marchingCubes_kernel.cu

/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
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#ifndef _MARCHING_CUBES_KERNEL_CU_
#define _MARCHING_CUBES_KERNEL_CU_

#include <stdio.h>
#include <string.h>
#include <helper_cuda.h>  // includes for helper CUDA functions
#include <helper_math.h>
#include <cuda_runtime_api.h>
#include <thrust/device_vector.h>
#include <thrust/scan.h>

#include "defines.h"
#include "tables.h"

// textures containing look-up tables
cudaTextureObject_t triTex;
cudaTextureObject_t numVertsTex;

// volume data
cudaTextureObject_t volumeTex;

extern "C" void allocateTextures(uint **d_edgeTable, uint **d_triTable,
                                 uint **d_numVertsTable) {
  checkCudaErrors(cudaMalloc((void **)d_edgeTable, 256 * sizeof(uint)));
  checkCudaErrors(cudaMemcpy((void *)*d_edgeTable, (void *)edgeTable,
                             256 * sizeof(uint), cudaMemcpyHostToDevice));
  cudaChannelFormatDesc channelDesc =
      cudaCreateChannelDesc(32, 0, 0, 0, cudaChannelFormatKindUnsigned);

  checkCudaErrors(cudaMalloc((void **)d_triTable, 256 * 16 * sizeof(uint)));
  checkCudaErrors(cudaMemcpy((void *)*d_triTable, (void *)triTable,
                             256 * 16 * sizeof(uint), cudaMemcpyHostToDevice));

  cudaResourceDesc texRes;
  memset(&texRes, 0, sizeof(cudaResourceDesc));

  texRes.resType = cudaResourceTypeLinear;
  texRes.res.linear.devPtr = *d_triTable;
  texRes.res.linear.sizeInBytes = 256 * 16 * sizeof(uint);
  texRes.res.linear.desc = channelDesc;

  cudaTextureDesc texDescr;
  memset(&texDescr, 0, sizeof(cudaTextureDesc));

  texDescr.normalizedCoords = false;
  texDescr.filterMode = cudaFilterModePoint;
  texDescr.addressMode[0] = cudaAddressModeClamp;
  texDescr.readMode = cudaReadModeElementType;

  checkCudaErrors(cudaCreateTextureObject(&triTex, &texRes, &texDescr, NULL));

  checkCudaErrors(cudaMalloc((void **)d_numVertsTable, 256 * sizeof(uint)));
  checkCudaErrors(cudaMemcpy((void *)*d_numVertsTable, (void *)numVertsTable,
                             256 * sizeof(uint), cudaMemcpyHostToDevice));

  memset(&texRes, 0, sizeof(cudaResourceDesc));

  texRes.resType = cudaResourceTypeLinear;
  texRes.res.linear.devPtr = *d_numVertsTable;
  texRes.res.linear.sizeInBytes = 256 * sizeof(uint);
  texRes.res.linear.desc = channelDesc;

  memset(&texDescr, 0, sizeof(cudaTextureDesc));

  texDescr.normalizedCoords = false;
  texDescr.filterMode = cudaFilterModePoint;
  texDescr.addressMode[0] = cudaAddressModeClamp;
  texDescr.readMode = cudaReadModeElementType;

  checkCudaErrors(
      cudaCreateTextureObject(&numVertsTex, &texRes, &texDescr, NULL));
}

extern "C" void createVolumeTexture(uchar *d_volume, size_t buffSize) {
  cudaResourceDesc texRes;
  memset(&texRes, 0, sizeof(cudaResourceDesc));

  texRes.resType = cudaResourceTypeLinear;
  texRes.res.linear.devPtr = d_volume;
  texRes.res.linear.sizeInBytes = buffSize;
  texRes.res.linear.desc =
      cudaCreateChannelDesc(8, 0, 0, 0, cudaChannelFormatKindUnsigned);

  cudaTextureDesc texDescr;
  memset(&texDescr, 0, sizeof(cudaTextureDesc));

  texDescr.normalizedCoords = false;
  texDescr.filterMode = cudaFilterModePoint;
  texDescr.addressMode[0] = cudaAddressModeClamp;
  texDescr.readMode = cudaReadModeNormalizedFloat;

  checkCudaErrors(
      cudaCreateTextureObject(&volumeTex, &texRes, &texDescr, NULL));
}

extern "C" void destroyAllTextureObjects() {
  checkCudaErrors(cudaDestroyTextureObject(triTex));
  checkCudaErrors(cudaDestroyTextureObject(numVertsTex));
  checkCudaErrors(cudaDestroyTextureObject(volumeTex));
}

