Mesh picking fixes (#16110)

# Objective

- Mesh picking is noisy when a non triangle list is used
- Mesh picking runs even when users don't need it
- Resolve #16065 

## Solution

- Don't add the mesh picking plugin by default
- Remove error spam

benches/benches/bevy_picking/ray_mesh_intersection.rs

@@ -1,5 +1,5 @@
 use bevy_math::{Dir3, Mat4, Ray3d, Vec3};
-use bevy_picking::{mesh_picking::ray_cast, prelude::*};
+use bevy_picking::mesh_picking::ray_cast;
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
 fn ptoxznorm(p: u32, size: u32) -> (f32, f32) {

crates/bevy_picking/src/lib.rs

@@ -277,24 +277,10 @@ pub struct DefaultPickingPlugins;
 
 impl PluginGroup for DefaultPickingPlugins {
     fn build(self) -> PluginGroupBuilder {
-        #[cfg_attr(
-            not(feature = "bevy_mesh"),
-            expect(
-                unused_mut,
-                reason = "Group is not mutated when `bevy_mesh` is not enabled."
-            )
-        )]
-        let mut group = PluginGroupBuilder::start::<Self>()
+        PluginGroupBuilder::start::<Self>()
             .add(input::PointerInputPlugin::default())
             .add(PickingPlugin::default())
-            .add(InteractionPlugin);
-
-        #[cfg(feature = "bevy_mesh")]
-        {
-            group = group.add(mesh_picking::MeshPickingPlugin);
-        };
-
-        group
+            .add(InteractionPlugin)
     }
 }
 

crates/bevy_picking/src/mesh_picking/ray_cast/intersections.rs

@@ -1,7 +1,6 @@
 use bevy_math::{bounding::Aabb3d, Dir3, Mat4, Ray3d, Vec3, Vec3A};
 use bevy_reflect::Reflect;
-use bevy_render::mesh::{Indices, Mesh, PrimitiveTopology, VertexAttributeValues};
-use bevy_utils::tracing::{error, warn};
+use bevy_render::mesh::{Indices, Mesh, PrimitiveTopology};
 
 use super::Backfaces;
 
@@ -17,7 +16,7 @@ pub struct RayMeshHit {
     /// The distance from the ray origin to the intersection point.
     pub distance: f32,
     /// The vertices of the triangle that was hit.
-    pub triangle: Option<[Vec3A; 3]>,
+    pub triangle: Option<[Vec3; 3]>,
     /// The index of the triangle that was hit.
     pub triangle_index: Option<usize>,
 }
@@ -32,84 +31,41 @@ pub struct RayTriangleHit {
 /// Casts a ray on a mesh, and returns the intersection.
 pub(super) fn ray_intersection_over_mesh(
     mesh: &Mesh,
-    mesh_transform: &Mat4,
+    transform: &Mat4,
     ray: Ray3d,
-    backface_culling: Backfaces,
+    culling: Backfaces,
 ) -> Option<RayMeshHit> {
     if mesh.primitive_topology() != PrimitiveTopology::TriangleList {
-        error!(
-            "Invalid intersection check: `TriangleList` is the only supported `PrimitiveTopology`"
-        );
-        return None;
+        return None; // ray_mesh_intersection assumes vertices are laid out in a triangle list
     }
+    // Vertex positions are required
+    let positions = mesh.attribute(Mesh::ATTRIBUTE_POSITION)?.as_float3()?;
 
