Math / Rendering Primitives

Back to examples View in GitHub

Support Warning

WebGPU is currently only supported on Chrome starting with version 113, and only on desktop. If they don't work on your configuration, you can check the WebGL2 examples here.

render_primitives.rs:
//! This example demonstrates how each of Bevy's math primitives look like in 2D and 3D with meshes
//! and with gizmos
#![allow(clippy::match_same_arms)]

use bevy::{
    input::common_conditions::input_just_pressed, prelude::*, sprite::MaterialMesh2dBundle,
};

const LEFT_RIGHT_OFFSET_2D: f32 = 200.0;
const LEFT_RIGHT_OFFSET_3D: f32 = 2.0;

fn main() {
    let mut app = App::new();

    app.add_plugins(DefaultPlugins)
        .init_state::<PrimitiveSelected>()
        .init_state::<CameraActive>();

    // cameras
    app.add_systems(Startup, (setup_cameras, setup_lights, setup_ambient_light))
        .add_systems(
            Update,
            (
                update_active_cameras.run_if(state_changed::<CameraActive>),
                switch_cameras.run_if(input_just_pressed(KeyCode::KeyC)),
            ),
        );

    // text

    // PostStartup since we need the cameras to exist
    app.add_systems(PostStartup, setup_text);
    app.add_systems(
        Update,
        (update_text.run_if(state_changed::<PrimitiveSelected>),),
    );

    // primitives
    app.add_systems(Startup, (spawn_primitive_2d, spawn_primitive_3d))
        .add_systems(
            Update,
            (
                switch_to_next_primitive.run_if(input_just_pressed(KeyCode::ArrowUp)),
                switch_to_previous_primitive.run_if(input_just_pressed(KeyCode::ArrowDown)),
                draw_gizmos_2d.run_if(in_mode(CameraActive::Dim2)),
                draw_gizmos_3d.run_if(in_mode(CameraActive::Dim3)),
                update_primitive_meshes.run_if(
                    state_changed::<PrimitiveSelected>.or_else(state_changed::<CameraActive>),
                ),
                rotate_primitive_2d_meshes,
                rotate_primitive_3d_meshes,
            ),
        );

    app.run();
}

/// State for tracking which of the two cameras (2D & 3D) is currently active
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, States, Default, Reflect)]
enum CameraActive {
    #[default]
    /// 2D Camera is active
    Dim2,
    /// 3D Camera is active
    Dim3,
}

/// State for tracking which primitives are currently displayed
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, States, Default, Reflect)]
enum PrimitiveSelected {
    #[default]
    RectangleAndCuboid,
    CircleAndSphere,
    Ellipse,
    Triangle,
    Plane,
    Line,
    Segment,
    Polyline,
    Polygon,
    RegularPolygon,
    Capsule,
    Cylinder,
    Cone,
    ConicalFrustum,
    Torus,
    Tetrahedron,
    Arc,
    CircularSector,
    CircularSegment,
}

impl std::fmt::Display for PrimitiveSelected {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let name = match self {
            PrimitiveSelected::RectangleAndCuboid => String::from("Rectangle/Cuboid"),
            PrimitiveSelected::CircleAndSphere => String::from("Circle/Sphere"),
            other => format!("{other:?}"),
        };
        write!(f, "{name}")
    }
}

impl PrimitiveSelected {
    const ALL: [Self; 19] = [
        Self::RectangleAndCuboid,
        Self::CircleAndSphere,
        Self::Ellipse,
        Self::Triangle,
        Self::Plane,
        Self::Line,
        Self::Segment,
        Self::Polyline,
        Self::Polygon,
        Self::RegularPolygon,
        Self::Capsule,
        Self::Cylinder,
        Self::Cone,
        Self::ConicalFrustum,
        Self::Torus,
        Self::Tetrahedron,
        Self::Arc,
        Self::CircularSector,
        Self::CircularSegment,
    ];

    fn next(self) -> Self {
        Self::ALL
            .into_iter()
            .cycle()
            .skip_while(|&x| x != self)
            .nth(1)
            .unwrap()
    }

    fn previous(self) -> Self {
        Self::ALL
            .into_iter()
            .rev()
            .cycle()
            .skip_while(|&x| x != self)
            .nth(1)
            .unwrap()
    }
}

const SMALL_2D: f32 = 50.0;
const BIG_2D: f32 = 100.0;

const SMALL_3D: f32 = 0.5;
const BIG_3D: f32 = 1.0;