// an interesting field function
__device__ float tangle(float x, float y, float z) {
  x *= 3.0f;
  y *= 3.0f;
  z *= 3.0f;
  return (x * x * x * x - 5.0f * x * x + y * y * y * y - 5.0f * y * y +
          z * z * z * z - 5.0f * z * z + 11.8f) * 0.2f + 0.5f;
}

// evaluate field function at point
__device__ float fieldFunc(float3 p) { return tangle(p.x, p.y, p.z); }

// evaluate field function at a point
// returns value and gradient in float4
__device__ float4 fieldFunc4(float3 p) {
  float v = tangle(p.x, p.y, p.z);
  const float d = 0.001f;
  float dx = tangle(p.x + d, p.y, p.z) - v;
  float dy = tangle(p.x, p.y + d, p.z) - v;
  float dz = tangle(p.x, p.y, p.z + d) - v;
  return make_float4(dx, dy, dz, v);
}

// sample volume data set at a point
__device__ float sampleVolume(cudaTextureObject_t volumeTex, uchar *data,
                              uint3 p, uint3 gridSize) {
  p.x = min(p.x, gridSize.x - 1);
  p.y = min(p.y, gridSize.y - 1);
  p.z = min(p.z, gridSize.z - 1);
  uint i = (p.z * gridSize.x * gridSize.y) + (p.y * gridSize.x) + p.x;
  //    return (float) data[i] / 255.0f;
  return tex1Dfetch<float>(volumeTex, i);
}

// compute position in 3d grid from 1d index
// only works for power of 2 sizes
__device__ uint3 calcGridPos(uint i, uint3 gridSizeShift, uint3 gridSizeMask) {
  uint3 gridPos;
  gridPos.x = i & gridSizeMask.x;
  gridPos.y = (i >> gridSizeShift.y) & gridSizeMask.y;
  gridPos.z = (i >> gridSizeShift.z) & gridSizeMask.z;
  return gridPos;
}

// classify voxel based on number of vertices it will generate
// one thread per voxel
__global__ void classifyVoxel(uint *voxelVerts, uint *voxelOccupied,
                              uchar *volume, uint3 gridSize,
                              uint3 gridSizeShift, uint3 gridSizeMask,
                              uint numVoxels, float3 voxelSize, float isoValue,
                              cudaTextureObject_t numVertsTex,
                              cudaTextureObject_t volumeTex) {
  uint blockId = __mul24(blockIdx.y, gridDim.x) + blockIdx.x;
  uint i = __mul24(blockId, blockDim.x) + threadIdx.x;

  uint3 gridPos = calcGridPos(i, gridSizeShift, gridSizeMask);

// read field values at neighbouring grid vertices
#if SAMPLE_VOLUME
  float field[8];
  field[0] = sampleVolume(volumeTex, volume, gridPos, gridSize);
  field[1] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 0, 0), gridSize);
  field[2] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 1, 0), gridSize);
  field[3] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 1, 0), gridSize);
  field[4] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 0, 1), gridSize);
  field[5] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 0, 1), gridSize);
  field[6] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 1, 1), gridSize);
  field[7] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 1, 1), gridSize);
#else
  float3 p;
  p.x = -1.0f + (gridPos.x * voxelSize.x);
  p.y = -1.0f + (gridPos.y * voxelSize.y);
  p.z = -1.0f + (gridPos.z * voxelSize.z);

  float field[8];
  field[0] = fieldFunc(p);
  field[1] = fieldFunc(p + make_float3(voxelSize.x, 0, 0));
  field[2] = fieldFunc(p + make_float3(voxelSize.x, voxelSize.y, 0));
  field[3] = fieldFunc(p + make_float3(0, voxelSize.y, 0));
  field[4] = fieldFunc(p + make_float3(0, 0, voxelSize.z));
  field[5] = fieldFunc(p + make_float3(voxelSize.x, 0, voxelSize.z));
  field[6] = fieldFunc(p + make_float3(voxelSize.x, voxelSize.y, voxelSize.z));
  field[7] = fieldFunc(p + make_float3(0, voxelSize.y, voxelSize.z));
#endif

