Handling huge CAD files?

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  06 June 2013
Originally Posted by gristle: As soemone mentioned, maybe get the data from them in a mesh format instead of a nurbs format.

Don't do that. Usually the party handing you the files are Engineers or CAD people. They know way less about proper tesselation than you do even if you know little. And you will end up with more issues than good. Especially since the exporters for most CAD tools are hardly usable and many formats simply do not support everything needed (mostly Vertex Normal information, which probably is the reason for FBX working best for you).

I would also join the Showcase Bandwaggon. The tesselator (Aruba) is great and produces rather light, watertight meshes mostly. It also multithreads nicely via batch import and helps to handle much data.

That does not solve your single-file iges monster issue. But probably nothing will. Even CAD tools (or surfacing tools like Rhino as you mentioned) will have to import it and have a hard time doing so.

A few best practices:

- Start thinning data in the originating App if at all possible. It helps TONS.
- Use Step for incoming CAD data if possible
- Always seperate in logical groups to keep files in reasonable chunks and enable multithreaded conversion and tesselation.
- Use Showcase for conversion, normal flipping (it has some neat tools and face normals often get flipped)
- Make sure you preserve Vertex Normal data (using FBX from Showcase to DCC usually works). You can get away with WAY lighter mesher if the Vertex Normal Data is intact. Not even speaking about shading artifacts you might get otherwise.

  06 June 2013
Originally Posted by instinct-vfx: Don't do that. Usually the party handing you the files are Engineers or CAD people. They know way less about proper tesselation than you do even if you know little. And you will end up with more issues than good.

I disagree with you, my reply was in the context of the original poster. I'd prefer to have a crap mesh directly exported than tens of thousands of unjoined surfaces in Rhino. At least you'd be able to start setting up the job with the placeholder mesh while the client tried to get more useful data through to you.

In any job apart from this I agree, STL etc meshes are pretty bad (vertex normal??), but then again the formats were not designed with rendering in mind > for rapid prototype.
  06 June 2013
I'd like to know:

1) what is the deliverable showing: exterior surfaces only? cross-section views? exploded views?

2) is this for an animation or a still image?

3) what is the deliverable resolution? i.e. will tiny details be lost?

4) what is the originating CAD application?

5) can you request the originator "suppress" features which won't be visible (e.g. interior rounds, aso)?


I use different CAD applications (Creo 2, Alias, SolidWorks, occasionally Rhino3D) as well as animation/imaging apps (Maya, KeyShot) and deal with this issue with some regularity. These days I mostly use KeyShot for renders, either using the plug-in for Creo or using STEP for Alias or SolidWorks. If I model in Maya, I just render in Mental Ray.

I used to (and sometimes still) export from Pro/E (aka Creo) as a "render" file (which is .OBJ format) and take those into Maya. Whatever I do, I don't use .IGES formats for renders.

In Creo if different parts in the assembly are colored differently, then either going to KeyShot (as a STEP) or to Maya (as an .OBJ), the assembly should come in together but assigning the shaders is easy because the colored parts should be grouped automatically.

Additionally, a single part can have different surfaces uniquely colored. Those will generally obey the same rule. For example, if I'm in the early concept modeling stages, I won't separate all the parts and create a full blown assembly, but will be working in "master model" mode, so the assembly is really still just a single part file at this point. Thing is, I may want to generate concept renderings for a client, in which case I would assign a light blue color to the screen surface of the model, a bright red to the smooth housing areas, a dark color to regular textured housing areas, and different colors to things like buttons, port covers, switches, etc. On export all those surfaces are grouped by color so shading/texture/label assignment in the renderer is easy.
  06 June 2013
An issue with iges, is that the surfaces are not welded. So, C4D has to compute all that as it's importing the file.
If you're dealing with CAD, then you really need some CAD apps of your own, to pre-process the files. Personally, I use MOI, Rhino and ViaCAD.

MUCH better solution than bringing raw CAD into Cinema.