// primitives
const RECTANGLE: Rectangle = Rectangle {
    half_size: Vec2::new(SMALL_2D, BIG_2D),
};
const CUBOID: Cuboid = Cuboid {
    half_size: Vec3::new(BIG_3D, SMALL_3D, BIG_3D),
};

const CIRCLE: Circle = Circle { radius: BIG_2D };
const SPHERE: Sphere = Sphere { radius: BIG_3D };

const ELLIPSE: Ellipse = Ellipse {
    half_size: Vec2::new(BIG_2D, SMALL_2D),
};

const TRIANGLE_2D: Triangle2d = Triangle2d {
    vertices: [
        Vec2::new(BIG_2D, 0.0),
        Vec2::new(0.0, BIG_2D),
        Vec2::new(-BIG_2D, 0.0),
    ],
};

const TRIANGLE_3D: Triangle3d = Triangle3d {
    vertices: [
        Vec3::new(BIG_3D, 0.0, 0.0),
        Vec3::new(0.0, BIG_3D, 0.0),
        Vec3::new(-BIG_3D, 0.0, 0.0),
    ],
};

const PLANE_2D: Plane2d = Plane2d { normal: Dir2::Y };
const PLANE_3D: Plane3d = Plane3d {
    normal: Dir3::Y,
    half_size: Vec2::new(BIG_3D, BIG_3D),
};

const LINE2D: Line2d = Line2d { direction: Dir2::X };
const LINE3D: Line3d = Line3d { direction: Dir3::X };

const SEGMENT_2D: Segment2d = Segment2d {
    direction: Dir2::X,
    half_length: BIG_2D,
};
const SEGMENT_3D: Segment3d = Segment3d {
    direction: Dir3::X,
    half_length: BIG_3D,
};

const POLYLINE_2D: Polyline2d<4> = Polyline2d {
    vertices: [
        Vec2::new(-BIG_2D, -SMALL_2D),
        Vec2::new(-SMALL_2D, SMALL_2D),
        Vec2::new(SMALL_2D, -SMALL_2D),
        Vec2::new(BIG_2D, SMALL_2D),
    ],
};
const POLYLINE_3D: Polyline3d<4> = Polyline3d {
    vertices: [
        Vec3::new(-BIG_3D, -SMALL_3D, -SMALL_3D),
        Vec3::new(SMALL_3D, SMALL_3D, 0.0),
        Vec3::new(-SMALL_3D, -SMALL_3D, 0.0),
        Vec3::new(BIG_3D, SMALL_3D, SMALL_3D),
    ],
};

const POLYGON_2D: Polygon<5> = Polygon {
    vertices: [
        Vec2::new(-BIG_2D, -SMALL_2D),
        Vec2::new(BIG_2D, -SMALL_2D),
        Vec2::new(BIG_2D, SMALL_2D),
        Vec2::new(0.0, 0.0),
        Vec2::new(-BIG_2D, SMALL_2D),
    ],
};

const REGULAR_POLYGON: RegularPolygon = RegularPolygon {
    circumcircle: Circle { radius: BIG_2D },
    sides: 5,
};

const CAPSULE_2D: Capsule2d = Capsule2d {
    radius: SMALL_2D,
    half_length: SMALL_2D,
};
const CAPSULE_3D: Capsule3d = Capsule3d {
    radius: SMALL_3D,
    half_length: SMALL_3D,
};

const CYLINDER: Cylinder = Cylinder {
    radius: SMALL_3D,
    half_height: SMALL_3D,
};

const CONE: Cone = Cone {
    radius: BIG_3D,
    height: BIG_3D,
};

const CONICAL_FRUSTUM: ConicalFrustum = ConicalFrustum {
    radius_top: BIG_3D,
    radius_bottom: SMALL_3D,
    height: BIG_3D,
};

const ANNULUS: Annulus = Annulus {
    inner_circle: Circle { radius: SMALL_2D },
    outer_circle: Circle { radius: BIG_2D },
};

