OMI glTF Working Group Meeting 2023-01-18

[antpb]

This meeting is on 2024-1-18 at 9:30 PM (UTC) / 2:30 PM (PST) in the OMI Discord within the #omi-weekly-meeting channel. During the meeting, we will be using the #omi-gltf-extensions channel to manage a speaker queue, post links, and for any sidebar discussions.

To be notified of this meeting and others, subscribe to the OMI Meetings and Events Calendar or add yourself to the @omi-gltf-subgroup role in the #roles channel of the OMI Discord.

Current Agenda:

• KHR_Audio and physics discussion
• Open floor! Let's talk glTF extensions!

To propose another item for the agenda, comment below (preferably before the meeting).

[antpb]

General discussion around isKinematic:

We reviewed https://rapier.rs/docs/user_guides/rust/rigid_bodies/ to drive discussion and came to the agreement that it would be ideal for this property to be named type with a value type of enum. Example {"type": "kinematic"}

eoineoineoin/glTF_Physics#4

[antpb]

Joints discussion:
Lyuma made a comment "A joint implies connecting two bodies" which started a discussion around the relationship of two nodes that are not of a body type. Regarding which nodes are legal to connect.

Four Joint connect cases discussed:
1.) node is ref node not part of rigidbody - what do we do??? equal to connecting to a static. Example is a body being anchored to a location. Like a balloon attached to a fixed point. That fixed point would be a node not part of the rigid.
2.) is a rigidbody -ez to connect two of these
3.) descendent of rigidbody - relative to the rigidbody
4.) can it be attached to null? No. We identified that you must connect to something be it a static node or another body.

We noted that Microsoft spec also has the concept of motors in joints to provide animation to the joints. They are called "joint drive"

[antpb]

We discussed how character controllers are unique cases that sometimes result in weird states where bodies may change type or be dynamic in ways that are hard to factor in. It was mentioned that glTF is likely not in current state going to solve character controllers and they should be their own spec.

antpb used his own character controller as an example that dynamically changes between dynamic and fixed body type at runtime based on different states of the player (moving, falling, etc)