topic Prevent (!) Line elimination in GDL

Prevent (!) Line elimination

runxel — Tue, 14 Sep 2021 07:06:35 GMT

Hey folks, I have a TUBE{2} and need my lines to be NOT eliminated.
See this picture below, just two cubes (as dummy) to show the issue. If you stack them, they will join and I somehow need to prevent this from happening, since they need to be visually different.
The MASK parameter for the tube{2} is set to 1+2+16+32, which means, the line elimination flags are not set (especially looking at you, 1024!).
Yet, it still eliminates the line between the two objects.

Re: Prevent (!) Line elimination

Miha Nahtigal — Thu, 17 Jun 2021 10:48:24 GMT

I don't think you can do this. But you can change your layer's intersection priority to 0.

Re: Prevent (!) Line elimination

runxel — Thu, 17 Jun 2021 11:08:26 GMT

vuego wrote:
I don't think you can do this. But you can change your layer's intersection priority to 0.

D%mn. That would be quite silly. Why then even have the line elimination flags, if they are useless?
Hopefully Péter will drop by and sharing some knowledge.

In the end I could just go very ugly and make them tubes a fraction of a mm smaller.

Re: Prevent (!) Line elimination

Anonymous — Thu, 17 Jun 2021 11:54:22 GMT

Perhaps I am missing something, but I think this line eliminating thing is related to the coplanar adjacent surfaces hard coded within AC.
Either you change the layer priority number or create a different surface to show the line.
I have mentioned this on a Line/Surface Merging Control wish.
GS did give some prompt feedback at the time (Thanks Gergely Hari!). It seems they are more for including this in the BM definition. Lets hope this for AC25.

Re: Prevent (!) Line elimination

Jochen Suehlo — Thu, 17 Jun 2021 12:31:18 GMT

If you use BODY - 1 at the end of a PRISM_ command, you can merge the surfaces of 2 PRISM_, which surfaces are not merged by default. Maybe there is something that works in the opposite direction.

Re: Prevent (!) Line elimination

David Maudlin — Thu, 17 Jun 2021 12:37:39 GMT

runxel wrote:
In the end I could just go very ugly and make them tubes a fraction of a mm smaller.

Or use the Poly2 command to draw the lines. I have done this in similar circumstances.

David

Re: Prevent (!) Line elimination

runxel — Thu, 17 Jun 2021 12:50:07 GMT

David wrote:

runxel wrote:
In the end I could just go very ugly and make them tubes a fraction of a mm smaller.
Or use the Poly2 command to draw the lines. I have done this in similar circumstances.

Hey David, you mean with POLY_ set to `model wire`?
Mhm, that could be workaround.
Still a very dumb way, tho...

Re: Prevent (!) Line elimination

runxel — Thu, 17 Jun 2021 12:58:59 GMT

Oh I have to apologize by the way:
The example above is not TUBE{2} but a simple PRISM_. (I changed it later, that's why.)
Sorry!

So with Prisms it always eliminates lines, even without a BODY -1 being in place!

With TUBE{2} it works as advertised. It will eliminate lines if the mask flag has both 512 and 1024 bits set.

Sorry again for the confusion. I think I will just go back to a tube, even tho it's a bit more verbose than a prism, but at least the optics are like I want them 🙂

Re: Prevent (!) Line elimination

David Maudlin — Thu, 17 Jun 2021 13:05:41 GMT

runxel wrote:
Hey David, you mean with POLY_ set to `model wire`?

Yes, my mistake, I mixed up the 2D and 3D commands. Lin_ is also an option.

David

Re: Prevent (!) Line elimination

A_ Smith — Thu, 17 Jun 2021 20:06:14 GMT

runxel wrote:
The example above is not TUBE{2} but a simple PRISM_.

well, idk maybe i'm missing something

pen 20 !  red contour
material 99 ! grey material

prism_ 5, 1, 
0,0,15,
1,0,15,
1,1,15,
0,1,15,
0,0,15

addz 1

prism_ 5, 1, 
0,0,15,
1,0,15,
1,1,15,
0,1,15,
0,0,15

del top

Re: Prevent (!) Line elimination

runxel — Thu, 17 Jun 2021 20:32:17 GMT

A. wrote:
well, idk maybe i'm missing something

In my example above it is the same object, just placed twice, so it is stacked upon each other, which will lead to the line elimination.

Re: Prevent (!) Line elimination

Jochen Suehlo — Thu, 17 Jun 2021 20:58:32 GMT

In my example above it is the same object, just placed twice, so it is stacked upon each other, which will lead to the line elimination.

What is different in your script to the one from A. Smith, that you do not get the lines?

Re: Prevent (!) Line elimination

Lingwisyer — Fri, 18 Jun 2021 01:22:54 GMT

Joachim wrote:

In my example above it is the same object, just placed twice, so it is stacked upon each other, which will lead to the line elimination.
What is different in your script to the one from A. Smith, that you do not get the lines?

Two boxes in TWO objects vs two boxes in ONE object.

Re: Prevent (!) Line elimination

Jochen Suehlo — Fri, 18 Jun 2021 11:14:11 GMT

Two boxes in TWO objects vs two boxes in ONE object.

This is interesting, because 2 double boxes on top of each other have a separation line,
while 2 singles boxes don't have.

Re: Prevent (!) Line elimination

Peter Baksa — Mon, 21 Jun 2021 07:25:51 GMT

Hi all,

cprism_{3} can control line elimination:

cprism_{3} 0, 0, 0, 0,
	4, 1,
	0, 0, 0, 15, 0,
	0, 1, 0, 15, 0,
	1, 1, 0, 15, 0,
	1, 0, 0, 15, 0