  // calculate flag indicating if each vertex is inside or outside isosurface
  uint cubeindex;
  cubeindex = uint(field[0] < isoValue);
  cubeindex += uint(field[1] < isoValue) * 2;
  cubeindex += uint(field[2] < isoValue) * 4;
  cubeindex += uint(field[3] < isoValue) * 8;
  cubeindex += uint(field[4] < isoValue) * 16;
  cubeindex += uint(field[5] < isoValue) * 32;
  cubeindex += uint(field[6] < isoValue) * 64;
  cubeindex += uint(field[7] < isoValue) * 128;

  // read number of vertices from texture
  uint numVerts = tex1Dfetch<uint>(numVertsTex, cubeindex);

  if (i < numVoxels) {
    voxelVerts[i] = numVerts;
    voxelOccupied[i] = (numVerts > 0);
  }
}

extern "C" void launch_classifyVoxel(dim3 grid, dim3 threads, uint *voxelVerts,
                                     uint *voxelOccupied, uchar *volume,
                                     uint3 gridSize, uint3 gridSizeShift,
                                     uint3 gridSizeMask, uint numVoxels,
                                     float3 voxelSize, float isoValue) {
  // calculate number of vertices need per voxel
  classifyVoxel<<<grid, threads>>>(voxelVerts, voxelOccupied, volume, gridSize,
                                   gridSizeShift, gridSizeMask, numVoxels,
                                   voxelSize, isoValue, numVertsTex, volumeTex);
  getLastCudaError("classifyVoxel failed");
}

// compact voxel array
__global__ void compactVoxels(uint *compactedVoxelArray, uint *voxelOccupied,
                              uint *voxelOccupiedScan, uint numVoxels) {
  uint blockId = __mul24(blockIdx.y, gridDim.x) + blockIdx.x;
  uint i = __mul24(blockId, blockDim.x) + threadIdx.x;

  if (voxelOccupied[i] && (i < numVoxels)) {
    compactedVoxelArray[voxelOccupiedScan[i]] = i;
  }
}

extern "C" void launch_compactVoxels(dim3 grid, dim3 threads,
                                     uint *compactedVoxelArray,
                                     uint *voxelOccupied,
                                     uint *voxelOccupiedScan, uint numVoxels) {
  compactVoxels<<<grid, threads>>>(compactedVoxelArray, voxelOccupied,
                                   voxelOccupiedScan, numVoxels);
  getLastCudaError("compactVoxels failed");
}

// compute interpolated vertex along an edge
__device__ float3 vertexInterp(float isolevel, float3 p0, float3 p1, float f0,
                               float f1) {
  float t = (isolevel - f0) / (f1 - f0);
  return lerp(p0, p1, t);
}

// compute interpolated vertex position and normal along an edge
__device__ void vertexInterp2(float isolevel, float3 p0, float3 p1, float4 f0,
                              float4 f1, float3 &p, float3 &n) {
  float t = (isolevel - f0.w) / (f1.w - f0.w);
  p = lerp(p0, p1, t);
  n.x = lerp(f0.x, f1.x, t);
  n.y = lerp(f0.y, f1.y, t);
  n.z = lerp(f0.z, f1.z, t);
  //    n = normalize(n);
}

// generate triangles for each voxel using marching cubes
// interpolates normals from field function
__global__ void generateTriangles(
    float4 *pos, float4 *norm, uint *compactedVoxelArray, uint *numVertsScanned,
    uint3 gridSize, uint3 gridSizeShift, uint3 gridSizeMask, float3 voxelSize,
    float isoValue, uint activeVoxels, uint maxVerts,
    cudaTextureObject_t triTex, cudaTextureObject_t numVertsTex) {
  uint blockId = __mul24(blockIdx.y, gridDim.x) + blockIdx.x;
  uint i = __mul24(blockId, blockDim.x) + threadIdx.x;

  if (i > activeVoxels - 1) {
    // can't return here because of syncthreads()
    i = activeVoxels - 1;
  }

#if SKIP_EMPTY_VOXELS
  uint voxel = compactedVoxelArray[i];
#else
  uint voxel = i;
#endif

