路径追踪 SAH优化的Bvh

BVH 层次包围盒
SAH 优化BVH
BVH具体怎么做

我们加载模型用数组一个个记录模型的三角形和材质

光线追踪判断光线和模型相交时返回命中的三角形颜色材质
每次判断相交都是把整个场景三角形全部遍历可想而知会很慢

就需要我们优化把他们按照区域分类开来先判断光线和区域相交
再判断区域中的三角形，一层层下去避免浪费这就是Bvh结构

图片中的兔子就是按照250*250 直线判断相交，返回三角形表示命中，这个点就显示出颜色

for (int i = 0; i < WIDTH; i +=2){for (int j = 0; j < HEIGHT; j +=2){// 像素坐标转投影平面坐标double x = 2.0 * double(j) / double(WIDTH) - 1.0;double y = 2.0 * double(HEIGHT - i) / double(HEIGHT) - 1.0;// MSAAx += (randf() - 0.5f) / double(WIDTH);y += (randf() - 0.5f) / double(HEIGHT);vec3 coord = vec3(x, y, SCREEN_Z);          // 计算投影平面坐标vec3 direction = normalize(coord - EYE);    // 计算光线投射方向// 生成光线Ray ray;ray.startPoint = coord;ray.direction = direction;vec3 color = vec3(0, 0, 0);HitResult res = hitBVH(ray, triangles, root);if (res.triangle != NULL) { //判断是否命中  得到三角形既命中模型返回颜色color = vec3(0, 0.5, 0);}buffer[i][j] = RGB(color.x * 255, color.y * 255, color.z * 255);}}

上面就是一个简单的光线追踪实现，不反射不计算材质也没有材质
完整代码可以使用第一章的框架复制这份

#include <iostream>
#include <string>
#include <fstream>
#include <vector>
#include <sstream>
#include <iostream>
#include <algorithm>#include <GL/glew.h>
#include <freeglut.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>#define INF 114514.0#include<ctime>
#include<mmintrin.h>// 输出图像分辨率
const int WIDTH = 250;
const int HEIGHT = 250;
GLuint texture;
typedef unsigned int Color;
static  Color buffer[HEIGHT][WIDTH];
int frames; clock_t clocks;using namespace glm;
vec3 光线命中坐标 = vec3(0, 0, 0);  // 光线命中点
// ----------------------------------------------------------------------------- //GLuint program;                 // 着色器程序对象
std::vector<vec3> vertices;     // 顶点坐标
std::vector<GLuint> indices;    // 顶点索引
std::vector<vec3> lines;        // 线段端点坐标
vec3 rotateControl(0, 0, 0);    // 旋转参数
vec3 scaleControl(1, 1, 1);     // 缩放参数// BVH 树节点
struct BVHNode {BVHNode* left = NULL;       // 左右子树索引BVHNode* right = NULL;int n, index;               // 叶子节点信息               vec3 AA, BB;                // 碰撞盒
};typedef struct Triangle {vec3 p1, p2, p3;   // 三点vec3 center;       // 中心Triangle(vec3 a, vec3 b, vec3 c) {p1 = a, p2 = b, p3 = c;center = (p1 + p2 + p3) / vec3(3, 3, 3);}
} Triangle;
std::vector<Triangle> triangles;// 按照三角形中心排序 -- 比较函数
bool cmpx(const Triangle& t1, const Triangle& t2) {return t1.center.x < t2.center.x;
}
bool cmpy(const Triangle& t1, const Triangle& t2) {return t1.center.y < t2.center.y;
}
bool cmpz(const Triangle& t1, const Triangle& t2) {return t1.center.z < t2.center.z;
}// 求交结果
struct HitResult {Triangle* triangle = NULL;float distance = INF;vec3 光线命中点 = vec3(0, 0, 0);  // 光线命中点bool 是否命中 = 0;             // 是否命中
};// 光线
typedef struct Ray {vec3 startPoint = vec3(0, 0, 0);    // 起点vec3 direction = vec3(0, 0, 0);     // 方向
}Ray;// ----------------------------------------------------------------------------- //// 读取文件并且返回一个长字符串表示文件内容
std::string readShaderFile(std::string filepath) {std::string res, line;std::ifstream fin(filepath);if (!fin.is_open()){std::cout << "文件 " << filepath << " 打开失败" << std::endl;exit(-1);}while (std::getline(fin, line)){res += line + '\n';}fin.close();return res;
