6.1/6.1.Shading with Surface Normals

src/image.rs

@@ -10,6 +10,41 @@ impl Color {
     }
 }
 
+pub fn gen_ray_sphere_normal_ppm_p3(width: i32, height: i32, camera_center: Vec3, viewport_top_left_pixel_center: Vec3, viewport_u_delta: Vec3, viewport_v_delta: Vec3) -> String {
+    let mut img_content = format!("P3\n{} {}\n255\n", width, height);
+
+    for j in 0..height {
+       
+        if j % 10 == 0 {
+            println!("scan line {}/{} ", j + 1, height);
+        }
+
+        for i in 0..width {
+            // every pixcel's position
+            let pixel_center = viewport_top_left_pixel_center + (i as f32 * viewport_u_delta) + (j as f32 * viewport_v_delta);
+            // Vector(camera, pixcel)
+            let ray_direction = pixel_center - camera_center;
+            // ray
+            let r = Ray::new(camera_center,  ray_direction);
+
+            /*
+             球
+             */
+            let _sphere_center = Point::new(0.0, 0.0, -1.0);
+            let sphere_radius = 0.5;
+
+            // determind color
+            let color = ray_color_at_sphere_normal(&r, _sphere_center, sphere_radius);
+            // content
+            img_content.push_str(color.to_color().as_str());
+            img_content.push('\n');
+        }
+    }
+
+    img_content
+}
+
+
 pub fn gen_ray_sphere_ppm_p3(width: i32, height: i32, camera_center: Vec3, viewport_top_left_pixel_center: Vec3, viewport_u_delta: Vec3, viewport_v_delta: Vec3) -> String {
     let mut img_content = format!("P3\n{} {}\n255\n", width, height);
 
@@ -85,9 +120,51 @@ fn hit_sphere(r: &Ray, sphere_center: Point, sphere_radius: f32) -> bool {
 }
 
 
+fn hit_sphere_normal(r: &Ray, sphere_center: Point, sphere_radius: f32) -> f32 {
+    let a: f32 = r.direction.length_squared();
+    let h = r.direction.dot(sphere_center - r.point);
+    // let b = -2.0 * r.direction.dot(sphere_center - r.point);
+    let c = (sphere_center - r.point).length_squared() - sphere_radius * sphere_radius;
+
+    let discriminant = h*h - a*c;
+
+    // // 两个焦点
+    let disc_sqrt = discriminant.sqrt();
+    let near = (h - disc_sqrt) / a;
+    let far = (h + disc_sqrt) / a;
+
+    // 射线起点可能在球内的情况
+    if near >= 0.0 && far >= 0.0 {
+        return near.min(far);
+    } else if near > 0.0 {
+        return near;
+    } else if far > 0.0 {
+        return far;
+    } else {
+        return -1.0
+    }
+}
+
 /*
-get color of this ray; background
+ray color functions
 */
+fn ray_color_at_sphere_normal(r: &Ray, sphere_center: Point, sphere_radius: f32) -> Color {
+
+    let t = hit_sphere_normal(r, sphere_center, sphere_radius);
+    if t >= 0.0 {
+        let inter_point = r.at(t);
+        // 单位向量
+        let n = inter_point / inter_point.dot(inter_point);
+        // 法向量也是 -1～1  +1再x0.5让他落到颜色的区间
+        return 0.5 * (n - sphere_center + Point::new(1.0, 1.0, 1.0))
+    }
+
+    // v / |v|
+    let unit_direction = r.direction / r.direction.length();
+    let a = 0.5*(unit_direction.y + 1.0);
+    return (1.0-a)*Color::new(1.0, 1.0, 1.0) + a*Color::new(0.5, 0.7, 1.0);
+}
+
 fn ray_color_at_sphere(r: &Ray, sphere_center: Point, sphere_radius: f32) -> Color {
 
     // return RED if hit sphere

src/main.rs

@@ -4,7 +4,7 @@ use vec3::{Vec3};
 use point::{Point};
 use ray::{Ray};
 
-use crate::image::gen_ray_sphere_ppm_p3;
+use crate::image::{gen_ray_sphere_normal_ppm_p3, gen_ray_sphere_ppm_p3};
 
 mod image;
 mod write_file_util;
@@ -19,9 +19,47 @@ fn main() {
     println!("==================================");
     ray_sphere_scene_render();
     println!("==================================");
+    ray_sphere_normal_scene_render();
+    println!("==================================");
 }
 
 
+fn ray_sphere_normal_scene_render() {
+    let aspect_ratio = 16.0/9.0;
+    let image_width = 400;
+    // aleast 1px
+    let image_height = ((image_width as f32 / aspect_ratio) as i32).max(1);
+
+    let viewport_height = 2.0;
+    let viewport_width = viewport_height * (image_width as f32 / image_height as f32);
+
+    println!("set image({},{}), viewport({},{})", image_width, image_height, viewport_width, viewport_height);
+    let viewport_u = Vec3::new(viewport_width, 0.0, 0.0);
+    // image x--> right
+    //       |
+    //       y
+    // space: y up , x right , z back, -z front
+    let viewport_v = Vec3::new(0.0, -viewport_height, 0.0);
+
+    // width per pix
+    let viewport_u_delta = viewport_u / (image_width as f32);
+    // height per pix
+    let viewport_v_delta = viewport_v / (image_height as f32);
+
+    // camerea position
+    let camera_center = Point::new(0.0, 0.0, 0.0);
+    // -z  1.0  viewport to camera
+    let focal_length = Vec3::new(0.0, 0.0, -1.0);
+    // camera position --> viewport center ---> top center --> top left
+    let viewport_top_left_pixel = camera_center + focal_length - viewport_u / 2.0 - viewport_v / 2.0;
+    // padding 0.5* delta u/v
+    let viewport_top_left_pixel_center = viewport_top_left_pixel - viewport_u_delta / 2.0 - viewport_v_delta / 2.0;
+
+    let ppm_content = gen_ray_sphere_normal_ppm_p3(image_width, image_height, camera_center, viewport_top_left_pixel_center, viewport_u_delta, viewport_v_delta);
+
+    write_image(ppm_content, "./target/ray_sphere_normal_scene_render.ppm".to_string())
+}
+
 fn ray_sphere_scene_render() {
     let aspect_ratio = 16.0/9.0;
     let image_width = 400;