//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//
//  Copyright 2015 National Technology & Engineering Solutions of Sandia, LLC (NTESS).
//  Copyright 2015 UT-Battelle, LLC.
//  Copyright 2015 Los Alamos National Security.
//
//  Under the terms of Contract DE-NA0003525 with NTESS,
//  the U.S. Government retains certain rights in this software.
//
//  Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
//  Laboratory (LANL), the U.S. Government retains certain rights in
//  this software.
//============================================================================

#include <math.h>

#include <vtkm/Math.h>
#include <vtkm/VectorAnalysis.h>

#include <vtkm/cont/Algorithm.h>
#include <vtkm/cont/DeviceAdapter.h>
#include <vtkm/cont/DeviceAdapterAlgorithm.h>
#include <vtkm/cont/RuntimeDeviceTracker.h>
#include <vtkm/cont/Timer.h>
#include <vtkm/cont/TryExecute.h>

#include <vtkm/cont/AtomicArray.h>

#include <vtkm/rendering/raytracing/BoundingVolumeHierarchy.h>
#include <vtkm/rendering/raytracing/Logger.h>
#include <vtkm/rendering/raytracing/MortonCodes.h>
#include <vtkm/rendering/raytracing/RayTracingTypeDefs.h>
#include <vtkm/rendering/raytracing/Worklets.h>

#include <vtkm/worklet/Invoker.h>
#include <vtkm/worklet/WorkletMapField.h>

#define AABB_EPSILON 0.00001f
namespace vtkm
{
namespace rendering
{
namespace raytracing
{
namespace detail
{

class LinearBVHBuilder
{
public:
  class CountingIterator;

  template <typename Device>
  class GatherFloat32;

  template <typename Device>
  class GatherVecCast;

  class CreateLeafs;

  class BVHData;

  template <typename Device>
  class PropagateAABBs;

  template <typename Device>
  class TreeBuilder;

  VTKM_CONT
  LinearBVHBuilder() {}

  template <typename Device>
  VTKM_CONT void SortAABBS(BVHData& bvh, Device vtkmNotUsed(device), bool);

  template <typename Device>
  VTKM_CONT void BuildHierarchy(BVHData& bvh);

  template <typename Device>
  VTKM_CONT void RunOnDevice(LinearBVH& linearBVH, Device device);
}; // class LinearBVHBuilder

class LinearBVHBuilder::CountingIterator : public vtkm::worklet::WorkletMapField
{
public:
  VTKM_CONT
  CountingIterator() {}
  using ControlSignature = void(FieldOut);
  using ExecutionSignature = void(WorkIndex, _1);
  VTKM_EXEC
  void operator()(const vtkm::Id& index, vtkm::Id& outId) const { outId = index; }
}; //class countingIterator

template <typename Device>
class LinearBVHBuilder::GatherFloat32 : public vtkm::worklet::WorkletMapField
{
private:
  using FloatArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::Float32>;
  using PortalConst = typename FloatArrayHandle::ExecutionTypes<Device>::PortalConst;
  using Portal = typename FloatArrayHandle::ExecutionTypes<Device>::Portal;
  PortalConst InputPortal;
  Portal OutputPortal;

public:
  VTKM_CONT
  GatherFloat32(const FloatArrayHandle& inputPortal,
                FloatArrayHandle& outputPortal,
                const vtkm::Id& size)
    : InputPortal(inputPortal.PrepareForInput(Device()))
  {
    this->OutputPortal = outputPortal.PrepareForOutput(size, Device());
  }
  using ControlSignature = void(FieldIn);
  using ExecutionSignature = void(WorkIndex, _1);
  VTKM_EXEC
  void operator()(const vtkm::Id& outIndex, const vtkm::Id& inIndex) const
  {
    OutputPortal.Set(outIndex, InputPortal.Get(inIndex));
  }
}; //class GatherFloat

class LinearBVHBuilder::CreateLeafs : public vtkm::worklet::WorkletMapField
{

public:
  VTKM_CONT
  CreateLeafs() {}

  typedef void ControlSignature(FieldIn, WholeArrayOut);
  typedef void ExecutionSignature(_1, _2, WorkIndex);

  template <typename LeafPortalType>
  VTKM_EXEC void operator()(const vtkm::Id& dataIndex,
                            LeafPortalType& leafs,
                            const vtkm::Id& index) const
  {
    const vtkm::Id offset = index * 2;
    leafs.Set(offset, 1);             // number of primitives
    leafs.Set(offset + 1, dataIndex); // number of primitives
  }
}; //class createLeafs

