Baking textures on headless machine (batch baking)

Question

Is it possible to bake textures from the command line?

This is useful for setting up batch jobs, baking an entire level for example.

Answer 1

Yes, the bake operator can run in background mode, for both Blender-Internal and Cycles Baking.

A very simple script could look like this:

Bake Once

bake.py:

 import bpy

 # Like pressing the 'Bake' button in Blender
 # this will remain locked until the bake is complete.
 bpy.ops.object.bake(type='COMBINED')

 # You might want to inspect the materials and extract images
 # but for this example, simply select by name
 image = bpy.data.images["Untitled"]

 # save-as by setting the target path and saving
 image.file_format = 'PNG'
 image.filepath_raw = "//my_new_bake.png"
 image.save()

Execute the bake with:

 blender --background bake_test.blend --python bake.py

For batch jobs you would have to change the selection before calling bpy.ops.object.bake each time.

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Bake Everything

This next example is more comprehensive, and uses the is_dirty image flag to detect which images to save, giving each image a _bake suffix.

bake_all.py:

# Blender v2.8x +
import bpy
import os

scene = bpy.context.scene
for obj in scene.objects:
    obj.select_set(False)

for obj in scene.objects:
    if obj.type != 'MESH':
        continue

    bpy.context.view_layer.objects.active = obj
    obj.select_set(True)

    bpy.ops.object.bake(type='COMBINED')
    obj.select_set(False)

# save all baked images
for image in bpy.data.images:
    if image.is_dirty:
        # foo.png -> foo_bake.png
        filepath, filepath_ext = os.path.splitext(image.filepath_raw)
        image.filepath_raw = filepath + "_bake" + filepath_ext
        image.save()

Execute the bake with:

 blender --background bake_test.blend --python bake_all.py

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Further ideas for batch baking which might be useful.

• Automate baking an entire game-level:

  loop over each group and bake its objects (or each group matching a naming convention, ending with .bake for example)

• Automate baking existing models:

  A utility script which loads in models from an external format (OBJ, FBX, 3DS... etc), unwrap, assign images, bake and exports.

• Automate low-poly mesh creation with the decimate modifier, and bake normal maps (high->low poly meshes).

• Bake textures over time (create a baked image sequence).

• Create a utility which runs back in a background process so you can keep on using Blender.