How to render some of view layers only (instead of single or all of them)

Question

I have LOTS of View Layers (generated in Python), and I only want to render and composite several of them at once.

When I checked "Render Single Layer" in View Layer options, only the active one in the UI would be rendered.

When I unchecked "Render Single Layer", all of them are rendered, including those I'm not using in compositor. Even I have only one Render Layers node and one Composite node in the compositor, when I press F12 Blender still renders every single view layer.

Is it possible to only render the layers I'm using in the compositor? Or it can only be achieved by more scripting?

Answer 1

Set ViewLayer.use for all view layers based on render layer nodes

Iterate through the nodes, get the Render Layer nodes used in comp, read their RLayers.layer property and compare against Scene.view_layers. If part of the list, set each ViewLayer.use property to True, else set it to False:

import bpy

C = bpy.context

# List of render layer nodes
rl_comp = []
for node in C.scene.node_tree.nodes:
    if node.type == 'R_LAYERS':
        rl_comp.append(node)

# Set of view_layer_names used in the compositor
view_layer_names = set()
for vl in C.scene.view_layers:
    if vl.name in set([l.layer for l in rl_comp]):
        view_layer_names.add(vl.name)

# Set use property
for vl in C.scene.view_layers:
    if vl.name in view_layer_names:
        vl.use = True
    else:
        vl.use = False

Answer 2

If you have several layers, every layer has an "Use for Rendering" option. Tick this on all the layers you want and untick all you do not need. That's it.

The python property is ViewLayer.use, which you can access for each layer per data-block: bpy.data.scenes["Scene"].view_layers["LayerName"].use or per scene in context: bpy.context.scene.view_layers["LayerName"].use.