          /*! two children are hit, push far child, and continue with closer child */
          NodeRef c0 = node->child(r); const float d0 = tNear[r];
          r = bitscan(mask); mask = __btc(mask,r);
          NodeRef c1 = node->child(r); const float d1 = tNear[r];
          assert(c0 != BVH4::emptyNode);
          assert(c1 != BVH4::emptyNode);
          if (likely(mask == 0)) {
            assert(stackPtr < stackEnd);
            if (d0 < d1) { *stackPtr = c1; stackPtr++; cur = c0; continue; }
            else         { *stackPtr = c0; stackPtr++; cur = c1; continue; }
          }
          assert(stackPtr < stackEnd);
          *stackPtr = c0; stackPtr++;
          assert(stackPtr < stackEnd);
          *stackPtr = c1; stackPtr++;
          
          /*! three children are hit */
          r = bitscan(mask); mask = __btc(mask,r); cur = node->child(r); 
          assert(cur != BVH4::emptyNode);
          if (likely(mask == 0)) continue;
          assert(stackPtr < stackEnd);
          *stackPtr = cur; stackPtr++;
          
          /*! four children are hit */
          cur = node->child(3);
          assert(cur != BVH4::emptyNode);
        }
        
        /*! this is a leaf node */
        STAT3(shadow.trav_leaves,1,1,1);
        size_t num; Primitive* prim = (Primitive*) cur.leaf(num);
        if (PrimitiveIntersector4::occluded(ray,k,prim,num,bvh->geometry)) {
          ray.geomID[k] = 0;
          return true;
        }
      }
      return false;
    }
    __forceinline void BVH4Intersector4Hybrid<PrimitiveIntersector4>::intersect1(const BVH4* bvh, NodeRef root, size_t k, Ray4& ray, 
                                                                                 const sse3f& ray_org, const sse3f& ray_dir, const sse3f& ray_rdir, 
                                                                                 const ssef& ray_tnear, const ssef& ray_tfar)
    {
      /*! stack state */
      StackItem stack[stackSizeSingle];  //!< stack of nodes 
      StackItem* stackPtr = stack+1;        //!< current stack pointer
      StackItem* stackEnd = stack+stackSizeSingle;
      stack[0].ptr = root;
      stack[0].dist = neg_inf;
      
      /*! offsets to select the side that becomes the lower or upper bound */
      const size_t nearX = ray_dir.x[k] >= 0.0f ? 0*sizeof(ssef) : 1*sizeof(ssef);
      const size_t nearY = ray_dir.y[k] >= 0.0f ? 2*sizeof(ssef) : 3*sizeof(ssef);
      const size_t nearZ = ray_dir.z[k] >= 0.0f ? 4*sizeof(ssef) : 5*sizeof(ssef);
      
      /*! load the ray into SIMD registers */
      const sse3f org (ray_org .x[k],ray_org .y[k],ray_org .z[k]);
      const sse3f rdir(ray_rdir.x[k],ray_rdir.y[k],ray_rdir.z[k]);
      const sse3f norg = -org, org_rdir(org*rdir);
      ssef rayNear(ray_tnear[k]), rayFar(ray_tfar[k]); 
      
      /* pop loop */
      while (true) pop:
      {
        /*! pop next node */
        if (unlikely(stackPtr == stack)) break;
        stackPtr--;
        NodeRef cur = NodeRef(stackPtr->ptr);
        
        /*! if popped node is too far, pop next one */
        if (unlikely(stackPtr->dist > ray.tfar[k]))
          continue;
        
        /* downtraversal loop */
        while (true)
        {
          /*! stop if we found a leaf */
          if (unlikely(cur.isLeaf())) break;
          STAT3(normal.trav_nodes,1,1,1);
          
