• 使用全局内存的光线跟踪实验


     使用全局内存来存储球面对象,项目打包下载

      1 /*
      2 * Copyright 1993-2010 NVIDIA Corporation.  All rights reserved.
      3 *
      4 * NVIDIA Corporation and its licensors retain all intellectual property and
      5 * proprietary rights in and to this software and related documentation.
      6 * Any use, reproduction, disclosure, or distribution of this software
      7 * and related documentation without an express license agreement from
      8 * NVIDIA Corporation is strictly prohibited.
      9 *
     10 * Please refer to the applicable NVIDIA end user license agreement (EULA)
     11 * associated with this source code for terms and conditions that govern
     12 * your use of this NVIDIA software.
     13 *
     14 */
     15 #include <GLglut.h>
     16 #include "cuda.h"
     17 #include "cuda_runtime.h"
     18 #include "device_launch_parameters.h"
     19 #include "../common/book.h"
     20 #include "../common/cpu_bitmap.h"
     21 #include "device_functions.h"
     22 
     23 #define DIM 1024
     24 
     25 #define rnd( x ) (x * rand() / RAND_MAX)
     26 #define INF     2e10f
     27 
     28 struct Sphere {
     29     float   r, b, g;
     30     float   radius;
     31     float   x, y, z;
     32     __device__ float hit(float ox, float oy, float *n) {
     33         //将中心坐标移动到图像中间,dx和dy就是相对于新的中心坐标ox和oy的新坐标
     34         float dx = ox - x;
     35         float dy = oy - y;
     36         //只处理点在圆内的Sphere对象
     37         if (dx*dx + dy*dy < radius*radius) {
     38             /*
     39             计算的dz为离圆心轴的距离
     40             */
     41             float dz = sqrtf(radius*radius - dx*dx - dy*dy);
     42             /*
     43             和半径相除,由于dz是float类型,所以结果也为float类型
     44             也就是说结果为0.xxx这样的数字,
     45             n为一个指针,*n为解析指针n,存放的也就是值0.xxx这样的值
     46             呈现在最后的结果就是图像颜色的渐变效果
     47             */
     48             *n = dz / sqrtf(radius * radius);
     49             /*
     50             在三维空间中,已经将xoy投影到为图上,z轴垂直于位图
     51             距离圆心的距离dz再加上原来的Z轴坐标就是当前坐标对应于xoy面的Z轴方向距离
     52             */
     53             return dz + z;
     54         }
     55         return -INF;
     56     }
     57 };
     58 #define SPHERES 20
     59 
     60 
     61 __global__ void kernel(Sphere *s, unsigned char *ptr) {
     62     // 映射到图像像素上的位置
     63     int x = threadIdx.x + blockIdx.x * blockDim.x;
     64     int y = threadIdx.y + blockIdx.y * blockDim.y;
     65     int offset = x + y * blockDim.x * gridDim.x;//步长
     66     //移动使得Z轴在图像中心
     67     float   ox = (x - DIM / 2);
     68     float   oy = (y - DIM / 2);
     69 
     70     float   r = 0, g = 0, b = 0;
     71     float   maxz = -INF;
     72     //每个像素递归判断SPHERES个对象在这个像素点上的值
     73     for (int i = 0; i<SPHERES; i++) {
     74         float   n;
     75         float   t = s[i].hit(ox, oy, &n);
     76         if (t > maxz) {
     77             //这里取n的地址,hit函数将结果存放在&n地址所指的空间,不同的n对应不同的颜色及深度
     78             float fscale = n;
     79             r = s[i].r * fscale;
     80             g = s[i].g * fscale;
     81             b = s[i].b * fscale;
     82             maxz = t;
     83         }
     84     }
     85 
     86     ptr[offset * 4 + 0] = (int)(r * 255);
     87     ptr[offset * 4 + 1] = (int)(g * 255);
     88     ptr[offset * 4 + 2] = (int)(b * 255);
     89     ptr[offset * 4 + 3] = 255;
     90 }
     91 
     92 
     93 // globals needed by the update routine
     94 struct DataBlock {
     95     unsigned char   *dev_bitmap;
     96     Sphere          *s;
     97 };
     98 
     99 int main(void) {
    100     DataBlock   data;
    101     //获取时间
    102     cudaEvent_t     start, stop;
    103     HANDLE_ERROR(cudaEventCreate(&start));
    104     HANDLE_ERROR(cudaEventCreate(&stop));
    105     HANDLE_ERROR(cudaEventRecord(start, 0));
    106 
    107     CPUBitmap bitmap(DIM, DIM, &data);
    108     unsigned char   *dev_bitmap;
    109     Sphere          *s;
    110 
    111 
    112     // allocate memory on the GPU for the output bitmap
    113     HANDLE_ERROR(cudaMalloc((void**)&dev_bitmap,
    114         bitmap.image_size()));
    115     //在全局内存中分配s
    116     HANDLE_ERROR(cudaMalloc((void**)&s,
    117         sizeof(Sphere)* SPHERES));
    118 
    119     //主机上申请存储空间
    120     Sphere *temp_s = (Sphere*)malloc(sizeof(Sphere)* SPHERES);
    121     for (int i = 0; i<SPHERES; i++) {
    122         temp_s[i].r = rnd(1.0f);
    123         temp_s[i].g = rnd(1.0f);
    124         temp_s[i].b = rnd(1.0f);
    125         temp_s[i].x = rnd(1000.0f) - 500;
    126         temp_s[i].y = rnd(1000.0f) - 500;
    127         temp_s[i].z = rnd(1000.0f) - 500;
    128         temp_s[i].radius = rnd(100.0f) + 20;
    129     }
    130     HANDLE_ERROR(cudaMemcpy(s, temp_s,
    131         sizeof(Sphere)* SPHERES,
    132         cudaMemcpyHostToDevice));
    133     free(temp_s);
    134 
    135     // generate a bitmap from our sphere data
    136     dim3    grids(DIM / 16, DIM / 16);
    137     dim3    threads(16, 16);
    138     kernel <<<grids, threads >>>(s, dev_bitmap);
    139 
    140     // copy our bitmap back from the GPU for display
    141     HANDLE_ERROR(cudaMemcpy(bitmap.get_ptr(), dev_bitmap,
    142         bitmap.image_size(),
    143         cudaMemcpyDeviceToHost));
    144 
    145     // get stop time, and display the timing results
    146     HANDLE_ERROR(cudaEventRecord(stop, 0));
    147     HANDLE_ERROR(cudaEventSynchronize(stop));
    148     float   elapsedTime;
    149     HANDLE_ERROR(cudaEventElapsedTime(&elapsedTime,
    150         start, stop));
    151     printf("Time to generate:  %3.1f ms
    ", elapsedTime);
    152 
    153     HANDLE_ERROR(cudaEventDestroy(start));
    154     HANDLE_ERROR(cudaEventDestroy(stop));
    155 
    156     HANDLE_ERROR(cudaFree(dev_bitmap));
    157     HANDLE_ERROR(cudaFree(s));
    158 
    159     // display
    160     bitmap.display_and_exit();
    161 }

     结果如下图所示:

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  • 原文地址:https://www.cnblogs.com/liangliangdetianxia/p/3987745.html
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