(New to the forum and have no idea where to post)
I have a fairly beefy PC at home, not the best but it does an awesome job when it needs to.
I have been given a 600mb fbx for a job and god it’s a nightmare.
I can’t navigate the scene with it in there and I can’t even import it into Maya to break it down.
If it’s not even running in editor when its the only thing in there at this stage then I will assume any game I make with it will really struggle.
Any pointers?
Send it back and make sure they adhere to spec next time.
Haha, unfortunately, in this case, I am the 3D artist and thought I could cut some corners by getting the fbx from AutoCAD so that I didn’t have to model the environment from scratch… I guess I am learning why polygon count limits exist, and that I probably need a better PC…
Don’t click on it in the inspector.
I am working on 1.8gb+ size FBX packages. I do the work via script but generally as long as you aren’t clicked on the giant prefab hierarchy it shouldn’t really be a problem… Assuming you have a decent PC and can fit everything in RAM without it kicking to a disk cache
The file size is unlikely to be the issue in and of itself. The problem is likely to be an insane object count, an insane triangle count, each object getting its own material generated on import, deep nesting of child objects, and various things like that.
You might get some increased mileage out of combining meshes and materials, depending on how bad those aspects of your particular model are.
You also might be able to get your client to provide a less detailed version of the model. From memory some CAD exporters allow you to select the detail level for when they triangulate the mesh. In my experience the first time most CAD users do this they think “well, we need ALL the detail!” and turn that up to max. Depending on the cause of your issues getting the poly count reduced in this way might do the trick enough to get you going, if it’s an option.
For future reference, when we used to get models from clients from their CAD software we’d usually use it as reference to model over. We often had to explain to clients why we couldn’t “just use the model we already have”, and you’ve found the answer to that the hard way. 
Depending on what’s in your PC upgrading it might not help meaningfully because the problem might not be hardware. The issue is that while some parts of CAD and game software are similar other parts of it really aren’t, and each have their own priorities about where detail and performance are required. Converting data made for one to the other often results in terrible compromises in both the quality and performance areas. Even so, I’d still say to check out the Performance tab of Task Manager (assuming Windows) to see if there are any obvious hardware bottlenecks.
Just had a talk with a coworker and the file has come from Navisworks. Apparently, it is notorious for flipping unity out… Going to try and break it up a little in Navis>DecreasePolycount in 3dsm> And then export to unity…
I am running a 4.5ghz i7, 32GB ram, a couple of SSD’s, and 4GB AMD G-Ram… The same co-worker thought it must be because I have an AMD graphics card but I don’t know how much traction that has…
None, as far as I’m aware. In my experience the difference between GPU vendors, aside from the performance of each model of card, is just reliability of drivers in various applications. Even there, I haven’t heard of issues with any vendor for years. In any case, if it’s not crashing and it’s not giving you graphical corruption then it’s fine.
You can’t cut those corners, you need to retopologize the mesh to have sensible polycount and adhere to best-practices for optimization based on your target plattform etc… Some detail you might need to bake into textures. The mesh exported from AutoCAD might still be useful to get proportions right or to straight up snap your new vertices of the retopologized mesh to. This is likely gonna be a hell of a lot of work, you might have quoted too low based on lack of experience with the worklflow or in general. Depending on budget and other factors I’d consider cutting your losses on the job, but only you can judge what the right call is.
There is a process between cad and 3D Max to bring in a proxy model into Max without having all the high polygon mesh data from cad imported while working on the file.
See if you can rummage up the workflow. It has been 10+ years since I used it. It should work the same regardless of what package the content is coming from.
If you can find it, once in Max, convert the proxy model into mesh boxes and then export to Unity. Might save some time - but poly reduction (retopo) is still going to have to be done - as @Martin_H stated.