template <typename Device>
class LinearBVHBuilder::GatherVecCast : public vtkm::worklet::WorkletMapField
{
private:
  using Vec4IdArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::Vec<vtkm::Id, 4>>;
  using Vec4IntArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::Vec<vtkm::Int32, 4>>;
  using PortalConst = typename Vec4IdArrayHandle::ExecutionTypes<Device>::PortalConst;
  using Portal = typename Vec4IntArrayHandle::ExecutionTypes<Device>::Portal;

private:
  PortalConst InputPortal;
  Portal OutputPortal;

public:
  VTKM_CONT
  GatherVecCast(const Vec4IdArrayHandle& inputPortal,
                Vec4IntArrayHandle& outputPortal,
                const vtkm::Id& size)
    : InputPortal(inputPortal.PrepareForInput(Device()))
  {
    this->OutputPortal = outputPortal.PrepareForOutput(size, Device());
  }
  using ControlSignature = void(FieldIn);
  using ExecutionSignature = void(WorkIndex, _1);
  VTKM_EXEC
  void operator()(const vtkm::Id& outIndex, const vtkm::Id& inIndex) const
  {
    OutputPortal.Set(outIndex, InputPortal.Get(inIndex));
  }
}; //class GatherVec3Id

class LinearBVHBuilder::BVHData
{
public:
  vtkm::cont::ArrayHandle<vtkm::UInt32> mortonCodes;
  vtkm::cont::ArrayHandle<vtkm::Id> parent;
  vtkm::cont::ArrayHandle<vtkm::Id> leftChild;
  vtkm::cont::ArrayHandle<vtkm::Id> rightChild;
  vtkm::cont::ArrayHandle<vtkm::Id> leafs;
  vtkm::cont::ArrayHandle<vtkm::Bounds> innerBounds;
  vtkm::cont::ArrayHandleCounting<vtkm::Id> leafOffsets;
  AABBs& AABB;

  template <typename Device>
  VTKM_CONT BVHData(vtkm::Id numPrimitives, AABBs& aabbs, Device vtkmNotUsed(device))
    : leafOffsets(0, 2, numPrimitives)
    , AABB(aabbs)
    , NumPrimitives(numPrimitives)
  {
    InnerNodeCount = NumPrimitives - 1;
    vtkm::Id size = NumPrimitives + InnerNodeCount;

    parent.PrepareForOutput(size, Device());
    leftChild.PrepareForOutput(InnerNodeCount, Device());
    rightChild.PrepareForOutput(InnerNodeCount, Device());
    innerBounds.PrepareForOutput(InnerNodeCount, Device());
    mortonCodes.PrepareForOutput(NumPrimitives, Device());
  }

  VTKM_CONT
  ~BVHData() {}

  VTKM_CONT
  vtkm::Id GetNumberOfPrimitives() const { return NumPrimitives; }
  VTKM_CONT
  vtkm::Id GetNumberOfInnerNodes() const { return InnerNodeCount; }

private:
  vtkm::Id NumPrimitives;
  vtkm::Id InnerNodeCount;

}; // class BVH

template <typename Device>
class LinearBVHBuilder::PropagateAABBs : public vtkm::worklet::WorkletMapField
{
private:
  using IdArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::Id>;
  using Int8Handle = typename vtkm::cont::ArrayHandle<vtkm::Int8>;
  using Float2ArrayHandle = typename vtkm::cont::ArrayHandle<Vec<vtkm::Float32, 2>>;
  using VecInt2Handle = typename vtkm::cont::ArrayHandle<vtkm::Vec<vtkm::Int32, 2>>;
  using Float4ArrayHandle = typename vtkm::cont::ArrayHandle<Vec<vtkm::Float32, 4>>;

  using IdConstPortal = typename IdArrayHandle::ExecutionTypes<Device>::PortalConst;
  using Float2ArrayPortal = typename Float2ArrayHandle::ExecutionTypes<Device>::Portal;
  using Int2ArrayPortal = typename VecInt2Handle::ExecutionTypes<Device>::Portal;
  using Int8ArrayPortal = typename Int8Handle::ExecutionTypes<Device>::Portal;
  using Float4ArrayPortal = typename Float4ArrayHandle::ExecutionTypes<Device>::Portal;

