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2021/01/11に公開

# チャプター5

cgmathのドキュメント見てたら、castってのがあったので、それを使ってto_colorの実装を書き直しました。
あとは記事通り実装するだけでしたね。

``````fn to_color(v: Vector3<f32>) -> Vector3<i32>
{
const scale: f32 = 255.99;

return vec3(scale * v.x, scale * v.y, scale * v.z).cast().unwrap();
}

fn ray_color(ray: &Ray) -> Vector3<i32>
{
const white: Vector3<f32> = vec3(1.0, 1.0, 1.0);
const blue: Vector3<f32> = vec3(0.5, 0.7, 1.0);
const red: Vector3<f32> = vec3(1.0, 0.0, 0.0);

const center: Vector3<f32> = vec3(0.0, 0.0, -1.0);

if (hit_sphere(center, 0.5, &ray)) {
}

let unit_direction = ray.direction.normalize();
let t = 0.5 * (unit_direction.y + 1.0);
let rgb = white.lerp(blue, t);

}

fn hit_sphere(center: Vector3<f32>, radius: f32, ray:&Ray) -> bool {
let oc = ray.origin - center;
let a = dot(ray.direction, ray.direction);
let b = 2.0 * dot(oc, ray.direction);

return  b * b - 4.0 * a * c > 0.0;
}
``````

# チャプター 6.1

blenderで法線ベクトル表示するところはこんな感じなのかなー。
vec3(1.0, 1.0, 1.0)じゃなくて、Vector3::Oneとかでやりたいな。

``````fn ray_color(ray: &Ray) -> Vector3<i32>
{
const white: Vector3<f32> = vec3(1.0, 1.0, 1.0);
const blue: Vector3<f32> = vec3(0.5, 0.7, 1.0);

const center: Vector3<f32> = vec3(0.0, 0.0, -1.0);

let t = hit_sphere(center, 0.5, &ray);

if (t > 0.0) {
let n = (ray.at(t) - center).normalize();
}

let unit_direction = ray.direction.normalize();
let t = 0.5 * (unit_direction.y + 1f32);
let rgb = white.lerp(blue, t);

}

fn hit_sphere(center: Vector3<f32>, radius: f32, ray:&Ray) -> f32 {
let oc = ray.origin - center;
let a = dot(ray.direction, ray.direction);
let b = 2.0 * dot(oc, ray.direction);

let discriminant = b * b - 4.0 * a * c;

if (discriminant < 0.0) {
return -1.0;
}
else {
return (- b - discriminant.sqrt()) / (2.0 * a);
}
}
``````

# チャプター6.2

``````fn length_squared(v: Vector3<f32>) -> f32 {
v.x * v.x + v.y * v.y + v.z * v.z
}

fn hit_sphere(center: Vector3<f32>, radius: f32, ray:&Ray) -> f32 {
let oc = ray.origin - center;
let a = length_squared(ray.direction);
let half_b = dot(oc, ray.direction);

let discriminant = half_b * half_b - a * c;

if discriminant < 0.0 {
return -1.0;
}
else {
return (- half_b - discriminant.sqrt()) / a;
}
}
``````

# チャプター6.3 - 6.7

• set_face_normalをやろうとするとmutにしなきゃいけないのが嫌だったので、Sphereでは直接計算してます。
• Vector3でi32はColorって名前で扱えるように変更。コードがかっこよくなるかなと。