  // compute position in 3d grid
  uint3 gridPos = calcGridPos(voxel, gridSizeShift, gridSizeMask);

  float3 p;
  p.x = -1.0f + (gridPos.x * voxelSize.x);
  p.y = -1.0f + (gridPos.y * voxelSize.y);
  p.z = -1.0f + (gridPos.z * voxelSize.z);

  // calculate cell vertex positions
  float3 v[8];
  v[0] = p;
  v[1] = p + make_float3(voxelSize.x, 0, 0);
  v[2] = p + make_float3(voxelSize.x, voxelSize.y, 0);
  v[3] = p + make_float3(0, voxelSize.y, 0);
  v[4] = p + make_float3(0, 0, voxelSize.z);
  v[5] = p + make_float3(voxelSize.x, 0, voxelSize.z);
  v[6] = p + make_float3(voxelSize.x, voxelSize.y, voxelSize.z);
  v[7] = p + make_float3(0, voxelSize.y, voxelSize.z);

  // evaluate field values
  float4 field[8];
  field[0] = fieldFunc4(v[0]);
  field[1] = fieldFunc4(v[1]);
  field[2] = fieldFunc4(v[2]);
  field[3] = fieldFunc4(v[3]);
  field[4] = fieldFunc4(v[4]);
  field[5] = fieldFunc4(v[5]);
  field[6] = fieldFunc4(v[6]);
  field[7] = fieldFunc4(v[7]);

  // recalculate flag
  // (this is faster than storing it in global memory)
  uint cubeindex;
  cubeindex = uint(field[0].w < isoValue);
  cubeindex += uint(field[1].w < isoValue) * 2;
  cubeindex += uint(field[2].w < isoValue) * 4;
  cubeindex += uint(field[3].w < isoValue) * 8;
  cubeindex += uint(field[4].w < isoValue) * 16;
  cubeindex += uint(field[5].w < isoValue) * 32;
  cubeindex += uint(field[6].w < isoValue) * 64;
  cubeindex += uint(field[7].w < isoValue) * 128;

// find the vertices where the surface intersects the cube

#if USE_SHARED
  // use partioned shared memory to avoid using local memory
  __shared__ float3 vertlist[12 * NTHREADS];
  __shared__ float3 normlist[12 * NTHREADS];

  vertexInterp2(isoValue, v[0], v[1], field[0], field[1], vertlist[threadIdx.x],
                normlist[threadIdx.x]);
  vertexInterp2(isoValue, v[1], v[2], field[1], field[2],
                vertlist[threadIdx.x + NTHREADS],
                normlist[threadIdx.x + NTHREADS]);
  vertexInterp2(isoValue, v[2], v[3], field[2], field[3],
                vertlist[threadIdx.x + (NTHREADS * 2)],
                normlist[threadIdx.x + (NTHREADS * 2)]);
  vertexInterp2(isoValue, v[3], v[0], field[3], field[0],
                vertlist[threadIdx.x + (NTHREADS * 3)],
                normlist[threadIdx.x + (NTHREADS * 3)]);
  vertexInterp2(isoValue, v[4], v[5], field[4], field[5],
                vertlist[threadIdx.x + (NTHREADS * 4)],
                normlist[threadIdx.x + (NTHREADS * 4)]);
  vertexInterp2(isoValue, v[5], v[6], field[5], field[6],
                vertlist[threadIdx.x + (NTHREADS * 5)],
                normlist[threadIdx.x + (NTHREADS * 5)]);
  vertexInterp2(isoValue, v[6], v[7], field[6], field[7],
                vertlist[threadIdx.x + (NTHREADS * 6)],
                normlist[threadIdx.x + (NTHREADS * 6)]);
  vertexInterp2(isoValue, v[7], v[4], field[7], field[4],
                vertlist[threadIdx.x + (NTHREADS * 7)],
                normlist[threadIdx.x + (NTHREADS * 7)]);
  vertexInterp2(isoValue, v[0], v[4], field[0], field[4],
                vertlist[threadIdx.x + (NTHREADS * 8)],
                normlist[threadIdx.x + (NTHREADS * 8)]);
  vertexInterp2(isoValue, v[1], v[5], field[1], field[5],
                vertlist[threadIdx.x + (NTHREADS * 9)],
                normlist[threadIdx.x + (NTHREADS * 9)]);
  vertexInterp2(isoValue, v[2], v[6], field[2], field[6],
                vertlist[threadIdx.x + (NTHREADS * 10)],
                normlist[threadIdx.x + (NTHREADS * 10)]);
  vertexInterp2(isoValue, v[3], v[7], field[3], field[7],
                vertlist[threadIdx.x + (NTHREADS * 11)],
                normlist[threadIdx.x + (NTHREADS * 11)]);
  __syncthreads();

