Rendering 1 random object from each collection

Question

I am working on generative art and I need to set up my renders to render only 1 object per collection (a different one each frame) without having to do that manually. I am not very familiar with geometry nodes yet so I am not sure if it is possible this way. Another possibility that crossed my mind is an addon, but I haven't found anything useful.

Do you guys have any idea?

Answer 1

You question is not a complete specification of what you want or not 100 percent clear to me. So I'll do an example for you to work with. I'll assume you want a render of one object from each of several Collections per render file, and that you want all combinations. I'll try to give pointers to a variation where you select an object at random from a Collection.

I would use a python script that first disables all objects from rendering and then varies what objects are render-enabled.

This may not be the simplest script, but is a variation on an existing script I have:

import bpy
import random

# constants
nCollections = len(bpy.data.collections)
frameCnt=0
filepathBase="//render/frame"
startFrameIdx=0
frameRenderCnt=999999

# set up a function to recurse through each collection
def renderCollection( collectionIdx, frameIdx: int, frameName ) -> int:
    if collectionIdx == (len(bpy.data.collections)):  # frame ready to render
        bpy.context.scene.render.filepath = frameName
        print('rendering', frameName)
        bpy.ops.render.render( write_still=True )
        frameIdx += 1         
    else:
        # if you only want one random from each collection, replace 'for' loop with
        #obj = random.choice(bpy.data.collections[collectionIdx].objects)
        for obj in bpy.data.collections[collectionIdx].objects:
            obj.hide_render = False  # allow object to render
            tempFrameName = frameName + "_" + obj.name
            frameIdx:int = renderCollection( collectionIdx + 1, frameIdx, tempFrameName )  # march onward until rendered
            obj.hide_render = True  # prevent object render
            if ( frameIdx >= frameRenderCnt):
                return;
    return frameIdx


# INITIALIZE: prevent all objects from rendering
for coll in bpy.data.collections:
    for obj in coll.objects:
        obj.hide_render = True

# for each collection
total = renderCollection( 0, 0, filepathBase )
print( total, ' frames rendered' )

And a proof of concept: (I'm getting the 'All uploaded files must be in the blend file format' 3.0 bug again from the upload site so...) here a link to my Public DropBox example blend file.