  Float4ArrayPortal FlatBVH;
  IdConstPortal Parents;
  IdConstPortal LeftChildren;
  IdConstPortal RightChildren;
  vtkm::Int32 LeafCount;
  vtkm::exec::AtomicArrayExecutionObject<vtkm::Int32, Device> Counters;

public:
  VTKM_CONT
  PropagateAABBs(IdArrayHandle& parents,
                 IdArrayHandle& leftChildren,
                 IdArrayHandle& rightChildren,
                 vtkm::Int32 leafCount,
                 Float4ArrayHandle flatBVH,
                 const vtkm::cont::AtomicArray<vtkm::Int32>& counters)
    : Parents(parents.PrepareForInput(Device()))
    , LeftChildren(leftChildren.PrepareForInput(Device()))
    , RightChildren(rightChildren.PrepareForInput(Device()))
    , LeafCount(leafCount)
    , Counters(counters.PrepareForExecution(Device()))

  {
    this->FlatBVH = flatBVH.PrepareForOutput((LeafCount - 1) * 4, Device());
  }
  using ControlSignature = void(WholeArrayIn,
                                WholeArrayIn,
                                WholeArrayIn,
                                WholeArrayIn,
                                WholeArrayIn,
                                WholeArrayIn,
                                WholeArrayIn);
  using ExecutionSignature = void(WorkIndex, _1, _2, _3, _4, _5, _6, _7);

  template <typename InputPortalType, typename OffsetPortalType>
  VTKM_EXEC_CONT void operator()(const vtkm::Id workIndex,
                                 const InputPortalType& xmin,
                                 const InputPortalType& ymin,
                                 const InputPortalType& zmin,
                                 const InputPortalType& xmax,
                                 const InputPortalType& ymax,
                                 const InputPortalType& zmax,
                                 const OffsetPortalType& leafOffsets) const
  {
    //move up into the inner nodes
    vtkm::Id currentNode = LeafCount - 1 + workIndex;
    vtkm::Vec<vtkm::Id, 2> childVector;
    while (currentNode != 0)
    {
      currentNode = Parents.Get(currentNode);

      vtkm::Int32 oldCount = Counters.Add(currentNode, 1);
      if (oldCount == 0)
        return;
      vtkm::Id currentNodeOffset = currentNode * 4;
      childVector[0] = LeftChildren.Get(currentNode);
      childVector[1] = RightChildren.Get(currentNode);
      if (childVector[0] > (LeafCount - 2))
      {
        //our left child is a leaf, so just grab the AABB
        //and set it in the current node
        childVector[0] = childVector[0] - LeafCount + 1;

        vtkm::Vec<vtkm::Float32, 4>
          first4Vec; // = FlatBVH.Get(currentNode); only this one needs effects this

        first4Vec[0] = xmin.Get(childVector[0]);
        first4Vec[1] = ymin.Get(childVector[0]);
        first4Vec[2] = zmin.Get(childVector[0]);
        first4Vec[3] = xmax.Get(childVector[0]);
        FlatBVH.Set(currentNodeOffset, first4Vec);

        vtkm::Vec<vtkm::Float32, 4> second4Vec = FlatBVH.Get(currentNodeOffset + 1);
        second4Vec[0] = ymax.Get(childVector[0]);
        second4Vec[1] = zmax.Get(childVector[0]);
        FlatBVH.Set(currentNodeOffset + 1, second4Vec);
        // set index to leaf
        vtkm::Id leafIndex = leafOffsets.Get(childVector[0]);
        childVector[0] = -(leafIndex + 1);
      }
      else
      {
        //our left child is an inner node, so gather
        //both AABBs in the child and join them for
        //the current node left AABB.
        vtkm::Id child = childVector[0] * 4;

        vtkm::Vec<vtkm::Float32, 4> cFirst4Vec = FlatBVH.Get(child);
        vtkm::Vec<vtkm::Float32, 4> cSecond4Vec = FlatBVH.Get(child + 1);
        vtkm::Vec<vtkm::Float32, 4> cThird4Vec = FlatBVH.Get(child + 2);

        cFirst4Vec[0] = vtkm::Min(cFirst4Vec[0], cSecond4Vec[2]);
        cFirst4Vec[1] = vtkm::Min(cFirst4Vec[1], cSecond4Vec[3]);
        cFirst4Vec[2] = vtkm::Min(cFirst4Vec[2], cThird4Vec[0]);
        cFirst4Vec[3] = vtkm::Max(cFirst4Vec[3], cThird4Vec[1]);
        FlatBVH.Set(currentNodeOffset, cFirst4Vec);

        vtkm::Vec<vtkm::Float32, 4> second4Vec = FlatBVH.Get(currentNodeOffset + 1);
        second4Vec[0] = vtkm::Max(cSecond4Vec[0], cThird4Vec[2]);
        second4Vec[1] = vtkm::Max(cSecond4Vec[1], cThird4Vec[3]);

