On Sat, 03 Oct 1998 13:33:50 -0400, jko <jko### [at] homecom> wrote:

>To all,
>
>The bug I've found is caused by several errors in the bump_map code of
>POV_ray which have been hiding there undiscovered since the DKB Trace
>days. 

>There is also a twist which places
>highlights and shadows at the wrong angles. The distortions vary
>depending on the rotation of the object in space, which should have no
>effect at all.

I've looked at Thorsten's test image and it doesn't appear to fix all
the problems.  Even if it fixes the bumptest scene you posted here in
the newsgroup, I'm not sure it'll fix the egg image you posted on
compuserve.

The problem with the   x  x  vs.    xx
                                      x            x

seems to be a real bug.  The extra normalization looks like a good
idea too.

The real problem (I think) is that we transform the evaluation point
into the pattern's space but we don't transform the normal.  So if the
pattern is rotated, it perturbs the normal the wrong direction.  My
original design for wood, bozo, gradient, etc. normals had the same
problem when I wrote that part of 3.0.  I found an alternative way to
purturb the normal in 3d instead of 2d but the results aren't as
acurate as they should be.  The artifacts in brick normal are a result
of this 3d compromise.  I need to do a big rewrite to transform the
normal.  We'll have to search the warp chain and lots of other messy
things.  We'll also have to find out if it slows things down and can
we only transform the normal as needed.  I'm not sure how hard this
will be.

I could be wrong.  Maybe a slight tweak of your fix really will fix it
but I don't think so.
	Chris Young, POV-Team Coordinator

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