# camera.rs - source
Source of the Rust file `maplibre/src/render/camera.rs`.

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    //! Main camera

    use cgmath::{num_traits::clamp, prelude::*, *};

    use crate::util::SignificantlyDifferent;

    #[rustfmt::skip]
    pub const OPENGL_TO_WGPU_MATRIX: Matrix4<f64> = Matrix4::new(
        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,
    );

    #[rustfmt::skip]
    pub const FLIP_Y: Matrix4<f64> = Matrix4::new(
        1.0, 0.0, 0.0, 0.0,
        0.0, -1.0, 0.0, 0.0,
        0.0, 0.0, 1.0, 0.0,
        0.0, 0.0, 0.0, 1.0,
    );

    #[derive(Debug, Clone, Copy)]
    pub struct ViewProjection(pub Matrix4<f64>);

    impl ViewProjection {
        #[tracing::instrument(skip_all)]
        pub fn invert(&self) -> InvertedViewProjection {
            InvertedViewProjection(self.0.invert().expect("Unable to invert view projection"))
        }

        pub fn project(&self, vector: Vector4<f64>) -> Vector4<f64> {
            self.0 * vector
        }

        #[tracing::instrument(skip_all)]
        pub fn to_model_view_projection(&self, projection: Matrix4<f64>) -> ModelViewProjection {
            ModelViewProjection(self.0 * projection)
        }

        pub fn downcast(&self) -> Matrix4<f32> {
            self.0
                .cast::<f32>()
                .expect("Unable to cast view projection to f32")
        }
    }

    pub struct InvertedViewProjection(Matrix4<f64>);

    impl InvertedViewProjection {
        pub fn project(&self, vector: Vector4<f64>) -> Vector4<f64> {
            self.0 * vector
        }
    }

    pub struct ModelViewProjection(Matrix4<f64>);

    impl ModelViewProjection {
        pub fn downcast(&self) -> Matrix4<f32> {
            self.0
                .cast::<f32>()
                .expect("Unable to cast view projection to f32")
        }
    }

    const MIN_PITCH: Deg<f64> = Deg(-30.0);
    const MAX_PITCH: Deg<f64> = Deg(30.0);

    const MIN_YAW: Deg<f64> = Deg(-30.0);
    const MAX_YAW: Deg<f64> = Deg(30.0);

    #[derive(Debug, Clone)]
    pub struct Camera {
        position: Point2<f64>,
        yaw: Rad<f64>,
        pitch: Rad<f64>,
        roll: Rad<f64>,
    }

    impl SignificantlyDifferent for Camera {
        type Epsilon = f64;

        fn ne(&self, other: &Self, epsilon: Self::Epsilon) -> bool {
            self.position.abs_diff_ne(&other.position, epsilon)
                || self.yaw.abs_diff_ne(&other.yaw, epsilon)
                || self.pitch.abs_diff_ne(&other.pitch, epsilon)
                || self.roll.abs_diff_ne(&other.roll, epsilon)
        }
    }

    impl Camera {
        pub fn new<V: Into<Point2<f64>>, Y: Into<Rad<f64>>, P: Into<Rad<f64>>>(
            position: V,
            yaw: Y,
            pitch: P,
        ) -> Self {
            Self {
                position: position.into(),
                yaw: yaw.into(),
                pitch: pitch.into(),
                roll: Rad::zero(), // TODO: initialize
            }
        }

        pub fn calc_matrix(&self, camera_height: f64) -> Matrix4<f64> {
            Matrix4::from_translation(Vector3::new(0.0, 0.0, -camera_height))
                * Matrix4::from_angle_x(self.pitch)
                * Matrix4::from_angle_y(self.yaw)
                * Matrix4::from_angle_z(self.roll)
                * Matrix4::from_translation(Vector3::new(-self.position.x, -self.position.y, 0.0))
        }

        pub fn position(&self) -> Point2<f64> {
            self.position
        }

        pub fn get_yaw(&self) -> Rad<f64> {
            self.yaw
        }

        pub fn yaw<P: Into<Rad<f64>>>(&mut self, delta: P) {
            let new_yaw = self.yaw + delta.into();

            if new_yaw <= MAX_YAW.into() && new_yaw >= MIN_YAW.into() {
                self.yaw = new_yaw;
            }
        }

        pub fn get_roll(&self) -> Rad<f64> {
            self.roll
        }

        pub fn roll<P: Into<Rad<f64>>>(&mut self, delta: P) {
            self.roll += delta.into();
        }

        pub fn get_pitch(&self) -> Rad<f64> {
            self.pitch
        }

        pub fn pitch<P: Into<Rad<f64>>>(&mut self, delta: P) {
            let new_pitch = self.pitch + delta.into();

