# Blender 3D: Noob to Pro/Compositing

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**Compositing** is the combination of multiple sources of visual input
into a single, final image. This is common functionality in expensive,
commercial video editors. Some of these (such as Adobe After Effects)
use a layer-based compositing engine. Others (such as Apple Shake, The
Foundry\'s Nuke, and eyeon fusion) use a more powerful node-based
compositing engine. Blender features a very advanced and powerful
compositing engine through the use of the Nodes Editor window. Although
the challenge of learning to use nodes may seem intimidating, it can be
very rewarding because of the professional-looking final products that
can be easily produced.

## Compositing Example

In this tutorial, we will see how compositing, combined with *render
layers*, can produce some effects that are difficult or impossible to
achieve just by straight rendering of a 3D model.

Start with a new Blender document. For a change, let's use the default
cube. Assign it a new material. Keep all the settings at default, but in
the Shading panel, set the Emit value to 1.0 and give it an interesting
diffuse colour.

Go to the Render context
![](Blender255RenderContextButton.png "Blender255RenderContextButton.png"),
look for the Post Processing panel, and check the "Edge" box. This will
draw a black outline around all objects. If you hit
 to render right now, you should see
something like this:

![](GlowingCubeWithEdgeOutline.png "GlowingCubeWithEdgeOutline.png")

So far, not very exciting. Now go to the Render Layers context
![](Blender267RenderLayersContextButton.png "Blender267RenderLayersContextButton.png").
You should see there is already an initial default layer called
"RenderLayer". If you look in its Layer panel, you should see checkboxes
indicating all the passes of the rendering process to include in this
layer. Look for the "Edge" checkbox, and uncheck that. Now click the
 icon next to the list of layers, to add a
new layer. Look in its Layer panel, make sure "Edge" is checked, and
*un*check all the other checkboxes in the "Include:" section.

Now open up a Node Editor window, and look for the three icons to the
right of the menus, showing what kind of nodes to edit:
![](Node_Tree_Types.png "Node_Tree_Types.png"){width="60" height="60"};
click on the middle one (if it's not already selected) to enable
compositing nodes. Now check the "Use Nodes" box to the right of it. You
should now see the initial default node setup, with a single Render
Layers node feeding the initial default render layer directly to the
output:

![](Blender267DefaultCompositingNodes.png "Blender267DefaultCompositingNodes.png")

Add another Render Layers node. From its layer popup menu, select the
second render layer you created, the one producing the edge outlines
(which should be called "RenderLayer.001" if you didn't change its
name).

Now, add a Blur node (Filter submenu of the Add menu). The default
Gaussian kind of blur will do fine. Put nonzero values (e.g. 1) into the
X and Y fields (otherwise the blur Size value will have no effect). Give
it a Size value of, say, 20. Connect the Image output of the first
render layer (the one doing everything except the edge outlines) into
its Image input.

Add an Alpha Over node (from the Color submenu of the Add menu). Feed
the Image output from the Blur node into its *upper* image input, and
the Image output from the second render layer (the one producing the
outline edges) into its *lower* image input. Leave the Factor at its
default 1.0. Connect the Image output of this Alpha Over node to the
Image input of the Composite node (the final output).

When you are done, check that your connections look like this (remember,
the exact positions of the nodes are unimportant, except for clarity;
what's important is the connections between them):

![](Blender267GlowingCubeCompositingNodes.png "Blender267GlowingCubeCompositingNodes.png")

The effect of this is to blur the rendering of the cube (apart from the
edge outline), and then put the edge outline back on top of it. If you
hit  to render now, you should see
something like this:

![](GlowingCubeWithEdgeOutlineBlurred.png "GlowingCubeWithEdgeOutlineBlurred.png")

## Things to Try

What happens if you put different values into the X and Y fields of the
Blur node? Try making the X value different from the Y value.

What happens if you get the inputs the wrong way round into the Alpha
Over node?

Try the other blur types available from the menu in the Blur node.

## Other Tutorials

Composite Nodes Video Tutorial (2.49b):
<http://www.youtube.com/watch?v=AAnxoJsdAAM>\
Vector Blur Tutorial (2.49b):
<http://www.youtube.com/watch?v=qY4WcNgEXv8>

Depth of Field (DOF) Using Composite Nodes (2.49b):
<http://www.youtube.com/watch?v=HBomEv-bEtw>