          /*! single ray intersection with 4 boxes */
          const Node* node = cur.node();
          const size_t farX  = nearX ^ 16, farY  = nearY ^ 16, farZ  = nearZ ^ 16;
#if defined (__AVX2__)
          const ssef tNearX = msub(load4f((const char*)node+nearX), rdir.x, org_rdir.x);
          const ssef tNearY = msub(load4f((const char*)node+nearY), rdir.y, org_rdir.y);
          const ssef tNearZ = msub(load4f((const char*)node+nearZ), rdir.z, org_rdir.z);
          const ssef tFarX  = msub(load4f((const char*)node+farX ), rdir.x, org_rdir.x);
          const ssef tFarY  = msub(load4f((const char*)node+farY ), rdir.y, org_rdir.y);
          const ssef tFarZ  = msub(load4f((const char*)node+farZ ), rdir.z, org_rdir.z);
#else
          const ssef tNearX = (norg.x + load4f((const char*)node+nearX)) * rdir.x;
          const ssef tNearY = (norg.y + load4f((const char*)node+nearY)) * rdir.y;
          const ssef tNearZ = (norg.z + load4f((const char*)node+nearZ)) * rdir.z;
          const ssef tFarX  = (norg.x + load4f((const char*)node+farX )) * rdir.x;
          const ssef tFarY  = (norg.y + load4f((const char*)node+farY )) * rdir.y;
          const ssef tFarZ  = (norg.z + load4f((const char*)node+farZ )) * rdir.z;
#endif

#if defined(__SSE4_1__)
          const ssef tNear = maxi(maxi(tNearX,tNearY),maxi(tNearZ,rayNear));
          const ssef tFar  = mini(mini(tFarX ,tFarY ),mini(tFarZ ,rayFar ));
          const sseb vmask = cast(tNear) > cast(tFar);
          size_t mask = movemask(vmask)^0xf;
#else
          const ssef tNear = max(tNearX,tNearY,tNearZ,rayNear);
          const ssef tFar  = min(tFarX ,tFarY ,tFarZ ,rayFar);
          const sseb vmask = tNear <= tFar;
          size_t mask = movemask(vmask);
#endif
          
          /*! if no child is hit, pop next node */
          if (unlikely(mask == 0))
            goto pop;
          
          /*! one child is hit, continue with that child */
          size_t r = bitscan(mask); mask = __btc(mask,r);
          if (likely(mask == 0)) {
            cur = node->child(r);
            assert(cur != BVH4::emptyNode);
            continue;
          }
          
          /*! two children are hit, push far child, and continue with closer child */
          NodeRef c0 = node->child(r); const float d0 = tNear[r];
          r = bitscan(mask); mask = __btc(mask,r);
          NodeRef c1 = node->child(r); const float d1 = tNear[r];
          assert(c0 != BVH4::emptyNode);
          assert(c1 != BVH4::emptyNode);
          if (likely(mask == 0)) {
            assert(stackPtr < stackEnd); 
            if (d0 < d1) { stackPtr->ptr = c1; stackPtr->dist = d1; stackPtr++; cur = c0; continue; }
            else         { stackPtr->ptr = c0; stackPtr->dist = d0; stackPtr++; cur = c1; continue; }
          }
          
          /*! Here starts the slow path for 3 or 4 hit children. We push
           *  all nodes onto the stack to sort them there. */
          assert(stackPtr < stackEnd); 
          stackPtr->ptr = c0; stackPtr->dist = d0; stackPtr++;
          assert(stackPtr < stackEnd); 
          stackPtr->ptr = c1; stackPtr->dist = d1; stackPtr++;
          
          /*! three children are hit, push all onto stack and sort 3 stack items, continue with closest child */
          assert(stackPtr < stackEnd); 
          r = bitscan(mask); mask = __btc(mask,r);
          NodeRef c = node->child(r); float d = tNear[r]; stackPtr->ptr = c; stackPtr->dist = d; stackPtr++;
          assert(c != BVH4::emptyNode);
          if (likely(mask == 0)) {
            sort(stackPtr[-1],stackPtr[-2],stackPtr[-3]);
            cur = (NodeRef) stackPtr[-1].ptr; stackPtr--;
            continue;
          }
          
          /*! four children are hit, push all onto stack and sort 4 stack items, continue with closest child */
          assert(stackPtr < stackEnd); 
          r = bitscan(mask); mask = __btc(mask,r);
          c = node->child(r); d = tNear[r]; stackPtr->ptr = c; stackPtr->dist = d; stackPtr++;
          assert(c != BVH4::emptyNode);
          sort(stackPtr[-1],stackPtr[-2],stackPtr[-3],stackPtr[-4]);
          cur = (NodeRef) stackPtr[-1].ptr; stackPtr--;
        }
        