チャプター６はけっこうなボリュームでした。

コードを全部書いておきます。

``````use std::fmt;
use cgmath::prelude::*;
use cgmath::{Vector3, vec3, dot};

type Color = Vector3<i32>;

pub struct HitRecord {
pub p: Vector3<f32>,
pub normal: Vector3<f32>,
pub t: f32,
pub front_face: bool
}

impl HitRecord {
pub fn set_face_normal(&mut self, ray: &Ray, outward_normal: Vector3<f32>) {
self.front_face = dot(ray.direction, outward_normal) < 0.0;
self.normal = if self.front_face {
outward_normal
} else {
-outward_normal
}
}
}

pub trait HitTable {
fn hit(&self, ray: &Ray, t_min: f32, t_max: f32) -> Option<HitRecord>;
}

pub struct HitTableList {
list: Vec<Box<dyn HitTable>>
}

impl HitTableList {
pub fn new() -> Self {
HitTableList {
list: vec![],
}
}

pub fn push(&mut self, hitable: impl HitTable + 'static) {
self.list.push(Box::new(hitable))
}

pub fn clear(&mut self) {
self.list.clear()
}
}

impl HitTable for HitTableList {
fn hit(&self, ray: &Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
let mut closest_so_far = t_max;
let mut hit_anything: Option<HitRecord> = None;
for h in self.list.iter() {
if let Some(hit) = h.hit(ray, t_min, closest_so_far) {
closest_so_far = hit.t;
hit_anything = Some(hit);
}
}
hit_anything
}
}

pub struct Sphere {
center: Vector3<f32>,
}

impl Sphere {
pub fn new(center: Vector3<f32>, radius: f32) -> Self {
}
}

impl HitTable for Sphere {
fn hit(&self, ray: &Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
let oc = ray.origin - self.center;
let a = length_squared(ray.direction);
let half_b = dot(oc, ray.direction);

let discriminant = half_b.powi(2) - a * c;

if discriminant > 0.0 {
let sqrtd = discriminant.sqrt();

// Find the nearest root that lies in the acceptable range.
let mut root = (- half_b - sqrtd) / a;
if root < t_min || t_max < root {
root = (- half_b + sqrtd) / a;
if root < t_min || t_max < root {
return None
}
}

let p = ray.at(root);
let outward_normal = (p - self.center) / self.radius;

// set face normal
let front_face = dot(ray.direction, outward_normal) < 0.0;
let normal = if front_face {outward_normal} else {-outward_normal};

return Some(HitRecord{t: root, p: p, normal: normal, front_face: front_face});
}

None
}
}

pub struct Ray {
pub origin: Vector3<f32>,
pub direction: Vector3<f32>
}

impl Ray {
pub fn new(o:Vector3<f32>, d:Vector3<f32>) -> Self {
Ray{origin: o, direction: d}
}

pub fn at(&self, t: f32) -> Vector3<f32> {
self.origin + self.direction * t
}
}

impl fmt::Debug for Ray {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "({:?}, {:?})", self.origin, self.direction)
}
}

fn to_color(v: Vector3<f32>) -> Color
{
const scale: f32 = 255.99;

return vec3(scale * v.x, scale * v.y, scale * v.z).cast().unwrap();
}

fn ray_color(ray: &Ray, world: &HitTable) -> Color
{
const white: Vector3<f32> = vec3(1.0, 1.0, 1.0);
const blue: Vector3<f32> = vec3(0.5, 0.7, 1.0);

if let Some(hit) = world.hit(ray, 0.0, f32::INFINITY) {
}

let unit_direction = ray.direction.normalize();
let t = 0.5 * (unit_direction.y + 1f32);
let rgb = white.lerp(blue, t);

}

fn length_squared(v: Vector3<f32>) -> f32 {
v.x * v.x + v.y * v.y + v.z * v.z
}

fn hit_sphere(center: Vector3<f32>, radius: f32, ray:&Ray) -> f32 {
let oc = ray.origin - center;
let a = length_squared(ray.direction);
let half_b = dot(oc, ray.direction);

let discriminant = half_b * half_b - a * c;

if discriminant < 0.0 {
return -1.0;
}
else {
return (- half_b - discriminant.sqrt()) / a;
}
}

fn main() {

// Image

const aspect_ratio: f32 = 16.0 / 9.0;
const image_width: i32 = 400;
const image_height: i32 = (image_width as f32 / aspect_ratio) as i32;

// World

let mut world = HitTableList::new();
world.push(Sphere::new(vec3(0.0, 0.0, -1.0), 0.5));
world.push(Sphere::new(vec3(0.0, -100.5, -1.0), 100.0));

// Camera

let viewport_height: f32 = 2.0;
let viewport_width = aspect_ratio * viewport_height;
let focal_length = 1.0;

let origin: Vector3<f32> = Vector3::zero();
let horizontal: Vector3<f32> = vec3(viewport_width, 0.0, 0.0);
let vertical: Vector3<f32> = vec3(0.0, viewport_height, 0.0);
let lower_left_corner = origin - horizontal / 2.0 - vertical / 2.0 - vec3(0.0, 0.0, focal_length);

// Render

println!("P3\n {} {} \n255", image_width, image_height);

for j in (0..image_height).rev() {
for i in 0..image_width {
let u = i as f32/(image_width - 1) as f32;
let v = j as f32/(image_height - 1) as f32;
let r = Ray::new(origin, lower_left_corner + u * horizontal + v * vertical - origin);
let pixel_color = ray_color(&r, &world);
println!("{} {} {}", pixel_color.x, pixel_color.y, pixel_color.z);

}
}
}
``````

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