D2 log 012 – Blender pipeline

Devastro2

The new Blender 2.8 is great. Unfortunately it broke my batch render script.

Fixing the script and the rendering setup were quite a challenge due to the major UI changes in 2.8, but eventually I figured it out. Even learned a few new tricks along the way. How did I manage to write the original script without the built-in scripting console? So helpful!

My Blender export pipeline looks like this:

  1. master.blend file with fixed camera & lighting setup
  2. extra .blend file for each asset
  3. link assets into master
  4. for each asset, render object & shadow into separate PNG

First draft of the new script for 2.8:

import bpy
import os
import subprocess

# Requires Blender 2.8
#
# /Applications/blender.app/Contents/MacOS/Blender -b -P render28.py
#
# Notes:
# 
# Node setup: see master.blend -> Compositing
# Render menu -> Film -> transparent
# Shadow catcher plane -> Object menu -> Visibility -> Shadow catcher
# Adding more objects: File -> Link... -> "Collection" from ext. file -> Move to Assets collection in master

basepath = os.path.normpath(os.path.dirname(os.path.abspath(__file__)))
master_blend = "blender28-batch-render-test-master.blend"

src = os.path.join(basepath, master_blend)

bpy.ops.wm.open_mainfile(filepath=src)

bpy.context.scene.render.resolution_percentage = 50
bpy.context.scene.render.resolution_x = 1280
bpy.context.scene.render.resolution_y = 960
bpy.context.scene.cycles.samples = 20

assets_name = "Assets" # name of collection in master.blend
assets_collection = None

for collection in bpy.data.collections:
	if collection.name == assets_name:
		assets_collection = collection
		break

if assets_collection is None:
	print( "Error: %s collection not found in master" % assets_name )
	quit()

# Save original filenames for output nodes
output_nodes = []
for node in bpy.context.scene.node_tree.nodes:
	if ( node.type == "OUTPUT_FILE" ):
		output_nodes.append( ( node, node.file_slots[0].path ) )

for target in assets_collection.objects:
	# Show only the current object
	for obj in assets_collection.objects:
		obj.hide_render = obj.name != target.name

	# Set output filename
	for node, path in output_nodes:
		node.file_slots[0].path = target.name + "_" + path

	bpy.ops.render.render(animation=False)

Master & test .blend files here: blender28-batch-render-test.zip

Example output:

Object
Object

Shadow
Shadow

Composite
Composite

Additionally, I created a simple pipeline for rendering weapon silhouettes for the HUD. With a single click, it pulls in each weapon model, renders it from a side-view, then uses just the alpha to write a single-color transparent PNG.

And similar setup for pickup icons, with a subtle “glow” pass.