Stupid Physics with rust and Rapier2D

main.rs

use rapier2d::prelude::*;
use raylib::prelude::*;

pub struct Entity {
    radius: f32,
    physics_handle: RigidBodyHandle,
}

fn main() {
    let (mut rl, thread) = raylib::init().size(640, 480).title("Hello, World").build();

    let mut entities: Vec<Entity> = vec![];
    let mut rigid_body_set = RigidBodySet::new();
    let mut collider_set = ColliderSet::new();

    let gravity = vector![0.0, 0.0];
    let integration_parameters = IntegrationParameters::default();
    let mut physics_pipeline = PhysicsPipeline::new();
    let mut island_manager = IslandManager::new();
    let mut broad_phase = BroadPhase::new();
    let mut narrow_phase = NarrowPhase::new();
    let mut impulse_joint_set = ImpulseJointSet::new();
    let mut multibody_joint_set = MultibodyJointSet::new();
    let mut ccd_solver = CCDSolver::new();
    let physics_hooks = ();
    let event_handler = ();

    // build the floor, ceiling, and walls
    collider_set.insert(
        ColliderBuilder::cuboid(320.0, 2.0)
            .translation(vector![320.0, 476.0])
            .build(),
    );
    collider_set.insert(
        ColliderBuilder::cuboid(320.0, 2.0)
            .translation(vector![320.0, 2.0])
            .build(),
    );
    collider_set.insert(
        ColliderBuilder::cuboid(2.0, 240.0)
            .translation(vector![636.0, 240.0])
            .build(),
    );
    collider_set.insert(
        ColliderBuilder::cuboid(2.0, 240.0)
            .translation(vector![2.0, 240.0])
            .build(),
    );

    while !rl.window_should_close() {
        if rl.is_mouse_button_down(MouseButton::MOUSE_LEFT_BUTTON) {
            let mut pos = rl.get_mouse_position();
            pos.x += rand::random::<f32>() * 2.0 - 1.0;
            pos.y += rand::random::<f32>() * 2.0 - 1.0;
            let radius = 4.0;
            let rb = RigidBodyBuilder::dynamic()
                .translation(vector![pos.x, pos.y])
                .build();
            let c = ColliderBuilder::ball(radius).restitution(0.1).build();
            let bbh = rigid_body_set.insert(rb);
            collider_set.insert_with_parent(c, bbh, &mut rigid_body_set);
            let ent = Entity {
                radius,
                physics_handle: bbh,
            };
            entities.push(ent);
        }

        let _dt = rl.get_frame_time();

        physics_pipeline.step(
            &gravity,
            &integration_parameters,
            &mut island_manager,
            &mut broad_phase,
            &mut narrow_phase,
            &mut rigid_body_set,
            &mut collider_set,
            &mut impulse_joint_set,
            &mut multibody_joint_set,
            &mut ccd_solver,
            &physics_hooks,
            &event_handler,
        );

        let mut d = rl.begin_drawing(&thread);
        d.clear_background(Color::new(30, 20, 30, 255));

        // draw the entities
        for e in &entities {
            let bb = &rigid_body_set[e.physics_handle];
            d.draw_circle_v(
                Vector2::new(bb.translation().x as f32, bb.translation().y as f32),
                e.radius,
                Color::GREEN,
            );
        }

        // draw the number of entities
        d.draw_text(
            &format!("Entities: {}", entities.len()),
            13,
            13,
            20,
            Color::BLACK,
        );
        d.draw_text(
            &format!("Entities: {}", entities.len()),
            12,
            12,
            20,
            Color::RAYWHITE,
        );

        // draw the framerate
        d.draw_text(&format!("FPS: {}", d.get_fps()), 13, 33, 20, Color::BLACK);
        d.draw_text(
            &format!("FPS: {}", d.get_fps()),
            12,
            32,
            20,
            Color::RAYWHITE,
        );
    }
}