Documentation Clarification: Triangles / order of vertices

[jmcauley04]

Hey team,

I'm fairly new to game dev and Rust and Bevy so I, first, just wanted to say I'm very much enjoying the Rapier2d plugin and will be recommending it to my friends and colleagues as a must-have for their development.

I ran into an issue while working on environment collision and I think I understand why but I'm not able to find verification that this is the issue.

The triangle on the left has its vertices defined in a counter-clockwise order while the triangle on the right has its vertices defined in a clockwise order:

The triangle on the left behaves how I hoped it would while the triangle on the right acts less reliably. I think this is because the normal directions are associated with the order that the vertices are defined and so when defined counter-clockwise, the boundaries want to push into the triangle.

Being fairly new to game development, I suspect that if I'm correct about why it's occurring that it may be common knowledge amongst experienced game devs, but I wonder if this could be included on the bevy plugin documentation.

Thanks,
Michael

Relevant points in the code

• the plane has CCD, a RigidBody (Dynamic), and a capsule collider
• the environment tile is a collider with no rigid body

Relevant code:

pub fn spawn_player(
    mut commands: Commands,
    window_query: Query<&Window, With<PrimaryWindow>>,
    asset_server: Res<AssetServer>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
) {    
      // some code omitted for brevity    

        commands.spawn((
                SpriteSheetBundle {
                    texture_atlas: texture_atlas_handle,                    
                    sprite: TextureAtlasSprite {
                        index: animation_indices.first,
                        custom_size: Some(Vec2::new(88.0 * 0.7,73.0 * 0.7)),
                        ..default()
                    },
                    transform: Transform::from_xyz(window.width() / 3.0 - x_delta, window.height() / 2.0, 500.0),
                    ..default()
                },
                animation_indices,
                AnimationTimer(Timer::from_seconds(0.05, TimerMode::Repeating)),
                FireSpeedTimer(Timer::from_seconds(0.15, TimerMode::Repeating)),
            ))
            .insert(InputManagerBundle::<Action> {
                action_state: ActionState::default(),
                input_map: InputMap::default() 
                    .insert(DualAxis::left_stick(), Action::Move)
                    .insert(VirtualDPad::wasd(), Action::Move)
                    .insert(VirtualDPad::arrow_keys(), Action::Move)
                    .build(),
            })
            .insert(Name::new(player_name))
            .insert(RigidBody::Dynamic) // 
            .insert(Ccd::enabled())
            .insert(Velocity::default())
            .insert(Collider::capsule_x(14.0, 20.0)) // shape of collider
            .insert(ExternalForce { // used for physics and to control movement
                force: Vec2::new(0.0, 0.0),
                torque: 0.0,
            })
            .insert(Damping { // friction
                linear_damping: 0.1,
                angular_damping: 5.0,
            })
            .insert(Restitution::coefficient(1.0))
            .insert(Player)
            .insert(Glider)            
            .insert(CollisionGroups::new(Group::GROUP_1,Group::GROUP_2));
    }
}


pub fn spawn_tiles (
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
)
{
      // some code omitted for brevity    
            commands.spawn(
                    SpriteBundle {
                        texture: asset_server.load(image),
                        transform: transform,
                        ..default()
                    }
                )
                .insert(get_collider(c, width, height))
                .insert(ActiveEvents::COLLISION_EVENTS)
                .insert(Environment);
        }
    }
}

fn get_collider(c: char, width: f32, height: f32) -> Collider {
    return match c {
            // this triangle works as expected
            '/' => Collider::triangle(
                       Vec2::new(width / 2.0,-height / 2.0),
                       Vec2::new(width / 2.0, height / 2.0),  
                       Vec2::new(-width / 2.0,-height / 2.0)
                       ),
            // this triangle is unreliable
            '\\' => Collider::triangle(
                        Vec2::new(-width / 2.0, height / 2.0), 
                        Vec2::new(width / 2.0,-height / 2.0), 
                        Vec2::new(-width / 2.0,-height / 2.0)
                        ),
            _ => Collider::cuboid(width / 2.0, height / 2.0),
    }