}// 获取着色器对象
GLuint getShaderProgram(std::string fshader, std::string vshader) {// 读取shader源文件std::string vSource = readShaderFile(vshader);std::string fSource = readShaderFile(fshader);const char* vpointer = vSource.c_str();const char* fpointer = fSource.c_str();// 容错GLint success;GLchar infoLog[512];// 创建并编译顶点着色器GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);glShaderSource(vertexShader, 1, (const GLchar**)(&vpointer), NULL);glCompileShader(vertexShader);glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);   // 错误检测if (!success){glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);std::cout << "顶点着色器编译错误\n" << infoLog << std::endl;exit(-1);}// 创建并且编译片段着色器GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);glShaderSource(fragmentShader, 1, (const GLchar**)(&fpointer), NULL);glCompileShader(fragmentShader);glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);   // 错误检测if (!success){glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);std::cout << "片段着色器编译错误\n" << infoLog << std::endl;exit(-1);}// 链接两个着色器到program对象GLuint shaderProgram = glCreateProgram();glAttachShader(shaderProgram, vertexShader);glAttachShader(shaderProgram, fragmentShader);glLinkProgram(shaderProgram);// 删除着色器对象glDeleteShader(vertexShader);glDeleteShader(fragmentShader);return shaderProgram;
}// 读取 obj
void readObj(std::string filepath, std::vector<vec3>& vertices, std::vector<GLuint>& indices) {// 打开文件流std::ifstream fin(filepath);std::string line;if (!fin.is_open()) {std::cout << "文件 " << filepath << " 打开失败" << std::endl;exit(-1);}// 增量读取int offset = vertices.size();// 按行读取while (std::getline(fin, line)) {std::istringstream sin(line);   // 以一行的数据作为 string stream 解析并且读取std::string type;GLfloat x, y, z;int v0, v1, v2;// 读取obj文件sin >> type;if (type == "v") {sin >> x >> y >> z;vertices.push_back(vec3(x, y, z));}if (type == "f") {sin >> v0 >> v1 >> v2;indices.push_back(v0 - 1 + offset);indices.push_back(v1 - 1 + offset);indices.push_back(v2 - 1 + offset);}}
}void addLine(vec3 p1, vec3 p2) {lines.push_back(p1);lines.push_back(p2);
}void addBox(BVHNode* root) {float x1 = root->AA.x, y1 = root->AA.y, z1 = root->AA.z;float x2 = root->BB.x, y2 = root->BB.y, z2 = root->BB.z;lines.push_back(vec3(x1, y1, z1)), lines.push_back(vec3(x2, y1, z1));lines.push_back(vec3(x1, y1, z1)), lines.push_back(vec3(x1, y1, z2));lines.push_back(vec3(x1, y1, z1)), lines.push_back(vec3(x1, y2, z1));lines.push_back(vec3(x2, y1, z1)), lines.push_back(vec3(x2, y1, z2));lines.push_back(vec3(x2, y1, z1)), lines.push_back(vec3(x2, y2, z1));lines.push_back(vec3(x1, y2, z1)), lines.push_back(vec3(x2, y2, z1));lines.push_back(vec3(x1, y1, z2)), lines.push_back(vec3(x1, y2, z2));lines.push_back(vec3(x1, y2, z1)), lines.push_back(vec3(x1, y2, z2));lines.push_back(vec3(x1, y2, z2)), lines.push_back(vec3(x2, y2, z2));lines.push_back(vec3(x1, y1, z2)), lines.push_back(vec3(x2, y1, z2));lines.push_back(vec3(x2, y2, z1)), lines.push_back(vec3(x2, y2, z2));lines.push_back(vec3(x2, y1, z2)), lines.push_back(vec3(x2, y2, z2));
