Rendering multiple files / scenes via python API

Coding Python Support
1

Hello,

I’ve been looking for a way to automate rendering of several scenes in Blender, either from the same file or from different files, and I can’t seem to get it working.

There are two ways to do this, as far as I can see. Option 1 is to save many different scenes to the same .blend file, and cycle through each scene, rendering it as I go. That code would look something like this:

for Scn in bpy.data.scenes:
# Set active scene
bpy.context.screen.scene = Scn
# Set rendering options
Scn.render.file_format = ‘PNG’
Scn.render.filepath = ‘/some/unique/file/path.png’ # (I of course vary this with each loop iteration)
# Render
bpy.ops.render.render(write_still=True,scene=Scn.name)

… However, this doesn’t work - the render command at the end of the loop will repeatedly render whichever scene is active as the script is called. Basically, the “scene=” argument in the render() command seems not to work.

The second way I could do this is to store all my scenes in different .blend files, open each one and render it in sequence. However, it seems that once a .blend file is opened via

bpy.ops.wm.open_mainfile(filepath=‘FileName.blend’,load_ui=False)

… then the script stops dead in its tracks and no further commands are executed. That is:

bpy.ops.wm.open_mainfile(filepath=‘FileName.blend’,load_ui=False)

This never executes.

Scn = bpy.context.scene
print(Scn.name)

Anyone have any idea how I might proceed? Is there some other option I haven’t considered? Also, even if it’s not the best way, I’m particularly interested in whether the python API can handle opening and closing multiple files within the same script…

Thanks!

2

A third option, btw, is to import each scene into an empty .blend file, but if you do that you run into the same problem as before - namely, that you can’t switch to the new scene and then render it.

Again - any help would be much appreciated. Cheers.

3

Solved this problem eventually by using compositor nodes (thanks to a suggestion from Atom). I now have files with many scenes in them, and in the first scene, I add a compositor “File Output” node and connect it to the render layer node.

I then change the input of the render layer node via a python script, and repeatedly render the first scene. This is an OK work-around, but it would be nice if the bpy.data.scenes[n].update() command took effect before any subsequent render commands.

4

The original poster already found a solution for his problem, but I came upon this thread while searching for a solution to a similar problem.
On IRC I was pointed to the following code (part of addons/io_mesh_uv_layout/export_uv_png.py):

data_context = {"blend_data": bpy.context.blend_data, "scene": scene}
bpy.ops.render.render(data_context)

I’m posting it here, because other people who come upon this thread by searching, might find it useful.

5

Hmm… I’m surprised at the problem - is the 2.5x API really that unfinished? In 2.49 this works perfectly:

for tScene in bpy.data.scenes:
  tScene.makeCurrent()
  print "Rendering " + tScene.getName()
  tRenderData = tScene.getRenderingContext()
  tRenderData.render()

(I went through about ten edits to get this post to display correctly…)

6

So the complete code to render all scenes in your blend file using their original settings would be as follows:

import bpy
for scene in bpy.data.scenes:
    data_context = {"blend_data": bpy.context.blend_data, "scene": scene}
    bpy.ops.render.render(data_context, animation=True)
7

note, you can do this…


import bpy
data_context = bpy.context.copy()

for scene in bpy.data.scenes:
    data_context["scene"] = some_scene
    bpy.ops.render.render(data_context, animation=True)
8

After a bit of tinkering, I found a oneliner to render a specific scene (single image).

bpy.ops.render.render({'scene': bpy.data.scenes['SpecificScene']}, write_still=True)

(for future searches, like the one I made to find this thread)