glium 0.36.0

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
Documentation 
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pub struct CameraState {
    aspect_ratio: f32,
    position: (f32, f32, f32),
    direction: (f32, f32, f32),

    moving_up: bool,
    moving_left: bool,
    moving_down: bool,
    moving_right: bool,
    moving_forward: bool,
    moving_backward: bool,
}

impl CameraState {
    pub fn new() -> CameraState {
        CameraState {
            aspect_ratio: 1024.0 / 768.0,
            position: (0.1, 0.1, 1.0),
            direction: (0.0, 0.0, -1.0),
            moving_up: false,
            moving_left: false,
            moving_down: false,
            moving_right: false,
            moving_forward: false,
            moving_backward: false,
        }
    }

    pub fn set_position(&mut self, pos: (f32, f32, f32)) {
        self.position = pos;
    }

    pub fn set_direction(&mut self, dir: (f32, f32, f32)) {
        self.direction = dir;
    }

    pub fn get_perspective(&self) -> [[f32; 4]; 4] {
        let fov: f32 = 3.141592 / 2.0;
        let zfar = 1024.0;
        let znear = 0.1;

        let f = 1.0 / (fov / 2.0).tan();

        // note: remember that this is column-major, so the lines of code are actually columns
        [
            [f / self.aspect_ratio,    0.0,              0.0              ,   0.0],
            [         0.0         ,     f ,              0.0              ,   0.0],
            [         0.0         ,    0.0,  (zfar+znear)/(zfar-znear)    ,   1.0],
            [         0.0         ,    0.0, -(2.0*zfar*znear)/(zfar-znear),   0.0],
        ]
    }

    pub fn get_view(&self) -> [[f32; 4]; 4] {
        let f = {
            let f = self.direction;
            let len = f.0 * f.0 + f.1 * f.1 + f.2 * f.2;
            let len = len.sqrt();
            (f.0 / len, f.1 / len, f.2 / len)
        };

        let up = (0.0, 1.0, 0.0);

        let s = (f.1 * up.2 - f.2 * up.1,
                 f.2 * up.0 - f.0 * up.2,
                 f.0 * up.1 - f.1 * up.0);

        let s_norm = {
            let len = s.0 * s.0 + s.1 * s.1 + s.2 * s.2;
            let len = len.sqrt();
            (s.0 / len, s.1 / len, s.2 / len)
        };

        let u = (s_norm.1 * f.2 - s_norm.2 * f.1,
                 s_norm.2 * f.0 - s_norm.0 * f.2,
                 s_norm.0 * f.1 - s_norm.1 * f.0);

        let p = (-self.position.0 * s.0 - self.position.1 * s.1 - self.position.2 * s.2,
                 -self.position.0 * u.0 - self.position.1 * u.1 - self.position.2 * u.2,
                 -self.position.0 * f.0 - self.position.1 * f.1 - self.position.2 * f.2);

        // note: remember that this is column-major, so the lines of code are actually columns
        [
            [s_norm.0, u.0, f.0, 0.0],
            [s_norm.1, u.1, f.1, 0.0],
            [s_norm.2, u.2, f.2, 0.0],
            [p.0, p.1,  p.2, 1.0],
        ]
    }

    pub fn update(&mut self) {
        let f = {
            let f = self.direction;
            let len = f.0 * f.0 + f.1 * f.1 + f.2 * f.2;
            let len = len.sqrt();
            (f.0 / len, f.1 / len, f.2 / len)
        };

        let up = (0.0, 1.0, 0.0);

        let s = (f.1 * up.2 - f.2 * up.1,
                 f.2 * up.0 - f.0 * up.2,
                 f.0 * up.1 - f.1 * up.0);

        let s = {
            let len = s.0 * s.0 + s.1 * s.1 + s.2 * s.2;
            let len = len.sqrt();
            (s.0 / len, s.1 / len, s.2 / len)
        };

        let u = (s.1 * f.2 - s.2 * f.1,
                 s.2 * f.0 - s.0 * f.2,
                 s.0 * f.1 - s.1 * f.0);

        if self.moving_up {
            self.position.0 += u.0 * 0.01;
            self.position.1 += u.1 * 0.01;
            self.position.2 += u.2 * 0.01;
        }

        if self.moving_left {
            self.position.0 -= s.0 * 0.01;
            self.position.1 -= s.1 * 0.01;
            self.position.2 -= s.2 * 0.01;
        }

        if self.moving_down {
            self.position.0 -= u.0 * 0.01;
            self.position.1 -= u.1 * 0.01;
            self.position.2 -= u.2 * 0.01;
        }

        if self.moving_right {
            self.position.0 += s.0 * 0.01;
            self.position.1 += s.1 * 0.01;
            self.position.2 += s.2 * 0.01;
        }

        if self.moving_forward {
            self.position.0 += f.0 * 0.01;
            self.position.1 += f.1 * 0.01;
            self.position.2 += f.2 * 0.01;
        }

        if self.moving_backward {
            self.position.0 -= f.0 * 0.01;
            self.position.1 -= f.1 * 0.01;
            self.position.2 -= f.2 * 0.01;
        }
    }

    pub fn process_input(&mut self, event: &glium::winit::event::WindowEvent) {
        use glium::winit::keyboard::{PhysicalKey, KeyCode};
        let glium::winit::event::WindowEvent::KeyboardInput { event, .. } = event else {
            return
        };
        let pressed = event.state == glium::winit::event::ElementState::Pressed;
        match &event.physical_key {
            PhysicalKey::Code(KeyCode::ArrowUp) => self.moving_up = pressed,
            PhysicalKey::Code(KeyCode::ArrowDown) => self.moving_down = pressed,
            PhysicalKey::Code(KeyCode::KeyA) => self.moving_left = pressed,
            PhysicalKey::Code(KeyCode::KeyD) => self.moving_right = pressed,
            PhysicalKey::Code(KeyCode::KeyW) => self.moving_forward = pressed,
            PhysicalKey::Code(KeyCode::KeyS) => self.moving_backward = pressed,
            _ => (),
        };
    }
}