-    // Get the vertex positions and normals from the mesh.
-    let vertex_positions: &Vec<[f32; 3]> = match mesh.attribute(Mesh::ATTRIBUTE_POSITION) {
-        None => {
-            error!("Mesh does not contain vertex positions");
-            return None;
+    // Normals are optional
+    let normals = mesh
+        .attribute(Mesh::ATTRIBUTE_NORMAL)
+        .and_then(|normal_values| normal_values.as_float3());
+
+    match mesh.indices() {
+        Some(Indices::U16(indices)) => {
+            ray_mesh_intersection(ray, transform, positions, normals, Some(indices), culling)
         }
-        Some(vertex_values) => match &vertex_values {
-            VertexAttributeValues::Float32x3(positions) => positions,
-            _ => {
-                error!("Unexpected types in {:?}", Mesh::ATTRIBUTE_POSITION);
-                return None;
-            }
-        },
-    };
-    let vertex_normals: Option<&[[f32; 3]]> =
-        if let Some(normal_values) = mesh.attribute(Mesh::ATTRIBUTE_NORMAL) {
-            match &normal_values {
-                VertexAttributeValues::Float32x3(normals) => Some(normals),
-                _ => None,
-            }
-        } else {
-            None
-        };
-
-    if let Some(indices) = &mesh.indices() {
-        match indices {
-            Indices::U16(vertex_indices) => ray_mesh_intersection(
-                ray,
-                mesh_transform,
-                vertex_positions,
-                vertex_normals,
-                Some(vertex_indices),
-                backface_culling,
-            ),
-            Indices::U32(vertex_indices) => ray_mesh_intersection(
-                ray,
-                mesh_transform,
-                vertex_positions,
-                vertex_normals,
-                Some(vertex_indices),
-                backface_culling,
-            ),
+        Some(Indices::U32(indices)) => {
+            ray_mesh_intersection(ray, transform, positions, normals, Some(indices), culling)
         }
-    } else {
-        ray_mesh_intersection(
-            ray,
-            mesh_transform,
-            vertex_positions,
-            vertex_normals,
-            None::<&[usize]>,
-            backface_culling,
-        )
+        None => ray_mesh_intersection::<usize>(ray, transform, positions, normals, None, culling),
     }
 }
 
 /// Checks if a ray intersects a mesh, and returns the nearest intersection if one exists.
-pub fn ray_mesh_intersection<Index: Clone + Copy>(
+pub fn ray_mesh_intersection<I: TryInto<usize> + Clone + Copy>(
     ray: Ray3d,
     mesh_transform: &Mat4,
-    vertex_positions: &[[f32; 3]],
+    positions: &[[f32; 3]],
     vertex_normals: Option<&[[f32; 3]]>,
-    indices: Option<&[Index]>,
+    indices: Option<&[I]>,
     backface_culling: Backfaces,
-) -> Option<RayMeshHit>
-where
-    usize: TryFrom<Index>,
-{
+) -> Option<RayMeshHit> {
     // The ray cast can hit the same mesh many times, so we need to track which hit is
     // closest to the camera, and record that.
     let mut closest_hit_distance = f32::MAX;
@@ -123,38 +79,36 @@ where
     );
 
     if let Some(indices) = indices {
-        // Make sure this chunk has 3 vertices to avoid a panic.
+        // The index list must be a multiple of three. If not, the mesh is malformed and the raycast
+        // result might be nonsensical.
         if indices.len() % 3 != 0 {
-            warn!("Index list not a multiple of 3");
             return None;
         }
 
-        // Now that we're in the vector of vertex indices, we want to look at the vertex
-        // positions for each triangle, so we'll take indices in chunks of three, where each
-        // chunk of three indices are references to the three vertices of a triangle.
-        for index_chunk in indices.chunks_exact(3) {
-            let [index1, index2, index3] = [
-                usize::try_from(index_chunk[0]).ok()?,
-                usize::try_from(index_chunk[1]).ok()?,
-                usize::try_from(index_chunk[2]).ok()?,
+        for triangle in indices.chunks_exact(3) {
+            let [a, b, c] = [
+                triangle[0].try_into().ok()?,
+                triangle[1].try_into().ok()?,
+                triangle[2].try_into().ok()?,
             ];
-            let triangle_index = Some(index1);
-            let tri_vertex_positions = [
-                Vec3A::from(vertex_positions[index1]),
-                Vec3A::from(vertex_positions[index2]),
-                Vec3A::from(vertex_positions[index3]),
+
+            let triangle_index = Some(a);
+            let tri_vertex_positions = &[
+                Vec3::from(positions[a]),
+                Vec3::from(positions[b]),
+                Vec3::from(positions[c]),
             ];
             let tri_normals = vertex_normals.map(|normals| {
                 [
-                    Vec3A::from(normals[index1]),
-                    Vec3A::from(normals[index2]),
-                    Vec3A::from(normals[index3]),
+                    Vec3::from(normals[a]),
+                    Vec3::from(normals[b]),
+                    Vec3::from(normals[c]),
                 ]
             });
 
