Add a method to compute a bounding box enclosing a set of points (bev…

…yengine#9630)

# Objective

Make it easier to create bounding boxes in user code by providing a
constructor that computes a box surrounding an arbitrary number of
points.

## Solution

Add `Aabb::enclosing`, which accepts iterators, slices, or arrays.

---------

Co-authored-by: Tristan Guichaoua <[email protected]>

crates/bevy_render/src/mesh/mesh/mod.rs

@@ -464,27 +464,13 @@ impl Mesh {
 
     /// Compute the Axis-Aligned Bounding Box of the mesh vertices in model space
     pub fn compute_aabb(&self) -> Option<Aabb> {
-        if let Some(VertexAttributeValues::Float32x3(values)) =
+        let Some(VertexAttributeValues::Float32x3(values)) =
             self.attribute(Mesh::ATTRIBUTE_POSITION)
-        {
-            let mut minimum = VEC3_MAX;
-            let mut maximum = VEC3_MIN;
-            for p in values {
-                minimum = minimum.min(Vec3::from_slice(p));
-                maximum = maximum.max(Vec3::from_slice(p));
-            }
-            if minimum.x != std::f32::MAX
-                && minimum.y != std::f32::MAX
-                && minimum.z != std::f32::MAX
-                && maximum.x != std::f32::MIN
-                && maximum.y != std::f32::MIN
-                && maximum.z != std::f32::MIN
-            {
-                return Some(Aabb::from_min_max(minimum, maximum));
-            }
-        }
+        else {
+            return None;
+        };
 
-        None
+        Aabb::enclosing(values.iter().map(|p| Vec3::from_slice(p)))
     }
 
     /// Whether this mesh has morph targets.
@@ -635,9 +621,6 @@ struct MeshAttributeData {
     values: VertexAttributeValues,
 }
 
-const VEC3_MIN: Vec3 = Vec3::splat(std::f32::MIN);
-const VEC3_MAX: Vec3 = Vec3::splat(std::f32::MAX);
-
 fn face_normal(a: [f32; 3], b: [f32; 3], c: [f32; 3]) -> [f32; 3] {
     let (a, b, c) = (Vec3::from(a), Vec3::from(b), Vec3::from(c));
     (b - a).cross(c - a).normalize().into()

crates/bevy_render/src/primitives/mod.rs

@@ -1,3 +1,5 @@
+use std::borrow::Borrow;
+
 use bevy_ecs::{component::Component, prelude::Entity, reflect::ReflectComponent};
 use bevy_math::{Affine3A, Mat3A, Mat4, Vec3, Vec3A, Vec4, Vec4Swizzles};
 use bevy_reflect::Reflect;
@@ -29,7 +31,7 @@ use bevy_utils::HashMap;
 /// [`CalculateBounds`]: crate::view::visibility::VisibilitySystems::CalculateBounds
 /// [`Mesh`]: crate::mesh::Mesh
 /// [`Handle<Mesh>`]: crate::mesh::Mesh
-#[derive(Component, Clone, Copy, Debug, Default, Reflect)]
+#[derive(Component, Clone, Copy, Debug, Default, Reflect, PartialEq)]
 #[reflect(Component)]
 pub struct Aabb {
     pub center: Vec3A,
@@ -49,6 +51,30 @@ impl Aabb {
         }
     }
 
+    /// Returns a bounding box enclosing the specified set of points.
+    ///
+    /// Returns `None` if the iterator is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use bevy_math::{Vec3, Vec3A};
+    /// # use bevy_render::primitives::Aabb;
+    /// let bb = Aabb::enclosing([Vec3::X, Vec3::Z * 2.0, Vec3::Y * -0.5]).unwrap();
+    /// assert_eq!(bb.min(), Vec3A::new(0.0, -0.5, 0.0));
+    /// assert_eq!(bb.max(), Vec3A::new(1.0, 0.0, 2.0));
+    /// ```
+    pub fn enclosing<T: Borrow<Vec3>>(iter: impl IntoIterator<Item = T>) -> Option<Self> {
+        let mut iter = iter.into_iter().map(|p| *p.borrow());
+        let mut min = iter.next()?;
+        let mut max = min;
+        for v in iter {
+            min = Vec3::min(min, v);
+            max = Vec3::max(max, v);
+        }
+        Some(Self::from_min_max(min, max))
+    }
+
     /// Calculate the relative radius of the AABB with respect to a plane
     #[inline]
     pub fn relative_radius(&self, p_normal: &Vec3A, model: &Mat3A) -> f32 {
@@ -455,4 +481,28 @@ mod tests {
         };
         assert!(frustum.intersects_sphere(&sphere, true));
     }
+
+    #[test]
+    fn aabb_enclosing() {
+        assert_eq!(Aabb::enclosing(<[Vec3; 0]>::default()), None);
+        assert_eq!(
+            Aabb::enclosing(vec![Vec3::ONE]).unwrap(),
+            Aabb::from_min_max(Vec3::ONE, Vec3::ONE)
+        );
+        assert_eq!(
+            Aabb::enclosing(&[Vec3::Y, Vec3::X, Vec3::Z][..]).unwrap(),
+            Aabb::from_min_max(Vec3::ZERO, Vec3::ONE)
+        );
+        assert_eq!(
+            Aabb::enclosing([
+                Vec3::NEG_X,
+                Vec3::X * 2.0,
+                Vec3::NEG_Y * 5.0,
+                Vec3::Z,
+                Vec3::ZERO
+            ])
+            .unwrap(),
+            Aabb::from_min_max(Vec3::new(-1.0, -5.0, 0.0), Vec3::new(2.0, 0.0, 1.0))
+        );
+    }
 }