        FlatBVH.Set(currentNodeOffset + 1, second4Vec);
      }

      if (childVector[1] > (LeafCount - 2))
      {
        //our right child is a leaf, so just grab the AABB
        //and set it in the current node
        childVector[1] = childVector[1] - LeafCount + 1;


        vtkm::Vec<vtkm::Float32, 4> second4Vec = FlatBVH.Get(currentNodeOffset + 1);

        second4Vec[2] = xmin.Get(childVector[1]);
        second4Vec[3] = ymin.Get(childVector[1]);
        FlatBVH.Set(currentNodeOffset + 1, second4Vec);

        vtkm::Vec<vtkm::Float32, 4> third4Vec;
        third4Vec[0] = zmin.Get(childVector[1]);
        third4Vec[1] = xmax.Get(childVector[1]);
        third4Vec[2] = ymax.Get(childVector[1]);
        third4Vec[3] = zmax.Get(childVector[1]);
        FlatBVH.Set(currentNodeOffset + 2, third4Vec);

        // set index to leaf
        vtkm::Id leafIndex = leafOffsets.Get(childVector[1]);
        childVector[1] = -(leafIndex + 1);
      }
      else
      {
        //our left child is an inner node, so gather
        //both AABBs in the child and join them for
        //the current node left AABB.
        vtkm::Id child = childVector[1] * 4;

        vtkm::Vec<vtkm::Float32, 4> cFirst4Vec = FlatBVH.Get(child);
        vtkm::Vec<vtkm::Float32, 4> cSecond4Vec = FlatBVH.Get(child + 1);
        vtkm::Vec<vtkm::Float32, 4> cThird4Vec = FlatBVH.Get(child + 2);

        vtkm::Vec<vtkm::Float32, 4> second4Vec = FlatBVH.Get(currentNodeOffset + 1);
        second4Vec[2] = vtkm::Min(cFirst4Vec[0], cSecond4Vec[2]);
        second4Vec[3] = vtkm::Min(cFirst4Vec[1], cSecond4Vec[3]);
        FlatBVH.Set(currentNodeOffset + 1, second4Vec);

        cThird4Vec[0] = vtkm::Min(cFirst4Vec[2], cThird4Vec[0]);
        cThird4Vec[1] = vtkm::Max(cFirst4Vec[3], cThird4Vec[1]);
        cThird4Vec[2] = vtkm::Max(cSecond4Vec[0], cThird4Vec[2]);
        cThird4Vec[3] = vtkm::Max(cSecond4Vec[1], cThird4Vec[3]);
        FlatBVH.Set(currentNodeOffset + 2, cThird4Vec);
      }
      vtkm::Vec<vtkm::Float32, 4> fourth4Vec;
      vtkm::Int32 leftChild =
        static_cast<vtkm::Int32>((childVector[0] >= 0) ? childVector[0] * 4 : childVector[0]);
      memcpy(&fourth4Vec[0], &leftChild, 4);
      vtkm::Int32 rightChild =
        static_cast<vtkm::Int32>((childVector[1] >= 0) ? childVector[1] * 4 : childVector[1]);
      memcpy(&fourth4Vec[1], &rightChild, 4);
      FlatBVH.Set(currentNodeOffset + 3, fourth4Vec);
    }
  }
}; //class PropagateAABBs

template <typename Device>
class LinearBVHBuilder::TreeBuilder : public vtkm::worklet::WorkletMapField
{
public:
  using UIntArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::UInt32>;
  using IdArrayHandle = typename vtkm::cont::ArrayHandle<vtkm::Id>;
  using UIntPortalType = typename UIntArrayHandle::ExecutionTypes<Device>::PortalConst;
  using IdPortalType = typename IdArrayHandle::ExecutionTypes<Device>::Portal;

private:
  UIntPortalType MortonCodePortal;
  IdPortalType ParentPortal;
  vtkm::Id LeafCount;
  vtkm::Id InnerCount;
  //TODO: get intrinsic support
  VTKM_EXEC
  inline vtkm::Int32 CountLeadingZeros(vtkm::UInt32& x) const
  {
    vtkm::UInt32 y;
    vtkm::UInt32 n = 32;
    y = x >> 16;
    if (y != 0)
    {
      n = n - 16;
      x = y;
    }
    y = x >> 8;
    if (y != 0)
    {
      n = n - 8;
      x = y;
    }
    y = x >> 4;
    if (y != 0)
    {
      n = n - 4;
      x = y;
    }
    y = x >> 2;
    if (y != 0)
    {
      n = n - 2;
      x = y;
    }
    y = x >> 1;
    if (y != 0)
      return vtkm::Int32(n - 2);
    return vtkm::Int32(n - x);
  }

