blender-compositing

Blender Compositing

Overview

Build node-based compositing pipelines in Blender using Python. Set up render passes, add post-processing effects (blur, glare, color correction), combine layers, key green screens, and output final composited images — all scriptable from the terminal.

Instructions

1. Enable compositing and set up the node tree

import bpy

scene = bpy.context.scene
scene.use_nodes = True

tree = scene.node_tree
nodes = tree.nodes
links = tree.links

# Clear default nodes
nodes.clear()

# Every compositor needs at minimum: Render Layers → Composite
rl_node = nodes.new('CompositorNodeRLayers')
rl_node.location = (0, 0)

comp_node = nodes.new('CompositorNodeComposite')
comp_node.location = (600, 0)

links.new(rl_node.outputs['Image'], comp_node.inputs['Image'])

2. Add a Viewer node for preview

import bpy

tree = bpy.context.scene.node_tree
nodes = tree.nodes

viewer = nodes.new('CompositorNodeViewer')
viewer.location = (600, -200)

# Connect to see the result
rl = nodes.get('Render Layers') or nodes['Render Layers']
tree.links.new(rl.outputs['Image'], viewer.inputs['Image'])

3. Color correction nodes

import bpy

tree = bpy.context.scene.node_tree
nodes = tree.nodes
links = tree.links

# Brightness/Contrast
bc = nodes.new('CompositorNodeBrightContrast')
bc.location = (300, 0)
bc.inputs['Bright'].default_value = 10
bc.inputs['Contrast'].default_value = 20

# Hue/Saturation/Value
hsv = nodes.new('CompositorNodeHueSat')
hsv.location = (300, -200)
hsv.inputs['Hue'].default_value = 0.5       # 0.5 = no change
hsv.inputs['Saturation'].default_value = 1.2
hsv.inputs['Value'].default_value = 1.0

# Color Balance (Lift/Gamma/Gain)
cb = nodes.new('CompositorNodeColorBalance')
cb.location = (300, -400)
cb.correction_method = 'LIFT_GAMMA_GAIN'
cb.lift = (0.95, 0.95, 1.0)    # cool shadows
cb.gamma = (1.0, 1.0, 1.0)
cb.gain = (1.1, 1.05, 1.0)     # warm highlights

# Color Curves
curves = nodes.new('CompositorNodeCurveRGB')
curves.location = (300, -600)
# Access curve data via curves.mapping

# Gamma
gamma = nodes.new('CompositorNodeGamma')
gamma.location = (300, -800)
gamma.inputs['Gamma'].default_value = 1.2