Donnerstag, 22. Januar 2015

Working with CAD files

Working with CAD files in 3ds Max is the single most annoying thing I had to deal with in the past 2 years.

You´re reading this, so you probably know the issues:
You get some obscure file formats (.stl, .stp. .jt) and try to import it.
And then you either have already tesselated meshes, or "body objects". If you have body objects, you are tryin to convert to editable poly or editable mesh and that is were it starts to get real messy:

Messed up smoothing groups, thousands of unweld vertices, a mesh way too dense to do any unwrapping etc.
So you are wondering, if there are simply some import options you missed, because there has got to be an easy solution for that problem.

At least, thats what I thought.
So I did some research...

The most common tips for a one-click solution I found were:

1. Use Rhino to export CAD Objects to poly objects. You can get a demo license that will let you export a couple of times, which might be enough for your project.
I tried it and in some cases the meshes looked better, but still far away from what I was used to from modelling my own stuff.

2. Use MoI for export.
I tried this aswell and again: Sometimes the results were better, but most of the times they were still too messy for my taste.

So I did some experimenting on my own and here is what I got so far:

1. If you don´t need to use the files in animation...

A) Get a file format from the client, that exports to body objects if possible. If you import the file and you already have a tesselated mesh, then you are short a couple of options you would have had, if you had body objects. I had good experiences with .jt files for example.

B) If you have large files, get he client to split it for you. I spent numerous hours trying to export files that were just too bug to handle. I have a fairly capable workstation and I found anything above 50 MB too big to handle.

C) Either leave the files as body objects, or (if the scene is too heavy), change to "coarse" in Body Object options, add Edit Mesh modifier on top and collapse. Edit mesh for some reasons gives a way cleaner look than edit poly modifier. You can use the incredibly useful scrip "modifier modifier zorb" to change settings on multiple objects at once, add modifiers, collapse etc.

D) For UVs I usually try to get away with simple box/planar/cylindrical mapping. and avoid unwrapping. Cou can get pretty complex stuff done using just that or only unwrapping small parts of the model and composite maps (Decals, for example).

2. If you have to deal with animations/ complex UV layouts...

But, and this is the most important tip of all:

Only for objects you actually need to!!

Use any tools you are comfortable with (I mostly use the graphite modeling tools for retopo), in some cases you can use the base geometry (body objects set to coarse and collapsed to mesh) as a starting point. Use "quadrify" from graphite modelling tools or the "quadify mesh modifier" and clean up the rest, but with more complex shapes it´s often faster to just retopo or even remodel from scratch.

It´s annoying as hell (especially since Autodesk owns most of those products and should be able to use their expertise to get better results for exporting/importing...), but there just is no "one-click" solution, get over it...
I spent way to much time looking for one.
Just remember that you only need really clean meshes for some reasons (deformations, complex unwrapping) and can get away with "ugly" meshes for a lot of purposes!

1 Kommentar:

  1. old post, but I bookmarked it anyway, I found out the same problem/solution still in 3dsmax 2017, it's pretty rediculous still, I somethimse use MOI, had great quads in it, but complex meshes might end up with holes..
    - next option is zbrush, dynameshing, and then zremesh..
    - but I try to get away with the original body objects, and I use edit poly on top, as that way it shows up properly in octane render..
    - maybe use power nurbs for adding chamfers but didn't try it yet..