#else
  float3 vertlist[12];
  float3 normlist[12];

  vertexInterp2(isoValue, v[0], v[1], field[0], field[1], vertlist[0],
                normlist[0]);
  vertexInterp2(isoValue, v[1], v[2], field[1], field[2], vertlist[1],
                normlist[1]);
  vertexInterp2(isoValue, v[2], v[3], field[2], field[3], vertlist[2],
                normlist[2]);
  vertexInterp2(isoValue, v[3], v[0], field[3], field[0], vertlist[3],
                normlist[3]);

  vertexInterp2(isoValue, v[4], v[5], field[4], field[5], vertlist[4],
                normlist[4]);
  vertexInterp2(isoValue, v[5], v[6], field[5], field[6], vertlist[5],
                normlist[5]);
  vertexInterp2(isoValue, v[6], v[7], field[6], field[7], vertlist[6],
                normlist[6]);
  vertexInterp2(isoValue, v[7], v[4], field[7], field[4], vertlist[7],
                normlist[7]);

  vertexInterp2(isoValue, v[0], v[4], field[0], field[4], vertlist[8],
                normlist[8]);
  vertexInterp2(isoValue, v[1], v[5], field[1], field[5], vertlist[9],
                normlist[9]);
  vertexInterp2(isoValue, v[2], v[6], field[2], field[6], vertlist[10],
                normlist[10]);
  vertexInterp2(isoValue, v[3], v[7], field[3], field[7], vertlist[11],
                normlist[11]);
#endif

  // output triangle vertices
  uint numVerts = tex1Dfetch<uint>(numVertsTex, cubeindex);

  for (int i = 0; i < numVerts; i++) {
    uint edge = tex1Dfetch<uint>(triTex, cubeindex * 16 + i);

    uint index = numVertsScanned[voxel] + i;

    if (index < maxVerts) {
#if USE_SHARED
      pos[index] = make_float4(vertlist[(edge * NTHREADS) + threadIdx.x], 1.0f);
      norm[index] =
          make_float4(normlist[(edge * NTHREADS) + threadIdx.x], 0.0f);
#else
      pos[index] = make_float4(vertlist[edge], 1.0f);
      norm[index] = make_float4(normlist[edge], 0.0f);
#endif
    }
  }
}

extern "C" void launch_generateTriangles(
    dim3 grid, dim3 threads, float4 *pos, float4 *norm,
    uint *compactedVoxelArray, uint *numVertsScanned, uint3 gridSize,
    uint3 gridSizeShift, uint3 gridSizeMask, float3 voxelSize, float isoValue,
    uint activeVoxels, uint maxVerts) {
  generateTriangles<<<grid, NTHREADS>>>(
      pos, norm, compactedVoxelArray, numVertsScanned, gridSize, gridSizeShift,
      gridSizeMask, voxelSize, isoValue, activeVoxels, maxVerts, triTex,
      numVertsTex);
  getLastCudaError("generateTriangles failed");
}

// calculate triangle normal
__device__ float3 calcNormal(float3 *v0, float3 *v1, float3 *v2) {
  float3 edge0 = *v1 - *v0;
  float3 edge1 = *v2 - *v0;
  // note - it's faster to perform normalization in vertex shader rather than
  // here
  return cross(edge0, edge1);
}

// version that calculates flat surface normal for each triangle
__global__ void generateTriangles2(
    float4 *pos, float4 *norm, uint *compactedVoxelArray, uint *numVertsScanned,
    uchar *volume, uint3 gridSize, uint3 gridSizeShift, uint3 gridSizeMask,
    float3 voxelSize, float isoValue, uint activeVoxels, uint maxVerts,
    cudaTextureObject_t triTex, cudaTextureObject_t numVertsTex,
    cudaTextureObject_t volumeTex) {
  uint blockId = __mul24(blockIdx.y, gridDim.x) + blockIdx.x;
  uint i = __mul24(blockId, blockDim.x) + threadIdx.x;

  if (i > activeVoxels - 1) {
    i = activeVoxels - 1;
  }

#if SKIP_EMPTY_VOXELS
  uint voxel = compactedVoxelArray[i];
#else
  uint voxel = i;
#endif

