Thank you for posting that explanation.

> I have toyed with some ideas of how to change that and do make use of
> surface orientation to address the issue at least for certain standard
> cases, but it would require some major changes, and my supply of
> king-size Round Tuits(TM) is running low, as always.

Here's something that you could do with a much smaller tuit:

Put a paraphrase of the words that you wrote here (or the words that
Alain wrote here) in the documentation, wherever the current wording
obscures or contradicts what you wrote here.

For example, these words in the documentation:

    In general we have to make the subtracted object a little bit
    larger in a CSG difference. We just have to look for coincident
    surfaces and increase the subtracted object appropriately to get
    rid of those surfaces.

are misleading; their suggested remedy of "increasing the subtracted
object" wouldn't help at all, in the situation being discussed here.

P.S.  I downloaded BRL-CAD, and learned just enough of it to model the
CSG shape from the top of this thread, and ray-trace it, and export it
as STL.  I'll attach a BRL-CAD geometry database (in human-readable .asc
form) below, in case anyone here wants to experiment with it.  baz.c is
the geometric shape, and baz.r is a red plastic object with that shape.

Using the database attached below:

$ PATH=/usr/brlcad/bin:$PATH
$
$ # deserialize the database
$ asc2g pov-csg-problem.asc p-c-p.g
$
$ # ray-trace the object
$ rt -a 0 -e 5.71 -o baz.png -p 30 -E 5.9 p-c-p.g baz.r
 [ output elided ]
$
$ # export the CSG shape as STL
$ g-stl -o baz.stl p-c-p.g baz.c
 {foo.s} - {bar1.s}
 {(foo.s - bar1.s)} - {bar2.s}
44 triangles written
$

Post a reply to this message

Attachments:
Download 'us-ascii' (1 KB)