             let Some(hit) = triangle_intersection(
                 tri_vertex_positions,
-                tri_normals,
+                tri_normals.as_ref(),
                 closest_hit_distance,
                 &mesh_space_ray,
                 backface_culling,
@@ -171,33 +125,33 @@ where
                     .length(),
                 triangle: hit.triangle.map(|tri| {
                     [
-                        mesh_transform.transform_point3a(tri[0]),
-                        mesh_transform.transform_point3a(tri[1]),
-                        mesh_transform.transform_point3a(tri[2]),
+                        mesh_transform.transform_point3(tri[0]),
+                        mesh_transform.transform_point3(tri[1]),
+                        mesh_transform.transform_point3(tri[2]),
                     ]
                 }),
                 triangle_index,
             });
             closest_hit_distance = hit.distance;
         }
     } else {
-        for (i, chunk) in vertex_positions.chunks_exact(3).enumerate() {
-            let &[a, b, c] = chunk else {
+        for (i, triangle) in positions.chunks_exact(3).enumerate() {
+            let &[a, b, c] = triangle else {
                 continue;
             };
             let triangle_index = Some(i);
-            let tri_vertex_positions = [Vec3A::from(a), Vec3A::from(b), Vec3A::from(c)];
+            let tri_vertex_positions = &[Vec3::from(a), Vec3::from(b), Vec3::from(c)];
             let tri_normals = vertex_normals.map(|normals| {
                 [
-                    Vec3A::from(normals[i]),
-                    Vec3A::from(normals[i + 1]),
-                    Vec3A::from(normals[i + 2]),
+                    Vec3::from(normals[i]),
+                    Vec3::from(normals[i + 1]),
+                    Vec3::from(normals[i + 2]),
                 ]
             });
 
             let Some(hit) = triangle_intersection(
                 tri_vertex_positions,
-                tri_normals,
+                tri_normals.as_ref(),
                 closest_hit_distance,
                 &mesh_space_ray,
                 backface_culling,
@@ -214,9 +168,9 @@ where
                     .length(),
                 triangle: hit.triangle.map(|tri| {
                     [
-                        mesh_transform.transform_point3a(tri[0]),
-                        mesh_transform.transform_point3a(tri[1]),
-                        mesh_transform.transform_point3a(tri[2]),
+                        mesh_transform.transform_point3(tri[0]),
+                        mesh_transform.transform_point3(tri[1]),
+                        mesh_transform.transform_point3(tri[2]),
                     ]
                 }),
                 triangle_index,
@@ -228,15 +182,14 @@ where
     closest_hit
 }
 
-#[inline(always)]
 fn triangle_intersection(
-    tri_vertices: [Vec3A; 3],
-    tri_normals: Option<[Vec3A; 3]>,
+    tri_vertices: &[Vec3; 3],
+    tri_normals: Option<&[Vec3; 3]>,
     max_distance: f32,
     ray: &Ray3d,
     backface_culling: Backfaces,
 ) -> Option<RayMeshHit> {
-    let hit = ray_triangle_intersection(ray, &tri_vertices, backface_culling)?;
+    let hit = ray_triangle_intersection(ray, tri_vertices, backface_culling)?;
 
     if hit.distance < 0.0 || hit.distance > max_distance {
         return None;
@@ -258,25 +211,24 @@ fn triangle_intersection(
 
     Some(RayMeshHit {
         point,
-        normal: normal.into(),
+        normal,
         barycentric_coords: barycentric,
         distance: hit.distance,
-        triangle: Some(tri_vertices),
+        triangle: Some(*tri_vertices),
         triangle_index: None,
     })
 }
 
