Calculate UVs and Normals in ConvexPolygonMeshBuilder (#23540)

# Objective

Fixes #23526

## Solution

- Added UVs to `ConvexPolygonMeshBuilder`
- Whilst testing I noticed that normals were also not generated for the
mesh so i've added these as well.

## Testing

- Added `test_convex_polygon` to bevy_mesh which imitates a different
test but for regular polygons.
- Added `Extrusion<ConvexPolygon>` to the 3d_shapes example - you can
use this example to validate UVs and Normals are working as expected.

Author: mpowell90

crates/bevy_mesh/src/primitives/dim2.rs

@@ -431,9 +431,24 @@ impl MeshBuilder for ConvexPolygonMeshBuilder {
         let len = self.vertices.len();
         let mut indices = Vec::with_capacity((len - 2) * 3);
         let mut positions = Vec::with_capacity(len);
+        let normals = vec![[0.0, 0.0, 1.0]; len];
+        let mut uvs = Vec::with_capacity(len);
+
+        let mut min = Vec2::splat(f32::INFINITY);
+        let mut max = Vec2::splat(f32::NEG_INFINITY);
+
+        for vertex in &self.vertices {
+            min = min.min(*vertex);
+            max = max.max(*vertex);
+        }
+
+        let size = (max - min).max(Vec2::splat(f32::EPSILON));
 
         for vertex in &self.vertices {
             positions.push([vertex.x, vertex.y, 0.0]);
+            let uv = (*vertex - min) / size;
+            // Map each axis independently into [0, 1] over the polygon's AABB.
+            uvs.push([uv.x, uv.y]);
         }
         for i in 2..len as u32 {
             indices.extend_from_slice(&[0, i - 1, i]);
@@ -443,6 +458,8 @@ impl MeshBuilder for ConvexPolygonMeshBuilder {
             RenderAssetUsages::default(),
         )
         .with_inserted_attribute(Mesh::ATTRIBUTE_POSITION, positions)
+        .with_inserted_attribute(Mesh::ATTRIBUTE_NORMAL, normals)
+        .with_inserted_attribute(Mesh::ATTRIBUTE_UV_0, uvs)
         .with_inserted_indices(Indices::U32(indices))
     }
 }
@@ -1526,7 +1543,11 @@ where
 
 #[cfg(test)]
 mod tests {
-    use bevy_math::{prelude::Annulus, primitives::RegularPolygon, FloatOrd};
+    use bevy_math::{
+        prelude::Annulus,
+        primitives::{ConvexPolygon, RegularPolygon},
+        FloatOrd, Vec2,
+    };
     use bevy_platform::collections::HashSet;
 
     use crate::{Mesh, MeshBuilder, Meshable, VertexAttributeValues};
@@ -1605,4 +1626,53 @@ mod tests {
 
         assert_eq!(&[[0.0, 0.0, 1.0]; 4], &normals[..]);
     }
+
+    #[test]
+    fn test_convex_polygon() {
+        let polygon = ConvexPolygon::new(vec![
+            Vec2::new(-2.0, -1.0),
+            Vec2::new(2.0, -1.0),
+            Vec2::new(1.0, 3.0),
+            Vec2::new(-1.0, 2.0),
+        ])
+        .unwrap();
+
+        let mut mesh = Mesh::from(polygon);
+
+        let Some(VertexAttributeValues::Float32x3(mut positions)) =
+            mesh.remove_attribute(Mesh::ATTRIBUTE_POSITION)
+        else {
+            panic!("Expected positions f32x3");
+        };
+        let Some(VertexAttributeValues::Float32x2(mut uvs)) =
+            mesh.remove_attribute(Mesh::ATTRIBUTE_UV_0)
+        else {
+            panic!("Expected uvs f32x2");
+        };
+        let Some(VertexAttributeValues::Float32x3(normals)) =
+            mesh.remove_attribute(Mesh::ATTRIBUTE_NORMAL)
+        else {
+            panic!("Expected normals f32x3");
+        };
+
+        fix_floats(&mut positions);
+        fix_floats(&mut uvs);
+
+        assert_eq!(
+            [
+                [-2.0, -1.0, 0.0],
+                [2.0, -1.0, 0.0],
+                [1.0, 3.0, 0.0],
+                [-1.0, 2.0, 0.0],
+            ],
+            &positions[..]
+        );
+
+        assert_eq!(
+            [[0.0, 0.0], [1.0, 0.0], [0.75, 1.0], [0.25, 0.75]],
+            &uvs[..]
+        );
+
+        assert_eq!(&[[0.0, 0.0, 1.0]; 4], &normals[..]);
+    }
 }

examples/3d/3d_shapes.rs

@@ -91,6 +91,17 @@ fn setup(
         meshes.add(Extrusion::new(Ellipse::default(), 1.)),
         meshes.add(Extrusion::new(RegularPolygon::default(), 1.)),
         meshes.add(Extrusion::new(Triangle2d::default(), 1.)),
+        meshes.add(Extrusion::new(
+            ConvexPolygon::new(vec![
+                Vec2::new(0.0, 0.8),
+                Vec2::new(-0.47, 0.25),
+                Vec2::new(-0.47, -0.65),
+                Vec2::new(0.47, -0.65),
+                Vec2::new(0.47, 0.25),
+            ])
+            .unwrap(),
+            1.0,
+        )),
     ];
 
     let ring_extrusions = [