const TORUS: Torus = Torus {
    minor_radius: SMALL_3D / 2.0,
    major_radius: SMALL_3D * 1.5,
};

const TETRAHEDRON: Tetrahedron = Tetrahedron {
    vertices: [
        Vec3::new(-BIG_3D, 0.0, 0.0),
        Vec3::new(BIG_3D, 0.0, 0.0),
        Vec3::new(0.0, 0.0, -BIG_3D * 1.67),
        Vec3::new(0.0, BIG_3D * 1.67, -BIG_3D * 0.5),
    ],
};

const ARC: Arc2d = Arc2d {
    radius: BIG_2D,
    half_angle: std::f32::consts::FRAC_PI_4,
};

const CIRCULAR_SECTOR: CircularSector = CircularSector {
    arc: Arc2d {
        radius: BIG_2D,
        half_angle: std::f32::consts::FRAC_PI_4,
    },
};

const CIRCULAR_SEGMENT: CircularSegment = CircularSegment {
    arc: Arc2d {
        radius: BIG_2D,
        half_angle: std::f32::consts::FRAC_PI_4,
    },
};

fn setup_cameras(mut commands: Commands) {
    let start_in_2d = true;
    let make_camera = |is_active| Camera {
        is_active,
        ..Default::default()
    };

    commands.spawn(Camera2dBundle {
        camera: make_camera(start_in_2d),
        ..Default::default()
    });

    commands.spawn(Camera3dBundle {
        camera: make_camera(!start_in_2d),
        transform: Transform::from_xyz(0.0, 10.0, 0.0).looking_at(Vec3::ZERO, Vec3::Z),
        ..Default::default()
    });
}

fn setup_ambient_light(mut ambient_light: ResMut<AmbientLight>) {
    ambient_light.brightness = 50.0;
}

fn setup_lights(mut commands: Commands) {
    commands.spawn(PointLightBundle {
        point_light: PointLight {
            intensity: 5000.0,
            ..default()
        },
        transform: Transform::from_translation(Vec3::new(-LEFT_RIGHT_OFFSET_3D, 2.0, 0.0))
            .looking_at(Vec3::new(-LEFT_RIGHT_OFFSET_3D, 0.0, 0.0), Vec3::Y),
        ..default()
    });
}

/// Marker component for header text
#[derive(Debug, Clone, Component, Default, Reflect)]
pub struct HeaderText;

/// Marker component for header node
#[derive(Debug, Clone, Component, Default, Reflect)]
pub struct HeaderNode;

fn update_active_cameras(
    state: Res<State<CameraActive>>,
    mut camera_2d: Query<(Entity, &mut Camera), With<Camera2d>>,
    mut camera_3d: Query<(Entity, &mut Camera), (With<Camera3d>, Without<Camera2d>)>,
    mut text: Query<&mut TargetCamera, With<HeaderNode>>,
) {
    let (entity_2d, mut cam_2d) = camera_2d.single_mut();
    let (entity_3d, mut cam_3d) = camera_3d.single_mut();
    let is_camera_2d_active = matches!(*state.get(), CameraActive::Dim2);

    cam_2d.is_active = is_camera_2d_active;
    cam_3d.is_active = !is_camera_2d_active;

    let active_camera = if is_camera_2d_active {
        entity_2d
    } else {
        entity_3d
    };

    text.iter_mut().for_each(|mut target_camera| {
        *target_camera = TargetCamera(active_camera);
    });
}

fn switch_cameras(current: Res<State<CameraActive>>, mut next: ResMut<NextState<CameraActive>>) {
    let next_state = match current.get() {
        CameraActive::Dim2 => CameraActive::Dim3,
        CameraActive::Dim3 => CameraActive::Dim2,
    };
    next.set(next_state);
}

fn setup_text(mut commands: Commands, cameras: Query<(Entity, &Camera)>) {
    let active_camera = cameras
        .iter()
        .find_map(|(entity, camera)| camera.is_active.then_some(entity))
        .expect("run condition ensures existence");
    let text = format!("{text}", text = PrimitiveSelected::default());
    let style = TextStyle::default();
    let instructions = "Press 'C' to switch between 2D and 3D mode\n\
        Press 'Up' or 'Down' to switch to the next/previous primitive";
    let text = [
        TextSection::new("Primitive: ", style.clone()),
        TextSection::new(text, style.clone()),
        TextSection::new("\n\n", style.clone()),
        TextSection::new(instructions, style.clone()),
        TextSection::new("\n\n", style.clone()),
        TextSection::new(
            "(If nothing is displayed, there's no rendering support yet)",
            style.clone(),
        ),
    ];