            if new_pitch <= MAX_PITCH.into() && new_pitch >= MIN_PITCH.into() {
                self.pitch = new_pitch;
            }
        }

        pub fn move_relative(&mut self, delta: Vector2<f64>) {
            self.position += delta;
        }

        pub fn move_to(&mut self, new_position: Point2<f64>) {
            self.position = new_position;
        }

        pub fn position_vector(&self) -> Vector2<f64> {
            self.position.to_vec()
        }

        pub fn to_3d(&self, camera_height: f64) -> Point3<f64> {
            Point3::new(self.position.x, self.position.y, camera_height)
        }
        pub fn set_yaw<P: Into<Rad<f64>>>(&mut self, yaw: P) {
            let new_yaw = yaw.into();
            let max: Rad<_> = MAX_YAW.into();
            let min: Rad<_> = MIN_YAW.into();
            self.yaw = Rad(new_yaw.0.min(max.0).max(min.0))
        }
        pub fn set_pitch<P: Into<Rad<f64>>>(&mut self, pitch: P) {
            let new_pitch = pitch.into();
            let max: Rad<_> = MAX_PITCH.into();
            let min: Rad<_> = MIN_PITCH.into();
            self.pitch = Rad(new_pitch.0.min(max.0).max(min.0))
        }
        pub fn set_roll<P: Into<Rad<f64>>>(&mut self, roll: P) {
            self.roll = roll.into();
        }
    }

    #[derive(PartialEq, Copy, Clone, Default)]
    pub struct EdgeInsets {
        pub top: f64,
        pub bottom: f64,
        pub left: f64,
        pub right: f64,
    }

    impl EdgeInsets {
        /**
         * Utility method that computes the new apprent center or vanishing point after applying insets.
         * This is in pixels and with the top left being (0.0) and +y being downwards.
         *
         * @param {number} width the width
         * @param {number} height the height
         * @returns {Point} the point
         * @memberof EdgeInsets
         */
        pub fn center(&self, width: f64, height: f64) -> Point2<f64> {
            // Clamp insets so they never overflow width/height and always calculate a valid center
            let x = clamp((self.left + width - self.right) / 2.0, 0.0, width);
            let y = clamp((self.top + height - self.bottom) / 2.0, 0.0, height);

            return Point2::new(x, y);
        }
    }

    pub struct Perspective {
        fovy: Rad<f64>,
    }

    impl Perspective {
        pub fn new<F: Into<Rad<f64>>>(fovy: F) -> Self {
            let rad = fovy.into();
            Self { fovy: rad }
        }

        pub fn fovy(&self) -> Rad<f64> {
            self.fovy
        }
        pub fn fovx(&self, width: f64, height: f64) -> Rad<f64> {
            let aspect = width / height;
            Rad(2.0 * ((self.fovy / 2.0).tan() * aspect).atan())
        }

        pub fn y_tan(&self) -> f64 {
            let half_fovy = self.fovy / 2.0;
            half_fovy.tan()
        }
        pub fn x_tan(&self, width: f64, height: f64) -> f64 {
            let half_fovx = self.fovx(width, height) / 2.0;
            half_fovx.tan()
        }

        pub fn offset_x(&self, center_offset: Point2<f64>, width: f64) -> f64 {
            center_offset.x * 2.0 / width
        }

        pub fn offset_y(&self, center_offset: Point2<f64>, height: f64) -> f64 {
            center_offset.y * 2.0 / height
        }

        pub fn calc_matrix(&self, aspect: f64, near_z: f64, far_z: f64) -> Matrix4<f64> {
            perspective(self.fovy, aspect, near_z, far_z)
        }

        pub fn calc_matrix_with_center(
            &self,
            width: f64,
            height: f64,
            near_z: f64,
            far_z: f64,
            center_offset: Point2<f64>,
        ) -> Matrix4<f64> {
            let ymax = near_z * self.y_tan();

            //TODO maybe just: let xmax = ymax * aspect;
            let xmax = near_z * self.x_tan(width, height);

            let offset_x = self.offset_x(center_offset, width);
            let offset_y = self.offset_y(center_offset, height);
            frustum(
                // https://webglfundamentals.org/webgl/lessons/webgl-qna-how-can-i-move-the-perspective-vanishing-point-from-the-center-of-the-canvas-.html
                xmax * (-1.0 + offset_x), /* = -xmax + (center_offset.x * screen_to_near_factor_x)
                                                     where:
                                                      screen_to_near_factor_x = near_width / width
                                                      where:
                                                        near_width = xmax * 2.0
                                          */
                xmax * (1.0 + offset_x),
                ymax * (-1.0 + offset_y),
                ymax * (1.0 + offset_y),
                near_z,
                far_z,
            )
        }
    }