OutlinePass does not support InstancedMesh

Description of the problem

OutlinePass does not appear to properly support InstancedMesh. I’ve created an example here that uses the same setup of OutlinePass in the example in the docs. The sphere is a regular Mesh and the squares are the instances of InstancedMesh. https://jsfiddle.net/anthonysimone/dL8s2qmv/

It seems like there’s a couple things going on here.

1. If you hover over the regular mesh first (sphere), then one of the instanced mesh instances, the base position of the InstancedMesh is outlined any time you’re hovering over any of the instances. In the above example all of the instances have been moved from the default position to demonstrate this clearly.
2. If you first hover over any of the box instances, the entire collection of instances (though not the base position) of the InstancedMesh are outlined, but then hovering over a regular mesh (the sphere) causes an error.

I dug into OutlinePass a bit and it seems like it might just not be taking into account handling instanced meshes separately from regular meshes. I’m still pretty new to Three.js, so I don’t have a potential fix to suggest at this point.

Three.js version

• r113

Browser

• All of them
• Chrome
• Firefox
• Internet Explorer

OS

• All of them
• Windows
• macOS
• Linux
• Android
• iOS

[Mugen87]

Fixed via #20135, see https://jsfiddle.net/quf0p415/1/.

No runtime errors occur anymore. Point 1 of the original post is solved. Also the artifact mentioned in https://github.com/mrdoob/three.js/issues/18533#issuecomment-581782781. Point 2 is partially solved since all instanced meshes are highlighted when one is selected. But that is an acceptable behavior for now since some use cases require it anyway. A solution for individual highlighting is explained here: https://github.com/mrdoob/three.js/issues/18533#issuecomment-581782781

@mrdoob I guess this is a good example of what you mean in https://github.com/mrdoob/three.js/pull/20975#issuecomment-805349659. By removing skinning, the same effect would be achieved and a single overrideMaterial can be used for normal, instanced and skinned meshes 🎉 .

[mrdoob]

@mrdoob I guess this is a good example of what you mean in https://github.com/mrdoob/three.js/pull/20975#issuecomment-805349659. By removing skinning, the same effect would be achieved and a single overrideMaterial can be used for normal, instanced and skinned meshes 🎉 .

Yes 😉