Ambient occlusion is a lighting technique that is commonly used to create soft shadows on objects. Ambient occlusion isn’t used to create the type of shadows that are cast from objects with a light shining directly on them. Instead, ambient occlusion generates the type of deep shadows that appear in the corners or creases of things, where it is hard for the light to reach.

Technically speaking, ambient occlusion is a global illumination technique. However, in common usage of the term it is often referred to as a cheap alternative to global illumination. To clear up any confusion, what most renderers refer to as “global illumination” is actually an amalgamation of several techniques such as radiosity, metropolis light transport, image-based lighting or photon mapping. The actual techniques used differ slightly from renderer to renderer. Some renderers include an ambient occlusion term as part of their global illumination calculation; others do not.

Like most global illumination techniques, ambient occlusion is dependent on the other geometry in the scene. Ambient occlusion on its own generates less realistic lighting than “full” global illumination. However, ambient occlusion is much faster and less complex to calculate than other methods which is why it is still popular among game developers and in production animation.

(Left) Without Ambient Occlusion. (Right) With Ambient Occlusion
Click for larger image.

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This step-by-step guide will show you how to make a torus in AC3D using the Revolve tool.

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So you’ve created your 3D model… now what? Many 3D design programs have their own renderer built in, but some don’t. You may need an external program to create images. In other cases, the software may include its own renderer, but it may not have all of the features that a stand-alone renderer provides.

If you’ve never tried a stand-alone renderer before and want to try one, here is a list of well-known stand-alone 3D rendering programs that are available from their creators free-of-charge:

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New to 3D? Make sure you know which axis is “up” with this primer on 3D coordinate systems. (more…)

If you want to excel as a 3D artist, one of the best things you can do is to learn how to draw.

Most experts recommend gesture drawing and life drawing as the most important exercises. I’d agree, and I don’t think you can ever get enough practice at either. Even if you don’t think you are any good at it, you should still do it. Drawing is an important exercise in “visually dissecting” an object. It’s not about what goes on the paper; it is about learning to be observant.

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