It is no longer possible to set TriMeshFlags::FIX_INTERNAL_EDGES when using Collider::from_bevy_mesh

[rparrett]

TriMeshFlags::FIX_INTERNAL_EDGES is no longer the default behavior, but Bevy users don't really have a good way of setting it.

The workaround is pretty annoying due to extract_mesh_vertices_indices not being pub and containing a bunch of nalgebra types.

Workaround:

let mut flags = TriMeshFlags::default();
flags.set(TriMeshFlags::FIX_INTERNAL_EDGES, true);
let (vtx, idx) =
    extract_mesh_vertices_indices(meshes.get(mesh_handle).unwrap()).unwrap();
let collider: Collider = SharedShape::trimesh_with_flags(vtx, idx, flags).into();

// ...

fn extract_mesh_vertices_indices(
    mesh: &Mesh,
) -> Option<(
    Vec<bevy_rapier3d::na::Point3<bevy_rapier3d::prelude::Real>>,
    Vec<[u32; 3]>,
)> {
    use bevy_rapier3d::math::Real;
    use bevy_rapier3d::na::Point3;

    let vertices = mesh.attribute(Mesh::ATTRIBUTE_POSITION)?;
    let indices = mesh.indices()?;

    let vtx: Vec<_> = match vertices {
        VertexAttributeValues::Float32(vtx) => Some(
            vtx.chunks(3)
                .map(|v| Point3::new(v[0] as Real, v[1] as Real, v[2] as Real))
                .collect(),
        ),
        VertexAttributeValues::Float32x3(vtx) => Some(
            vtx.iter()
                .map(|v| Point3::new(v[0] as Real, v[1] as Real, v[2] as Real))
                .collect(),
        ),
        _ => None,
    }?;

    let idx = match indices {
        Indices::U16(idx) => idx
            .chunks_exact(3)
            .map(|i| [i[0] as u32, i[1] as u32, i[2] as u32])
            .collect(),
        Indices::U32(idx) => idx.chunks_exact(3).map(|i| [i[0], i[1], i[2]]).collect(),
    };

    Some((vtx, idx))
}

[Vrixyz]

I'm surprised TriMeshFlags::FIX_INTERNAL_EDGES was the default somewhere :o, if you can pinpoint how/where exactly I'm curious.

• I think this change we're discussing comes from Add TriMeshFlags to ComputedColliderShape::TriMesh #559

you should be able to pass within ComputedColliderShape the flags inside the TriMesh variant.

if that's not enough, we can probably consider making extract_mesh_vertices_indices public.

[rparrett]

It looks like #559 should fix me up whenever it makes it into a release.

Thanks!

[rparrett]

I'm surprised TriMeshFlags::FIX_INTERNAL_EDGES was the default somewhere

Sorry, bit of an assumption / misreading of this changelog entry by me.

Internal edge correction is now opt-in with the TriMeshFlags::FIX_INTERNAL_EDGES and HeightFieldFlags::FIX_INTERNAL_EDGES flags.

I read that as if the flag existed previously, but was enabled by default. Upgrading from 0.25 -> 0.27 seemed to regress trimesh collisions though, resulting in colliders bumping wildly on "smooth" edges.

So I think that the TriMeshFlags::FIX_INTERNAL_EDGES flag itself is new, but there was something making trimesh edge collisions more stable in rapier 0.18 that was happening by default. And now to get the same behavior, I have to enable that flag.

I have vague memories of this being an issue in much older versions of rapier and then not an issue in later ones, and now an issue again.