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use crate::core::*;

pub struct Camera {
    position: Vec3,
    target: Vec3,
    up: Vec3,
    fov: Degrees,
    z_near: f32,
    z_far: f32,
    view: Mat4,
    projection: Mat4,
    screen2ray: Mat4,
    matrix_buffer: UniformBuffer,
    frustrum: [Vec4; 6]
}

impl Camera
{
    fn new(gl: &Gl) -> Camera
    {
        Camera {matrix_buffer: UniformBuffer::new(gl, &vec![16, 16, 16, 3, 1]).unwrap(), frustrum: [vec4(0.0, 0.0, 0.0, 0.0); 6], fov: degrees(0.0), z_near: 0.0, z_far: 0.0,
            position: vec3(0.0, 0.0, 5.0), target: vec3(0.0, 0.0, 0.0), up: vec3(0.0, 1.0, 0.0),
            view: Mat4::identity(), projection: Mat4::identity(), screen2ray: Mat4::identity()}
    }

    pub fn new_orthographic(gl: &Gl, position: Vec3, target: Vec3, up: Vec3, width: f32, height: f32, depth: f32) -> Camera
    {
        let mut camera = Camera::new(gl);
        camera.set_view(position, target, up);
        camera.set_orthographic_projection(width, height, depth);
        camera
    }

    pub fn new_perspective(gl: &Gl, position: Vec3, target: Vec3, up: Vec3, fovy: Degrees, aspect: f32, z_near: f32, z_far: f32) -> Camera
    {
        let mut camera = Camera::new(gl);
        camera.set_view(position, target, up);
        camera.set_perspective_projection(fovy, aspect, z_near, z_far);
        camera
    }

    pub fn set_perspective_projection(&mut self, fovy: Degrees, aspect: f32, z_near: f32, z_far: f32)
    {
        if z_near < 0.0 || z_near > z_far { panic!("Wrong perspective camera parameters") };
        self.fov = fovy;
        self.z_near = z_near;
        self.z_far = z_far;
        self.projection = perspective(fovy, aspect, z_near, z_far);
        self.update_screen2ray();
        self.update_matrix_buffer();
        self.update_frustrum();
    }

    pub fn set_orthographic_projection(&mut self, width: f32, height: f32, depth: f32)
    {
        self.fov = degrees(0.0);
        self.z_near = 0.0;
        self.z_far = depth;
        self.projection = ortho(-0.5 * width, 0.5 * width, -0.5 * height, 0.5 * height, 0.0, depth);
        self.update_screen2ray();
        self.update_matrix_buffer();
        self.update_frustrum();
    }

    pub fn set_size(&mut self, width: f32, height: f32) {
        if self.fov == degrees(0.0) {
            self.set_orthographic_projection(width, height, self.z_far);
        }
        else {
            self.set_perspective_projection(self.fov, width as f32 / height as f32, self.z_near, self.z_far);
        }
    }

    pub fn set_view(&mut self, position: Vec3, target: Vec3, up: Vec3)
    {
        self.position = position;
        self.target = target;
        let dir = (target - position).normalize();
        self.up = dir.cross(up.normalize().cross(dir));
        self.view = Mat4::look_at(Point::from_vec(self.position), Point::from_vec(self.target), self.up);
        self.update_screen2ray();
        self.update_matrix_buffer();
        self.update_frustrum();
    }

    pub fn mirror_in_xz_plane(&mut self)
    {
        self.view[1][0] = -self.view[1][0];
        self.view[1][1] = -self.view[1][1];
        self.view[1][2] = -self.view[1][2];
        self.update_screen2ray();
        self.update_matrix_buffer();
        self.update_frustrum();
    }

    pub fn view_direction_at(&self, screen_coordinates: (f64, f64)) -> Vec3
    {
        let screen_pos = vec4(2. * screen_coordinates.0 as f32 - 1., 1. - 2. * screen_coordinates.1 as f32, 0., 1.);
        (self.screen2ray * screen_pos).truncate().normalize()
    }