  // returns the count of largest shared prefix between
  // two morton codes. Ties are broken by the indexes
  // a and b.
  //
  // returns count of the largest binary prefix

  VTKM_EXEC
  inline vtkm::Int32 delta(const vtkm::Int32& a, const vtkm::Int32& b) const
  {
    bool tie = false;
    bool outOfRange = (b < 0 || b > LeafCount - 1);
    //still make the call but with a valid adderss
    vtkm::Int32 bb = (outOfRange) ? 0 : b;
    vtkm::UInt32 aCode = MortonCodePortal.Get(a);
    vtkm::UInt32 bCode = MortonCodePortal.Get(bb);
    //use xor to find where they differ
    vtkm::UInt32 exOr = aCode ^ bCode;
    tie = (exOr == 0);
    //break the tie, a and b must always differ
    exOr = tie ? vtkm::UInt32(a) ^ vtkm::UInt32(bb) : exOr;
    vtkm::Int32 count = CountLeadingZeros(exOr);
    if (tie)
      count += 32;
    count = (outOfRange) ? -1 : count;
    return count;
  }

public:
  VTKM_CONT
  TreeBuilder(const UIntArrayHandle& mortonCodesHandle,
              IdArrayHandle& parentHandle,
              const vtkm::Id& leafCount)
    : MortonCodePortal(mortonCodesHandle.PrepareForInput(Device()))
    , LeafCount(leafCount)
  {
    InnerCount = LeafCount - 1;
    this->ParentPortal = parentHandle.PrepareForOutput(InnerCount + LeafCount, Device());
  }
  using ControlSignature = void(FieldOut, FieldOut);
  using ExecutionSignature = void(WorkIndex, _1, _2);
  VTKM_EXEC
  void operator()(const vtkm::Id& index, vtkm::Id& leftChild, vtkm::Id& rightChild) const
  {
    vtkm::Int32 idx = vtkm::Int32(index);
    //something = MortonCodePortal.Get(index) + 1;
    //determine range direction
    vtkm::Int32 d = 0 > (delta(idx, idx + 1) - delta(idx, idx - 1)) ? -1 : 1;

    //find upper bound for the length of the range
    vtkm::Int32 minDelta = delta(idx, idx - d);
    vtkm::Int32 lMax = 2;
    while (delta(idx, idx + lMax * d) > minDelta)
      lMax *= 2;

    //binary search to find the lower bound
    vtkm::Int32 l = 0;
    for (int t = lMax / 2; t >= 1; t /= 2)
    {
      if (delta(idx, idx + (l + t) * d) > minDelta)
        l += t;
    }

    vtkm::Int32 j = idx + l * d;
    vtkm::Int32 deltaNode = delta(idx, j);
    vtkm::Int32 s = 0;
    vtkm::Float32 divFactor = 2.f;
    //find the split position using a binary search
    for (vtkm::Int32 t = (vtkm::Int32)ceil(vtkm::Float32(l) / divFactor);;
         divFactor *= 2, t = (vtkm::Int32)ceil(vtkm::Float32(l) / divFactor))
    {
      if (delta(idx, idx + (s + t) * d) > deltaNode)
      {
        s += t;
      }

      if (t == 1)
        break;
    }

    vtkm::Int32 split = idx + s * d + vtkm::Min(d, 0);
    //assign parent/child pointers
    if (vtkm::Min(idx, j) == split)
    {
      //leaf
      ParentPortal.Set(split + InnerCount, idx);
      leftChild = split + InnerCount;
    }
    else
    {
      //inner node
      ParentPortal.Set(split, idx);
      leftChild = split;
    }


    if (vtkm::Max(idx, j) == split + 1)
    {
      //leaf
      ParentPortal.Set(split + InnerCount + 1, idx);
      rightChild = split + InnerCount + 1;
    }
    else
    {
      ParentPortal.Set(split + 1, idx);
      rightChild = split + 1;
    }
  }
}; // class TreeBuilder

template <typename Device>
VTKM_CONT void LinearBVHBuilder::SortAABBS(BVHData& bvh, Device device, bool singleAABB)
{
  vtkm::worklet::Invoker invoke(device);

