3D Interoperability

[hanabear]

Hello.

I would like to know how people are solving the model dimension error issues.

In my application, I was using the autohealing api to recover face normal direction automatically with iges model, since it was easy and acceptable.

And it solved some problems due to the model check errors, too.

But, I found that auto-healing process could change the model dimensions recently.

Though it was smaller than the maximum tolerance (1.0) of auto-healinig process, I think 1.0 is too big for the mechanical design.

So, I am trying to get the information what I should consider for the healing of the model.

1. Do you use the recommended healing workflow of help document? Is it best way to solve the errors in model topology?

2. What can(should) I do to preserve the original model dimension as accurate as possible, when translating cad model with InterOp and healing the model?

3. When the tightening gaps operation is necessary? Is it okay to ignore if I don't care about the gap? Which api is related with the gaps?

Thanks,

Hanabear

Message Edited by hanabear on 09-19-2007 11:46 AM

[Stacey]

Hello,

Since it sounds like you are translating an IGES model using InterOp, it is always recommended to use the InterOp healing functionality during translation.  During the translation process, the algorithms have information about the origin of the data.  This allows InterOp healing to fix some problems more effectively than can be automated by ACIS healing without this data knowledge. 

InterOp healing is controlled by the "Healing" option in the Connect interface. This type of healing includes surface trimming, splitting at discontinuities, removal of sliver edges and faces, removal of duplicate vertices, edge and face sense correction, and tolerant topology improvement.

Whether additional healing is needed then depends on the quality of the model after InterOp translation and healing and the downstream requirements for the model.  At this point, we often recommend the workflow outlined in the online help, which calls for performing tolerant stitching, simplification, and tightening of gaps. (It may be notable here that these are the steps performed in the autoheal API, but calling the individual steps allows for greater control of tolerances, as well as allows users to eliminate steps that are not right for them.)

Without specifics about requirements, the basic outline might be summed up as follows:

Usage                  Recommendation

 

Visualization        Translate without healing

 

CAE                     Translate with the healing option TRUE and post-process with ACIS Stitching

 

CAD/CAM            Translate with healing option TRUE and post-process with ACIS Stitching, Simplification, and Gap Tightening

These recommendations are generalized based on the difficulty of the downstream operations expected, and should be tailored to an individual's specific needs.

Gap tightening attempts to fill in model gaps with actual geometry by extending surrounding surfaces.  To address your final question, gap tightening is necessary only when the their size is too large for your downstream needs.  (For instance, a CNC operation may have a max tolerance of 1e-3, and if the gaps in the model exceed that, they may need to be filled in to provide the geometry the algorithm requires.)  However, if the desire is to improve the quality of the model for downstream modeling operations, tolerant topology is sufficient, and often preferable due to not increasing model complexity.

Best Regards,
Stacey