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extern crate nalgebra;

use self::nalgebra::Matrix4;
use self::nalgebra::Orthographic3;
use self::nalgebra::Rotation3;
use self::nalgebra::Vector3;

pub struct OrthoCamera {
    position: Vector3<f32>,
    width: f32,
    height: f32,
    zoom: f32,
    near: f32,
    far: f32,

    rotation: f32,

    ppu: f32,
}

impl OrthoCamera {
    pub fn new(width: f32, height: f32) -> Self {
        OrthoCamera {
            position: Vector3::new(0.0, 0.0, 0.0),
            width: width,
            height: height,
            zoom: 1.0,
            near: -100.0,
            far: 100.0,
            ppu: 256.0,
            rotation: 0.0,
        }
    }

    pub fn set_dimensions(&mut self, width: f32, height: f32) {
        self.width = width;
        self.height = height;
    }

    pub fn set_zoom(&mut self, zoom: f32) {
        self.zoom = zoom;
    }

    pub fn translate(&mut self, dx: f32, dy: f32) {
        self.position.x += dx;
        self.position.y += dy;
    }

    pub fn rotate(&mut self, rads: f32) {
        self.rotation += rads;
    }

    pub fn set_rotation(&mut self, rad: f32) {
        self.rotation = rad;
    }

    fn projection(&self) -> Matrix4<f32> {
        let effective_width = self.width / (self.zoom * self.ppu);
        let effective_height = self.height / (self.zoom * self.ppu);

        let half_width = effective_width / 2.0;
        let half_height = effective_height / 2.0;

        Orthographic3::new(
            -half_width,
            half_width,
            -half_height,
            half_height,
            self.near,
            self.far,
        ).unwrap()
    }

    fn rotation(&self) -> Matrix4<f32> {
        Rotation3::from_axis_angle(&Vector3::z_axis(), self.rotation).to_homogeneous()
    }

    fn view(&self) -> Matrix4<f32> {
        Matrix4::new_translation(&self.position)
    }

    pub fn combined(&self) -> [[f32; 4]; 4] {
        (self.projection() * (self.view() * self.rotation())).into()
    }
}