}void addTriangle(Triangle* tri) {if (tri) {lines.push_back(tri->p1 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p2 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p2 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p3 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p3 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p1 - vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p1 + vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p2 + vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p2 + vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p3 + vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p3 + vec3(0.0005, 0.0005, 0.0005));lines.push_back(tri->p1 + vec3(0.0005, 0.0005, 0.0005));}
}// 光线和三角形求交
float hitTriangle(Triangle* triangle, Ray ray) {vec3 p1 = triangle->p1, p2 = triangle->p2, p3 = triangle->p3;vec3 S = ray.startPoint;        // 射线起点vec3 d = ray.direction;         // 射线方向vec3 N = normalize(cross(p2 - p1, p3 - p1));    // 法向量if (dot(N, d) > 0.0f) N = -N;   // 获取正确的法向量// 如果视线和三角形平行if (fabs(dot(N, d)) < 0.00001f) return INF;// 距离float t = (dot(N, p1) - dot(S, N)) / dot(d, N);if (t < 0.0005f) return INF;    // 如果三角形在光线背面// 交点计算vec3 P = S + d * t;// 判断交点是否在三角形中vec3 c1 = cross(p2 - p1, P - p1);vec3 c2 = cross(p3 - p2, P - p2);vec3 c3 = cross(p1 - p3, P - p3);if (dot(c1, N) > 0 && dot(c2, N) > 0 && dot(c3, N) > 0) return t;if (dot(c1, N) < 0 && dot(c2, N) < 0 && dot(c3, N) < 0) return t;光线命中坐标 = P;return INF;
}
//float intersect2(Ray ray)
//{//  光线求交结果 res;
//
//  vec3 S = ray.startPoint;        // 射线起点
//  vec3 d = ray.direction;         // 射线方向
//
//  float OS = length(O - S);
//  float SH = dot(O - S, d);
//  float OH = sqrt(pow(OS, 2) - pow(SH, 2));
//
//  if (OH > R) return res; // OH大于半径则不相交
//
//  float PH = sqrt(pow(R, 2) - pow(OH, 2));
//
//  float t1 = length(SH) - PH;
//  float t2 = length(SH) + PH;
//  float t = (t1 < 0) ? (t2) : (t1);   // 最近距离
//  vec3 P = S + t * d;     // 交点
//
//                          // 防止自己交自己
//  if (fabs(t1) < 0.0005f || fabs(t2) < 0.0005f) return res;
//
//  // 装填返回结果
//  res.是否命中 = true;
//  res.与交点的距离 = t;
//  res.光线命中点 = P;
//  //res.material = material;
//  //res.material.normal = normalize(P - O); // 要返回正确的法向
//  return INF;
//}// 构建 BVH
BVHNode* buildBVH(std::vector<Triangle>& triangles, int l, int r, int n) {if (l > r) return 0;BVHNode* node = new BVHNode();node->AA = vec3(1145141919, 1145141919, 1145141919);node->BB = vec3(-1145141919, -1145141919, -1145141919);// 计算 AABBfor (int i = l; i <= r; i++) {// 最小点 AAfloat minx = min(triangles[i].p1.x, min(triangles[i].p2.x, triangles[i].p3.x));float miny = min(triangles[i].p1.y, min(triangles[i].p2.y, triangles[i].p3.y));float minz = min(triangles[i].p1.z, min(triangles[i].p2.z, triangles[i].p3.z));node->AA.x = min(node->AA.x, minx);node->AA.y = min(node->AA.y, miny);node->AA.z = min(node->AA.z, minz);// 最大点 BBfloat maxx = max(triangles[i].p1.x, max(triangles[i].p2.x, triangles[i].p3.x));float maxy = max(triangles[i].p1.y, max(triangles[i].p2.y, triangles[i].p3.y));float maxz = max(triangles[i].p1.z, max(triangles[i].p2.z, triangles[i].p3.z));node->BB.x = max(node->BB.x, maxx);node->BB.y = max(node->BB.y, maxy);node->BB.z = max(node->BB.z, maxz);}// 不多于 n 个三角形 返回叶子节点if ((r - l + 1) <= n) {node->n = r - l + 1;node->index = l;return node;}// 否则递归建树float lenx = node->BB.x - node->AA.x;float leny = node->BB.y - node->AA.y;float lenz = node->BB.z - node->AA.z;// 按 x 划分if (lenx >= leny && lenx >= lenz)std::sort(triangles.begin() + l, triangles.begin() + r + 1, cmpx);// 按 y 划分if (leny >= lenx && leny >= lenz)std::sort(triangles.begin() + l, triangles.begin() + r + 1, cmpy);// 按 z 划分if (lenz >= lenx && lenz >= leny)std::sort(triangles.begin() + l, triangles.begin() + r + 1, cmpz);// 递归int mid = (l + r) / 2;node->left = buildBVH(triangles, l, mid, n);node->right = buildBVH(triangles, mid + 1, r, n);return node;
}// SAH 优化构建 BVH
BVHNode* buildBVHwithSAH(std::vector<Triangle>& triangles, int l, int r, int n) {if (l > r) return 0;BVHNode* node = new BVHNode();node->AA = vec3(1145141919, 1145141919, 1145141919);node->BB = vec3(-1145141919, -1145141919, -1145141919);// 计算 AABBfor (int i = l; i <= r; i++) {// 最小点 AAfloat minx = min(triangles[i].p1.x, min(triangles[i].p2.x, triangles[i].p3.x));float miny = min(triangles[i].p1.y, min(triangles[i].p2.y, triangles[i].p3.y));float minz = min(triangles[i].p1.z, min(triangles[i].p2.z, triangles[i].p3.z));node->AA.x = min(node->AA.x, minx);node->AA.y = min(node->AA.y, miny);node->AA.z = min(node->AA.z, minz);// 最大点 BBfloat maxx = max(triangles[i].p1.x, max(triangles[i].p2.x, triangles[i].p3.x));float maxy = max(triangles[i].p1.y, max(triangles[i].p2.y, triangles[i].p3.y));float maxz = max(triangles[i].p1.z, max(triangles[i].p2.z, triangles[i].p3.z));node->BB.x = max(node->BB.x, maxx);node->BB.y = max(node->BB.y, maxy);node->BB.z = max(node->BB.z, maxz);}// 不多于 n 个三角形 返回叶子节点if ((r - l + 1) <= n) {node->n = r - l + 1;node->index = l;return node;}// 否则递归建树float Cost = INF;int Axis = 0;int Split = (l + r) / 2;for (int axis = 0; axis < 3; axis++) {// 分别按 x，y，z 轴排序if (axis == 0) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpx);if (axis == 1) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpy);if (axis == 2) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpz);// leftMax[i]: [l, i] 中最大的 xyz 值// leftMin[i]: [l, i] 中最小的 xyz 值std::vector<vec3> leftMax(r - l + 1, vec3(-INF, -INF, -INF));std::vector<vec3> leftMin(r - l + 1, vec3(INF, INF, INF));// 计算前缀 注意 i-l 以对齐到下标 0for (int i = l; i <= r; i++) {Triangle& t = triangles[i];int bias = (i == l) ? 