topic Re: Curved wall problem in Modeling

Curved wall problem

Anonymous — Tue, 04 Sep 2007 16:42:14 GMT

Is there any way to avoid this lines on edges of two parts of this wall (of course, wall is created as one part)

Re: Curved wall problem

Dwight — Tue, 04 Sep 2007 17:33:01 GMT

A small overlap will do it.

Re: Curved wall problem

Anonymous — Wed, 05 Sep 2007 18:36:08 GMT

What kind of overlap? I couldn't make that...

Re: Curved wall problem

Dwight — Wed, 05 Sep 2007 18:48:19 GMT

I'm sorry. I saw this problem before and solved it by an overlap of about 2 feet, but trying it again today, I can join the walls end-to-end without seeing the join.

Try making your material less metallic and see if the rendering problem goes away.....

Re: Curved wall problem

Dwight — Wed, 05 Sep 2007 19:01:18 GMT

And another thing: where is the hotline? In or out? Does it make a difference?

Re: Curved wall problem

Anonymous — Thu, 06 Sep 2007 03:49:45 GMT

I believe this is a 3D resolution issue that has been with us since
circular walls were introduced. You can draw draw 360° walls
of varying radii and some pairs show a joint line others do not.
Curved wall resolution is controlled internally in AC.
You can verify this by making a window subtype library part
that has only one line of code "Print wall_resol". and insert
this "window" into any wall to see what the value is.
If you set the 3D view to top view and focus in on the joint between
the pairs you will see a small jog at the joint when a joint is seen
in dimetric axonometric view. This issue of wall resolution I do not
know much about but Olivier Dentan knows a great deal about.
One possible fix is to stretch one of the walls away from the joint
with the other and insert a third wall to fill the gap. Or, as Dwight
suggests, stretch one of the walls slightly. I have found that the
stretch can be very small like even 1/64". You stretch the wall
just enough to solve the problem.
Peter Devlin

Re: Curved wall problem

Anonymous — Thu, 06 Sep 2007 15:59:37 GMT

Peter is right, this is as old as curved walls. It is difficult to predict or reproduce, according to further reasons.

Image below shows the way AC handles curved walls (proportions are exagerated, for the purpose).

The algorythm used by AC to calculate step angle "a" is function of wall resolution and wall radius, as Peter explained.
Changing reference line position does not affect "a". In short, User can not predict step angle "a".

Artefacts (in rendering) may occur for small values of "aEnd". Particulary if "aEnd" = 0.
Because last segment is not tangential (perpendicular) to ending radius. This is visible too in 3D window when zooming.

Workarounds : change wall radius, or wall angle.
If this is not possible, cut the wall in two parts. In most situations, a tiny angle is suffisant.
If the problem persists, move the junction point along the arc.

Re: Curved wall problem

Link — Thu, 06 Sep 2007 16:03:58 GMT

Now that is a good explanation! Thanks Olivier.

Cheers,
Link.

Re: Curved wall problem

Anonymous — Thu, 06 Sep 2007 16:20:14 GMT

Hi Link, thanks. This is just observation.

By any chance, do you remember the name of the thread where you explained how to create
twisted roofs directly in the 3D window. Your demonstration was absolutely amazing.

Cheers.
Olivier

Re: Curved wall problem

Link — Thu, 06 Sep 2007 16:42:11 GMT

I did a search and found this. That's the only one I can recall right now, but again it's about my bedtime...

Cheers,
Link.

Re: Curved wall problem

Anonymous — Thu, 06 Sep 2007 16:46:18 GMT

That is. Great.

Thank you.