 /// Takes a ray and triangle and computes the intersection.
-#[inline(always)]
 fn ray_triangle_intersection(
     ray: &Ray3d,
-    triangle: &[Vec3A; 3],
+    triangle: &[Vec3; 3],
     backface_culling: Backfaces,
 ) -> Option<RayTriangleHit> {
     // Source: https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-tracing-rendering-a-triangle/moller-trumbore-ray-triangle-intersection
-    let vector_v0_to_v1: Vec3A = triangle[1] - triangle[0];
-    let vector_v0_to_v2: Vec3A = triangle[2] - triangle[0];
-    let p_vec: Vec3A = (Vec3A::from(*ray.direction)).cross(vector_v0_to_v2);
+    let vector_v0_to_v1: Vec3 = triangle[1] - triangle[0];
+    let vector_v0_to_v2: Vec3 = triangle[2] - triangle[0];
+    let p_vec: Vec3 = ray.direction.cross(vector_v0_to_v2);
     let determinant: f32 = vector_v0_to_v1.dot(p_vec);
 
     match backface_culling {
@@ -298,14 +250,14 @@ fn ray_triangle_intersection(
 
     let determinant_inverse = 1.0 / determinant;
 
-    let t_vec = Vec3A::from(ray.origin) - triangle[0];
+    let t_vec = ray.origin - triangle[0];
     let u = t_vec.dot(p_vec) * determinant_inverse;
     if !(0.0..=1.0).contains(&u) {
         return None;
     }
 
     let q_vec = t_vec.cross(vector_v0_to_v1);
-    let v = Vec3A::from(*ray.direction).dot(q_vec) * determinant_inverse;
+    let v = (*ray.direction).dot(q_vec) * determinant_inverse;
     if v < 0.0 || u + v > 1.0 {
         return None;
     }

examples/picking/mesh_picking.rs

@@ -1,10 +1,23 @@
 //! A simple 3D scene to demonstrate mesh picking.
 //!
-//! By default, all meshes are pickable. Picking can be disabled for individual entities
-//! by adding [`PickingBehavior::IGNORE`].
+//! [`bevy::picking::backend`] provides an API for adding picking hit tests to any entity. To get
+//! started with picking 3d meshes, the [`MeshPickingPlugin`] is provided as a simple starting
+//! point, especially useful for debugging. For your game, you may want to use a 3d picking backend
+//! provided by your physics engine, or a picking shader, depending on your specific use case.
 //!
-//! If you want mesh picking to be entirely opt-in, you can set [`MeshPickingSettings::require_markers`]
-//! to `true` and add a [`RayCastPickable`] component to the desired camera and target entities.
+//! [`bevy::picking`] allows you to compose backends together to make any entity on screen pickable
+//! with pointers, regardless of how that entity is rendered. For example, `bevy_ui` and
+//! `bevy_sprite` provide their own picking backends that can be enabled at the same time as this
+//! mesh picking backend. This makes it painless to deal with cases like the UI or sprites blocking
+//! meshes underneath them, or vice versa.
+//!
+//! If you want to build more complex interactions than afforded by the provided pointer events, you
+//! may want to use [`MeshRayCast`] or a full physics engine with raycasting capabilities.
+//!
+//! By default, the mesh picking plugin will raycast against all entities, which is especially
+//! useful for debugging. If you want mesh picking to be opt-in, you can set
+//! [`MeshPickingSettings::require_markers`] to `true` and add a [`RayCastPickable`] component to
+//! the desired camera and target entities.
 
 use std::f32::consts::PI;
 
@@ -19,7 +32,12 @@ use bevy::{
 
 fn main() {
     App::new()
-        .add_plugins(DefaultPlugins)
+        .add_plugins((
+            DefaultPlugins,
+            // The mesh picking plugin is not enabled by default, because raycasting against all
+            // meshes has a performance cost.
+            MeshPickingPlugin,
+        ))
         .init_resource::<SceneMaterials>()
         .add_systems(Startup, setup)
         .add_systems(Update, (on_mesh_hover, rotate))