0 : 1;  // 第一个元素特殊处理leftMax[i - l].x = max(leftMax[i - l - bias].x, max(t.p1.x, max(t.p2.x, t.p3.x)));leftMax[i - l].y = max(leftMax[i - l - bias].y, max(t.p1.y, max(t.p2.y, t.p3.y)));leftMax[i - l].z = max(leftMax[i - l - bias].z, max(t.p1.z, max(t.p2.z, t.p3.z)));leftMin[i - l].x = min(leftMin[i - l - bias].x, min(t.p1.x, min(t.p2.x, t.p3.x)));leftMin[i - l].y = min(leftMin[i - l - bias].y, min(t.p1.y, min(t.p2.y, t.p3.y)));leftMin[i - l].z = min(leftMin[i - l - bias].z, min(t.p1.z, min(t.p2.z, t.p3.z)));}// rightMax[i]: [i, r] 中最大的 xyz 值// rightMin[i]: [i, r] 中最小的 xyz 值std::vector<vec3> rightMax(r - l + 1, vec3(-INF, -INF, -INF));std::vector<vec3> rightMin(r - l + 1, vec3(INF, INF, INF));// 计算后缀 注意 i-l 以对齐到下标 0for (int i = r; i >= l; i--) {Triangle& t = triangles[i];int bias = (i == r) ? 0 : 1;  // 第一个元素特殊处理rightMax[i - l].x = max(rightMax[i - l + bias].x, max(t.p1.x, max(t.p2.x, t.p3.x)));rightMax[i - l].y = max(rightMax[i - l + bias].y, max(t.p1.y, max(t.p2.y, t.p3.y)));rightMax[i - l].z = max(rightMax[i - l + bias].z, max(t.p1.z, max(t.p2.z, t.p3.z)));rightMin[i - l].x = min(rightMin[i - l + bias].x, min(t.p1.x, min(t.p2.x, t.p3.x)));rightMin[i - l].y = min(rightMin[i - l + bias].y, min(t.p1.y, min(t.p2.y, t.p3.y)));rightMin[i - l].z = min(rightMin[i - l + bias].z, min(t.p1.z, min(t.p2.z, t.p3.z)));}// 遍历寻找分割float cost = INF;int split = l;for (int i = l; i <= r - 1; i++) {float lenx, leny, lenz;// 左侧 [l, i]vec3 leftAA = leftMin[i - l];vec3 leftBB = leftMax[i - l];lenx = leftBB.x - leftAA.x;leny = leftBB.y - leftAA.y;lenz = leftBB.z - leftAA.z;float leftS = 2.0 * ((lenx * leny) + (lenx * lenz) + (leny * lenz));float leftCost = leftS * (i - l + 1);// 右侧 [i+1, r]vec3 rightAA = rightMin[i + 1 - l];vec3 rightBB = rightMax[i + 1 - l];lenx = rightBB.x - rightAA.x;leny = rightBB.y - rightAA.y;lenz = rightBB.z - rightAA.z;float rightS = 2.0 * ((lenx * leny) + (lenx * lenz) + (leny * lenz));float rightCost = rightS * (r - i);// 记录每个分割的最小答案float totalCost = leftCost + rightCost;if (totalCost < cost) {cost = totalCost;split = i;}}// 记录每个轴的最佳答案if (cost < Cost) {Cost = cost;Axis = axis;Split = split;}}// 按最佳轴分割if (Axis == 0) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpx);if (Axis == 1) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpy);if (Axis == 2) std::sort(&triangles[0] + l, &triangles[0] + r + 1, cmpz);// 递归node->left = buildBVHwithSAH(triangles, l, Split, n);node->right = buildBVHwithSAH(triangles, Split + 1, r, n);return node;
}void dfsNlevel(BVHNode* root, int depth, int targetDepth) {if (root == NULL) return;if (targetDepth == depth) {addBox(root);return;}dfsNlevel(root->left, depth + 1, targetDepth);dfsNlevel(root->right, depth + 1, targetDepth);
}// 暴力查数组
HitResult hitTriangleArray(Ray ray, std::vector<Triangle>& triangles, int l, int r) {HitResult res;for (int i = l; i <= r; i++) {float d = hitTriangle(&triangles[i], ray);if (d < INF && d < res.distance) {res.distance = d;res.triangle = &triangles[i];}}return res;
}// 和 aabb 盒子求交，没有交点则返回 -1
