docs/bevy/examples/2d/mesh2d_arcs.rs 4.2 K · 117 lines · raw · history

1 //! Demonstrates UV mappings of the [`CircularSector`] and [`CircularSegment`] primitives.
2 //!
3 //! Also draws the bounding boxes and circles of the primitives.
4
5 use std::f32::consts::FRAC_PI_2;
6
7 use bevy::{
8 color::palettes::css::{BLUE, GRAY, RED},
9 math::Isometry2d,
10 mesh::{CircularMeshUvMode, CircularSectorMeshBuilder, CircularSegmentMeshBuilder},
11 prelude::*,
12 };
13
14 fn main() {
15 App::new()
16 .add_plugins(DefaultPlugins)
17 .add_systems(Startup, setup)
18 .add_systems(
19 Update,
20 (
21 draw_bounds::<CircularSector>,
22 draw_bounds::<CircularSegment>,
23 ),
24 )
25 .run();
26 }
27
28 #[derive(Component, Debug)]
29 struct DrawBounds<Shape: Bounded2d + Send + Sync + 'static>(Shape);
30
31 fn setup(
32 mut commands: Commands,
33 asset_server: Res<AssetServer>,
34 mut meshes: ResMut<Assets<Mesh>>,
35 mut materials: ResMut<Assets<ColorMaterial>>,
36 ) {
37 let material = materials.add(asset_server.load("branding/icon.png"));
38
39 commands.spawn((
40 Camera2d,
41 Camera {
42 clear_color: ClearColorConfig::Custom(GRAY.into()),
43 ..default()
44 },
45 ));
46
47 const NUM_SLICES: i32 = 8;
48 const SPACING_X: f32 = 100.0;
49 const OFFSET_X: f32 = SPACING_X * (NUM_SLICES - 1) as f32 / 2.0;
50
51 // This draws NUM_SLICES copies of the Bevy logo as circular sectors and segments,
52 // with successively larger angles up to a complete circle.
53 for i in 0..NUM_SLICES {
54 let fraction = (i + 1) as f32 / NUM_SLICES as f32;
55
56 let sector = CircularSector::from_turns(40.0, fraction);
57 // We want to rotate the circular sector so that the sectors appear clockwise from north.
58 // We must rotate it both in the Transform and in the mesh's UV mappings.
59 let sector_angle = -sector.half_angle();
60 let sector_mesh =
61 CircularSectorMeshBuilder::new(sector).uv_mode(CircularMeshUvMode::Mask {
62 angle: sector_angle,
63 });
64 commands.spawn((
65 Mesh2d(meshes.add(sector_mesh)),
66 MeshMaterial2d(material.clone()),
67 Transform {
68 translation: Vec3::new(SPACING_X * i as f32 - OFFSET_X, 50.0, 0.0),
69 rotation: Quat::from_rotation_z(sector_angle),
70 ..default()
71 },
72 DrawBounds(sector),
73 ));
74
75 let segment = CircularSegment::from_turns(40.0, fraction);
76 // For the circular segment, we will draw Bevy charging forward, which requires rotating the
77 // shape and texture by 90 degrees.
78 //
79 // Note that this may be unintuitive; it may feel like we should rotate the texture by the
80 // opposite angle to preserve the orientation of Bevy. But the angle is not the angle of the
81 // texture itself, rather it is the angle at which the vertices are mapped onto the texture.
82 // so it is the negative of what you might otherwise expect.
83 let segment_angle = -FRAC_PI_2;
84 let segment_mesh =
85 CircularSegmentMeshBuilder::new(segment).uv_mode(CircularMeshUvMode::Mask {
86 angle: -segment_angle,
87 });
88 commands.spawn((
89 Mesh2d(meshes.add(segment_mesh)),
90 MeshMaterial2d(material.clone()),
91 Transform {
92 translation: Vec3::new(SPACING_X * i as f32 - OFFSET_X, -50.0, 0.0),
93 rotation: Quat::from_rotation_z(segment_angle),
94 ..default()
95 },
96 DrawBounds(segment),
97 ));
98 }
99 }
100
101 fn draw_bounds<Shape: Bounded2d + Send + Sync + 'static>(
102 q: Query<(&DrawBounds<Shape>, &GlobalTransform)>,
103 mut gizmos: Gizmos,
104 ) {
105 for (shape, transform) in &q {
106 let (_, rotation, translation) = transform.to_scale_rotation_translation();
107 let translation = translation.truncate();
108 let rotation = rotation.to_euler(EulerRot::XYZ).2;
109 let isometry = Isometry2d::new(translation, Rot2::radians(rotation));
110
111 let aabb = shape.0.aabb_2d(isometry);
112 gizmos.rect_2d(aabb.center(), aabb.half_size() * 2.0, RED);
113
114 let bounding_circle = shape.0.bounding_circle(isometry);
115 gizmos.circle_2d(bounding_circle.center, bounding_circle.radius(), BLUE);
116 }
117 }