Empathy List Archives

JL

John Lussmyer

Sat, Oct 27, 2018 3:29 PM

I'm modifying a file from ThingVerse, and have run into an odd problem.
I added a couple more shapes to a long difference() (chopping a couple edges sloped instead of vertical)

and now I get the "WARNING: Object may not be a valid 2-manifold and may need repair!" message.

File is at http://casadelgato.com/work/v2.scad
(yes, it's messy...)

--
Worlds only All Electric F-250 truck! http://john.casadelgato.com/Electric-Vehicles/1995-Ford-F-250

I'm modifying a file from ThingVerse, and have run into an odd problem. I added a couple more shapes to a long difference() (chopping a couple edges sloped instead of vertical) and now I get the "WARNING: Object may not be a valid 2-manifold and may need repair!" message. File is at http://casadelgato.com/work/v2.scad (yes, it's messy...) -- Worlds only All Electric F-250 truck! http://john.casadelgato.com/Electric-Vehicles/1995-Ford-F-250

MF

Michael Frey

Sat, Oct 27, 2018 5:30 PM

Hi John,

/(Note: I send some more screenshoots to John directly - those are too
big for the mailing list.)/

Let us start bit the difference with the two "bits".

When I add the # modifier, I see Z-Fighting.

Z-Fighting occurs when faces are coincident - OpenSCAD does not like
that as it is not clear whether the surface belongs to the model or not.

Please move the second bit down and make it a longer:

adding the # modifier to if (cover > 0) {

that looks unclean:

so, let us move this cube up a bit:

and also the other cube, but the other cube has to be translated down a bit.

adding the modifier # to if (spx<0) {

again, Z-Fighting:

so, move it down a bit:

With kind regards,

Michael Frey

Hi John, /(Note: I send some more screenshoots to John directly - those are too big for the mailing list.)/ Let us start bit the difference with the two "bits". When I add the # modifier, I see Z-Fighting. Z-Fighting occurs when faces are coincident - OpenSCAD does not like that as it is not clear whether the surface belongs to the model or not. Please move the second bit down and make it a longer: --------- adding the # modifier to if (cover > 0) { that looks unclean: so, let us move this cube up a bit: and also the other cube, but the other cube has to be translated down a bit. --------- adding the modifier # to if (spx<0) { again, Z-Fighting: so, move it down a bit: With kind regards, Michael Frey

S

stonysmith

Sat, Oct 27, 2018 7:24 PM

Your hexagonal shapes sit directly upon the base. If you lower them by a very
tiny bit, even .001, then they will not be co-planar and will no longer
cause the error.

--
Sent from: http://forum.openscad.org/

Your hexagonal shapes sit directly upon the base. If you lower them by a very tiny bit, even .001, then they will not be co-planar and will no longer cause the error. -- Sent from: http://forum.openscad.org/

JL

John Lussmyer

Sun, Oct 28, 2018 2:33 AM

On Sat Oct 27 10:30:32 PDT 2018 michael.frey@gmx.ch said:

Let us start bit the difference with the two "bits".

When I add the # modifier, I see Z-Fighting.

Z-Fighting occurs when faces are coincident - OpenSCAD does not like
that as it is not clear whether the surface belongs to the model or not.

Please move the second bit down and make it a longer:

Interesting, the bit defintions were in the original code, and I hadn't changed them.
I fixed them, even though they weren't actually causing the problem.

adding the # modifier to if (cover > 0) {

that looks unclean:

so, let us move this cube up a bit:

and also the other cube, but the other cube has to be translated down a bit.

Yup. That's the stuff I added, and hadn't figured out that I aligned things too closely.
(I've only used OpenSCAD a couple time previously)

adding the modifier # to if (spx<0) {

again, Z-Fighting:

so, move it down a bit:

Again, old code, but I did fix it.

Thanks!! I also hadn't noticed the "#" modifier before. That REALLY helps!

--

Try my Sensible Email package! https://sourceforge.net/projects/sensibleemail/

On Sat Oct 27 10:30:32 PDT 2018 michael.frey@gmx.ch said: >Let us start bit the difference with the two "bits". > >When I add the # modifier, I see Z-Fighting. > >Z-Fighting occurs when faces are coincident - OpenSCAD does not like >that as it is not clear whether the surface belongs to the model or not. > >Please move the second bit down and make it a longer: Interesting, the bit defintions were in the original code, and I hadn't changed them. I fixed them, even though they weren't actually causing the problem. >adding the # modifier to if (cover > 0) { > >that looks unclean: > >so, let us move this cube up a bit: > >and also the other cube, but the other cube has to be translated down a bit. Yup. That's the stuff I added, and hadn't figured out that I aligned things too closely. (I've only used OpenSCAD a couple time previously) >adding the modifier # to if (spx<0) { > >again, Z-Fighting: > >so, move it down a bit: Again, old code, but I did fix it. Thanks!! I also hadn't noticed the "#" modifier before. That REALLY helps! -- Try my Sensible Email package! https://sourceforge.net/projects/sensibleemail/

MF

Michael Frey

Sun, Oct 28, 2018 7:51 AM

Hi John
On 28.10.18 03:33, John Lussmyer wrote:

Interesting, the bit defintions were in the original code, and I hadn't changed them.
I fixed them, even though they weren't actually causing the problem.

Not all Z-Fighting causes problems down the line.

It can, so it is always good to look out for it.

You never know for sure when Z-Fighting is an issue or not, so fixing
any you see is good practice.

Thanks!! I also hadn't noticed the "#" modifier before. That REALLY helps!

Awesome.

With kind regards,

Michael Frey

Hi John On 28.10.18 03:33, John Lussmyer wrote: > Interesting, the bit defintions were in the original code, and I hadn't changed them. > I fixed them, even though they weren't actually causing the problem. Not all Z-Fighting causes problems down the line. It can, so it is always good to look out for it. You never know for sure when Z-Fighting is an issue or not, so fixing any you see is good practice. > Thanks!! I also hadn't noticed the "#" modifier before. That REALLY helps! Awesome. With kind regards, Michael Frey

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adding a difference causes 2-manifold error?