Hi guys -

A curious one for you here, I'm running into problems using bump maps when
I'm using a uv_mapping.

The problem is that the bump-map normals seem to be dependent upon the
direction of the u/v vectors - for example, a triangle with UV coordinates
<1,0> <0,0> <0,1> will give different results than a triangle with UV
coordinates <-1,0> <0,0> <0,1> even though the bump map is symmetrical in
the U and V dimensions, and the triangle vertices are exactly the same and
in the
same order.

It almost seems like the way that the bump map affects the surface normal is
dependent upon the U and V 'direction' of the bump map.  Note that the
physical triangle
normal is not affected by the UV coordinates - just the normal that is
generated
by the bump-map.

See the attached POV file - note that in the U-axis (along the wall) the
bump-map behaves one way, and in the
V-axis (up and down) it behaves in another.  Set the declaration of
"u_factor" to 1 to see the desired result where
the bump-map behaves appropriately.

Is this a bug?  I would expect U/V coordinates to simply define source
points on a bump-map or
texture.  Why does it affect the normal?

John Pallett

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Download 'bump_inversion.pov.txt' (2 KB) Download 'bump_pyramids.jpg' (3 KB)

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