【RayTracer】（八）构建随机场景

到目前为止，最简单的光线追踪器就构建完成了，在开始进一步完善之前，我们先随机向场景中加入许多不同材质不同属性的球体，渲染第一张“完整的”光线追踪图片。

#include <iostream>
#include <string>
#include <omp.h>
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"
#include "hittable_list.h"
#include "sphere.h"
#include "color.h"
#include "camera.h"

// 随机构建场景
hittable_list random_scene() {
    hittable_list world;

    auto ground_material = make_shared<lambertian>(color(0.5, 0.5, 0.5));
    world.add(make_shared<sphere>(point3(0, -1000, 0), 1000, ground_material));

    for (int a = -11; a < 11; a++) {
        for (int b = -11; b < 11; b++) {
            auto choose_mat = random_double();
            point3 center(a + 0.9 * random_double(), 0.2, b + 0.9 * random_double());

            if ((center - point3(4, 0.2, 0)).length() > 0.9) {
                shared_ptr<material> sphere_material;

                if (choose_mat < 0.75) {
                    // diffuse
                    auto albedo = random_vec() * random_vec();
                    sphere_material = make_shared<lambertian>(albedo);
                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
                }
                else if (choose_mat < 0.95) {
                    // metal
                    auto albedo = random_vec(0.5, 1);
                    auto fuzz = random_double(0, 0.5);
                    sphere_material = make_shared<metal>(albedo, fuzz);
                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
                }
                else {
                    // glass
                    sphere_material = make_shared<dielectric>(1.5);
                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
                }
            }
        }
    }

    auto material1 = make_shared<dielectric>(1.5);
    world.add(make_shared<sphere>(point3(0, 1, 0), 1.0, material1));

    auto material2 = make_shared<lambertian>(color(0.4, 0.2, 0.1));
    world.add(make_shared<sphere>(point3(-4, 1, 0), 1.0, material2));

    auto material3 = make_shared<metal>(color(0.7, 0.6, 0.5), 0.0);
    world.add(make_shared<sphere>(point3(4, 1, 0), 1.0, material3));

    return world;
}


int main()
{
    /****图片保存，保存为png格式****/
    std::string SavePath = "D:\\TechStack\\ComputerGraphics\\Ray Tracing in One Weekend Series\\Results\\";
    std::string filename = "final.png";
    std::string filepath = SavePath + filename;
    
    /*******图片属性*******/ 
    // 宽高比
    const auto aspect_ratio = 3.0 / 2.0;
    const int image_width = 1200;
    // 使用static_cast可以明确告诉编译器，这种损失精度的转换是在知情的情况下进行的
    // 也可以让阅读程序的其他程序员明确你转换的目的而不是由于疏忽
    const int image_height = static_cast<int>(image_width / aspect_ratio);
    const int channel = 3;
    // 每个像素的采样数量
    const int samples_per_pixel = 500;
    // 光线至少弹射次数
    const int min_bounce = 45;
    // 俄罗斯轮盘赌算法生存概率
    const double RR = 0.9;

    /*******创建相机*******/
    point3 lookfrom(13, 2, 3);
    point3 lookat(0, 0, 0);
    vec3 vup(0, 1, 0);
    auto dist_to_focus = 10.0;
    auto aperture = 0.1;

    camera cam(lookfrom, lookat, vup, 20, aspect_ratio, aperture, dist_to_focus);

    /*******创建场景*******/
    auto world = random_scene();

    /******渲染部分*****/
    // 3通道图像存在一维数组中
    unsigned char* odata = (unsigned char*)malloc(image_width * image_height * channel);
    unsigned char* p = odata;
    for (int j = image_height - 1; j >= 0; --j) {
        // 标准错误流显示进度信息，单行刷新显示
        std::cerr << "\rScanlines remaining: " << j << ' ' << std::flush;
        #pragma omp parallel for
        for (int i = 0; i < image_width; ++i) {
            color pixel_color(0, 0, 0);
            for (int s = 0; s < samples_per_pixel; ++s) {
                // 在像素内部随机采样
                auto u = (i + random_double()) / (image_width - 1);
                auto v = (j + random_double()) / (image_height - 1);
                ray r = cam.get_ray(u, v);
                pixel_color += ray_color(r, world, min_bounce, RR);
            }
            write_color(p, pixel_color, samples_per_pixel);
        }
    }
    stbi_write_png(filepath.c_str(), image_width, image_height, channel, odata, 0);
    std::cerr << "\nDone.\n";
}

得到的效果如下：