Wall showing through roof

[Anonymous]

First roof in Archicad and there's a problem. As seems typical in learning a new software, after watching all the videos etc., the first time you do something, some weird error happens. I tried trimming the wall to the roof with both "trim elements to roof" and "solid element operations" but in both instances, the wall trims to the top surface of the roof, not the bottom surface. Anyone have an idea what is going in here?
KrisM

[Steve Jepson]

It's a known problem. But not really a bug either. This is common with other software too. I don't like it either.
There are ways to make it disappear if you need it bad enough. It will not affect you rendering.

[Karl Ottenstein]

I've never run into this, Kris. Read about Trim Elements to Roof
https://helpcenter.graphisoft.com/guides/archicad-21/archicad-21-reference-guide/elements-of-the-vir...

Be sure in the last step that you click on the lower part of the walls to keep them / trim off the top part.

The Trim command is dynamic, much like a Solid Element Op (which if you use THAT, you would use subtract with upwards extrusion).

The older Crop command - which was called Trim in its day - is a static cut. Even if you delete the roof plane, the wall remains trimmed:
https://helpcenter.graphisoft.com/guides/archicad-21/archicad-21-reference-guide/elements-of-the-vir...

[Barry Kelly · Accepted solution]

It is also a good idea to make sure the building materials in your roof composite are stronger than those in your walls.

Many elements in Archicad will trim base on the strength of these building materials.
Stronger materials will automatically cut the weaker ones.

Where the wall passes through the roof as in your gable, you will still need to connect/trim or SEO the top of the wall away.

Barry.

[Anonymous]

Thanks for all the advice. Some comments -
Steve - "This is common in other software too". Works fine in Revit. What might be the other ways to make this disappear?
Karl - Looked at all the instructions. Did all that. Doesn't work.
Barry - Tried that. Didn't make any difference.
What did work was to change the roof to a morph and use SEO. Looks fine now.
Kris

[Steve Jepson]

KrisM wrote:
...Steve ... What might be the other ways to make this disappear?

The see-through situation I am talking about is a cosmetic anomaly that you see, or don't see, in the 3D window depending on the view as you rotate. For example modeled trusses will show through a roof modeled as 5/8" plywood, even though there never was any sort of intersection. Rotate the view in the 3D window just right and you may not see it, or before you let you finger off the mouse in a rotation you wont see it. This does not show up in a rendering, but it does mess up your screen captures and looks bad or is distracting in live presentations. To get rid of this anomaly you can - for example - don't model the roof with Composites. Model the roof sheathing, 15# building felt, and roofing separately - just group roofs, in section copy-adjust for thickness, layers, elevation... you can leave a gap of 1/64" or something between the roofing and the building felt. You can use the Roof Surfacing Tool to put a standing seam metal roof on a "roof" and in the tool there is a place you can enter the gap between the roof you are using the roof accessory tool on. Sometimes moving a roof 1/128" vertical will do the job and will not show up in any dimensions. All a bunch of workarounds we should not need to make.

https://www.screencast.com/t/UMdhdRB8

[Barry Kelly]

Here is the same problem in a different post, which seems to have solved Kris' problem.

https://archicad-talk.graphisoft.com/viewtopic.php?f=11&t=61429&p=282854#p282854

The problem Steve raises is a problem when viewing 3D in OpenGL engine.
When there is an element very close to the surface of another element, then the edges cane "shine" through.
A Steve suggests, a slight rotation or zoom in/out can fix the issue (not always).
But it won't affect documentation as that doesn't use OpenGL (unless you are actually using the OpenGL image), and it shouldn't affect renderings.

Barry.

[Anonymous]

Hi all,

Thank you very much Barry.
Your suggestion solved my problem.

For all who have this issue :

Go to Options > Element Attributes > Building Materials
Make sure that the material of the roof has a stronger Intersection Priority than the material of the walls.

Voala !
Thanks again