float hitAABB(Ray r, vec3 AA, vec3 BB) {// 1.0 / directionvec3 invdir = vec3(1.0 / r.direction.x, 1.0 / r.direction.y, 1.0 / r.direction.z);vec3 in = (BB - r.startPoint) * invdir;vec3 out = (AA - r.startPoint) * invdir;vec3 tmax = max(in, out);vec3 tmin = min(in, out);float t1 = min(tmax.x, min(tmax.y, tmax.z));float t0 = max(tmin.x, max(tmin.y, tmin.z));return (t1 >= t0) ? ((t0 > 0.0) ? (t0) : (t1)) : (-1);
}// 在 BVH 上遍历求交
HitResult hitBVH(Ray ray, std::vector<Triangle>& triangles, BVHNode* root) {if (root == NULL) return HitResult();// 是叶子 暴力查if (root->n > 0) {return hitTriangleArray(ray, triangles, root->n, root->n + root->index - 1);}// 和左右子树 AABB 求交float d1 = INF, d2 = INF;if (root->left) d1 = hitAABB(ray, root->left->AA, root->left->BB);if (root->right) d2 = hitAABB(ray, root->right->AA, root->right->BB);// 递归结果HitResult r1, r2, r3;if (d1>0) r1 = hitBVH(ray, triangles, root->left);if (d2>0) r2 = hitBVH(ray, triangles, root->right);r3= r1.distance < r2.distance ? r1 : r2;r3.光线命中点 = 光线命中坐标;r3.是否命中 = 1;return  r3;
}// ----------------------------------------------------------------------------- //// 显示回调函数
void display() {// 构造模型变换矩阵mat4 unit(    // 单位矩阵vec4(1, 0, 0, 0),vec4(0, 1, 0, 0),vec4(0, 0, 1, 0),vec4(0, 0, 0, 1));mat4 scaleMat = scale(unit, scaleControl);   // xyz缩放0.6倍mat4 rotateMat = unit;    // 旋转rotateMat = rotate(rotateMat, radians(rotateControl.x), vec3(1, 0, 0)); // 绕x轴转rotateMat = rotate(rotateMat, radians(rotateControl.y), vec3(0, 1, 0)); // 绕y轴转rotateMat = rotate(rotateMat, radians(rotateControl.z), vec3(0, 0, 1)); // 绕z轴转mat4 modelMat = rotateMat * scaleMat;   // 变换级联 -- 生成模型变换矩阵GLuint mlocation = glGetUniformLocation(program, "model");  // 名为model的uniform变量的位置索引glUniformMatrix4fv(mlocation, 1, GL_FALSE, value_ptr(modelMat));GLuint clocation = glGetUniformLocation(program, "color");// 绘制glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);       // 清空窗口颜色缓存glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);glUniform3fv(clocation, 1, value_ptr(vec3(1, 0, 0)));glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0);// 绘制 AABB 盒子  glUniform3fv(clocation, 1, value_ptr(vec3(1, 1, 1)));glDrawArrays(GL_LINES, vertices.size(), lines.size());glutSwapBuffers();  // 交换缓冲区
}// 鼠标运动函数
double lastX = 0.0, lastY = 0.0;
void mouse(int x, int y)
{// 调整旋转rotateControl.y += -200 * (x - lastX) / 512;rotateControl.x += -200 * (y - lastY) / 512;lastX = x, lastY = y;glutPostRedisplay();    // 重绘
}// 鼠标按下
void mouseDown(int button, int state, int x, int y) {if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {lastX = x, lastY = y;}
}// 鼠标滚轮函数
void mouseWheel(int wheel, int direction, int x, int y) {scaleControl.x += 1 * direction * 0.1;scaleControl.y += 1 * direction * 0.1;scaleControl.z += 1 * direction * 0.1;glutPostRedisplay();    // 重绘
}#include <random>
// 0-1 随机数生成
std::uniform_real_distribution<> dis(0.0, 1.0);
std::random_device rd;
std::mt19937 gen(rd());
double randf()
{return dis(gen);
}// 相机参数
const double SCREEN_Z = 1.1;        // 视平面 z 坐标
const vec3 EYE = vec3(0, 0, 4.0);   // 相机位置
BVHNode*    root;
