在立方体贴图空间内发射光线（视线），计算球面光线（视线）会击中哪个面的哪个像素的像素值，最终生成Equirectangular全景图。

1. InitSceneTexture()：先获取Cubemaps并将其绑定在GPU中

void InitSceneTexture() { char* path = "./Cubemaps";myEnvironment.setFileRoute(path);myEnvironment.getImageSource();int sceneLength = myEnvironment.Top.width;int sceneHeight = myEnvironment.Top.height;bind2DTopTexture(sceneLength, sceneLength);bind2DBottomTexture(sceneLength, sceneLength);bind2DLeftTexture(sceneLength, sceneLength);bind2DRightTexture(sceneLength, sceneLength);bind2DFrontTexture(sceneLength, sceneLength);bind2DBackTexture(sceneLength, sceneLength);
}

最后6个函数就是绑定纹理的过程，以top面为例，其它完整的代码会放在后面

void bind2DTopTexture(int width, int height) { size_t pitch, tex_ofs;float4*arr_d = 0;cudaMallocPitch((void**)&arr_d, &pitch, width * sizeof(float4), height);cudaMemcpy2D(arr_d, pitch, myEnvironment.Top.normData, width * sizeof(float4),width * sizeof(float4), height, cudaMemcpyHostToDevice);texTopEnvironment.normalized = false;cudaBindTexture2D(&tex_ofs, &texTopEnvironment, arr_d, &texTopEnvironment.channelDesc, width, height, pitch);
}

• 需要注意的是：不要cudaFree(arr_d )

2. 根据视点viewPoint（默认是（0，0，0）)和视线方向viewVector来确定击中的像素。在这里我们立方体贴图是设置的1000x1000的，所以中心位置是500

DEVICE Color renderScene(point& viewPoint, Vector& viewVector) { //float tx, ty, tz;bool positiveX, positiveY, positiveZ;float boxBoder = 500;insideIntersect_x(viewPoint, viewVector, boxBoder, tx, positiveX);insideIntersect_y(viewPoint, viewVector, boxBoder, ty, positiveY);insideIntersect_z(viewPoint, viewVector, boxBoder, tz, positiveZ);if (tx <= ty&&tx <= tz) { if (positiveX) { viewPoint += tx*viewVector;float xPos = viewPoint.z + boxBoder;float yPos = viewPoint.y + boxBoder;float4 hagles = tex2D(texRightEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}else { viewPoint += tx*viewVector;float xPos = boxBoder - viewPoint.z;float yPos = viewPoint.y + boxBoder;float4 hagles = tex2D(texLeftEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}}else if (ty <= tx&&ty <= tz) { if (positiveY) { viewPoint += ty*viewVector;float xPos = boxBoder - viewPoint.x;float yPos = boxBoder - viewPoint.z;float4 hagles = tex2D(texTopEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}else { viewPoint += ty*viewVector;float xPos = boxBoder - viewPoint.x;float yPos = boxBoder + viewPoint.z;float4 hagles = tex2D(texBottomEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}}else if (tz <= ty&&tz <= tx) { if (positiveZ) { viewPoint += tz*viewVector;float xPos = boxBoder - viewPoint.x;float yPos = boxBoder + viewPoint.y;float4 hagles = tex2D(texBackEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}else { viewPoint += tz*viewVector;float xPos = viewPoint.x + boxBoder;float yPos = viewPoint.y + boxBoder;float4 hagles = tex2D(texFrontEnvironment, (xPos + 0.5), (yPos + 0.5));return Color(hagles.x, hagles.y, hagles.z);}}
}

Color, point, Vector都是类似于cv::Point3f，不过需要基于HOST_AND_DEVICE重构数据结构。

下面这三个函数是为了确定击中的是哪个面

	insideIntersect_x(viewPoint, viewVector, boxBoder, tx, positiveX);insideIntersect_y(viewPoint, viewVector, boxBoder, ty, positiveY);insideIntersect_z(viewPoint, viewVector, boxBoder, tz, positiveZ);

