bevy/src/render/camera.rs

use crate::math::Mat4;

pub struct ActiveCamera;
pub struct ActiveCamera2d;

pub enum CameraType {
    Projection {
        fov: f32,
        aspect_ratio: f32,
        near: f32,
        far: f32,
    },
    Orthographic {
        left: f32,
        right: f32,
        bottom: f32,
        top: f32,
        near: f32,
        far: f32,
    },
}

pub struct Camera {
    pub view_matrix: Mat4,
    pub camera_type: CameraType,
}

impl Camera {
    pub fn new(camera_type: CameraType) -> Self {
        Camera {
            view_matrix: Mat4::identity(),
            camera_type,
        }
    }

    pub fn update(&mut self, width: u32, height: u32) {
        match &mut self.camera_type {
            CameraType::Projection {
                aspect_ratio,
                fov,
                near,
                far,
            } => {
                *aspect_ratio = width as f32 / height as f32;
                self.view_matrix =
                    get_perspective_projection_matrix(*fov, *aspect_ratio, *near, *far)
            }
            CameraType::Orthographic {
                left,
                right,
                bottom,
                top,
                near,
                far,
            } => {
                *right = width as f32;
                *top = height as f32;
                self.view_matrix =
                    get_orthographic_projection_matrix(*left, *right, *bottom, *top, *near, *far)
            }
        }
    }
}

pub fn get_perspective_projection_matrix(fov: f32, aspect_ratio: f32, near: f32, far: f32) -> Mat4 {
    let projection = Mat4::perspective_rh_gl(fov, aspect_ratio, near, far);

    opengl_to_wgpu_matrix() * projection
}

pub fn get_orthographic_projection_matrix(
    left: f32,
    right: f32,
    bottom: f32,
    top: f32,
    near: f32,
    far: f32,
) -> Mat4 {
    let projection = Mat4::orthographic_rh_gl(left, right, bottom, top, near, far);

    opengl_to_wgpu_matrix() * projection
}

pub fn opengl_to_wgpu_matrix() -> Mat4 {
    Mat4::from_cols_array(&[
        1.0, 0.0, 0.0, 0.0, 0.0, -1.0, 0.0, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.5, 1.0,
    ])
}