I work for Siemens PLM, makers of NX and Solid Edge software. Though I usually never post much about work, I thought this information may help others in the graphics / motion graphics realm, especially those who do adverts for Car companies and the like. NX can really handle some massive data, like 4GB assembly big. Cinema 4D, not so much. I love C4D, and is my package of choice for motion graphics. So the question is, how do you convert those massive assemblies into a workable model in your 3d package, such as Maya, 3ds, Modo or C4D? It’s all about doing the correct export and conversion process.
Get some conversion software
If you’re like me, it’s a good chance you subscribe to either 3D World or 3D Artist. You might see an ad every once in a while for PolyTrans / NuGraf by Okino software. While it’s PC only software, it’s probably the best conversion software out there, albeit with its quirks. *Mac fanbois (Which I am), just get a copy of VMWare or Parallels and suck it up. Before you can ever actually own a copy, Robert Lansdale will most likely want to speak with you, either by email or phone, to discuss your needs. He’s very serious about his CAD conversions and wants to make sure you’ll end up a happy customer. I purchased the NuGraf package with the Granite/PACK plug-in to handle STEP and IGS. As a side note, being a slight introvert, the communication made this a little uncomfortable for me, but nevertheless, I persevered through the conversation.
*Rat Hole*: Yes, Cinema 4D Visualize and Studio come with Okino importers (only on the PC version) but those importers are not nearly as fast/accurate as having the standalone version.
Break it up
So the first thing I do, when dealing with a massive assembly is break it up into somewhat manageable chunks, or sub assemblies. Usually if your receiving the data from a design team, it’s probably already broken up into manageable sections/sub assemblies. What’s a manageable section? That’s up to your machine. My 12 Core MacPro with 24GB of ram can handle about a 300MB assembly at a time, and can go a bit higher.
Export to STEP
For me, when exporting an assembly, I export to STEP 214 (As recommended by Robert). The command in NX is File->Export->Step 214… The kicker though is to export with the option “Export Assembly as External References” in the advanced tab of the export dialog. This will create a new .stp file for each part in your assembly. Make sure to set your export data to a fresh directory, otherwise you will pollute your data folder very quickly with files. You will thank me later in the process for telling you this. Typically, I check “Surfaces” and “Solids” as the model data to export. Sometimes with older data, the surfaces data can be unruly and your best bet may be to retopologize those parts in your main 3D system. I keep the tolerance at the default level, but if your doing high detail, you may want to experiment on what tolerance meets your needs.
Start the conversion process
You need to get the data into an intermediary format, to convert to your 3D package. Importing the data is pretty painless. Most likely you should choose the advanced import choice and read through the help section to see what the options mean. You should import only your main assembly file and the NuGraf/PolyTrans software is smart enough to load in all the reference links. If you tried to export your big assembly into one file instead of “Export Assembly as External References” this is where you will get bit in the ass. If the export is broken up into small chunks of references files, the software will relatively do a quick job. A 100-300MB referenced assembly will take about 20-30 minutes to chunk through. If not setup correctly, the program may take overnight, or worse, you’ll find a crash error in the morning. If you still find loading up the main assembly STP file to be too slow, the NuGraf/PolyTrans software also has the wonderful ability to do batch conversions. If you decide to do the batch conversion, you can export all the separate items to your preferred format, then you can batch open the separate files into once scene file with NuGraf by shift selecting the files. I have found this can sometimes provide a HUGE difference in dealing with lots and lots of parts. As I use collada for the export format, it could be the NuGraf/PolyTrans software has a much better engine for the collada format, rather than the Granite/PACK for .stp
Look out for the super slow conversions
Sometimes when doing a batch conversion (my preferred method) the Nugraf/PolyTrans software will sit, for what seems like an eternity. Sometimes it doesn’t really matter about file size, it just gets hung. This could either be an issue with what NX exports, or how the Granite/PACK reads certain STP files. As a workaround for those items that love to sit and hang, I do a second conversion of those individual parts by loading into another CAD program, exporting as STEP and seeing how the conversion software will handle it. For the most part, albeit slow, it usually fixes the problem. In a worse case scenario, I export to VRML from NX… blech.
An important thing to remember, is don’t go overboard on the import/export quality. I know we all want the best, but specifically with CAD data, the detail can be overwhelming. The bolts, the threads, etc are not created with shaders, they use actual geometry… ewwwww. If you try to be too overzealous in what you try to transfer, you will only become frustrated. Sometimes, I use a hybrid approach, using a very rough model (low polycount) for certain sections and only a high poly model for close ups.
For me, it was recommended to export to Collada for the C4D import. Preferred exports will vary depending on your desired 3D package. I just go with the default export settings in NuGraf/PolyTrans and export out. Typically the models are now much smaller than the original and it’s just 1 .dae file. Sometimes I see as much as a 75% reduction in model size from the original NX data.
Import into Cinema 4D
If you’re using a mac, just open the new .dae file and start texturing. If you’re on a PC, as recommended by Robert, you’ll have to go to the preferences, go to the import/export section, and turn off the built in Okino importers.
At this point, you’ll have to most likely create more realistic materials and texturize your model. The only thing that every really comes through in the conversion process concerning materials is the color channel. If your materials all look washed out, it’s also a good chance that the luminance channel is turned on as well.
As a side note, while conventional thinking would tell you, you should have a master file, with all your sub assemblies as xrefs, I have noticed when working with these huge data sets in Cinema 4D, it can crush your system very quickly. I recommend merging all the assemblies into one file, rather than using xrefs. Your results may differ.
While working with massive data sets are usually a huge pain, (meaning slow, really slow or super sllllllooooooowwwww) hopefully this article will give you some tips on how to get a grip on what otherwise may be a hair pulling experience when dealing with CAD data from design/manufacturing agencies.