  //create array of indexes to be sorted with morton codes
  vtkm::cont::ArrayHandle<vtkm::Id> iterator;
  iterator.PrepareForOutput(bvh.GetNumberOfPrimitives(), device);
  invoke(CountingIterator{}, iterator);


  //sort the morton codes

  vtkm::cont::DeviceAdapterAlgorithm<Device>::SortByKey(bvh.mortonCodes, iterator);

  vtkm::Id arraySize = bvh.GetNumberOfPrimitives();
  vtkm::cont::ArrayHandle<vtkm::Float32> temp1;
  vtkm::cont::ArrayHandle<vtkm::Float32> temp2;


  //tempStorage = new vtkm::cont::ArrayHandle<vtkm::Float32>();
  //xmins
  invoke(GatherFloat32<Device>{ bvh.AABB.xmins, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.xmins;
  bvh.AABB.xmins = temp1;
  temp1 = temp2;
  //ymins
  invoke(GatherFloat32<Device>{ bvh.AABB.ymins, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.ymins;
  bvh.AABB.ymins = temp1;
  temp1 = temp2;
  //zmins
  invoke(GatherFloat32<Device>{ bvh.AABB.zmins, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.zmins;
  bvh.AABB.zmins = temp1;
  temp1 = temp2;
  //xmaxs
  invoke(GatherFloat32<Device>{ bvh.AABB.xmaxs, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.xmaxs;
  bvh.AABB.xmaxs = temp1;
  temp1 = temp2;
  //ymaxs
  invoke(GatherFloat32<Device>{ bvh.AABB.ymaxs, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.ymaxs;
  bvh.AABB.ymaxs = temp1;
  temp1 = temp2;
  //zmaxs
  invoke(GatherFloat32<Device>{ bvh.AABB.zmaxs, temp1, arraySize }, iterator);

  temp2 = bvh.AABB.zmaxs;
  bvh.AABB.zmaxs = temp1;
  temp1 = temp2;

  // Create the leaf references
  bvh.leafs.PrepareForOutput(arraySize * 2, Device());
  // we only actually have a single primitive, but the algorithm
  // requires 2. Make sure they both point to the original
  // primitive
  if (singleAABB)
  {
    auto iterPortal = iterator.GetPortalControl();
    for (int i = 0; i < 2; ++i)
    {
      iterPortal.Set(i, 0);
    }
  }
  invoke(CreateLeafs{}, iterator, bvh.leafs);

} // method SortAABB

// Adding this as a template parameter to allow restricted types and
// storage for dynamic coordinate system to limit crazy code bloat and
// compile times.
//
template <typename Device>
VTKM_CONT void LinearBVHBuilder::RunOnDevice(LinearBVH& linearBVH, Device device)
{
  vtkm::worklet::Invoker invoke(device);

  Logger* logger = Logger::GetInstance();
  logger->OpenLogEntry("bvh_constuct");

  vtkm::cont::Timer constructTimer{ Device() };
  constructTimer.Start();
  //
  //
  // This algorithm needs at least 2 AABBs
  //
  bool singleAABB = false;
  vtkm::Id numberOfAABBs = linearBVH.GetNumberOfAABBs();
  if (numberOfAABBs == 1)
  {
    numberOfAABBs = 2;
    singleAABB = true;
    vtkm::Float32 xmin = linearBVH.AABB.xmins.GetPortalControl().Get(0);
    vtkm::Float32 ymin = linearBVH.AABB.ymins.GetPortalControl().Get(0);
    vtkm::Float32 zmin = linearBVH.AABB.zmins.GetPortalControl().Get(0);
    vtkm::Float32 xmax = linearBVH.AABB.xmaxs.GetPortalControl().Get(0);
    vtkm::Float32 ymax = linearBVH.AABB.ymaxs.GetPortalControl().Get(0);
    vtkm::Float32 zmax = linearBVH.AABB.zmaxs.GetPortalControl().Get(0);

