Combining Normal Maps


Combining Normal Maps

I recently realized that long time game professionals still use the Overlay mode transfer to combine normal maps. This is not accurate and results in image degradation.
Let me show you.

In this test I will compair overlay mode transfer to an action file made by Rod Green. I combined two normal maps with both methods. They look very similar, it is hard to visually tell the difference. Luckily there is another method to measure accuracy.

Normalizing normal maps makes them mathematically correct. It fixes errors in the images. So if we normalize these results and compair them to before they were normalized we can see how far off they were form being correct. To do this I will use the differance mode transfer. Black is ideal and means there is no change, the more color the more different and the less accurate the image was.

As you can see using overlay changes the image and makes it less accurate. Since normal maps are not a visual map but a mathematical model this does make a difference. Of course you can use overlay and normalize the results, but its like resizing an image a couple of times. you are wearing out your pixels and this causes some image degradation. For best practices, when combining normal maps in Photoshop use Rob Green’s action which is found at the bottom of this link:

Posted on May 13, 2010 at 5:37 am by Mike · Permalink
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