cuda-samples/Samples/smokeParticles/ParticleSystem_cuda.cu

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/*
This file contains simple wrapper functions that call the CUDA kernels
*/
#define HELPERGL_EXTERN_GL_FUNC_IMPLEMENTATION
#include <helper_gl.h>
#include <helper_cuda.h>
#include <cstdlib>
#include <cstdio>
#include <string.h>
#include <cuda_gl_interop.h>

#include "thrust/device_ptr.h"
#include "thrust/for_each.h"
#include "thrust/iterator/zip_iterator.h"
#include "thrust/sort.h"

#include "particles_kernel_device.cuh"
#include "ParticleSystem.cuh"

extern "C" {

cudaArray *noiseArray;

void setParameters(SimParams *hostParams) {
  // copy parameters to constant memory
  checkCudaErrors(cudaMemcpyToSymbol(params, hostParams, sizeof(SimParams)));
}

// Round a / b to nearest higher integer value
int iDivUp(int a, int b) { return (a % b != 0) ? (a / b + 1) : (a / b); }

// compute grid and thread block size for a given number of elements
void computeGridSize(int n, int blockSize, int &numBlocks, int &numThreads) {
  numThreads = min(blockSize, n);
  numBlocks = iDivUp(n, numThreads);
}

inline float frand() { return rand() / (float)RAND_MAX; }

// create 3D texture containing random values
void createNoiseTexture(int w, int h, int d) {
  cudaExtent size = make_cudaExtent(w, h, d);
  size_t elements = size.width * size.height * size.depth;

  float *volumeData = (float *)malloc(elements * 4 * sizeof(float));
  float *ptr = volumeData;

  for (size_t i = 0; i < elements; i++) {
    *ptr++ = frand() * 2.0f - 1.0f;
    *ptr++ = frand() * 2.0f - 1.0f;
    *ptr++ = frand() * 2.0f - 1.0f;
    *ptr++ = frand() * 2.0f - 1.0f;
  }

  cudaChannelFormatDesc channelDesc = cudaCreateChannelDesc<float4>();
  checkCudaErrors(cudaMalloc3DArray(&noiseArray, &channelDesc, size));

  cudaMemcpy3DParms copyParams = {0};
  copyParams.srcPtr = make_cudaPitchedPtr(
      (void *)volumeData, size.width * sizeof(float4), size.width, size.height);
  copyParams.dstArray = noiseArray;
  copyParams.extent = size;
  copyParams.kind = cudaMemcpyHostToDevice;
  checkCudaErrors(cudaMemcpy3D(&copyParams));

  free(volumeData);

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

  texRes.resType = cudaResourceTypeArray;
  texRes.res.array.array = noiseArray;

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

  texDescr.normalizedCoords = true;
  texDescr.filterMode = cudaFilterModeLinear;
  texDescr.addressMode[0] = cudaAddressModeWrap;
  texDescr.addressMode[1] = cudaAddressModeWrap;
  texDescr.addressMode[2] = cudaAddressModeWrap;
  texDescr.readMode = cudaReadModeElementType;

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

void integrateSystem(float4 *oldPos, float4 *newPos, float4 *oldVel,
                     float4 *newVel, float deltaTime, int numParticles) {
  thrust::device_ptr<float4> d_newPos(newPos);
  thrust::device_ptr<float4> d_newVel(newVel);
  thrust::device_ptr<float4> d_oldPos(oldPos);
  thrust::device_ptr<float4> d_oldVel(oldVel);

  thrust::for_each(thrust::make_zip_iterator(thrust::make_tuple(
                       d_newPos, d_newVel, d_oldPos, d_oldVel)),
                   thrust::make_zip_iterator(thrust::make_tuple(
                       d_newPos + numParticles, d_newVel + numParticles,
                       d_oldPos + numParticles, d_oldVel + numParticles)),
                   integrate_functor(deltaTime, noiseTex));
}

void calcDepth(float4 *pos,
               float *keys,    // output
               uint *indices,  // output
               float3 sortVector, int numParticles) {
  thrust::device_ptr<float4> d_pos(pos);
  thrust::device_ptr<float> d_keys(keys);
  thrust::device_ptr<uint> d_indices(indices);

  thrust::for_each(thrust::make_zip_iterator(thrust::make_tuple(d_pos, d_keys)),
                   thrust::make_zip_iterator(thrust::make_tuple(
                       d_pos + numParticles, d_keys + numParticles)),
                   calcDepth_functor(sortVector));

  thrust::sequence(d_indices, d_indices + numParticles);
}

void sortParticles(float *sortKeys, uint *indices, uint numParticles) {
  thrust::sort_by_key(thrust::device_ptr<float>(sortKeys),
                      thrust::device_ptr<float>(sortKeys + numParticles),
                      thrust::device_ptr<uint>(indices));
}

}  // extern "C"