cyber_rider/src/camera.rs

use bevy::prelude::*;

use crate::{
    geometry::{CyberBike, SPAWN_ALTITUDE},
    input::InputState,
};

pub(crate) const CAM_DIST: f32 = 15.0;

// 85 degrees in radians
const MAX_PITCH: f32 = 1.48353;

#[derive(Component, Debug)]
pub struct CyberCam;

fn setup_cybercam(mut commands: Commands) {
    let projection = PerspectiveProjection {
        fov: std::f32::consts::FRAC_PI_3,
        ..Default::default()
    };
    commands
        .spawn_bundle(PerspectiveCameraBundle {
            transform: Transform::from_xyz(SPAWN_ALTITUDE + CAM_DIST, 0.0, 0.0)
                .looking_at(Vec3::ZERO, Vec3::Y),
            perspective_projection: projection,
            ..Default::default()
        })
        .insert(CyberCam);
}

fn follow_cyberbike(
    bike_query: Query<&Transform, (Without<CyberCam>, With<CyberBike>)>,
    mut cam_query: Query<&mut Transform, (With<CyberCam>, Without<CyberBike>)>,
    input: Res<InputState>,
) {
    let bike_xform = bike_query.single();
    let up = bike_xform.translation.normalize();

    let look_at = bike_xform.translation + (bike_xform.forward() * 200.0);
    let cam_pos = bike_xform.translation + (bike_xform.back() * 2.7) + (up * 2.4);

    let mut cam_xform = cam_query.single_mut();
    cam_xform.translation = cam_pos;
    cam_xform.look_at(look_at, up);

    // handle input pitch
    let angle = input.pitch.powi(3) * MAX_PITCH;
    let axis = cam_xform.right();
    cam_xform.rotate(Quat::from_axis_angle(axis, angle));
}

pub struct CyberCamPlugin;
impl Plugin for CyberCamPlugin {
    fn build(&self, app: &mut bevy::prelude::App) {
        app.add_startup_system(setup_cybercam)
            .add_system(follow_cyberbike);
    }
}