        /*! this is a leaf node */
        STAT3(normal.trav_leaves,1,1,1);
        size_t num; Primitive* prim = (Primitive*) cur.leaf(num);
        PrimitiveIntersector4::intersect(ray,k,prim,num,bvh->geometry);
        rayFar = ray.tfar[k];
      }
    }
  void BVH4Intersector4Chunk<TriangleIntersector4>::intersect(const BVH4Intersector4Chunk* This, Ray4& ray, const __m128 valid_i)
  {
    sseb valid = valid_i;
    NodeRef invalid = (NodeRef)1;
    const BVH4* bvh = This->bvh;

    /* load ray into registers */
    ssef ray_near = select(valid,ray.tnear,pos_inf);
    ssef ray_far  = select(valid,ray.tfar ,neg_inf);
    sse3f rdir = rcp_safe(ray.dir);
    ray.tfar = ray_far;

    /* allocate stack and push root node */
    NodeRef stack_node[3*BVH4::maxDepth+1];
    ssef  stack_near[3*BVH4::maxDepth+1];
    stack_node[0] = invalid;
    stack_near[0] = ssef(inf);
    stack_node[1] = bvh->root;
    stack_near[1] = ray_near;
    NodeRef* sptr_node = stack_node+2;
    ssef * sptr_near = stack_near+2;
 
    while (1)
    {
      /* pop next node from stack */
      sptr_node--;
      sptr_near--;
      ssef  curDist = *sptr_near;
      NodeRef curNode = *sptr_node;
      if (unlikely(curNode == invalid))
        break;

      /* cull node if behind closest hit point */
      const sseb m_dist = curDist < ray_far;
      if (unlikely(none(m_dist))) 
        continue;

      while (1)
      {
        /* test if this is a leaf node */
        if (unlikely(curNode.isLeaf())) 
          break;
        
        const Node* const node = curNode.node(bvh->nodePtr()); //NodeRef(curNode).node(nodes);
        //prefetch<PFHINT_L1>((ssef*)node + 1); // depth first order prefetch 
        
        /* pop of next node */
        sptr_node--;
        sptr_near--;
        curNode = *sptr_node;
        curDist = *sptr_near;
                
        for (unsigned i=0;i<4;i++)
  {
          const ssef dminx = (ssef(node->lower_x[i]) - ray.org.x) * rdir.x;
          const ssef dmaxx = (ssef(node->upper_x[i]) - ray.org.x) * rdir.x;
          const ssef dminy = (ssef(node->lower_y[i]) - ray.org.y) * rdir.y;
          const ssef dmaxy = (ssef(node->upper_y[i]) - ray.org.y) * rdir.y;
          const ssef dminz = (ssef(node->lower_z[i]) - ray.org.z) * rdir.z;
          const ssef dmaxz = (ssef(node->upper_z[i]) - ray.org.z) * rdir.z;
          
          const ssef dlowerx = min(dminx,dmaxx);
          const ssef dupperx = max(dminx,dmaxx);
          const ssef dlowery = min(dminy,dmaxy);
          const ssef duppery = max(dminy,dmaxy);
          const ssef dlowerz = min(dminz,dmaxz);
          const ssef dupperz = max(dminz,dmaxz);
          
          const ssef near = max(dlowerx,dlowery,dlowerz,ray_near);
          const ssef far  = min(dupperx,duppery,dupperz,ray_far );
          const sseb mhit = near <= far;
          
          const ssef childDist = select(mhit,near,inf);
          const sseb closer = childDist < curDist;

          /* if we hit the child we choose to continue with that child if it 
             is closer than the current next child, or we push it onto the stack */
          if (likely(any(mhit)))
          {
            const NodeRef child = node->child(i);
            //if (child != invalid)
            {
              sptr_node++;
              sptr_near++;
            
              /* push cur node onto stack and continue with hit child */
              if (any(closer)) {
                *(sptr_node-1) = curNode;
                *(sptr_near-1) = curDist; 
                curDist = childDist;
                curNode = child;
              } 
              
              /* push hit child onto stack*/
              else {
                *(sptr_node-1) = child;
                *(sptr_near-1) = childDist; 
              }          
            }       
          }
        }
      }
      
      /* return if stack is empty */
      if (unlikely(curNode == invalid)) 
        break;
      
      /* decode leaf node */
      size_t num;
      Triangle* tri = (Triangle*) curNode.leaf(bvh->triPtr(),num);
      
      /* intersect triangles */
      for (size_t i=0; i<num; i++)
        TriangleIntersector4::intersect(valid,ray,tri[i],bvh->vertices);
      
      ray_far = ray.tfar;
    }
  }
    void BVH4Intersector1Bezier<PrimitiveIntersector>::intersect(const BVH4* bvh, Ray& ray)
    {
      /*! perform per ray precalculations required by the primitive intersector */
      Precalculations pre(ray);

