topic Re: Issue hiding lines in 3D model in AutoCAD Forum

Issue hiding lines in 3D model

Anonymous — Mon, 19 Sep 2016 17:53:33 GMT

I searched the forum to no avail, so I hope I'm not duplicating something.

Basically, AutoCAD isn't hiding lines when I tell it to.

Below are two viewports, one of top of the other, and they both depict the same thing. The bottom viewport is set to a front parallel wireframe elevation, and the top viewport is the same elevation, same objects, rotated eeever so slightly in 3D space.

Both viewports have lines hidden through the mview -> h -> on command. So why are the lines in the bottom viewport totally visible?

All my google searching leads to me to line scale and transparency commands... why? IMO, this has nothing to do with either property. If a line is behind something and therefore occluded, don't depict it. I thought that was simple enough.

This has me feeling pretty dumb; I must be missing something. Anyway, here's the image:

Thanks for the help, and sorry again if this is a duplicate.

Re: Issue hiding lines in 3D model

pendean — Mon, 19 Sep 2016 19:30:12 GMT

One of your images is an 2D elevation?

Share the DWG file itself please, let's all have a look at your content.

Re: Issue hiding lines in 3D model

Anonymous — Mon, 19 Sep 2016 20:53:04 GMT

Alright, so, there were some sensitive work items in that .dwg file, so I saved-as as another .dwg file and removed all the sensitive stuff, and... the problem went away.

In other words:

- One .dwg file won't hide lines in a purely front elevation, but will hide lines when the model is at any other angle

- Another .dwg file, with the exact same model and viewports as the other .dwg file, hides lines normally in a purely front elevation and at any other angle

So it only fits that, after stumbling upon hard-to-describe problem, I stumble upon a hard-to-describe solution. My first thought is that there's some system variable at play, although that can't be due to the way I saved as (original was bcb.dwg, new is bcb2.dwg). I'm not sure what to say, but it looks the way it should, now, and I can proceed.

Thanks for looking into it anyway!

Re: Issue hiding lines in 3D model

Anonymous — Mon, 19 Sep 2016 21:54:03 GMT

OK, sorry, that strange solution didn't persist. After trying to add more elevations, I'm getting the same issue... AutoCAD seems to pick-and-choose when it wants to hide lines, which can't be right.

I zipped up BCB2.dwg and put it on my hosting: http://www.flowdex.net/files/BCB2.zip

I normally work with 2D blocks of elevations, which never give me any hidden lines but also never update with my model as I work on a project, so I'm trying to get back to my Sketchup style, ie. viewing the 3D model from the desired angle and dimensioning out the model itself. You can see the beginnings of that in the provided drawing file. It didn't take long for me to feel like an idiot.

So what am I dealing with, here? Is something wrong with the models or how some of my layers are set up? Are there some nuances to mview -> h -> on that I wasn't aware of?

Thanks again for the help, and for putting up with my stop-and-start troubleshooting process.

Re: Issue hiding lines in 3D model

Alfred.NESWADBA — Tue, 20 Sep 2016 07:20:14 GMT

Hi,

your lower view of layout 01 shows geometry at coordinates X= about 17000. When you move that geometry more close to X=0 (and adjust the view for that) you get a better hidden display.

Not sure why that things are moved that far away in modelspace, it looks for me like the same models are copyied, then rotated for different views, that is not necessary, if it's really just done for different view angles! Or I missed something.

At least high coordinates reduce the accuracy of rendering and so the calculation for hidden lines.

- alfred -

Re: Issue hiding lines in 3D model

Anonymous — Tue, 20 Sep 2016 13:31:56 GMT

Ok, WOW. Never a million years would I have thought the x-values of the geometry would affect whether or not lines will be hidden. How is that even a thing? And if so, why isn't there some kind of error that gets thrown, letting you know the values are too high and to expect weird results? Does this mean there's a hard limit to how far away from the origin geometry can be in any given drawing? Why is 17k too much? Why not 170? or 170k? Is the limit the same for each axis? Should my standard template have a sphere centered about the origin to represent that bound?

Truthfully, I was just spacing my geometry arbitrarily to make it easier to work with. Questions abound, but the fact is after moving the geometry closer to the origin the lines started hiding correctly. WEIRD.

And yes, I have multiple versions of the same geometry rotated, because I'm just using the standard front projection. I've set aside time in the next few days to dive into DVIEW and other commands so I can work with my camera views correctly. So please forgive that strangeness in my .dwg, it's just part of my learning process.

Anyway, thanks for the help. It seems to be working correctly after moving stuff closer to the origin. I'll keep my geometry close to there from now on.

Re: Issue hiding lines in 3D model

Alfred.NESWADBA — Wed, 21 Sep 2016 16:47:47 GMT

Hi,

>> Does this mean there's a hard limit to how far away from the origin geometry

No, not really. The thing is the higher the coordinates, or better, the more number-places in front of the decimal point the less numbers could be used for accuracy behind the decimal point. The background info is that for performance issues the display does not calculate double precision like CAD does for it's geometry, it reduces the accuracy for speeding the display up.

You can have geometry at high coordinates, as long as the objects are big too, so having objects at 300000,300000 will work well with hiding, as long as the objects (or distances between objects) are high enough, your not hidden objects are too close to the front door and so the are not identified as "behind".

- alfred -

Re: Issue hiding lines in 3D model

Anonymous — Wed, 21 Sep 2016 20:39:09 GMT

Thanks for the reply Al, I actually started to employ FLATSHOT to give me 2D blocks of what I want (never heard of the FLATSHOT command before yesterday...), but I have a question about something you said.

"your not hidden objects are too close to the front door and so the are not identified as "behind"."

Based on what? To me, whether something is behind something else is a boolean state - either it's behind, or it's not. It's weird to think of something as not being behind "enough." Does this have to do with lineweights or linetype scales?

Thanks again for the help.

Re: Issue hiding lines in 3D model

Alfred.NESWADBA — Wed, 21 Sep 2016 22:47:19 GMT

Hi,

>> To me, whether something is behind something else is a boolean state

No, not really, it's a distance measurement with limited number of decimal places. If you see something with 0.1 cm behind the other object, but the calculation only works based on cm without decimal places, then the distance is 0 ==> not behind.

- alfred -