Graphics Reference
In-Depth Information
Chapter 9
Compositing with Nodes
Blender's versatile and powerful nodes system enables you to access and manipulate a huge variety of com-
positional elements to combine rendered images in exactly the way you want. You can use nodes to composite
still images or video sequences that can later be edited in Blender's nonlinear Video Sequence Editor (VSE),
which you will learn about in Chapter 11, “Working with the Video Sequence Editor.” Here, you will look at
the fundamentals ofcompositing with nodes,usingrender layers tore-create ascene fromits component render
passes. After that, you will follow an in-depth example of one of the most common tasks in live-action video
compositing: the task of green screen compositing and garbage matting.
In this chapter, you will learn to
• Use the Blender composite node system to pull a green screen matte
• Use the AnimAll add-on for garbage matting
• Manipulate the video's color channels to reduce color spill
Compositing with Render Layers and
Passes
In Chapter 4, “Rendering and Render Engines,” you were introduced to the idea of render layers and render
passes. In that chapter, you saw how constituents of a rendered scene such as shadows, specular highlights,
and ambient occlusion could be rendered separately in passes. However, it wasn't clear from that chapter how
this could be useful. This is because we hadn't yet begun talking about compositing. Once you start working
withBlender'snode-based compositing system, theusefulness ofrenderlayers andrenderpasses becomes very
clear.
What Is Compositing?
Compositing is the process of combining data from two-dimensional images to create a new image. There are
manysituationsinwhichcompositingofsomekindisnecessary.Youmightwanttocombinelive-actionfootage
with CG. You might want to place a character or other element over a background that was filmed or rendered
separately. You might want to break down complex 3D scenes into components to be rendered more efficiently
and then build them up again in a comparatively less-resource-intensive 2D composite. You may simply want
to tweak the color of parts of the scene or add some atmospheric effects.
