Correcting Flipped Normal Maps

From FleshWorks

Flipped normal maps are manifested as textures looking "inside out", i.e. ridges look like indentations and vice versa.

If this happens, the first thing to do is to re-align the texture. Normally planar alignment will be used, and selecting this alignment often resolves the flipped normal problem. See Working with Textures for information on texture alignment.

If texture alignment does not solve the problem. follow the procedure below to correct a flipped normal map. Note: there are some doubts that this procedure works in all cases.

1. Ensure that the geometry is up-to-date, by doing a Build All from the Build menu. This is necessary to allow you to select a surface and edit its texture.
2. If the 3D view is not currently set to use the Flesh renderer, enable it by clicking the ION logo (with a green circle as its background).
3. Select the surface in question in the 3D window by left-clicking on it.
4. Right-click on the selected surface, and choose Surface Properties
5. In the surface properties dialog, activate the Pan/Rot/Scale tab.
6. Click either Flip U or Flip V (depending on what looks right) to flip the texture and its normal map. You can Flip either U or V, but not both (otherwise the original normal map orientation will be reinstated).
7. Perform another Build All to update the texture. The correct normal map should be displayed in the 3D window and in game.

Alternate Method (If the above method didn't work)

1. Right click the offending brush (the wireframe, not the face/texture)
2. In the popup menu, choose Transform->Mirror About Z (vertical)
3. Reposition the brush if necessary
4. Rebuild

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