    pub fn get_view(&self) -> &Mat4
    {
        &self.view
    }

    pub fn get_projection(&self) -> &Mat4
    {
        &self.projection
    }

    pub fn position(&self) -> &Vec3
    {
        &self.position
    }

    pub fn target(&self) -> &Vec3
    {
        &self.target
    }

    pub fn up(&self) -> &Vec3
    {
        &self.up
    }

    pub fn matrix_buffer(&self) -> &UniformBuffer
    {
        &self.matrix_buffer
    }

    fn update_screen2ray(&mut self)
    {
        let mut v = self.view.clone();
        v[3] = vec4(0.0, 0.0, 0.0, 1.0);
        self.screen2ray = (self.projection * v).invert().unwrap();
    }

    fn update_matrix_buffer(&mut self)
    {
        self.matrix_buffer.update(0, &(self.projection * self.view).to_slice()).unwrap();
        self.matrix_buffer.update(1, &self.view.to_slice()).unwrap();
        self.matrix_buffer.update(2, &self.projection.to_slice()).unwrap();
        self.matrix_buffer.update(3, &self.position.to_slice()).unwrap();
    }

    fn update_frustrum(&mut self)
    {
        let m = self.projection * self.view;
        self.frustrum = [vec4(m.x.w + m.x.x, m.y.w + m.y.x, m.z.w + m.z.x, m.w.w + m.w.x),
         vec4(m.x.w - m.x.x, m.y.w - m.y.x, m.z.w - m.z.x, m.w.w - m.w.x),
         vec4(m.x.w + m.x.y, m.y.w + m.y.y,m.z.w + m.z.y, m.w.w + m.w.y),
         vec4(m.x.w - m.x.y, m.y.w - m.y.y,m.z.w - m.z.y, m.w.w - m.w.y),
         vec4(m.x.w + m.x.z,m.y.w + m.y.z,m.z.w + m.z.z, m.w.w + m.w.z),
         vec4(m.x.w - m.x.z,m.y.w - m.y.z,m.z.w - m.z.z, m.w.w - m.w.z)];
    }

    // false if fully outside, true if inside or intersects
    pub fn in_frustrum(&self, min: &Vec3, max: &Vec3) -> bool
    {
        // check box outside/inside of frustum
        for i in 0..6
        {
            let mut out = 0;
            if self.frustrum[i].dot(vec4(min.x, min.y, min.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(max.x, min.y, min.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(min.x, max.y, min.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(max.x, max.y, min.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(min.x, min.y, max.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(max.x, min.y, max.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(min.x, max.y, max.z, 1.0)) < 0.0 {out += 1};
            if self.frustrum[i].dot(vec4(max.x, max.y, max.z, 1.0)) < 0.0 {out += 1};
            if out == 8 {return false;}
        }
        // TODO: Test the frustum corners against the box planes (http://www.iquilezles.org/www/articles/frustumcorrect/frustumcorrect.htm)

        return true;
    }

    pub fn translate(&mut self, change: &Vec3)
    {
        self.set_view(*self.position() + change, *self.target() + change, *self.up());
    }

    pub fn rotate(&mut self, xrel: f32, yrel: f32)
    {
        let x = -xrel;
        let y = yrel;
        let direction = (*self.target() - *self.position()).normalize();
        let up_direction = vec3(0., 1., 0.);
        let right_direction = direction.cross(up_direction);
        let mut camera_position = *self.position();
        let target = *self.target();
        let zoom = (camera_position - target).magnitude();
        camera_position = camera_position + (right_direction * x + up_direction * y) * 0.1;
        camera_position = target + (camera_position - target).normalize() * zoom;
        self.set_view(camera_position, target, up_direction);
    }

    pub fn zoom(&mut self, wheel: f32)
    {
        let mut position = *self.position();
        let target = *self.target();
        let up = *self.up();
        let mut zoom = (position - target).magnitude();
        zoom += wheel;
        zoom = zoom.max(1.0);
        position = target + (*self.position() - *self.target()).normalize() * zoom;
        self.set_view(position, target, up);
    }
}