I installed C4D on my second machine (a PC) and was able to open the C4D files and export the STLs without any artifacts. My primary machine is a 2016 iMac which has exceeded it's OS parameters - can't update beyond OS 12.7.1. I get frequent warnings from Adobe saying that it can't guarantee performance unless I update. My bet is there's something at the OS level that's flaking out causing the corrupted files. I'm going to keep testing it, but so far everything seems to be working as expected on the newer machine.

Back again

I did an experiment involving these three files:

https://drive.google.com/drive/folders/1WpjTKl59Hycuv6I8WgWK4shmMYxI61FI?usp=sharing

Scapula Model.c4d
This is the source file. Looks good. Seems to work OK in all respects.

Scapula Model.stl
This is the STL file exported from C4D. Immediately after export the file preview looks normal - as expected.

Scapula Model_STL Import.c4d
This is the same STL file re-imported back into C4D. Now it has spikes.

I have exhausted all troubleshooting I know how to do and can't come up with a reason why the STL file becomes corrupted with extra polygons minutes after it has been exported. Intially, the preview looks clean. But come back to it a few minutes later and it won't preview. Which is a sure sign that it's corrupted.

I have exported dozens of STL files for printing and have not had this problem before. Now - like in the last few weeks - I can't get any clean exports. I installed the latest version of C4D and I thought that might have fixed it, but the next batch out was corrupted same as the first.

If you can export a clean STL with no extra polygons, then there must be something flaky with my particular machine - a buggy operating system or some such thing. Have you seen a glitch of this sort before?

Thank you! Your clean up technique worked perfectly.

However, I'm still having issues with C4D exporting clean STL files without weird polygons. Here's an example file:

Scapula Mesh Clean_PolyRdc Exporter.c4d

And here's an STL exported from it:

https://drive.google.com/file/d/1_-CgjXRuLn9sg9faIolB6gpxfCHVKEuE/view?usp=sharing

The example file has a Remesh generator applied - which doesn't seem to be working. At least I don't get any results after 20 minutes of waiting. I assume there are glitches in the mesh that it doesn't like. Probably the same ones that are showing up in the STL.

It's very odd because I have been exporting meshes to ShapeWays without issue, but to my associate in COMSOL, they are non-operative. I wonder if my copy of C4D has developed a bug and needs to be re-installed. The STL export thing is just too consistent to be buggy meshes.

Via private link maybe? The models are proprietary.

Thank you. I had noticed the discrepancies in the coordinate manager but could not figure out how to reset them. The workaround resolved it perfectly.

The STL was created in Cinema, not COMSOL. I have several other examples of STLs with wildly splayed vertices. My guess is the problem originates somewhere inside Volume Mesher/Builder. The models are "normal" size when they go in, but become exponentially deranged when I export "current state to model." Is it possible that a deformer or mograph operator within the hierarchy inside VM might be generating an artifact that the VM thinks is geometry, and so tries to incorporate it?

I am exporting a prototype model as an STL file for engineering testing and evaluation in COMSOL. But the engineer involved is not able to consistently open the files. Some work, some don't. Some display one minute, but don't the next - same file. There doesn't seem to be a rhyme or reason.

I work on a Mac, so everything originates in Mac World. COMSOL is PC (I believe).

Sample non-functioning STL export here:
https://1drv.ms/u/s!Ao8UWwLJPdXjmkvKTIIIcw7AMp4i?e=ZPFRnv

(BTW: I was able to open this file in C4D but it came in very very small. There appear to be a couple of polygon artifacts that are making the model almost infinite in size. )

We hit on using Microsoft 3D Viewer as a common test bed that I could preview the files ahead of time, before sending them on (files that open in Microsoft viewer also open in COMSOL). But even Microsoft Viewer can't display some files.

I downloaded STL files of the same model that I had successfully printed at ShapeWays and tried these out in Microsoft 3D Viewer and they displayed flawlessly. Could ShapeWays be "cleaning up" the files to make them more accessible?

I have never had an issue with STL exports until bumping into COMSOL.

Pair Cloner.c4d

I have a roller conveyor model that I want to duplicate into right and left versions using the symmetry object. Then I want to clone the resulting pair of conveyors 6 times. This model is a simplification of the assembly (which is too large to send).

If I leave the all the cloners set to Instance, then the cloned symmetry objects don't work right - the clones get out of alignment. If I set the top level cloner to Multi Instance, then the symmetry works better, but the clones are offset.

I also have a configuration (not repeated here) where the roller clones just disappear. They appear normally in the symmetry object, but when I clone the symmetry object, the rollers are gone.

I have tried multiple variations of Instance/Render Instance/Multi Instance with all the cloners and get variations of unsatisfactory results.

I had this problem before and you fixed it for me, but when I went back to look up the solution, I discovered I couldn't access that exchange. I think it was in the old Cineversity. So maybe its lost forever

Do you get a day off? You're always there when we need you (which is nice) but must come at a price.

Ah! Of course. It is a physics engine after all, so it would naturally follow the rules. I was so taken with playing with the beautiful dynamics that I missed the obvious solution. Nice and simple step-wise approach with an end product of exactly the right curvature. In first iterations I attempted to use a rope tag and wrap the chain that way, but couldn't figure out how to get the links to alternate rotation - voila Formula - so that's what it's for! I am simultaneously energized by the unlimited cosmic power and demoralized by my small brain to hold it all.

The Simulation with Stickiness - would that be the one with spaghetti by Jonas Pilz?

I followed a most excellent tutorial from our good friend RocketLasso on how to make a dynamic chain system. It works brilliantly (as usual for anything from Chris Schmidt). And then I got to tinkering with it Model attached.

I'm looking to make an end-state mesh that I can print (via the volume mesher). The object is to get the chains to wrap around the sphere barber-pole fashion, and when they get to the sweet spot, export current state to object and I'm on my way to the printer.

So I added a motor to the sphere, bumped up the friction on everything, and let 'er rip. Works fantastic, except that the chains slip over the surface of the sphere and in the end line up pretty much in straight longitudinal paths regardless of how I try to trick it. I even tried using an atom array to make the sphere more bumpy, but that didn't help much.

My sense is the dynamics are rock solid, but Cinema friction and real-world friction are a little different. The alternative would be to have the bottom ring and top ring rotate at different rates, and so twist the chains around the sphere, rather than use friction. But given how the chain assembly is built, I can't figure out how to get independent control of the bottom ring.

I can always rebuild the rig and start the process over, but I hope I'm just missing a simple checkbox setting, which will solve all my issues. If such a thing exists, I'm sure you'll know where to find it

Dynamic Chain.c4d