    commands
        .spawn((
            HeaderNode,
            NodeBundle {
                style: Style {
                    justify_self: JustifySelf::Center,
                    top: Val::Px(5.0),
                    ..Default::default()
                },
                ..Default::default()
            },
            TargetCamera(active_camera),
        ))
        .with_children(|parent| {
            parent.spawn((
                HeaderText,
                TextBundle::from_sections(text).with_text_justify(JustifyText::Center),
            ));
        });
}

fn update_text(
    primitive_state: Res<State<PrimitiveSelected>>,
    mut header: Query<&mut Text, With<HeaderText>>,
) {
    let new_text = format!("{text}", text = primitive_state.get());
    header.iter_mut().for_each(|mut header_text| {
        if let Some(kind) = header_text.sections.get_mut(1) {
            kind.value.clone_from(&new_text);
        };
    });
}

fn switch_to_next_primitive(
    current: Res<State<PrimitiveSelected>>,
    mut next: ResMut<NextState<PrimitiveSelected>>,
) {
    let next_state = current.get().next();
    next.set(next_state);
}

fn switch_to_previous_primitive(
    current: Res<State<PrimitiveSelected>>,
    mut next: ResMut<NextState<PrimitiveSelected>>,
) {
    let next_state = current.get().previous();
    next.set(next_state);
}

fn in_mode(active: CameraActive) -> impl Fn(Res<State<CameraActive>>) -> bool {
    move |state| *state.get() == active
}

fn draw_gizmos_2d(mut gizmos: Gizmos, state: Res<State<PrimitiveSelected>>, time: Res<Time>) {
    const POSITION: Vec2 = Vec2::new(-LEFT_RIGHT_OFFSET_2D, 0.0);
    let angle = time.elapsed_seconds();
    let color = Color::WHITE;

    match state.get() {
        PrimitiveSelected::RectangleAndCuboid => {
            gizmos.primitive_2d(&RECTANGLE, POSITION, angle, color);
        }
        PrimitiveSelected::CircleAndSphere => {
            gizmos.primitive_2d(&CIRCLE, POSITION, angle, color);
        }
        PrimitiveSelected::Ellipse => drop(gizmos.primitive_2d(&ELLIPSE, POSITION, angle, color)),
        PrimitiveSelected::Triangle => gizmos.primitive_2d(&TRIANGLE_2D, POSITION, angle, color),
        PrimitiveSelected::Plane => gizmos.primitive_2d(&PLANE_2D, POSITION, angle, color),
        PrimitiveSelected::Line => drop(gizmos.primitive_2d(&LINE2D, POSITION, angle, color)),
        PrimitiveSelected::Segment => {
            drop(gizmos.primitive_2d(&SEGMENT_2D, POSITION, angle, color));
        }
        PrimitiveSelected::Polyline => gizmos.primitive_2d(&POLYLINE_2D, POSITION, angle, color),
        PrimitiveSelected::Polygon => gizmos.primitive_2d(&POLYGON_2D, POSITION, angle, color),
        PrimitiveSelected::RegularPolygon => {
            gizmos.primitive_2d(&REGULAR_POLYGON, POSITION, angle, color);
        }
        PrimitiveSelected::Capsule => gizmos.primitive_2d(&CAPSULE_2D, POSITION, angle, color),
        PrimitiveSelected::Cylinder => {}
        PrimitiveSelected::Cone => {}
        PrimitiveSelected::ConicalFrustum => {}
        PrimitiveSelected::Torus => drop(gizmos.primitive_2d(&ANNULUS, POSITION, angle, color)),
        PrimitiveSelected::Tetrahedron => {}
        PrimitiveSelected::Arc => gizmos.primitive_2d(&ARC, POSITION, angle, color),
        PrimitiveSelected::CircularSector => {
            gizmos.primitive_2d(&CIRCULAR_SECTOR, POSITION, angle, color);
        }
        PrimitiveSelected::CircularSegment => {
            gizmos.primitive_2d(&CIRCULAR_SEGMENT, POSITION, angle, color);
        }
    }
}

