用cuda写一个通视算法
时间: 2023-05-30 20:05:54 浏览: 79
通视算法是一种用于确定三维空间内物体是否可见的算法。在CUDA中,可以使用光线追踪来实现通视算法。下面是一个基于CUDA的通视算法的简单实现。
首先,需要定义一个光线结构体,用于表示光线的起点和方向:
```cuda
struct Ray {
float3 origin;
float3 direction;
};
```
然后,需要定义一个判断物体是否可见的函数,该函数接收一个光线和一个物体的位置和大小,返回一个布尔值表示物体是否可见。这里简单地使用球体来表示物体:
```cuda
__device__ bool isVisible(Ray ray, float3 center, float radius) {
float3 oc = ray.origin - center;
float a = dot(ray.direction, ray.direction);
float b = 2.0f * dot(oc, ray.direction);
float c = dot(oc, oc) - radius * radius;
float disc = b * b - 4.0f * a * c;
if (disc < 0.0f) {
return false;
}
float t = (-b - sqrtf(disc)) / (2.0f * a);
if (t < 0.0f) {
return false;
}
return true;
}
```
最后,需要在CUDA的核函数中对所有物体进行遍历,判断它们是否可见。这里假设每个线程负责一个像素,因此需要为每个像素生成一个光线,并对所有物体进行遍历:
```cuda
__global__ void visibilityKernel(Ray* rays, bool* visible, int numPixels, float3* centers, float* radii, int numObjects) {
int index = blockIdx.x * blockDim.x + threadIdx.x;
if (index >= numPixels) return;
Ray ray = rays[index];
for (int i = 0; i < numObjects; i++) {
if (isVisible(ray, centers[i], radii[i])) {
visible[index] = true;
break;
}
}
}
```
在主函数中,需要为每个像素生成一个光线,并将光线和物体数据复制到CUDA设备上。然后,可以调用核函数进行通视计算。最后,将结果从CUDA设备复制回CPU并保存为图像:
```cuda
int main() {
// Generate rays for each pixel
Ray* rays = generateRays();
// Copy rays and object data to device
Ray* d_rays;
cudaMalloc(&d_rays, numPixels * sizeof(Ray));
cudaMemcpy(d_rays, rays, numPixels * sizeof(Ray), cudaMemcpyHostToDevice);
float3* d_centers;
cudaMalloc(&d_centers, numObjects * sizeof(float3));
cudaMemcpy(d_centers, centers, numObjects * sizeof(float3), cudaMemcpyHostToDevice);
float* d_radii;
cudaMalloc(&d_radii, numObjects * sizeof(float));
cudaMemcpy(d_radii, radii, numObjects * sizeof(float), cudaMemcpyHostToDevice);
// Allocate memory for visibility results
bool* visible = new bool[numPixels];
bool* d_visible;
cudaMalloc(&d_visible, numPixels * sizeof(bool));
// Launch kernel to compute visibility
int blockSize = 256;
int numBlocks = (numPixels + blockSize - 1) / blockSize;
visibilityKernel<<<numBlocks, blockSize>>>(d_rays, d_visible, numPixels, d_centers, d_radii, numObjects);
// Copy visibility results from device to host
cudaMemcpy(visible, d_visible, numPixels * sizeof(bool), cudaMemcpyDeviceToHost);
// Save visibility results as image
saveImage(visible);
// Free memory
delete[] visible;
cudaFree(d_rays);
cudaFree(d_centers);
cudaFree(d_radii);
return 0;
}
```
这里的generateRays()和saveImage()函数分别用于生成光线和保存结果为图像,它们的具体实现可以根据具体需求进行编写。