"Peter J. Holzer" wrote:
> 
> On 14 Jun 2000 04:08:51 -0400, Warp wrote:
> >  Since it seems to be some kind of bug, it may be worth to post a bug
> >report to the appropriate group (or has it been posted already?).
> 
> Not yet. The posting guidelines for povray.bugreports say, that one
> should post the report here first, so that it can be verified by other
> people. If there is general consensus, I'll repost it to
> povray.bugreports.
> 

Well, then I think you can post it in povray.bugreports, as I
reproduce it and even find the correction.

The code modification is as follow (quoting code from memory):

in super.c, at the end of the intersect_box() local function,
right before the 

  return (TRUE)

there is two (bad) lines:

 *dmin = tmin;
 *dmax = tmax;

The correction is simple: remove these two lines !!!!

Not only does this solve the problem of the initial scene,
but with small rotate of the object, it also remove some
darker point (when not antialiasing), and also handle far more
better the nearly degenerate superellipsoid (you know, when 
the parameter are less than 0.1 [well, 0.01 for example]).

Moreover, when experimenting with the old code, from the
example scene provided, I once get a strange picture: I could
see what I interpreted as the back of the superellipsoid 
 (darker than the front face) intermixed with some points of
the front face. With the updated code, I get the correct view.

Shame on me, I did not keep this scene.

I am mathematically correct about the need to remove the two lines 
before the return(TRUE) of intersect_box in super.c, but
this is left as an exercice for the sceptics.

Post a reply to this message