#359 boolean operator subtract (-) is not working

[Fredrick Paul Eisele]

When I display regions (for example, with the shader) the subtracted areas are visible. This is true using Archer or mged. I have attached two files: one is a sample model, the second is a screen shot of the shaded image.

[Fredrick Paul Eisele]

Here is the db for the model. The holes are subtracted.

[Sean Morrison]

Does it display correctly if you use the raytrace button (or just type "rt" in the command prompt)?

In your screenshot, it looks like you might be just displaying all objects within the object you created, not the top-level combination that contains the booleans. For example, if you had modeled "box_with_hole.r" consisting of a "box" and subtracting a "hole", you're currently drawing box and hole, not box_with_hole.r That's also something to check. Running "who" on the command line will tell you what you have displayed. You want it to say link.r and if it doesn't, you can run "B link.r"

[Fredrick Paul Eisele]

'who' does show link.r.
and 'B link.r' produces exactly what I posted.
However, I think you are (partly) correct in what is happening.
I notice that the constituent parts are highlighted in the tree (in Archer)
which I believe indicates that they are displayed.
'B link.r' should not cause the constituent parts to be displayed but it does.

I have duplicated this problem on both Windows7 and Mint(Debian).
The first line from the about from Debian is...
BRL-CAD Release 7.24.2 Geometry Editor (MGED)

I have (once) seen the raytrace (rt) update the frame buffer. When it did so the model appeared as expected, but I have been unable to repeat the miracle.

[Fredrick Paul Eisele]

Incidentally, my motivation is to inter-operate with a geometric assembler.
https://github.com/phreed/freed-linkage-assembler
Once I see a working example of a simple linkage, the plan is to open another topic/thread/issue to make it work with BRL-CAD. It currently writes OpenSCAD files and I would think writing BRL-CAD files would be similar.

[Stefan Mirea]

Hi Fredrick,

The boolean expression doesn't seem to be correct. end_n.b and end_p.b are intersected with bar_main.b, which leads to an empty object even before extracting the two tgc's. Since unions are performed after intersections and substractions, I think that you'd better create a separate combination for the union of the first three, or create the region using the 'c' command with a parenthesized expression:

c -r link.r (bar_main.b u end_n.b u end_p.b) - hole_n.b - hole_p.b

[Fredrick Paul Eisele]

Thanks I will give that a try.

On Sun, Nov 23, 2014 at 6:04 PM, Stefan Mirea stefanmirea@users.sf.net
wrote:

Hi Fredrick,

The boolean expression doesn't seem to be correct. end_n.b and end_p.b are
intersected with bar_main.b, which leads to an empty object even before
extracting the two tgc's. Since unions are performed after intersections
and substractions, I think that you'd better create a separate combination
for the union of the first three, or create the region using the 'c'
command with a parenthesized expression:

c -r link.r (bar_main.b u end_n.b u end_p.b) - hole_n.b - hole_p.b

• [bugs:#359] http://sourceforge.net/p/brlcad/bugs/359 boolean operator
  subtract (-) is not working*

Status: open
Group: serious bug / no workaround
Created: Fri Oct 31, 2014 06:40 PM UTC by Fredrick Paul Eisele
Last Updated: Mon Nov 03, 2014 06:05 PM UTC
Owner: nobody

When I display regions (for example, with the shader) the subtracted areas
are visible. This is true using Archer or mged. I have attached two files:
one is a sample model, the second is a screen shot of the shaded image.

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[Fredrick Paul Eisele]

Ok, I see now.
Operator error.
I expected the shader to be different.
This ticket can be closed.