View Full Version : Tangent Normal Maps

08-07-2005, 01:09 AM
Hello I'm using the Lightwave Normal map create plugin. In the object space map I'm getting a nice gradient between the seams and it renders out fine. In the tangent map I get an abrupt change in color resulting in visible seams. I guess I'm not understanding how tangent maps work when generated. I need to know why this is happening:( Any direction would be great.

08-07-2005, 06:17 AM
In object space, the normal map considers the object to be it's co-ordinate space. In tangent space, it will consider each vertex/poly to be it's co-ordinate space.

For example, if you were to use the low poly model to make the normal map in tangent mode, the entire normal map would be "normal map blue" - flat. In object space it would still have red and green where it changes in slope.

Object normal maps are easier to setup because it isn't so dependent on your low poly mesh, however tangent space normal maps depend almost entirely on your low poly mesh. Firstly, they don't like absolute 90 degree edges, and secondly, set a smoothing angle at just enough so you dont see any hard edges on your model. Note that this only applies to organic models and not to models that require hard edges.

08-07-2005, 11:03 AM
What you've said about the tangent map makes sense except the problem is actually happening at the seams in the UV map no at the sharpest angles in the geometry. At the seams there is an abrupt change in color. I have no idea what is causing that. This does not happen with other Nmap generators I've seen people use, why is it happening with this one? My models are as smooth as I can make them so I don't think the smoothing angle is causing the abrupt change in color:)

08-08-2005, 01:24 PM
I found that the discoloration at the seams in a LW generated tangent map cannont really be eliminated but you can always decide where the seams will appear of course. Rotating the maps in the UV editor will also give you control over which axis the discoloration in at the seam will be visible.
I'm going to take the normal map into Zbrush and see if I can paint out the visible seams.