View Full Version : Tangent and Binormal Question

11-27-2003, 03:49 AM
Im using keyframed animation in my game, and to use bump mapping im storing normals and binormals for each vertice and for each keyframe( the tangent vector im calculating by crossing them), but the size of my models are huge...im thing in calculating the binormals on the fly, but i think that the normalization operation is very costly to use so many times...is it necessary to have the binormals- tangent normalized to do bump mapping? Will the normalization cube map work right?

11-27-2003, 05:06 AM
Yes, itīs absolutely necessary to have them normalized, or else you will get wrong results.
Using a normalization-cubemap wouldnīt be a good thing, because it costs you a whole texture-unit, which you will certainly need for other stuff. Only if you got one free, you can try it and test if itīs a speed-up.


11-27-2003, 05:54 AM
Thanx jan...another question ...how can i do bump mapping without normalization cube map?

11-27-2003, 10:54 AM
There is a paper by Cass Everitt, which explains how to normalize a vector in the register combiners. Itīs not a real normalization, but it comes close to it. The results are good enough if your geometry is a bit tesselated, else it will look crappy.

Sorry, i canīt give you the code, i donīt use it. You have to google for it ("normalization in register combiners" or so).

Anyway, if you have a modell, then i think it should be possible to precalculate the normals, etc. and then simply rotate them together with the rest, when you animate it. Donīt know if thatīs possible, but it might be. Then you donīt have to renormalize or recalculate the normals.

Of course you will need ONE normalization-cubemap for the light-to-vertex vector, but iīm sure you are aware of that.

Sorry dude, thatīs all the advice i can give you, i donīt have much experience with animated stuff.

Good luck,