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use crate::calculus::calculus::{Ray, Vec3};
use crate::global::{DisplayBuffer, Pixel, CAMERA_CENTER, FOCAL_LENGTH, IMG_HEIGHT, IMG_WIDTH, VIEWPORT_HEIGHT, VIEWPORT_WIDTH};
fn ray_color(ray: &Ray) -> Vec3 {
let unit_direction = ray.direction.unit();
let a = 0.5 * (unit_direction.y + 1.0);
let vec_1 = Vec3 { x:1.0, y: 1.0, z: 1.0 };
let vec_2 = Vec3 { x: 0.5, y: 0.7, z: 1.0 };
vec_1.scalar_mul(1.0 - a)
.add(&vec_2.scalar_mul(a))
}
pub fn render(display_buffer: &mut DisplayBuffer) {
let viewport_hor_vector = Vec3{ x: VIEWPORT_WIDTH as f32, y: 0.0, z: 0.0 };
let viewport_ver_vector = Vec3 { x: 0.0, y: -1f32 * VIEWPORT_HEIGHT as f32, z: 0.0 };
let delta_pixel_u = viewport_hor_vector.scalar_mul(1.0 / VIEWPORT_WIDTH as f32);
let delta_pixel_v = viewport_ver_vector.scalar_mul(1.0 / VIEWPORT_WIDTH as f32);
let viewport_upper_left = CAMERA_CENTER
.sub(&Vec3 { x: 0f32, y: 0f32, z: FOCAL_LENGTH})
.sub(&viewport_hor_vector.scalar_mul(0.5))
.sub(&viewport_ver_vector.scalar_mul(0.5));
let pixel_upper_left = viewport_upper_left.add(
&delta_pixel_u.add(&delta_pixel_u).scalar_mul(0.5)
);
(0..IMG_HEIGHT).for_each(|j| {
(0..IMG_WIDTH).for_each(|i| {
let pixel_center = pixel_upper_left
.add(&delta_pixel_u.scalar_mul(i as f32))
.add(&delta_pixel_v.scalar_mul(j as f32));
let ray_direction = pixel_center.sub(&CAMERA_CENTER);
let ray = Ray {
origin: &CAMERA_CENTER,
direction: &ray_direction,
};
let Vec3 {x, y, z} = ray_color(&ray);
display_buffer[j][i] = Pixel::from_frac(x, y, z);
})
})
}
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