/// Marker for primitive meshes to record in which state they should be visible in
#[derive(Debug, Clone, Component, Default, Reflect)]
pub struct PrimitiveData {
    camera_mode: CameraActive,
    primitive_state: PrimitiveSelected,
}

/// Marker for meshes of 2D primitives
#[derive(Debug, Clone, Component, Default)]
pub struct MeshDim2;

/// Marker for meshes of 3D primitives
#[derive(Debug, Clone, Component, Default)]
pub struct MeshDim3;

fn spawn_primitive_2d(
    mut commands: Commands,
    mut materials: ResMut<Assets<ColorMaterial>>,
    mut meshes: ResMut<Assets<Mesh>>,
) {
    const POSITION: Vec3 = Vec3::new(LEFT_RIGHT_OFFSET_2D, 0.0, 0.0);
    let material: Handle<ColorMaterial> = materials.add(Color::WHITE);
    let camera_mode = CameraActive::Dim2;
    [
        Some(RECTANGLE.mesh().build()),
        Some(CIRCLE.mesh().build()),
        Some(ELLIPSE.mesh().build()),
        Some(TRIANGLE_2D.mesh().build()),
        None, // plane
        None, // line
        None, // segment
        None, // polyline
        None, // polygon
        Some(REGULAR_POLYGON.mesh().build()),
        Some(CAPSULE_2D.mesh().build()),
        None, // cylinder
        None, // cone
        None, // conical frustum
        Some(ANNULUS.mesh().build()),
        None, // tetrahedron
    ]
    .into_iter()
    .zip(PrimitiveSelected::ALL)
    .for_each(|(maybe_mesh, state)| {
        if let Some(mesh) = maybe_mesh {
            commands.spawn((
                MeshDim2,
                PrimitiveData {
                    camera_mode,
                    primitive_state: state,
                },
                MaterialMesh2dBundle {
                    mesh: meshes.add(mesh).into(),
                    material: material.clone(),
                    transform: Transform::from_translation(POSITION),
                    ..Default::default()
                },
            ));
        }
    });
}

fn spawn_primitive_3d(
    mut commands: Commands,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut meshes: ResMut<Assets<Mesh>>,
) {
    const POSITION: Vec3 = Vec3::new(-LEFT_RIGHT_OFFSET_3D, 0.0, 0.0);
    let material: Handle<StandardMaterial> = materials.add(Color::WHITE);
    let camera_mode = CameraActive::Dim3;
    [
        Some(CUBOID.mesh().build()),
        Some(SPHERE.mesh().build()),
        None, // ellipse
        Some(TRIANGLE_3D.mesh().build()),
        Some(PLANE_3D.mesh().build()),
        None, // line
        None, // segment
        None, // polyline
        None, // polygon
        None, // regular polygon
        Some(CAPSULE_3D.mesh().build()),
        Some(CYLINDER.mesh().build()),
        None, // cone
        None, // conical frustum
        Some(TORUS.mesh().build()),
        Some(TETRAHEDRON.mesh().build()),
    ]
    .into_iter()
    .zip(PrimitiveSelected::ALL)
    .for_each(|(maybe_mesh, state)| {
        if let Some(mesh) = maybe_mesh {
            commands.spawn((
                MeshDim3,
                PrimitiveData {
                    camera_mode,
                    primitive_state: state,
                },
                PbrBundle {
                    mesh: meshes.add(mesh),
                    material: material.clone(),
                    transform: Transform::from_translation(POSITION),
                    ..Default::default()
                },
            ));
        }
    });
}

fn update_primitive_meshes(
    camera_state: Res<State<CameraActive>>,
    primitive_state: Res<State<PrimitiveSelected>>,
    mut primitives: Query<(&mut Visibility, &PrimitiveData)>,
) {
    primitives.iter_mut().for_each(|(mut vis, primitive)| {
        let visible = primitive.camera_mode == *camera_state.get()
            && primitive.primitive_state == *primitive_state.get();
        *vis = if visible {
            Visibility::Inherited
        } else {
            Visibility::Hidden
        };
    });
}