    linearBVH.AABB.xmins.Allocate(2);
    linearBVH.AABB.ymins.Allocate(2);
    linearBVH.AABB.zmins.Allocate(2);
    linearBVH.AABB.xmaxs.Allocate(2);
    linearBVH.AABB.ymaxs.Allocate(2);
    linearBVH.AABB.zmaxs.Allocate(2);
    for (int i = 0; i < 2; ++i)
    {
      linearBVH.AABB.xmins.GetPortalControl().Set(i, xmin);
      linearBVH.AABB.ymins.GetPortalControl().Set(i, ymin);
      linearBVH.AABB.zmins.GetPortalControl().Set(i, zmin);
      linearBVH.AABB.xmaxs.GetPortalControl().Set(i, xmax);
      linearBVH.AABB.ymaxs.GetPortalControl().Set(i, ymax);
      linearBVH.AABB.zmaxs.GetPortalControl().Set(i, zmax);
    }
  }


  logger->AddLogData("bvh_num_aabbs", numberOfAABBs);

  const vtkm::Id numBBoxes = numberOfAABBs;
  BVHData bvh(numBBoxes, linearBVH.GetAABBs(), device);


  vtkm::cont::Timer timer{ Device() };
  timer.Start();
  // Find the extent of all bounding boxes to generate normalization for morton codes
  vtkm::Vec<vtkm::Float32, 3> minExtent(vtkm::Infinity32(), vtkm::Infinity32(), vtkm::Infinity32());
  vtkm::Vec<vtkm::Float32, 3> maxExtent(
    vtkm::NegativeInfinity32(), vtkm::NegativeInfinity32(), vtkm::NegativeInfinity32());
  maxExtent[0] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.xmaxs, maxExtent[0], MaxValue());
  maxExtent[1] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.ymaxs, maxExtent[1], MaxValue());
  maxExtent[2] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.zmaxs, maxExtent[2], MaxValue());
  minExtent[0] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.xmins, minExtent[0], MinValue());
  minExtent[1] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.ymins, minExtent[1], MinValue());
  minExtent[2] =
    vtkm::cont::DeviceAdapterAlgorithm<Device>::Reduce(bvh.AABB.zmins, minExtent[2], MinValue());

  linearBVH.TotalBounds.X.Min = minExtent[0];
  linearBVH.TotalBounds.X.Max = maxExtent[0];
  linearBVH.TotalBounds.Y.Min = minExtent[1];
  linearBVH.TotalBounds.Y.Max = maxExtent[1];
  linearBVH.TotalBounds.Z.Min = minExtent[2];
  linearBVH.TotalBounds.Z.Max = maxExtent[2];

  vtkm::Float64 time = timer.GetElapsedTime();
  logger->AddLogData("calc_extents", time);
  timer.Start();

  vtkm::Vec<vtkm::Float32, 3> deltaExtent = maxExtent - minExtent;
  vtkm::Vec<vtkm::Float32, 3> inverseExtent;
  for (int i = 0; i < 3; ++i)
  {
    inverseExtent[i] = (deltaExtent[i] == 0.f) ? 0 : 1.f / deltaExtent[i];
  }

  //Generate the morton codes
  invoke(MortonCodeAABB{ inverseExtent, minExtent },
         bvh.AABB.xmins,
         bvh.AABB.ymins,
         bvh.AABB.zmins,
         bvh.AABB.xmaxs,
         bvh.AABB.ymaxs,
         bvh.AABB.zmaxs,
         bvh.mortonCodes);

  time = timer.GetElapsedTime();
  logger->AddLogData("morton_codes", time);
  timer.Start();

  linearBVH.Allocate(bvh.GetNumberOfPrimitives(), device);

  SortAABBS(bvh, device, singleAABB);

  time = timer.GetElapsedTime();
  logger->AddLogData("sort_aabbs", time);
  timer.Start();

  invoke(TreeBuilder<Device>{ bvh.mortonCodes, bvh.parent, bvh.GetNumberOfPrimitives() },
         bvh.leftChild,
         bvh.rightChild);

  time = timer.GetElapsedTime();
  logger->AddLogData("build_tree", time);
  timer.Start();

  const vtkm::Int32 primitiveCount = vtkm::Int32(bvh.GetNumberOfPrimitives());

  vtkm::cont::ArrayHandle<vtkm::Int32> counters;
  counters.PrepareForOutput(bvh.GetNumberOfPrimitives() - 1, device);

  vtkm::cont::ArrayHandleConstant<vtkm::Int32> zero(0, bvh.GetNumberOfPrimitives() - 1);
  vtkm::cont::DeviceAdapterAlgorithm<Device>::Copy(zero, counters);

  vtkm::cont::AtomicArray<vtkm::Int32> atomicCounters(counters);