      /*! stack state */
      StackItemInt32<NodeRef> stack[stackSize];  //!< stack of nodes 
      StackItemInt32<NodeRef>* stackPtr = stack+1;        //!< current stack pointer
      StackItemInt32<NodeRef>* stackEnd = stack+stackSize;
      stack[0].ptr = bvh->root;
      stack[0].dist = neg_inf;
      
      /*! offsets to select the side that becomes the lower or upper bound */
      const size_t nearX = ray.dir.x >= 0.0f ? 0*sizeof(ssef) : 1*sizeof(ssef);
      const size_t nearY = ray.dir.y >= 0.0f ? 2*sizeof(ssef) : 3*sizeof(ssef);
      const size_t nearZ = ray.dir.z >= 0.0f ? 4*sizeof(ssef) : 5*sizeof(ssef);
      
      /*! load the ray into SIMD registers */
      const sse3f norg(-ray.org.x,-ray.org.y,-ray.org.z);
      const Vec3fa ray_rdir = rcp_safe(ray.dir);
      const sse3f rdir(ray_rdir.x,ray_rdir.y,ray_rdir.z);
      const Vec3fa ray_org_rdir = ray.org*ray_rdir;
      const sse3f org_rdir(ray_org_rdir.x,ray_org_rdir.y,ray_org_rdir.z);
      const ssef  ray_near(ray.tnear);
      ssef ray_far(ray.tfar);

      /* pop loop */
      while (true) pop:
      {
        /*! pop next node */
        if (unlikely(stackPtr == stack)) break;
        stackPtr--;
        NodeRef cur = NodeRef(stackPtr->ptr);
        
        /*! if popped node is too far, pop next one */
        if (unlikely(*(float*)&stackPtr->dist > ray.tfar))
          continue;
        
        /* downtraversal loop */
        while (true)
        {
          /*! stop if we found a leaf */
          if (unlikely(cur.isLeaf())) break;
          STAT3(normal.trav_nodes,1,1,1);
          
          /*! single ray intersection with 4 boxes */
          const Node* node = cur.node();
          const size_t farX  = nearX ^ 16, farY  = nearY ^ 16, farZ  = nearZ ^ 16;

          const ssef tFarX0  = abs((norg.x + load4f((const char*)node+farX )) * rdir.x);
          const ssef tFarY0  = abs((norg.y + load4f((const char*)node+farY )) * rdir.y);
          const ssef tFarZ0  = abs((norg.z + load4f((const char*)node+farZ )) * rdir.z);
          const ssef tFar0  = min(tFarX0 ,tFarY0 ,tFarZ0);
          const ssef radius = abs(ssef(ray.org.w) + tFar0 * ssef(ray.dir.w));
          //const ssef radius = zero;
          //PRINT2(tFar0,radius);

          const ssef tLowerX = (norg.x + node->lower_x - radius) * rdir.x;
          const ssef tLowerY = (norg.y + node->lower_y - radius) * rdir.y;
          const ssef tLowerZ = (norg.z + node->lower_z - radius) * rdir.z;

          const ssef tUpperX = (norg.x + node->upper_x + radius) * rdir.x;
          const ssef tUpperY = (norg.y + node->upper_y + radius) * rdir.y;
          const ssef tUpperZ = (norg.z + node->upper_z + radius) * rdir.z;

          const ssef tNearX = min(tLowerX,tUpperX);
          const ssef tNearY = min(tLowerY,tUpperY);
          const ssef tNearZ = min(tLowerZ,tUpperZ);

          const ssef tFarX = max(tLowerX,tUpperX);
          const ssef tFarY = max(tLowerY,tUpperY);
          const ssef tFarZ = max(tLowerZ,tUpperZ);

          const ssef tNear = max(tNearX,tNearY,tNearZ,ray_near);
          const ssef tFar  = min(tFarX ,tFarY ,tFarZ ,ray_far);
          const sseb vmask = tNear <= tFar;
          size_t mask = movemask(vmask);
          
          /*! if no child is hit, pop next node */
          if (unlikely(mask == 0))
            goto pop;
          
          /*! one child is hit, continue with that child */
          size_t r = __bscf(mask);
          if (likely(mask == 0)) {
            cur = node->child(r);
            //assert(cur != BVH4::emptyNode); // FIXME: enable these assertions again, currently traversing empty children
            continue;
          }
          
