games101_Homework5
使用光线追踪来渲染图像,实现两个部分:光线的生成和光线与三角的求交
你需要修改的函数是:
• Renderer.cpp 中的 Render():这里你需要为每个像素生成一条对应的光 线,然后调用函数 castRay() 来得到颜色,最后将颜色存储在帧缓冲区的相 应像素中。
• Triangle.hpp 中的 rayTriangleIntersect(): v0, v1, v2 是三角形的三个 顶点,orig 是光线的起点,dir 是光线单位化的方向向量。tnear, u, v 是你需 要使用我们课上推导的 Moller-Trumbore 算法来更新的参数。
Render()
void Renderer::Render(const Scene& scene) { std::vector<Vector3f> framebuffer(scene.width * scene.height); //需要填充的frame_buffer float scale = std::tan(deg2rad(scene.fov * 0.5f)); // t / |n| float imageAspectRatio = scene.width / (float)scene.height; // r / t // Use this variable as the eye position to start your rays. Vector3f eye_pos(0); // 从(0, 0, 0)发出光线 int m = 0; for (int j = 0; j < scene.height; ++j) { for (int i = 0; i < scene.width; ++i) // 遍历每一个像素,像素点在n面上 { // generate primary ray direction // TODO: Find the x and y positions of the current pixel to get the direction vector that passes through it. // Also, don't forget to multiply both of them with the variable *scale*, and x (horizontal) variable with the *imageAspectRatio* // x对应于宽度,i = 0 对应 x = -r, i = width-1对应 x = r, 列方程解i和x的关系有:x = (2r / w-1) * i - r = [(2 / w-1) * i - 1] * r // y对应于高度,j = 0 对应 y = t, j = height-1对应 y = -t,列方程解j和y的关系有:y = (-2t / h-1) * j + t = [1 - (2 / h-1) * j] * t // n = -1则 |n| = 1, t = scale, r = t * asp = scale *imageAsp float x = (2 / (float)(scene.width - 1) * i - 1) * scale * imageAspectRatio; float y = (1 - 2 / (float)(scene.height - 1) * j) * scale; Vector3f dir = Vector3f(x, y, -1); // Don't forget to normalize this direction! framebuffer[m++] = castRay(eye_pos, normalize(dir), scene, 0); } UpdateProgress(j / (float)scene.height); } // save framebuffer to file FILE* fp = fopen("binary.ppm", "wb"); (void)fprintf(fp, "P6\n%d %d\n255\n", scene.width, scene.height); for (auto i = 0; i < scene.height * scene.width; ++i) { static unsigned char color[3]; color[0] = (char)(255 * clamp(0, 1, framebuffer[i].x)); color[1] = (char)(255 * clamp(0, 1, framebuffer[i].y)); color[2] = (char)(255 * clamp(0, 1, framebuffer[i].z)); fwrite(color, 1, 3, fp); } fclose(fp); }
rayTriangleIntersect()
bool rayTriangleIntersect(const Vector3f& v0, const Vector3f& v1, const Vector3f& v2, const Vector3f& orig, const Vector3f& dir, float& tnear, float& u, float& v) { // TODO: Implement this function that tests whether the triangle // that's specified bt v0, v1 and v2 intersects with the ray (whose origin is *orig* and direction is *dir*) // Also don't forget to update tnear, u and v. Vector3f E1 = v1 - v0; Vector3f E2 = v2 - v0; Vector3f S = orig - v0; Vector3f S1 = crossProduct(dir, E2); Vector3f S2 = crossProduct(S, E1); float det = dotProduct(E1, S1); if(det == 0 || det < 0) return false; float reS1E1 = 1. / det; float t = dotProduct(S2, E2) * reS1E1; float b1 = dotProduct(S1, S) * reS1E1; float b2 = dotProduct(S2, dir) *reS1E1; if(t >= 0 && b1 >= 0 && b2 >= 0 && 1 - b1 - b2 >= 0){ tnear = t; u = b1; v = b2; return true; } return tnear > 0; }
效果图