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Modelling and drafting in ARCHICAD. (Example: How can I model a Roof soffit/fascia?)

Moderators: Karl Ottenstein, LaszloNagy, ejrolon, Barry Kelly, gkmethy

Hi guys,

First of all, I have been reading the posts on this blog for a long time and I thank you all for the many times you have helped. Most of the times I haven't participated due to redundancy, but this time I feel compelled to adress this issue as I struggle to clean up my ArchiCAD files.

I have used polycount on my project and it is scoring an impressive 3.5 million polygons in total. However, most of those come from a relatively simple object (morphologically) which is creating an astounding ammount of polygons: 2.5 million of the whole project.
What I mean by "simple" is that I believe this object CAN (must) be simplified, not that my model is simple, of course.

The object (a multi-deck pedestrian pathway and cyclable bridge) is composed of complex profiles applied to railing objects: that is true regarding the railing itself as well the wooden cladding boards which cover the structure. The glazed pannels were also modelled resorting to this technique, which might have been one of the workaround responsible for the project bloating, I guess. - Any ideas on this particularly would be a bonus, but a side quest still, since the glazing score was actually quite low (30k polygons...) :roll:

The core of the structure was accomplished resorting to slabs , ramp objects and collumns. You will notice that score also to be high, that is due mainly to the curved railings, which include the structure itself. (curved ramp) - so this component of the structure includes the wooden cladding (1 million polygons of it across only 8 ramps (125k polygons EACH :shock: ).

As attachment, PolygonScore_Project illustrates the polygon score within the full project model context; PolygonScore_BridgeandPathways does the same but regarding to the Hotlinked Module File which only contains the geometry of the composite object (the whole bridge and adjacent pathways).

Polygon Scores:

Bicycle Path: 223k
Wooden Cladding: 168k
Railings: 693k
Glazing: 31k
Structure + Curved Ramps with wooden cladding: 1.18m

Bridge and Pathways SubTotal: 2m 158k
Project Total: 3.5 million:

So... I would like to bring this model to a workable state (around 2million max polygons in my machine - I guess). What do you guys think I am doing wrong? I tried to search the web and ArchiCAD-Talk forums about complex railing profiles, polygon count issues, etc. to no avail.

I hope the annexed files help you to understand more clearly the design and possibles issues.

Thank you in advance for all the time spent on this issue. I hope it will help others struggling with complex profile and railing modelling. Cheers all for your always helpful insights.

P.S.: Wasn't really quite sure if the actual railings of the project could be simplified, and was unsure about which characterictics to prtscrn... If you have any ideas regarding that, they will be very much appreciated.
Must the the resolution of profiles of Rails, Top Rails, Posts, etc.
Check the "Cross-section Resolution" parameter of these GDL Objects in the Railing Settings Dialog.
E.g. for Rails, it is on the "Rails" page, "Rail Component Settings" panel, "3D Representation" tab page, "Cross-section Resolution" parameter.
By default it is set to 36, so try to set it to 16 as a first step, see if that helps.
Thank you so much, Laszlo. The method you described worked like a charm for most elements.
However, there was an exception. The curved ramps still score the same 1.000.000 polygons, even if I bring the detail level to the minimum value cap of 3.

What might be causing this behaviour? :? The arc path for the railing? Should I consider creating linear segments?

The images I send now represent both the exception to the rule, and the results of the method applied to the bridges and pathways.
It is probably the arc path of the Railing Reference Line. I would have to see the geometry of the 2D Railing Reference Line and the Segment Pattern definition.
If you could just copy-paste a single one of these problematic Railings into a blank ARCHICAD file, save it as PLA and share it with me (might be too large to post it here, but Dropbox or similar can work), I would be interested in looking at it to see what is causing this.
I looked at the Railing. I can see that your Railing Profile is pretty complex, since it is very detailed, it has about 65 Fills in it with 260 Nodes in total. However, that means that to achieve 130 000 polygons that curved Railing Reference Line must be divided into up to 500 segments internally by ARCHICAD, which is way too many. Now it makes sense why you have 2 million polygons. A single circular Rail profile, which has a resolution of 36 was about 18000 (36x500) polygons in that case.

Interestingly, I ALT-clicked your Railing to pick up its settings, then drew an Arc on its Reference Line, dragged the Arc to another positions, and placed a new Railing with the same settings using Magic-Wand-clicking in the Arc, and the resulting Railing is now only about 40 000 polygons, about 1/3 of the other, supposedly exactly the same Railing. Curious.

So it seems to me that when the Railing Reference Line is an Arc, ARCHICAD does some internal calculations about how many segments to use to approximate that curve, and it "overdoes" it, which results in very high polygon count. I will forward this to GRAPHISOFT as I think this phenomenon is definitely something they should look at.
Actually, this could also have to do with the build number. I see you used build 3006 to create your Railing, I am using build 5009, maybe that is why my Railing has 1/3 of the polygons yours has. May be worth trying to update to the latest AC22 build, which is 6001 or something right now.

You could of course create the Railing Reference Line out of linear segments, doing so will drastically reduce the polygon count to 3-4-5000 polygons or something in that range. But unfortunately, in that case you will see lines in 3D where the individual segments connect.

By the way, you have 6 Beams with zero height on the 2. Story of your Project, which are therefore degenerated in 3D and give an error message (you can find which element it is from the Element ID after the error message). You should give them a height of 0.0001 meters for example (or even less). Then, in the Settings Dialog, Labels, Schedules, their reported Height will be zero, but they will still generate fine in 3D. Just a little trick.
Hey Laszlo, so glad you took your time to do a bit of testing.

I tried to do what you did but didn't get the same result. Are you sure you didn't forget to add the slope to the railing? if it is a plan circular railing it will certainly produce lighter geometry, but the path is actually a helix if you notice, hence the heavy polygon count, for sure. I obtained 40k polygons only when I took out the slope from the railing.

I also updated my build to 6001, but didn't notice any consequence. So far the cleaning has brought my project down to 2.7 million polygons. My machine still struggles with it, a single collumn accross multiple stories might cause a 20min 3d view update... unfeasible.

No further ideas to workaround this problem? Convert this object to morph and simplify it through some magic addon (speculating :roll: )? Simplify or model it elsewhere and (re)import to ArchiCAD? Would prefer an ArchiCAD solution as I pretend to further my skills in this software (just bought advanced training classes recently - maybe I'll get a solution there, if so will post here).

And again, thank you for your thorough analysis.
Yes, you are right, my Railing Reference Line was a planar arc, not a helix. When I moved the end node of the Railing Reference Line 1.2 m higher to achieve the helix, the Polygon count became 134K polygons, just like yours.
You can try converting it into a Morph. that may help. You could also try modeling it using linear segments for the Railing Reference Line, then convert it to a Morph. Then you can select individual edges of the Morph and set them to Hidden, this way you can get rid of the visible edges at the join of linear Reference Line segments.

In any case, I will forward this to GRAPHISOFT.