fn rotate_primitive_2d_meshes(
    mut primitives_2d: Query<
        (&mut Transform, &ViewVisibility),
        (With<PrimitiveData>, With<MeshDim2>),
    >,
    time: Res<Time>,
) {
    let rotation_2d = Quat::from_mat3(&Mat3::from_angle(time.elapsed_seconds()));
    primitives_2d
        .iter_mut()
        .filter(|(_, vis)| vis.get())
        .for_each(|(mut transform, _)| {
            transform.rotation = rotation_2d;
        });
}

fn rotate_primitive_3d_meshes(
    mut primitives_3d: Query<
        (&mut Transform, &ViewVisibility),
        (With<PrimitiveData>, With<MeshDim3>),
    >,
    time: Res<Time>,
) {
    let rotation_3d = Quat::from_rotation_arc(
        Vec3::Z,
        Vec3::new(
            time.elapsed_seconds().sin(),
            time.elapsed_seconds().cos(),
            time.elapsed_seconds().sin() * 0.5,
        )
        .try_normalize()
        .unwrap_or(Vec3::Z),
    );
    primitives_3d
        .iter_mut()
        .filter(|(_, vis)| vis.get())
        .for_each(|(mut transform, _)| {
            transform.rotation = rotation_3d;
        });
}

fn draw_gizmos_3d(mut gizmos: Gizmos, state: Res<State<PrimitiveSelected>>, time: Res<Time>) {
    const POSITION: Vec3 = Vec3::new(LEFT_RIGHT_OFFSET_3D, 0.0, 0.0);
    let rotation = Quat::from_rotation_arc(
        Vec3::Z,
        Vec3::new(
            time.elapsed_seconds().sin(),
            time.elapsed_seconds().cos(),
            time.elapsed_seconds().sin() * 0.5,
        )
        .try_normalize()
        .unwrap_or(Vec3::Z),
    );
    let color = Color::WHITE;
    let resolution = 10;

    match state.get() {
        PrimitiveSelected::RectangleAndCuboid => {
            gizmos.primitive_3d(&CUBOID, POSITION, rotation, color);
        }
        PrimitiveSelected::CircleAndSphere => drop(
            gizmos
                .primitive_3d(&SPHERE, POSITION, rotation, color)
                .resolution(resolution),
        ),
        PrimitiveSelected::Ellipse => {}
        PrimitiveSelected::Triangle => gizmos.primitive_3d(&TRIANGLE_3D, POSITION, rotation, color),
        PrimitiveSelected::Plane => drop(gizmos.primitive_3d(&PLANE_3D, POSITION, rotation, color)),
        PrimitiveSelected::Line => gizmos.primitive_3d(&LINE3D, POSITION, rotation, color),
        PrimitiveSelected::Segment => gizmos.primitive_3d(&SEGMENT_3D, POSITION, rotation, color),
        PrimitiveSelected::Polyline => gizmos.primitive_3d(&POLYLINE_3D, POSITION, rotation, color),
        PrimitiveSelected::Polygon => {}
        PrimitiveSelected::RegularPolygon => {}
        PrimitiveSelected::Capsule => drop(
            gizmos
                .primitive_3d(&CAPSULE_3D, POSITION, rotation, color)
                .resolution(resolution),
        ),
        PrimitiveSelected::Cylinder => drop(
            gizmos
                .primitive_3d(&CYLINDER, POSITION, rotation, color)
                .resolution(resolution),
        ),
        PrimitiveSelected::Cone => drop(
            gizmos
                .primitive_3d(&CONE, POSITION, rotation, color)
                .resolution(resolution),
        ),
        PrimitiveSelected::ConicalFrustum => {
            gizmos.primitive_3d(&CONICAL_FRUSTUM, POSITION, rotation, color);
        }

        PrimitiveSelected::Torus => drop(
            gizmos
                .primitive_3d(&TORUS, POSITION, rotation, color)
                .minor_resolution(resolution)
                .major_resolution(resolution),
        ),
        PrimitiveSelected::Tetrahedron => {
            gizmos.primitive_3d(&TETRAHEDRON, POSITION, rotation, color);
        }

        PrimitiveSelected::Arc => {}
        PrimitiveSelected::CircularSector => {}
        PrimitiveSelected::CircularSegment => {}
    }
}