Sean Olson



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Friday, January 30, 2009

Extracting Normal Maps from Photo Textures

I've been playing with normal maps recently and learned a cool trick. Usually, you have to have a 3d object to make a normal map of the object. But, I learned a way to "Recover" normals from a photo texture, thus giving the texture the illusion of depth.

Original Texture

To do this you:
1. run the texture through a normal map filter in your chosen photo manipulation application.
2. Blur the image slightly to remove the fine details (I did not do this step enough on the example)
3. Create a new layer in "overlay" mode
4. Use a Gaussian Blur on the layer. (I used 3 pixels here)
5. Repeat steps 3-4 a bunch of times. I created 15 layers for this example.
6. Flatten the image
7. Run the Normal map filter again, but this time in "Normalize" mode.
8. Yay, you have an "extracted" normal map!

Extracted Normal Map
After extracting your Normal map, you can apply it to any surface in your 3d modeling package. Here are some pictures of my normal map applied to a simple plane. This illusion of 3d holds up until the viewer is almost at a 90 degree angle to the viewing surface. It's best used on surfaces that you know the viewer will not be able to get near or are usually seen from a distance.

3d rendering of textured plane with no normal map

3d rendering of same textured plane with normal map

This gives a great sense of depth!

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