  PropagateAABBs<Device> propagateWorklet(
    bvh.parent, bvh.leftChild, bvh.rightChild, primitiveCount, linearBVH.FlatBVH, atomicCounters);
  invoke(propagateWorklet,
         bvh.AABB.xmins,
         bvh.AABB.ymins,
         bvh.AABB.zmins,
         bvh.AABB.xmaxs,
         bvh.AABB.ymaxs,
         bvh.AABB.zmaxs,
         bvh.leafOffsets);

  linearBVH.Leafs = bvh.leafs;
  time = timer.GetElapsedTime();
  logger->AddLogData("propagate_aabbs", time);

  time = constructTimer.GetElapsedTime();
  logger->CloseLogEntry(time);
}
} //namespace detail

struct LinearBVH::ConstructFunctor
{
  LinearBVH* Self;
  VTKM_CONT
  ConstructFunctor(LinearBVH* self)
    : Self(self)
  {
  }
  template <typename Device>
  bool operator()(Device)
  {
    Self->ConstructOnDevice(Device());
    return true;
  }
};

LinearBVH::LinearBVH()
  : IsConstructed(false)
  , CanConstruct(false){};

VTKM_CONT
LinearBVH::LinearBVH(AABBs& aabbs)
  : AABB(aabbs)
  , IsConstructed(false)
  , CanConstruct(true)
{
}

VTKM_CONT
LinearBVH::LinearBVH(const LinearBVH& other)
  : AABB(other.AABB)
  , FlatBVH(other.FlatBVH)
  , Leafs(other.Leafs)
  , LeafCount(other.LeafCount)
  , IsConstructed(other.IsConstructed)
  , CanConstruct(other.CanConstruct)
{
}
template <typename Device>
VTKM_CONT void LinearBVH::Allocate(const vtkm::Id& leafCount, Device deviceAdapter)
{
  LeafCount = leafCount;
  FlatBVH.PrepareForOutput((leafCount - 1) * 4, deviceAdapter);
}

void LinearBVH::Construct()
{
  if (IsConstructed)
    return;
  if (!CanConstruct)
    throw vtkm::cont::ErrorBadValue(
      "Linear BVH: coordinates and triangles must be set before calling construct!");

  ConstructFunctor functor(this);
  vtkm::cont::TryExecute(functor);
  IsConstructed = true;
}

VTKM_CONT
void LinearBVH::SetData(AABBs& aabbs)
{
  AABB = aabbs;
  IsConstructed = false;
  CanConstruct = true;
}

template <typename Device>
void LinearBVH::ConstructOnDevice(Device device)
{
  Logger* logger = Logger::GetInstance();
  vtkm::cont::Timer timer{ Device() };
  timer.Start();
  logger->OpenLogEntry("bvh");
  if (!CanConstruct)
    throw vtkm::cont::ErrorBadValue(
      "Linear BVH: coordinates and triangles must be set before calling construct!");
  if (!IsConstructed)
  {
    detail::LinearBVHBuilder builder;
    builder.RunOnDevice(*this, device);
    IsConstructed = true;
  }

  vtkm::Float64 time = timer.GetElapsedTime();
  logger->CloseLogEntry(time);
}

// explicitly export
template VTKM_RENDERING_EXPORT void LinearBVH::ConstructOnDevice<
  vtkm::cont::DeviceAdapterTagSerial>(vtkm::cont::DeviceAdapterTagSerial);
#ifdef VTKM_ENABLE_TBB
template VTKM_RENDERING_EXPORT void LinearBVH::ConstructOnDevice<vtkm::cont::DeviceAdapterTagTBB>(
  vtkm::cont::DeviceAdapterTagTBB);
#endif
#ifdef VTKM_ENABLE_OPENMP
template VTKM_CONT_EXPORT void LinearBVH::ConstructOnDevice<vtkm::cont::DeviceAdapterTagOpenMP>(
  vtkm::cont::DeviceAdapterTagOpenMP);
#endif
#ifdef VTKM_ENABLE_CUDA
template VTKM_RENDERING_EXPORT void LinearBVH::ConstructOnDevice<vtkm::cont::DeviceAdapterTagCuda>(
  vtkm::cont::DeviceAdapterTagCuda);
#endif

VTKM_CONT
bool LinearBVH::GetIsConstructed() const
{
  return IsConstructed;
}

vtkm::Id LinearBVH::GetNumberOfAABBs() const
{
  return AABB.xmins.GetPortalConstControl().GetNumberOfValues();
}

AABBs& LinearBVH::GetAABBs()
{
  return AABB;
}
}
}
} // namespace vtkm::rendering::raytracing
