我需要在 CUDA 中执行三线性插值。这是问题定义:

给定三个点向量:x[nx],y[ny],z[nz] 和一个函数值矩阵func[nx][ny][nz]，我想在 x,và 范围之间的一些随机点处找到函数值和 z.

我可以在 CUDA 中编写自己的插值内核，但我想知道是否已经存在一个可以完成这项工作的内核。

Cảm ơn!

1 Câu trả lời

如@Farzad 所述，您可以使用纹理过滤在 CUDA 中执行三线性插值。 simpleTexture3D示例提供了有关如何使用它的完整示例。然而，就目前而言，它可能不会立即使用，因为它涉及使用 OpenGL 和 glut 等库以及其他外部依赖项，如 cutil.h.

因此，我发现将上述代码缩减为显示概念的“最小尺寸”示例很有用。正如您将看到的，代码加载位于名为 Bucky.raw 的文件中的外部数据，我从上面链接的 github 页面“借用”了该文件。

下面的代码将一个长方体数据插值到位于其中心切片中的规则笛卡尔网格。如果一切顺利，您将重建的图像就是下面报告的图像。

Mã như sau:

#include 
#include 
#include  

#include 
#include 

typedef unsigned char uchar;

#define BLOCKSIZE 16

float w = 0.5; // texture coordinate in z

/********************/
/* CUDA ERROR CHECK */
/********************/
#define gpuErrchk(ans) { gpuAssert((ans), __FILE__, __LINE__); }
inline void gpuAssert(cudaError_t code, char *file, int line, bool abort=true)
{
    if (code != cudaSuccess) 
    {
        fprintf(stderr,"GPUassert: %s %s %d\n", cudaGetErrorString(code), file, line);
        if (abort) { getchar(); exit(code); }
    }
}

typedef unsigned int uint;
typedef unsigned char uchar;

texture tex; // 3D texture

cudaArray *d_volumeArray = 0;

uint *d_output = NULL;
uint *h_output = NULL;

/************************************************/
/* TEXTURE-BASED TRILINEAR INTERPOLATION KERNEL */
/************************************************/
__global__ void
d_render(uint *d_output, uint imageW, uint imageH, float w)
{
    uint x = __umul24(blockIdx.x, blockDim.x) + threadIdx.x;
    uint y = __umul24(blockIdx.y, blockDim.y) + threadIdx.y;

    float u = x / (float) imageW;
    float v = y / (float) imageH;

    // read from 3D texture
    float voxel = tex3D(tex, u, v, w);

    if ((x < imageW) && (y < imageH)) {
        // write output color
        uint i = __umul24(y, imageW) + x;
        d_output[i] = voxel*255;
   }
}

void main() {

    int N = 32;
    int imageH = 512;
    int imageW = 512;

    const char* filename = "Bucky.raw";

    // --- Loading data from file
    FILE *fp = fopen(filename, "rb");
    if (!fp) { fprintf(stderr, "Error opening file '%s'\n", filename); getchar(); return; }

    uchar *data = (uchar*)malloc(N*N*N*sizeof(uchar));
    size_t read = fread(data, 1, N*N*N, fp);
    fclose(fp);

    printf("Read '%s', %lu bytes\n", filename, read);

    gpuErrchk(cudaMalloc((void**)&d_output, imageH*imageW*sizeof(uint)));

    // --- Create 3D array
    const cudaExtent volumeSize = make_cudaExtent(N, N, N);

    cudaChannelFormatDesc channelDesc = cudaCreateChannelDesc();
    gpuErrchk(cudaMalloc3DArray(&d_volumeArray, &channelDesc, volumeSize));

    // --- Copy data to 3D array (host to device)
    cudaMemcpy3DParms copyParams = {0};
    copyParams.srcPtr = make_cudaPitchedPtr((void*)data, volumeSize.width*sizeof(uchar), volumeSize.width, volumeSize.height);
    copyParams.dstArray = d_volumeArray;
    copyParams.extent = volumeSize;
    copyParams.kind = cudaMemcpyHostToDevice;
    gpuErrchk(cudaMemcpy3D(©Params));

    // --- Set texture parameters
    tex.normalized = true; // access with normalized texture coordinates
    tex.filterMode = cudaFilterModeLinear; // linear interpolation
    tex.addressMode[0] = cudaAddressModeWrap; // wrap texture coordinates
    tex.addressMode[1] = cudaAddressModeWrap;
    tex.addressMode[2] = cudaAddressModeWrap;

    // --- Bind array to 3D texture
    gpuErrchk(cudaBindTextureToArray(tex, d_volumeArray, channelDesc));

    // --- Launch the interpolation kernel
    const dim3 blockSize(BLOCKSIZE, BLOCKSIZE, 1);
    const dim3 gridSize(imageW / blockSize.x, imageH / blockSize.y);
    d_render<<>>(d_output, imageW, imageH, w);
    gpuErrchk(cudaPeekAtLastError());
    gpuErrchk(cudaDeviceSynchronize());

    // --- Copy the interpolated data to host
    h_output = (uint*)malloc(imageW*imageH*sizeof(uint));
    gpuErrchk(cudaMemcpy(h_output,d_output,imageW*imageH*sizeof(uint),cudaMemcpyDeviceToHost));

    std::ofstream outfile;
    outfile.open("out_texture.dat", std::ios::out | std::ios::binary);
    outfile.write((char*)h_output, imageW*imageH*sizeof(uint));
    outfile.close();

    getchar();

}

代码将结果以二进制格式保存在 out_texture.dat 中。您可以根据 Matlab 加载二进制数据

fd = fopen('out_texture.dat','r');
U = fread(fd,imageH*imageW,'unsigned int');
fclose(fd);

关于cuda - CUDA 中的三线性插值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22970361/