Skip to content

Clarify TRS properties in the Object Model #2559

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
lexaknyazev merged 1 commit into from
Feb 3, 2026
Merged

Clarify TRS properties in the Object Model #2559

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 10 additions & 0 deletions specification/2.0/ObjectModel.adoc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,16 @@ The following pointer templates represent mutable properties defined in the core
| `/nodes/{}/weights/{}` | `float`
|====

The `/nodes/{}/translation`, `/nodes/{}/rotation`, and `/nodes/{}/scale` pointers represent the current TRS properties of the node. If the static `matrix` property is defined on the node object in JSON, the corresponding rotation and scale pointers are undefined.

[NOTE]
.Rationale
====
Since the glTF 2.0 specification allows negative scale factors, TRS matrix decomposition is ambiguous with regard to rotation and scale. Two implementations that choose different scale factor signs for the same matrix may produce two different rotation quaternions for it. Therefore, updating only the rotation or the scale may result in different node transformation matrices in different implementations.

This restriction does not apply to the translation because the translation vector directly corresponds to the first three values of the last column of the transformation matrix regardless of the decomposition process.
====

The `/nodes/{}/weights` and `/nodes/{}/weights/{}` pointers represent the current morph target weights (as an array and as individual scalars respectively) of the mesh instantiated by the node regardless of whether the static `weights` property is defined on the node object in JSON. If the node instantiates no mesh or if the mesh has no morph targets, these pointers are undefined.

[NOTE]
Expand Down