raytracing/src/camera.rs

use std::f32::consts::PI;

use crate::{ray::Ray, vec3::Vec3};

#[derive(Debug)]
pub struct Camera {
    // raytracing
    pub anti_alias_rate: u32,
    pub pixel00_loc: Vec3,
    pub pixel_delta_u: Vec3,
    pub pixel_delta_v: Vec3,

    // camera
    dirty: bool,
    pub fov: f32,
    pub look_from: Vec3,
    pub look_at: Vec3,
    vup: Vec3,
    pub defocus_angle: f32,
    pub focus_dist: f32,

    // camera helpers
    u: Vec3,
    v: Vec3,
    w: Vec3,
    defocus_disk_u: Vec3,
    defocus_disk_v: Vec3,
}

// FIXME: kinda out of place in this file.
fn deg_to_rad(deg: f32) -> f32 {
    deg * PI / 180.
}

impl Camera {
    pub fn new() -> Self {
        Self {
            anti_alias_rate: 1,
            dirty: true,
            fov: 60.,
            pixel00_loc: Vec3::default(),
            pixel_delta_u: Vec3::default(),
            pixel_delta_v: Vec3::default(),
            look_from: Vec3::nil(),
            look_at: Vec3::new(0., 0., -1.),
            vup: Vec3::new(0., 1., 0.),
            defocus_angle: 0.,
            focus_dist: 10.,
            u: Vec3::default(),
            v: Vec3::default(),
            w: Vec3::default(),
            defocus_disk_u: Vec3::default(),
            defocus_disk_v: Vec3::default(),
        }
    }

    pub fn new_full(
        anti_alias_rate: u32,
        fov: f32,
        look_from: Vec3,
        look_at: Vec3,
        vup: Vec3,
        defocus_angle: f32,
        focus_dist: f32,
    ) -> Self {
        Self {
            anti_alias_rate,
            pixel00_loc: Vec3::default(),
            pixel_delta_u: Vec3::default(),
            pixel_delta_v: Vec3::default(),
            dirty: true,
            fov,
            look_from,
            look_at,
            vup,
            defocus_angle,
            focus_dist,
            u: Vec3::default(),
            v: Vec3::default(),
            w: Vec3::default(),
            defocus_disk_u: Vec3::default(),
            defocus_disk_v: Vec3::default(),
        }
    }

    pub fn init(&mut self, w: f32, hi: f32) {
        if !self.dirty {
            return;
        }

        // camera
        let theta = deg_to_rad(self.fov);
        let h = (theta / 2.).tan();
        self.w = (self.look_from - self.look_at).get_unit();
        self.u = self.vup.cross(&self.w).get_unit();
        self.v = self.w.cross(&self.u);

        // viewport
        let viewport_height = 2. * h * self.focus_dist;
        let viewport_width = viewport_height * (w / hi);
        let viewport_u = viewport_width * self.u;
        let viewport_v = viewport_height * -self.v;

        // variables
        self.pixel_delta_u = viewport_u / w;
        self.pixel_delta_v = viewport_v / hi;
        self.pixel00_loc =
            self.look_from - (self.focus_dist * self.w) - viewport_u / 2. - viewport_v / 2.;
        self.dirty = false;

        if self.defocus_angle != 0. {
            let defocus_radius = self.focus_dist * deg_to_rad(self.defocus_angle / 2.).tan();
            self.defocus_disk_u = self.u * defocus_radius;
            self.defocus_disk_v = self.v * defocus_radius;
        }
    }

    pub fn get_ray(&self, pixel_tl: Vec3, x: u32, y: u32) -> Ray {
        let pixel_loc = pixel_tl
            + (x * self.pixel_delta_u / (self.anti_alias_rate + 1) as f32)
            + (y * self.pixel_delta_v / (self.anti_alias_rate + 1) as f32);
        let ray_orig = if self.defocus_angle > 0. {
            self.defocus_disk_sample()
        } else {
            self.look_from
        };
        let ray_dir = pixel_loc - ray_orig;
        Ray::new(ray_orig, ray_dir)
    }

    pub fn set_fov(&mut self, fov: f32) {
        if self.fov != fov {
            self.fov = fov;
            self.dirty = true;
        }
    }

    pub fn set_anti_alias_rate(&mut self, rate: u32) {
        if self.anti_alias_rate != rate {
            self.anti_alias_rate = rate;
            self.dirty = true;
        }
    }

    pub fn set_look_from(&mut self, look_from: Vec3) {
        if self.look_from != look_from {
            self.look_from = look_from;
            self.dirty = true;
        }
    }

    pub fn set_look_at(&mut self, look_at: Vec3) {
        if self.look_at != look_at {
            self.look_at = look_at;
            self.dirty = true;
        }
    }

    pub fn set_vup(&mut self, vup: Vec3) {
        if self.vup != vup {
            self.vup = vup;
            self.dirty = true;
        }
    }

    pub fn add_defocus_blur(&mut self, defocus_angle: f32, focus_dist: f32) {
        if self.defocus_angle != defocus_angle || self.focus_dist != focus_dist {
            self.defocus_angle = defocus_angle;
            self.focus_dist = focus_dist;
            self.dirty = true;
        }
    }

    pub fn defocus_disk_sample(&self) -> Vec3 {
        let p = Vec3::random_in_unit_disk();
        self.look_from + (p.x() * self.defocus_disk_u) + (p.y() * self.defocus_disk_v)
    }
}