//vec3 小图采样2[200 * 200]; void 渲染(){#include<mmintrin.h>for (int i = 0; i < WIDTH; i +=2){for (int j = 0; j < HEIGHT; j +=2){// 像素坐标转投影平面坐标double x = 2.0 * double(j) / double(WIDTH) - 1.0;double y = 2.0 * double(HEIGHT - i) / double(HEIGHT) - 1.0;// MSAAx += (randf() - 0.5f) / double(WIDTH);y += (randf() - 0.5f) / double(HEIGHT);vec3 coord = vec3(x, y, SCREEN_Z);          // 计算投影平面坐标vec3 direction = normalize(coord - EYE);    // 计算光线投射方向// 生成光线Ray ray;ray.startPoint = coord;ray.direction = direction;vec3 color = vec3(0, 0, 0);/* Ray ray;ray.startPoint = vec3(0, 0, 1);ray.direction = normalize(vec3(0.1, -0.1, -0.7));*/// HitResult res = hitTriangleArray(ray, triangles, 0, triangles.size()-1); // 暴力验证HitResult res = hitBVH(ray, triangles, root);//addTriangle(res.triangle);//addLine(ray.startPoint, ray.startPoint + ray.direction * vec3(5, 5, 5));if (res.triangle != NULL) { //判断是否命中  得到三角形既命中模型返回颜色color = vec3(0, 0.5, 0);//小图采样2[i + j] = color;}buffer[i][j] = RGB(color.x * 255, color.y * 255, color.z * 255);//buffer[i][j] = RGB(小图采样2[i + j].x * 255, 小图采样2[i + j].y * 255, 小图采样2[i + j].z * 255);}}glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, WIDTH, HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, buffer);glLoadIdentity();glBegin(GL_QUADS);glTexCoord2f(0, 0);glVertex2f(-1, 1);glTexCoord2f(0, 1);glVertex2f(-1, -1);glTexCoord2f(1, 1);glVertex2f(1, -1);glTexCoord2f(1, 0);glVertex2f(1, 1);glEnd();glutSwapBuffers();++frames;if (clock() - clocks>CLOCKS_PER_SEC){char title[64];sprintf(title, "光线追踪路径追踪混合  FPS:%d", frames);glutSetWindowTitle(title);clocks = clock();frames = 0;}
}int main() {// ------------------------------------------------------------------------------------------- //// 读 objreadObj("2.obj", vertices, indices);for (auto& v : vertices) {v.x *= 5.0, v.y *= 5.0, v.z *= 5.0;v.y -= 0.5;}//readObj("./models/quad.obj", vertices, indices);// 构建 Triangle 数组for (int i = 0; i < indices.size(); i += 3) {triangles.push_back(Triangle(vertices[indices[i]], vertices[indices[i + 1]], vertices[indices[i + 2]]));}// 建立 BVH 树//root = buildBVH(triangles, 0, triangles.size() - 1, 8);root = buildBVHwithSAH(triangles, 0, triangles.size() - 1, 80);//addBox(root->left); //addBox(root->right);dfsNlevel(root, 0, 1);   // 可视化第 n 层 bvh/**/// ------------------------------------------------------------------------------------------- //int argc = 1;char* argv[] = { "MFC_GLUT" };clocks = clock();frames = 0;glutInitWindowSize(WIDTH, HEIGHT);glutInit(&argc, argv);glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);glutCreateWindow("RayTracing");glutDisplayFunc(渲染);glutIdleFunc(渲染);glEnable(GL_TEXTURE_2D);glGenTextures(1, &texture);glBindTexture(GL_TEXTURE_2D, texture);glTexImage2D(GL_TEXTURE_2D, 0, 4, WIDTH, HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);   // 线形滤波glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);    // 线形滤波glutMainLoop();return 0;
}

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