[brlcad-tracker] [ brlcad-Bugs-1525332 ] Rt (and Rtedge) Clips Image

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Bugs item #1525332, was opened at 2006-07-19 09:34
Message generated for change (Comment added) made by tbrowder2
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Category: Image/Data Conversion
Group: serious bug / workaround
Status: Closed
Resolution: Fixed
Priority: 9
Private: No
Submitted By: Tom Browder (tbrowder2)
Assigned to: Bob Parker (bob1961)
Summary: Rt (and Rtedge) Clips Image

Initial Comment:
The attached tgm demonstrates the problem.  Use the 
following commands:

% mged rtbug.g
> ae 270 0
> B grp 
# notice region Hidden.r is seen in view upper-right
> rt 
# notice region Hidden.r is seen in pix upper-right
> ae 35 25
> B grp 
# notice region Hidden.r is seen in view upper-right
> rt 
# notice region Hidden.r is NOT seen in pix upper-right

I believe the eye point is not being calculated 
properly, but I can't pinpoint it in the source code.

When I ray trace the group "grp" programmatically I 
see all the objects, including Hidden.r.  I calculate 
the eye point by using the diagonal of the bounding 
box as the distance to translate toward the viewer 
from the center of the bounding box, all in model 
coordinates.  I don't think the transformation used by 
rt or rtedge ensures enough distance is backed out 
from the bbox centroid, or it is not being applied to 
the correct point.

This problem is evidenced using BRL-CAD version 7.8.0 
compiled using gcc 4.1.1 on i386 Linux hosts using 
both Fedora Core 2 and 5.

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Comment By: Tom Browder (tbrowder2)
Date: 2009-09-14 06:31

Message:
Hm. I can't figure out how to add a file--help!

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Comment By: Tom Browder (tbrowder2)
Date: 2009-09-14 06:29

Message:
I see this problem again.  When I programmatically use rtedge, the objetc
is not filling the view so I get very few pixels compared to doing rtedge
in mged.  I've attached xpart.g.  Try rtedge on object "curved" inside and
outside mged to observe the difference.

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Comment By: Sean Morrison (brlcad)
Date: 2008-05-06 18:35

Message:
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Tom,

Some additional details if you're interested, it did look like rt/rtedge
were indeed incorrectly clipping the render due to an invalid eye point
calculation that was specific to the commands being invoked from within
mged.  The problem was traced down to code committed all the way back in
1997 (circa release 5.0) where the longest dimension of the bounding box
was used as the default eye point.  This in turn could cause clipping if
the diagonal distance was considerably larger and when rendering from a
non-orthogonal view and where geometry expanded into that space of course.

The fix should be in the next release of BRL-CAD (7.12.4+), and thank you
again for all your patience.  If you need a patch before then, svn revision
31004 has the change.

Cheers!
Sean



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Comment By: Bob Parker (bob1961)
Date: 2008-05-06 12:55

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Fixed in latest SVN

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Comment By: Tom Browder (tbrowder2)
Date: 2007-08-30 09:06

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We have determined that lgt still works correctly (i.e., no clipping) from
version 7.0.0 through 7.8.0 (and, conversely, rtedge exhibits the same
problem all the way back to 7.0.0).  I have changed the severity to reflect
that there  is a workaround (as long as lgt is still available!).

-Tom

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Comment By: Tom Browder (tbrowder2)
Date: 2007-08-27 15:50

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We just went back in time to BRL-CAD versions 7.2.6, 7.2.4, and 7.0.0, and
the same problem exists.   I'm not sure what the fix is, but we need tis to
work correctly! 

I will try to compile from source and try lgt on recent versions if you
can tell me how to get it to work without the error message.

Thanks.

-Tom

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Comment By: Sean Morrison (brlcad)
Date: 2006-07-26 12:17

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Just wanted to note that I have started looking into this problem and it
indeed 
is a rather significant bug.  The exact cause is still not evident but
seems to 
be related to the extent of the bounding box extending behind the
rt/rtedge 
view plane (which should NOT be happening for non-perspective, autoview). 

It would be useful to know whether this bug is also present in either 7.0
or 
7.2 since if it was only recently introduced, it makes it considerably
easier to 
trace down.  I'll keep looking into this and see if a workaround can be 
identified as well as a proper fix, of course.


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