Where is this going?
├── Web (Three.js, Babylon.js, model-viewer, AR Quick Look) → glTF / GLB
├── Game engine (Unity, Unreal, Godot)
│   ├── Animated/rigged → FBX (or glTF for modern engines)
│   └── Static → OBJ or FBX or glTF
├── Apple AR (USDZ) → USDZ (special, see Recipe 6)
├── 3D printing → STL (geometry only, must be watertight)
├── VFX pipeline (Maya, Houdini, Nuke) → USD
└── DCC roundtrip → FBX (industry standard)

import bpy

bpy.ops.export_scene.gltf(
    filepath='/tmp/output.glb',
    export_format='GLB',                 # single-file binary; preferred
    export_apply=True,                   # apply modifiers before export
    export_materials='EXPORT',
    export_image_format='AUTO',          # PNG; AUTO falls back to JPEG for opaque images
    export_yup=True,                     # Y-up convention (most engines / web expect this)
    export_animations=True,              # toggle off for static models
    export_morph=True,                   # shape keys
    export_skins=True,                   # armatures + weights
    export_normals=True,
    export_tangents=False,               # skip unless target uses tangent-space normals beyond standard
)

**glTF caveats**:
- Only Principled BSDF materials export cleanly. Procedural shaders are dropped or simplified.
- Hard cap: 15 MB; soft target: 8 MB.
- No KTX2 / Draco compression (unless target supports those loaders).
- PNG textures only (max 1024×1024 typical).

import bpy

obj = bpy.data.objects['GEO-target']
bpy.context.view_layer.objects.active = obj

mod = obj.modifiers.new('Decimate', type='DECIMATE')
mod.ratio = 0.7    # keep 70% of faces; lower = more reduction
mod.use_collapse_degenerate = True
bpy.ops.object.modifier_apply(modifier=mod.name)

print(f"decimated:{obj.name} verts:{len(obj.data.vertices)}")

import bpy

bpy.ops.export_scene.fbx(
    filepath='/tmp/output.fbx',
    use_selection=False,
    apply_unit_scale=True,
    apply_scale_options='FBX_SCALE_ALL',
    bake_space_transform=True,        # critical: applies rotation to mesh
    object_types={'MESH', 'ARMATURE', 'EMPTY'},
    use_mesh_modifiers=True,
    mesh_smooth_type='FACE',
    use_armature_deform_only=True,
    bake_anim=True,
    bake_anim_use_all_bones=True,
    bake_anim_use_nla_strips=True,
    bake_anim_use_all_actions=True,
    bake_anim_force_startend_keying=True,
    embed_textures=True,              # critical: embed textures into FBX
    path_mode='COPY',
    axis_forward='-Z',
    axis_up='Y',
)
print('export:fbx')

import bpy

bpy.ops.wm.obj_export(
    filepath='/tmp/output.obj',
    export_animation=False,
    apply_modifiers=True,
    export_eval_mode='DAG_EVAL_VIEWPORT',
    export_uv=True,
    export_normals=True,
    export_materials=True,
    export_triangulated_mesh=False,
    forward_axis='NEGATIVE_Z',
    up_axis='Y',
)
print('export:obj')

import bpy

bpy.ops.wm.stl_export(
    filepath='/tmp/output.stl',
    ascii_format=False,    # binary STL (smaller, faster)
    apply_modifiers=True,
)
print('export:stl')

import bpy

bpy.ops.wm.usd_export(
    filepath='/tmp/scene.usdc',
    export_animation=True,
    export_uvmaps=True,
    export_normals=True,
    export_materials=True,
    use_instancing=True,
    export_textures=True,
    overwrite_textures=True,
)
print('export:usd')

import bpy

undefined

import os

filepath = '/tmp/output.glb'
if not os.path.exists(filepath):
    print(f"ERROR:not_found {filepath}")
else:
    size_mb = os.path.getsize(filepath) / (1024 * 1024)
    print(f"verified:{filepath} {size_mb:.2f}MB")