MAXAR_collision_geometry

[erikdahlstrom]

A draft extension for being able to associate collision meshes with meshes inside a glTF.

[donmccurdy]

Had two clarifying questions here for my own curiosity, but not meant as concerns with the extension! :)

[rsahlin]

Hi @erikdahlstrom - great that you are looking into collisions :-)

We are also very interested in being able to use meshes for collision, for many usecases a decimated version (LOD) will suffice but for some cases these may not be convex hulls.

Our ideal usecase would be to convert to convex hulls on the client side at load-time, is this something you have looked into and considered?
For this we may use some version of HACD, however at the moment this seems to be somewhat too time consuming to do on the client side.

Just out of curiosity - have you considered simply adding the boundingbox reference as metadata (extras) to the visible mesh?

ps
Another way of doing boundingboxes could be to put the non visible collision meshes as a node hierarchy in a separate scene.
Ie, scene 0 contains all visible nodes and scene 1 contains collision meshes.
ds

Best regards
/Richard

[aaronfranke]

OMI has been working on an extension called OMI_collider which allows glTF files to define collision geometry. It also includes primitive shapes such as boxes and convex hulls, so it's a superset of MAXAR_collision_geometry in terms of supported features. Also note MAXAR_collision_geometry has some weird limitations like being attached to meshes, OMI_collider has no such restriction.

OMI_collider is progressing nicely, it has been implemented in Godot Engine (both import and export), it has full schemas, example files, and a validator implementation. OMI_collider likely makes MAXAR_collision_geometry obsolete, though I'd love to hear your feedback if OMI_collider won't fork for a particular use case you have.

EDIT: Replaced by other extensions.

[erikdahlstrom]

I'm going to refer to @bjornblissing for this, as I'm no longer with Maxar.

From memory, we shipped some content using this extension, so this is documenting that snapshot. However, I don't see why changes couldn't be made in the future (or now even), or that another suitable alternative for colliders is found that is acceptable to Maxar. However, I can't speak for Maxar.

[bjornblissing]

@erikdahlstrom Can you close this since it has been replaced and deprecated?

[javagl]

@bjornblissing Looking at the Git activity, it's not obvious that this will come through.

I assume that this is obsolete due to

• KHR_implicit_shapes extension Draft Proposal #2370
• KHR_physics_rigid_bodies Draft Proposal #2424

and will close it accordingly. If there is anything more to add here, just drop a note.