Add Meshable trait and implement meshing for 2D primitives

Cargo.toml

@@ -396,7 +396,7 @@ doc-scrape-examples = true
 
 [package.metadata.example.2d_shapes]
 name = "2D Shapes"
-description = "Renders a rectangle, circle, and hexagon"
+description = "Renders simple 2D primitive shapes like circles and polygons"
 category = "2D Rendering"
 wasm = true
 

crates/bevy_math/src/primitives/dim2.rs

@@ -87,6 +87,13 @@ pub struct Circle {
 }
 impl Primitive2d for Circle {}
 
+impl Default for Circle {
+    /// Returns the default [`Circle`] with a radius of `0.5`.
+    fn default() -> Self {
+        Self { radius: 0.5 }
+    }
+}
+
 impl Circle {
     /// Finds the point on the circle that is closest to the given `point`.
     ///
@@ -118,6 +125,15 @@ pub struct Ellipse {
 }
 impl Primitive2d for Ellipse {}
 
+impl Default for Ellipse {
+    /// Returns the default [`Ellipse`] with a half-width of `1.0` and a half-height of `0.5`.
+    fn default() -> Self {
+        Self {
+            half_size: Vec2::new(1.0, 0.5),
+        }
+    }
+}
+
 impl Ellipse {
     /// Create a new `Ellipse` from half of its width and height.
     ///
@@ -161,6 +177,15 @@ pub struct Plane2d {
 }
 impl Primitive2d for Plane2d {}
 
+impl Default for Plane2d {
+    /// Returns the default [`Plane2d`] with a normal pointing in the `+Y` direction.
+    fn default() -> Self {
+        Self {
+            normal: Direction2d::Y,
+        }
+    }
+}
+
 impl Plane2d {
     /// Create a new `Plane2d` from a normal
     ///
@@ -188,7 +213,7 @@ impl Primitive2d for Line2d {}
 
 /// A segment of a line along a direction in 2D space.
 #[doc(alias = "LineSegment2d")]
-#[derive(Clone, Debug)]
+#[derive(Clone, Copy, Debug)]
 pub struct Segment2d {
     /// The direction of the line segment
     pub direction: Direction2d,
@@ -288,16 +313,25 @@ impl BoxedPolyline2d {
 }
 
 /// A triangle in 2D space
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Triangle2d {
     /// The vertices of the triangle
     pub vertices: [Vec2; 3],
 }
 impl Primitive2d for Triangle2d {}
 
+impl Default for Triangle2d {
+    /// Returns the default [`Triangle2d`] with the vertices `[0.0, 0.5]`, `[-0.5, -0.5]`, and `[0.5, -0.5]`.
+    fn default() -> Self {
+        Self {
+            vertices: [Vec2::Y * 0.5, Vec2::new(-0.5, -0.5), Vec2::new(0.5, -0.5)],
+        }
+    }
+}
+
 impl Triangle2d {
     /// Create a new `Triangle2d` from points `a`, `b`, and `c`
-    pub fn new(a: Vec2, b: Vec2, c: Vec2) -> Self {
+    pub const fn new(a: Vec2, b: Vec2, c: Vec2) -> Self {
         Self {
             vertices: [a, b, c],
         }
@@ -367,6 +401,15 @@ pub struct Rectangle {
     pub half_size: Vec2,
 }
 
+impl Default for Rectangle {
+    /// Returns the default [`Rectangle`] with a half-width and half-height of `0.5`.
+    fn default() -> Self {
+        Self {
+            half_size: Vec2::splat(0.5),
+        }
+    }
+}
+
 impl Rectangle {
     /// Create a rectangle from a full width and height
     pub fn new(width: f32, height: f32) -> Self {
@@ -456,18 +499,28 @@ pub struct RegularPolygon {
 }
 impl Primitive2d for RegularPolygon {}
 
+impl Default for RegularPolygon {
+    /// Returns the default [`RegularPolygon`] with six sides (a hexagon) and a circumradius of `0.5`.
+    fn default() -> Self {
+        Self {
+            circumcircle: Circle { radius: 0.5 },
+            sides: 6,
+        }
+    }
+}
+
 impl RegularPolygon {
     /// Create a new `RegularPolygon`
-    /// from the radius of the circumcircle and number of sides
+    /// from the radius of the circumcircle and a number of sides
     ///
     /// # Panics
     ///
-    /// Panics if `circumcircle_radius` is non-positive
-    pub fn new(circumcircle_radius: f32, sides: usize) -> Self {
-        assert!(circumcircle_radius > 0.0);
+    /// Panics if `circumradius` is non-positive
+    pub fn new(circumradius: f32, sides: usize) -> Self {
+        assert!(circumradius > 0.0);
         Self {
             circumcircle: Circle {
-                radius: circumcircle_radius,
+                radius: circumradius,
             },
             sides,
         }

crates/bevy_render/src/lib.rs

@@ -34,7 +34,7 @@ pub mod prelude {
             Projection,
         },
         color::Color,
-        mesh::{morph::MorphWeights, shape, Mesh},
+        mesh::{morph::MorphWeights, primitives::Meshable, shape, Mesh},
         render_resource::Shader,
         spatial_bundle::SpatialBundle,
         texture::{Image, ImagePlugin},

crates/bevy_render/src/mesh/mod.rs

@@ -1,10 +1,12 @@
 #[allow(clippy::module_inception)]
 mod mesh;
 pub mod morph;
+pub mod primitives;
 /// Generation for some primitive shape meshes.
 pub mod shape;
 
 pub use mesh::*;
+pub use primitives::*;
 
 use crate::{prelude::Image, render_asset::RenderAssetPlugin};
 use bevy_app::{App, Plugin};