完整代码：

//irradiance.cu 
__global__ void kernel8(int range_W, int range_H, cv::cuda::PtrStepSz<vec3f> outPano)
{ point viewpoint = point(0, 0, 0);int X = blockIdx.x * blockDim.x + threadIdx.x;int Y = blockIdx.y * blockDim.y + threadIdx.y;if (X < range_W && Y < range_H) { vec3f& pixel = outPano(1000 - Y, X);float theta = 2 * PI * (float)X / (float)range_W - PI;float phi = PI * (float)Y / (float)range_H - PI / 2.0;Vector dir = Vector(sin(theta) * cos(phi), cos(phi) * cos(theta), sin(phi));Color hit_color = renderScene(viewpoint, dir);pixel[0] = hit_color.z * 255.0;pixel[1] = hit_color.y * 255.0;pixel[2] = hit_color.x * 255.0;}}cv::Mat Cube2Pano()
{ InitSceneTexture();dim3 thread(32, 32);dim3 block((2000 + thread.x - 1) / thread.x, (1000 + thread.y - 1) / thread.y);cv::cuda::GpuMat device_panorama = cv::cuda::GpuMat(1000, 2000, CV_32FC3);kernel8 << <block, thread >> > (2000, 1000, device_panorama);cudaThreadSynchronize();cv::Mat host_pano;device_panorama.download(host_pano);return host_pano;
}

//irradiance.cuh
#pragma once
#include "Enviro.cuh"
#include "cuda_runtime.h"
#include "device_launch_parameters.h"extern "C" cv::Mat Cube2Pano();

//Enviro.cuh
#pragma once
#include "string"
#include 
#include "environment.h"
#define DEVICE __device__
#define HOD __host__ __device__
using namespace xcx;texture<float4, cudaTextureType2D, cudaReadModeElementType> texBottomEnvironment;
texture<float4, cudaTextureType2D, cudaReadModeElementType> texTopEnvironment;
texture<float4, cudaTextureType2D, cudaReadModeElementType> texLeftEnvironment;
texture<float4, cudaTextureType2D, cudaReadModeElementType> texRightEnvironment;
texture<float4, cudaTextureType2D, cudaReadModeElementType> texFrontEnvironment;
texture<float4, cudaTextureType2D, cudaReadModeElementType> texBackEnvironment;void bind2DTopTexture(int width, int height);
void bind2DBottomTexture(int width, int height);
void bind2DLeftTexture(int width, int height);
void bind2DRightTexture(int width, int height);
void bind2DFrontTexture(int width, int height);
void bind2DBackTexture(int width, int height);environment myEnvironment;void InitSceneTexture() { char* path = "./Image_out/segmentation";myEnvironment.setFileRoute(path);myEnvironment.getImageSource();int sceneLength = myEnvironment.Top.width;int sceneHeight = myEnvironment.Top.height;bind2DTopTexture(sceneLength, sceneLength);bind2DBottomTexture(sceneLength, sceneLength);bind2DLeftTexture(sceneLength, sceneLength);bind2DRightTexture(sceneLength, sceneLength);bind2DFrontTexture(sceneLength, sceneLength);bind2DBackTexture(sceneLength, sceneLength);}void bind2DTopTexture(int width, int height) { size_t pitch, tex_ofs;float4*arr_d = 0;cudaMallocPitch((void**)&arr_d, &pitch, width * sizeof(float4), height);cudaMemcpy2D(arr_d, pitch, myEnvironment.Top.normData, width * sizeof(float4),width * sizeof(float4), height, cudaMemcpyHostToDevice);texTopEnvironment.normalized = false;cudaBindTexture2D(&tex_ofs, &texTopEnvironment, arr_d, &texTopEnvironment.channelDesc, width, height, pitch);
}
void bind2DBottomTexture(int width