There are a few guides on this, but most are videos. I’m not a video person, so here’s a REALLY simplistic and easy to follow set of just the steps:
Switch FBX from A pose to T pose:
- Import FBX, under armature select ‘automatic bone orientation’
- Select the armature, switch to the pose mode, and select the arm upper arm joint. Rotate it -45/45 respectively
- Switch to Object mode, select the MESH and select Add Modifier:
- Here’s where it gets interesting… Add a deform modifier to the armature:
It’s going to look just like this. Select ‘Preserve Volume’ and apply.
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Select the armature again, select all, and switch to pose mode.
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Select ‘Apply Pose as Rest Pose’
- It’ll now look correct, and sit in T pose.
- Export as GLB/glTF, and re-import, the pose is now a T pose.
