Saturday, August 18, 2012

Sculpting and Inventor

So it's been over a week now and I've only begun to scratch the surface of interoperability between inventor and other non-native 3D formats.
I've found that there is a way to get objects from Sculptris into inventor. But, it is not the optimal way of doing things. The objects are very very facet heavy and inventor buckles under the weight of all those facets.
So, rather than posting a "how to" on placing memory hogging faceted objects into Inventor. Instead I will share what I learned that led me to finding another, better way of getting organic sculpted shapes into inventor. 

After a week of research i found myself feeling a bit foolish. The Autodesk Product Design Suite that i've been using has Mudbox as part of the package. So, I've been sitting on Mudbox this whole time. Sculptris is still great, but since Mudbox is part of the suite, i should probably be using it. Plus, it does have some pretty neat features. like sculpt layers.The workflow for moving the sculpted data between Mudbox and Inventor is totally ridiculous for a suite. Not much better than just using Sculptris and Inventor. Although, who in their right mind would be using Mudbox and Inventor at the same time? Just us Dr. Frankenstein types I guess. Anyway, let's get started.

There's 2 to 3 additional pieces of software needed to make a round trip from Inventor to Mudbox and back.At the bare minimum you will need
1) MeshLab,
2) AutoCad
If you have 3DS Max, there's some benefit to including it in the workflow. but for sake of simplicity we leave it out of the equation for now.

In the world of 3D there are a number of different types of objects.
The two we will be dealing with are Solids and Meshes.
Inventor creates and wants Solids.
Scluptris and Mudbox create Meshes.

I'm not going to pretend that I know a lot about 3D Meshes, because i don't. But, in their simplest form they are a series of points (vertexes) in a 3 dimensional space connected by lines (normals).
These vertexes and normals typically create a series of polygons or triangles that can be used to create a surface. In some cases the lines may be straight which creates facets (this is what inventor chokes on), but in other cases they may be curved to give smooth appearance to the model. Someone can correct me if I'm wrong but I believe the curved ones are called NURBS.

The second entity is the Solid. Solids are, or can be, a lot like meshes, with one important difference. The mesh that creates them is closed and filled with imaginary matter. Imagine the earth with the longitude and latitude lines painted on it. Those lines represent the mesh. The mesh is fully connected to itself. It doesn't detach at any point and drift off into space. It is a grid that is closed and connected to itself which creates a "water tight" surface. Beneath that surface is the soil, which makes the earth solid. Like the earth, any object that has a "water tight" mesh can be converted to a solid.

So, now that I've explained what we're dealing with here. Here is the workflow.
For additional detail, I've done video tutorials for both Part 1 and Part 2 of the workflow.

Please excuse the sound quality. I was using headphones for a mic, and I was a bit stuffed up from allergies.

Part 1: Inventor to Sculptris.
1) Export base mesh from inventor as an STL file.
2) Import STL into MeshLab
3) Export from MeshLab to OBJ.
4) Import OBJ into MudBox or Sculptris
After doing your sculpting in Sculptris or Mudbox  you can move on to getting it back into Inventor.

Part 2: Sculptris to Inventor
1) Export new OBJ file from Sculptrix / Mudbox
2) Open OBJ in MeshLab
3) Export from MeshLab as 3DS
4) Open AutoCAD, and set your environment to 3D Modeling
5) On the Insert Tab, choose Import and select your recently exported 3DS file.
6) Move to the Mesh Tab, and choose "Smooth Object" or type in CONVTOMESH
7) Again on the Mesh Tab, choose Convert to Surface or type CONVTOSURFACE
8) Save as DWG (2010 version).
9) Import DWG into Inventor.
10) Use the stich tool in Inventor to stitch the surfaces into a solid.

The videos are worth taking a look at, particularly for Part 2 of the workflow.
There are some choices to be made in the import and export dialogs which are explained in the video which may not be obvious at first glance.

Thanks for reading!

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