          /*! two children are hit, push far child, and continue with closer child */
          NodeRef c0 = node->child(r); const unsigned int d0 = ((unsigned int*)&tNear)[r];
          r = __bscf(mask);
          NodeRef c1 = node->child(r); const unsigned int d1 = ((unsigned int*)&tNear)[r];
          //assert(c0 != BVH4::emptyNode);
          //assert(c1 != BVH4::emptyNode);
          if (likely(mask == 0)) {
            assert(stackPtr < stackEnd); 
            if (d0 < d1) { stackPtr->ptr = c1; stackPtr->dist = d1; stackPtr++; cur = c0; continue; }
            else         { stackPtr->ptr = c0; stackPtr->dist = d0; stackPtr++; cur = c1; continue; }
          }
          
          /*! Here starts the slow path for 3 or 4 hit children. We push
           *  all nodes onto the stack to sort them there. */
          assert(stackPtr < stackEnd); 
          stackPtr->ptr = c0; stackPtr->dist = d0; stackPtr++;
          assert(stackPtr < stackEnd); 
          stackPtr->ptr = c1; stackPtr->dist = d1; stackPtr++;
          
          /*! three children are hit, push all onto stack and sort 3 stack items, continue with closest child */
          assert(stackPtr < stackEnd); 
          r = __bscf(mask);
          NodeRef c = node->child(r); unsigned int d = ((unsigned int*)&tNear)[r]; stackPtr->ptr = c; stackPtr->dist = d; stackPtr++;
          //assert(c != BVH4::emptyNode);
          if (likely(mask == 0)) {
            sort(stackPtr[-1],stackPtr[-2],stackPtr[-3]);
            cur = (NodeRef) stackPtr[-1].ptr; stackPtr--;
            continue;
          }
          
          /*! four children are hit, push all onto stack and sort 4 stack items, continue with closest child */
          assert(stackPtr < stackEnd); 
          r = __bscf(mask);
          c = node->child(r); d = *(unsigned int*)&tNear[r]; stackPtr->ptr = c; stackPtr->dist = d; stackPtr++;
          //assert(c != BVH4::emptyNode);
          sort(stackPtr[-1],stackPtr[-2],stackPtr[-3],stackPtr[-4]);
          cur = (NodeRef) stackPtr[-1].ptr; stackPtr--;
        }
        
        /*! this is a leaf node */
        STAT3(normal.trav_leaves,1,1,1);
        size_t num; Primitive* prim = (Primitive*) cur.leaf(num);
        PrimitiveIntersector::intersect(pre,ray,prim,num,bvh->geometry);
        ray_far = ray.tfar;
      }
    }
    void BVH4Intersector1Bezier<PrimitiveIntersector>::occluded(const BVH4* bvh, Ray& ray)
    {
      /*! perform per ray precalculations required by the primitive intersector */
      Precalculations pre(ray);

      /*! stack state */
      NodeRef stack[stackSize];  //!< stack of nodes that still need to get traversed
      NodeRef* stackPtr = stack+1;        //!< current stack pointer
      NodeRef* stackEnd = stack+stackSize;
      stack[0] = bvh->root;
      
      /*! offsets to select the side that becomes the lower or upper bound */
      const size_t nearX = ray.dir.x >= 0 ? 0*sizeof(ssef) : 1*sizeof(ssef);
      const size_t nearY = ray.dir.y >= 0 ? 2*sizeof(ssef) : 3*sizeof(ssef);
      const size_t nearZ = ray.dir.z >= 0 ? 4*sizeof(ssef) : 5*sizeof(ssef);
      
      /*! load the ray into SIMD registers */
      const sse3f norg(-ray.org.x,-ray.org.y,-ray.org.z);
      const Vec3fa ray_rdir = rcp_safe(ray.dir);
      const sse3f rdir(ray_rdir.x,ray_rdir.y,ray_rdir.z);
      const Vec3fa ray_org_rdir = ray.org*ray_rdir;
      const sse3f org_rdir(ray_org_rdir.x,ray_org_rdir.y,ray_org_rdir.z);
      const ssef  ray_near(ray.tnear);
      ssef ray_far(ray.tfar);
      
      /* pop loop */
      while (true) pop:
      {
        /*! pop next node */
        if (unlikely(stackPtr == stack)) break;
        stackPtr--;
        NodeRef cur = (NodeRef) *stackPtr;
        
