"clipka" <nomail@nomail> wrote in message 
news:web.493114d0114da4434dea3830@news.povray.org...
> Anyone ever noticed that bump maps are somewhat queer - and definitely 
> wrong -
> in PoV-ray?
>
> Check out the following scene; it will need a file named bump_map.png - 
> anything
> that gives a nice clear dent will do, although I suggest a simple big 
> black
> blurred splotch on a white background, maybe with some small indicators 
> added
> to show orientation.
>
> Output will be a cube (well, seven differently oriented copies to be 
> exact) with
> three dents on each side (well, on three of the sides that is):
>
> - a real modeled dent for reference (uncolored)
> - a bump-mapped dent using simple projection mapping (red/green/blue)
> - a bump-mapped dent using UV mapping (gray)
>
> Light is from the camera location (with three colored helper lights offset 
> a
> bit).
>
> Notice how some of the dents do not only bulge outwards instead of 
> inwards -
> some even go "SIDEWAYS" somehow. You gotta see this to know what I mean.
>
> Also notice how this changes for even the very same dent, depending on the
> orientation of the whole object.
>
> This is what I'd call weird (and actually broken). Am I the first to see 
> this??

Some of the normals on your mesh triangles are inverted,
you are looking at the back side of them.

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