"clipka" <nomail@nomail> wrote:

> I guess the mapped image is considered something in 3D space (which just
> happens to be identical along a certain axis), so first you have to get a slope
> out of the bump map; but that slope already needs to take into account the
> orientation of the plane that should be "bumped" if I'm not totally mistaken.
> Maybe the developer of the algorithm forgot about that.

I seem to remember, in the dim past, posting a problem that also concerned (or
*possibly* concerned) the default slope_map that is built into some/all pigment
patterns. Wish I could remember when, and what it was all about; I'll post a
link if I can find it.
>
> And nobody ever noticed, because such strange effects in bump mapping are
> visually hard to identify...

Absolutely!!

> The bump map usually doesn't look plain wrong,
> because our brain blames it on a different lighting direction. Which gives us
> some impression that "something is weird", but it's hard to pinpoint unless
> you design a picture specifically for that purpose.

Yes, it sometimes QUITE difficult to construct just the 'right' scene. I had to
do similar detective work in trying to nail down a radiosity-from-media
problem. (Hmm, I need to post that experiment...sometime soon...)

Unless my eyes are playing tricks on me (which is possible, of course!), I still
cannot get your red and green areas to look *wrong*, no matter what I try. Blue
and gray, yes; red and green, no.  Although I can't imagine how, I wonder if
there's a clue hidden somewhere in this? (BTW, I tried eliminating the scale
block from your blue texture; but that didn't help it.)

I even set up an animation (using monkeyjam,
a great little Windows app for doing quick tests.) Using a single 'orbiting'
point_light, and your seven cubes rotated into all sorts of
orientations, I never saw anything amiss with red and green. What's your
opinion?

Ken W.

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