        /* downtraversal loop */
        while (true)
        {
          /*! stop if we found a leaf */
          if (unlikely(cur.isLeaf())) break;
          STAT3(shadow.trav_nodes,1,1,1);
          
          /*! single ray intersection with 4 boxes */
          const Node* node = cur.node();
          const size_t farX  = nearX ^ 16, farY  = nearY ^ 16, farZ  = nearZ ^ 16;
#if defined (__AVX2__)
          const ssef tNearX = msub(load4f((const char*)node+nearX), rdir.x, org_rdir.x);
          const ssef tNearY = msub(load4f((const char*)node+nearY), rdir.y, org_rdir.y);
          const ssef tNearZ = msub(load4f((const char*)node+nearZ), rdir.z, org_rdir.z);
          const ssef tFarX  = msub(load4f((const char*)node+farX ), rdir.x, org_rdir.x);
          const ssef tFarY  = msub(load4f((const char*)node+farY ), rdir.y, org_rdir.y);
          const ssef tFarZ  = msub(load4f((const char*)node+farZ ), rdir.z, org_rdir.z);
#else
          const ssef tNearX = (norg.x + load4f((const char*)node+nearX)) * rdir.x;
          const ssef tNearY = (norg.y + load4f((const char*)node+nearY)) * rdir.y;
          const ssef tNearZ = (norg.z + load4f((const char*)node+nearZ)) * rdir.z;
          const ssef tFarX  = (norg.x + load4f((const char*)node+farX )) * rdir.x;
          const ssef tFarY  = (norg.y + load4f((const char*)node+farY )) * rdir.y;
          const ssef tFarZ  = (norg.z + load4f((const char*)node+farZ )) * rdir.z;
#endif
          
#if defined(__SSE4_1__)
          const ssef tNear = maxi(maxi(tNearX,tNearY),maxi(tNearZ,ray_near));
          const ssef tFar  = mini(mini(tFarX ,tFarY ),mini(tFarZ ,ray_far ));
          const sseb vmask = cast(tNear) > cast(tFar);
          size_t mask = movemask(vmask)^0xf;
#else
          const ssef tNear = max(tNearX,tNearY,tNearZ,ray_near);
          const ssef tFar  = min(tFarX ,tFarY ,tFarZ ,ray_far);
          const sseb vmask = tNear <= tFar;
          size_t mask = movemask(vmask);
#endif
          
          /*! if no child is hit, pop next node */
          if (unlikely(mask == 0))
            goto pop;
          
          /*! one child is hit, continue with that child */
          size_t r = __bscf(mask);
          if (likely(mask == 0)) {
            cur = node->child(r);
            //assert(cur != BVH4::emptyNode);
            continue;
          }
          
          /*! two children are hit, push far child, and continue with closer child */
          NodeRef c0 = node->child(r); const unsigned int d0 = ((unsigned int*)&tNear)[r];
          r = __bscf(mask);
          NodeRef c1 = node->child(r); const unsigned int d1 = ((unsigned int*)&tNear)[r];
          //assert(c0 != BVH4::emptyNode);
          //assert(c1 != BVH4::emptyNode);
          if (likely(mask == 0)) {
            assert(stackPtr < stackEnd);
            if (d0 < d1) { *stackPtr = c1; stackPtr++; cur = c0; continue; }
            else         { *stackPtr = c0; stackPtr++; cur = c1; continue; }
          }
          assert(stackPtr < stackEnd);
          *stackPtr = c0; stackPtr++;
          assert(stackPtr < stackEnd);
          *stackPtr = c1; stackPtr++;
          
          /*! three children are hit */
          r = __bscf(mask);
          cur = node->child(r); 
          //assert(cur != BVH4::emptyNode);
          if (likely(mask == 0)) continue;
          assert(stackPtr < stackEnd);
          *stackPtr = cur; stackPtr++;
          
          /*! four children are hit */
          cur = node->child(3);
          //assert(cur != BVH4::emptyNode);
        }
        
        /*! this is a leaf node */
        STAT3(shadow.trav_leaves,1,1,1);
        size_t num; Primitive* prim = (Primitive*) cur.leaf(num);
        if (PrimitiveIntersector::occluded(pre,ray,prim,num,bvh->geometry)) {
          ray.geomID = 0;
          break;
        }
      }
      AVX_ZERO_UPPER();
    }