  // compute position in 3d grid
  uint3 gridPos = calcGridPos(voxel, gridSizeShift, gridSizeMask);

  float3 p;
  p.x = -1.0f + (gridPos.x * voxelSize.x);
  p.y = -1.0f + (gridPos.y * voxelSize.y);
  p.z = -1.0f + (gridPos.z * voxelSize.z);

  // calculate cell vertex positions
  float3 v[8];
  v[0] = p;
  v[1] = p + make_float3(voxelSize.x, 0, 0);
  v[2] = p + make_float3(voxelSize.x, voxelSize.y, 0);
  v[3] = p + make_float3(0, voxelSize.y, 0);
  v[4] = p + make_float3(0, 0, voxelSize.z);
  v[5] = p + make_float3(voxelSize.x, 0, voxelSize.z);
  v[6] = p + make_float3(voxelSize.x, voxelSize.y, voxelSize.z);
  v[7] = p + make_float3(0, voxelSize.y, voxelSize.z);

#if SAMPLE_VOLUME
  float field[8];
  field[0] = sampleVolume(volumeTex, volume, gridPos, gridSize);
  field[1] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 0, 0), gridSize);
  field[2] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 1, 0), gridSize);
  field[3] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 1, 0), gridSize);
  field[4] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 0, 1), gridSize);
  field[5] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 0, 1), gridSize);
  field[6] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(1, 1, 1), gridSize);
  field[7] =
      sampleVolume(volumeTex, volume, gridPos + make_uint3(0, 1, 1), gridSize);
#else
  // evaluate field values
  float field[8];
  field[0] = fieldFunc(v[0]);
  field[1] = fieldFunc(v[1]);
  field[2] = fieldFunc(v[2]);
  field[3] = fieldFunc(v[3]);
  field[4] = fieldFunc(v[4]);
  field[5] = fieldFunc(v[5]);
  field[6] = fieldFunc(v[6]);
  field[7] = fieldFunc(v[7]);
#endif

  // recalculate flag
  uint cubeindex;
  cubeindex = uint(field[0] < isoValue);
  cubeindex += uint(field[1] < isoValue) * 2;
  cubeindex += uint(field[2] < isoValue) * 4;
  cubeindex += uint(field[3] < isoValue) * 8;
  cubeindex += uint(field[4] < isoValue) * 16;
  cubeindex += uint(field[5] < isoValue) * 32;
  cubeindex += uint(field[6] < isoValue) * 64;
  cubeindex += uint(field[7] < isoValue) * 128;

// find the vertices where the surface intersects the cube

#if USE_SHARED
  // use shared memory to avoid using local
  __shared__ float3 vertlist[12 * NTHREADS];

  vertlist[threadIdx.x] =
      vertexInterp(isoValue, v[0], v[1], field[0], field[1]);
  vertlist[NTHREADS + threadIdx.x] =
      vertexInterp(isoValue, v[1], v[2], field[1], field[2]);
  vertlist[(NTHREADS * 2) + threadIdx.x] =
      vertexInterp(isoValue, v[2], v[3], field[2], field[3]);
  vertlist[(NTHREADS * 3) + threadIdx.x] =
      vertexInterp(isoValue, v[3], v[0], field[3], field[0]);
  vertlist[(NTHREADS * 4) + threadIdx.x] =
      vertexInterp(isoValue, v[4], v[5], field[4], field[5]);
  vertlist[(NTHREADS * 5) + threadIdx.x] =
      vertexInterp(isoValue, v[5], v[6], field[5], field[6]);
  vertlist[(NTHREADS * 6) + threadIdx.x] =
      vertexInterp(isoValue, v[6], v[7], field[6], field[7]);
  vertlist[(NTHREADS * 7) + threadIdx.x] =
      vertexInterp(isoValue, v[7], v[4], field[7], field[4]);
  vertlist[(NTHREADS * 8) + threadIdx.x] =
      vertexInterp(isoValue, v[0], v[4], field[0], field[4]);
  vertlist[(NTHREADS * 9) + threadIdx.x] =
      vertexInterp(isoValue, v[1], v[5], field[1], field[5]);
  vertlist[(NTHREADS * 10) + threadIdx.x] =
      vertexInterp(isoValue, v[2], v[6], field[2], field[6]);
  vertlist[(NTHREADS * 11) + threadIdx.x] =
      vertexInterp(isoValue, v[3], v[7], field[3], field[7]);
  __syncthreads();
#else

