snippets: Unreal glTF preset scales meshes 100x but leaves object locations in meters

[TMHSDigital]

Why it matters

export_preset_unreal_gltf is sold as the Unreal centimeter preset. It multiplies each mesh's scale by 100 and applies it, but never scales object locations. A single object at the origin exports correctly. Any real scene with more than one object comes out with centimeter-sized geometry laid out at meter spacing: objects overlap or collapse together in Unreal.

Readers copy this snippet as-is, and the engine-export-presets skill points at it.

Evidence

snippets/export_preset_unreal.py:30-36 (HEAD 54e7f71):

def export_preset_unreal_gltf(filepath, selected_only=True, draco=False):
    apply_selected_mesh_transforms()
    for obj in list(bpy.context.selected_objects):
        if obj.type != "MESH":
            continue
        obj.scale = (obj.scale[0] * 100.0, obj.scale[1] * 100.0, obj.scale[2] * 100.0)
    apply_selected_mesh_transforms()   # transform_apply(location=False, ...)

obj.location is never touched, so the distance between objects stays in meters while mesh extents grow 100x.

Reproduced headless on .scratch/5.2/blender-5.2.1-windows-x64/blender.exe (reports Blender 5.2.1 LTS): three cubes placed 3 m apart, selected, then export_preset_unreal_gltf(...) was called:

PROBE2 inter-object distance 3.000 -> 3.000; cube width 4.000 -> 400.000

Mesh extents grew ×100, spacing stayed ×1.

Suggested approach

Pick one:

• Scale obj.location by 100 alongside obj.scale. Parented objects need care: only scale roots, or use matrix_world.
• Parent the selection under a temporary root empty, scale the root 100x, apply, then unparent.

Also check whether the existing examples/ export-preset smoke only uses a single object at the origin, which would explain why CI never saw this.

Done when

• Multi-object selections keep their relative layout, measured in centimeters.
• A smoke check (catalog row or example assertion) exports at least two objects placed apart and asserts the inter-object distance grows ×100. The check has a recorded falsifier run against the current code.