rustray/src/ray.rs

use cgmath::{vec2, vec3, InnerSpace, Vector3};

use super::view::View;

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

impl Ray {
    pub fn new(origin: Vector3<f32>, direction: Vector3<f32>) -> Ray {
        let inv_direction = 1.0 / direction;

        let x = (inv_direction.x < 0.0) as usize;
        let y = (inv_direction.y < 0.0) as usize;
        let z = (inv_direction.z < 0.0) as usize;

        Ray {
            origin,
            direction,
            inv_direction,
            signs: Vector3::new(x, y, z),
        }
    }

    pub fn primary_ray(x: f32, y: f32, dim_x: f32, dim_y: f32, view: &View) -> Ray {
        let aspect_ratio = dim_x / dim_y;

        let uv = vec2((x + 0.5) / dim_x, (y + 0.5) / dim_y);

        let (up, right) = view.axises();

        let trans = 2.0 * uv - vec2(1.0, 1.0);
        let raw_dir = view.look_at + right * trans.x + up * trans.y;

        let dir = vec3(
            raw_dir.x * aspect_ratio,
            raw_dir.y,
            raw_dir.z * aspect_ratio,
        )
        .normalize();

        return Self::new(view.position, dir);
    }
}