As a side note, I also must sing the praises of MOI's user help forum. It's fantastic, and Michael, the developer must never sleep. Becuase whenever I post a question, he's always the first to help. Just amazing.
  06 June 2013
Thanks sneather, yeah I do have Moi and Rhino and a couple other utilities that are floating around out there. I spent a couple days trying to get the 1GB file to open in either program to no avail, so I've gone back to the producer and asked for the files to at least be broken into components, so they can be opened, cleaned up, and put back together. I don't work with enough CAD to justify the cost of more software, but if I did have a lot of work I'd most likely buy what's been mentioned.
  06 June 2013
This thread is a goldmine of useful tips, thanks guys. Especially Kabab and instinct-vfx, I had no idea showcase could export CAD data for use in DCC apps
Michael Wentworth-Bell | 3D Artist & VR Designer | Melbourne, Australia

Espire 1: My VR Stealth game - CGTalk thread
  06 June 2013
Large files. Rule one buy some more memory!

deus es
  06 June 2013
The repeated mention of the Aruba Mesher in Showcase made me curious. I had a look at the online reference of Showcase - the meshing section is -well - quite compact. Are there any other online resources which show what it can do?
  06 June 2013
Just down load the free trial.
Vizual-Element | Automotive Superstore
  06 June 2013
Quote: Just down load the free trial.

That's exactly what I wanted to avoid - blindly downloading huge software - packages. I come along with my tools especially as Zbrush R6 with Zremesher is now there. From some answers in this thread I got curious in what Showcase does exactly under the hood and if it really differs greatly from what e.g. MoI does - as I actually can not imagine so. Some docs and closeup before/after pictures would be sufficient to get an idea.
  06 June 2013
Basically it makes a very nice adaptive mesh the biggest thing it manages that no one else can well that I have seen is that it matches the tessalation along patch boundaries so you get a water tight mesh.

It creates decent hierarchy to.
Vizual-Element | Automotive Superstore
  06 June 2013
Quote: the biggest thing it manages that no one else can well that I have seen is that it matches the tessalation along patch boundaries so you get a water tight mesh

I'm confused now - it is the only goal of every Nurbs mesher to create watertight meshes. Given the Nurbs model is closed and valid a closed and valid mesh is the only expected result. Saying one could not achieve this with most products was nonsense. Do you model with Nurbs at all or are you only converting third party geometry to meshes?
  06 June 2013
What your missing is that when you create a nurbs object or solids the patch topology doesn't always match up.

For instance you get shapes like


Where 2 patches have a G0-G1-G2 relationship with a larger patch or even more complex configurations you see this a lot nf filleted edges.

Most tessellators create very bad topology when tessellating patches and joining them for the scenario above, really ugly n-gons etc but showcase does a very good job of these situations..

Also trimmed edges are handled nicely to.
Vizual-Element | Automotive Superstore

Last edited by Kabab : 06 June 2013 at 09:52 AM.
  06 June 2013
That seam you show may be perfectly valid and watertight.
It's merely not what Mesh Modellers would consider a particularly nice mesh.
You are saying that showcase indeed manages to come along without triangles and without Ngons while sticking to the Nurbs patch layout. I wonder how this is possible, as industrial production grade CAD may consist of myriads of patches. Keeping all existing seams, while being sufficiently accurate as well as adaptive in density - all this without using a single triangle or Ngon seemed like a miracle to me. But I'm open for miracles.
Could you maybe mesh this stupid sample in Showcase - I'm curious how it deals with it (it's saved as step 214). The just released Zremesher indeed could redo this thing in all quads and even partially loop based and therefore sub-dividable which alone is completely insane. But Zbrush of course recreated the whole structure, it got rid of underlying patch structure, also it wasn't able to mesh planar sections loser than areas with curvature.
  06 June 2013
Originally Posted by Hoja: That seam you show may be perfectly valid and watertight.

The problem many tesselators have is not topology, but not beeing watertight. In the example the center vertex would belong to the bottom 2 polygons and the upper quad would be a single 4 sided poly. Hence the center edge would actually be 3 edges with a gap. Even worse issues are that when both sides are differently tesselated with the verts offset slightly. E.g. a boundary between two patches and one patch would have a different amount of edge vertices than the other. You simply cannot fix that on the poly mesh. Autowelding is out of question, manual welding will often kill any vertex normal data and you'd have to manually generate smoothing groups that would give WAY worse shading etc. Showcase is really doing a nice job there. Setting up presets etc used to be rather rough (in txt files). Have not played with any of the recent versions myself tho.

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