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# Thread: Why do some voids not cut?

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## Why do some voids not cut?

Are there any rules of thumb when in the family editor and working with voids? I'm trying to round some corners and shave off some edges using void extrusions and arbitrarily (or what seems arbitrary to me) some of the voids just won't cut. I get the "Can't keep elements joined" error. But I can’t think of why this is happening. Any recommendations like, “don’t get too close to the edge of the solid” or “only two voids can cut one solid” or “do a rain dance then snap your fingers three times before you try to cut”?

Because it’s not just happening in one family I feel like there is fundamentally something I’m missing.

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From my old post

If a void is finished AND it intersects a solid it will cut automatically.
If a void is finished AND DOES NOT intersect a solid it will not cut automatically when it does intersect with a solid.
If a void is created FIRST it will not cut any solids that are created afterward.

Use Cut or Don't Cut Geometry to resolve the cutting or lack thereof...

All that written...Revit hates tiny slivers so if a void doesn't completely cut the element it may complain. Best to let the outside edge of the blade hang out away from the solid if possible. Think router bit, half the bit spins in open air (and can cut you). If you extend the sketch of the void away from the solid, the part of the void that won't touch anything you can't end up with slivers.

By the way, you were late for dinner last night. Actually you didn't show up, but then I don't think we let you know either, sorry! I didn't know till last night that you are in Dallas.

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Hmmm... well:

The solid was created first.
The void DOES intersect with the solid - although the edges of the void and solid get mighty close to each other.
Using Cut Geometry produces the error, "Can't keep elements joined."
So I'm lost.

Awww... I'm so sorry I stood people up for a dinner I didn't know about. Now I'm disappointed! Next time, I'm there!

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I blame Aaron. He knows you. He knows you are in Dallas. Now, you've missed out on meeting us. Yeah, it's Aaron's fault.

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Originally Posted by mfrietze
Hmmm... well:
The void DOES intersect with the solid - although the edges of the void and solid get mighty close to each other.
Using Cut Geometry produces the error, "Can't keep elements joined."
So I'm lost.
Sounds like you are suffering from "sliver" effect then. How about a image capture of the sketch of the void at the solid?

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Sorry for interruption Steve, i have the same problem if you would take a look in this table that has sweep on its edges i can not cut the void sweep from table edge.

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Yes, there does seem to be some sliver-esque edges in here. But I don't know how else to do it. Am I just SOL?

I suppose dumbing down the original shape won't be the end of the world. So, is that it? Won't cut voids if there are slivers?

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There are documented Support Requests about the Sliver effect, and i even have an email from development sitting on a flash drive stating that they dont really know what to do about it, unfortunately. It also doesnt pertain to just voids, but solids with pick line as well. Based on my understanding from the Support Request (Filed in R2010, but i dont have access to that account anymore) it has to do with Revit mathematically being *uncertain* that certain things are actually coplaner, even though they definitively are.

In one instance, i took a curved extrusions, and sheared a wood panel area out with another void extrusion that used pick lines to define it (so the lines were difinitevely in the correct place). It worked fine. One solid, one void. I then tried to make a solid sweet, using Pick Lines (not pick in sketch mode) and i picked the four edges of the void forms surround. It failed to create. It allowed me to do it with any three sides, but it insisted the fourth side made it "two loops" even though all 4 edges touched one another.

I validated this because you can do it with ANY three sides and it works, meaning every side IS coincident with the two juxtaposed sides. However a 4th side breaks it. Making two sweeps in horseshoes that overlap, then performing join geometry, however... Works.

I could probably reproduce it, but it doesnt help with the problem at all. Bottom line: Make the void form bigger.

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I've seen some pretty detailed stuff done for film and stage (pretty sure it's in the 2012 version of Mastering Revit Architecture) that makes me think it must be possible. I have no idea how they do it but the level of detail they produce is damn impressive.

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Make the void bigger (slice off more) or make the form bigger so the void isn't cutting such a thin piece to remove. Kind of like the wiggle/wave of a circular saw blade as it spins will cut more material than you want if the blade isn't balanced well.

Ahmed_Hassan - Looks like you can fix it if the part of the void sketch that is away from the interior of the solid farther. Don't put a void sketch directly on the surface of a solid.

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