  float3 vertlist[12];

  vertlist[0] = vertexInterp(isoValue, v[0], v[1], field[0], field[1]);
  vertlist[1] = vertexInterp(isoValue, v[1], v[2], field[1], field[2]);
  vertlist[2] = vertexInterp(isoValue, v[2], v[3], field[2], field[3]);
  vertlist[3] = vertexInterp(isoValue, v[3], v[0], field[3], field[0]);

  vertlist[4] = vertexInterp(isoValue, v[4], v[5], field[4], field[5]);
  vertlist[5] = vertexInterp(isoValue, v[5], v[6], field[5], field[6]);
  vertlist[6] = vertexInterp(isoValue, v[6], v[7], field[6], field[7]);
  vertlist[7] = vertexInterp(isoValue, v[7], v[4], field[7], field[4]);

  vertlist[8] = vertexInterp(isoValue, v[0], v[4], field[0], field[4]);
  vertlist[9] = vertexInterp(isoValue, v[1], v[5], field[1], field[5]);
  vertlist[10] = vertexInterp(isoValue, v[2], v[6], field[2], field[6]);
  vertlist[11] = vertexInterp(isoValue, v[3], v[7], field[3], field[7]);
#endif

  // output triangle vertices
  uint numVerts = tex1Dfetch<uint>(numVertsTex, cubeindex);

  for (int i = 0; i < numVerts; i += 3) {
    uint index = numVertsScanned[voxel] + i;

    float3 *v[3];
    uint edge;
    edge = tex1Dfetch<uint>(triTex, (cubeindex * 16) + i);
#if USE_SHARED
    v[0] = &vertlist[(edge * NTHREADS) + threadIdx.x];
#else
    v[0] = &vertlist[edge];
#endif

    edge = tex1Dfetch<uint>(triTex, (cubeindex * 16) + i + 1);
#if USE_SHARED
    v[1] = &vertlist[(edge * NTHREADS) + threadIdx.x];
#else
    v[1] = &vertlist[edge];
#endif

    edge = tex1Dfetch<uint>(triTex, (cubeindex * 16) + i + 2);
#if USE_SHARED
    v[2] = &vertlist[(edge * NTHREADS) + threadIdx.x];
#else
    v[2] = &vertlist[edge];
#endif

    // calculate triangle surface normal
    float3 n = calcNormal(v[0], v[1], v[2]);

    if (index < (maxVerts - 3)) {
      pos[index] = make_float4(*v[0], 1.0f);
      norm[index] = make_float4(n, 0.0f);

      pos[index + 1] = make_float4(*v[1], 1.0f);
      norm[index + 1] = make_float4(n, 0.0f);

      pos[index + 2] = make_float4(*v[2], 1.0f);
      norm[index + 2] = make_float4(n, 0.0f);
    }
  }
}

extern "C" void launch_generateTriangles2(
    dim3 grid, dim3 threads, float4 *pos, float4 *norm,
    uint *compactedVoxelArray, uint *numVertsScanned, uchar *volume,
    uint3 gridSize, uint3 gridSizeShift, uint3 gridSizeMask, float3 voxelSize,
    float isoValue, uint activeVoxels, uint maxVerts) {
  generateTriangles2<<<grid, NTHREADS>>>(
      pos, norm, compactedVoxelArray, numVertsScanned, volume, gridSize,
      gridSizeShift, gridSizeMask, voxelSize, isoValue, activeVoxels, maxVerts,
      triTex, numVertsTex, volumeTex);
  getLastCudaError("generateTriangles2 failed");
}

extern "C" void ThrustScanWrapper(unsigned int *output, unsigned int *input,
                                  unsigned int numElements) {
  thrust::exclusive_scan(thrust::device_ptr<unsigned int>(input),
                         thrust::device_ptr<unsigned int>(input + numElements),
                         thrust::device_ptr<unsigned int>(output));
}

#endif