In the previous post we reviewed the problems users were encountering with the CAD Integration feature set in Visio 2003 and the fixes that were made in Visio 2007. In this post we look at the remaining issues with CAD and Visio.
Converting CAD drawings to Visio shapes
Visio 2003 changed the way that CAD drawings are converted to Visio shapes. Instead of converting each entity and adding it as a Visio shape, the entities are converted in bulk to an intermediate document and then the entire document is merged into the current drawing in one big Paste operation. This change makes conversion up to 10 times faster – a significant improvement. However, Visio now requires quite a bit more memory to accomplish the task. On PCs without sufficient memory, performance degrades because Visio must page memory to disk.
Additionally we have found that some really large CAD files fail to convert. There is a limit to the number of entities that can be converted at once, though this limit is not easily expressed as a quantifiable number. Unfortunately the failure comes near the end of the lengthy operation rather than at the beginning. Visio 2007 does not remedy this situation. Your best bet is to divide up the diagram into more layers and then convert the layers individually. While Visio should handle this situation better, keep in mind that CAD programs are designed to deal with hundreds of thousands of simple entities and Visio is designed to deal with thousands of complex entities. It's difficult to scale up to support the largest CAD drawings out there. Simplifying the drawing before bringing it into Visio is recommended.
DWG file formats supported by Visio
A frequent complaint from users is that Visio refuses to open a DWG file because it was saved in a newer format. Visio 2003 and 2007 do not support the latest file formats used in AutoCAD programs. That means CAD files must be saved back to a compatible version before they can be used with Visio. Visio 2003 and 2007 support the R15 version of the DWG format. This was the default format used by AutoCAD 2000 and AutoCAD 2002. Newer versions of AutoCAD save to newer versions of the DWG format by default.
Additionally, Visio does not support all the entities defined in the R15 version of the DWG format. In terms of entity support, Visio handles the entities defined in the R14 version of the DWG format with a few exceptions. A specific entity list is beyond the scope of this blog post. The point is that the level of entity support and the version of the file format supported are not identical.
Note that there was a specific problem where files saved out from AutoCAD 2007 would not open in Visio 2007 even when saved back to the R15 format. This was corrected in Visio 2007 SP1.
What's next for CAD integration
It's too soon to announce our plans for the next release. We continue to gather information from customers about their needs for CAD with Visio. Your input on specific issues or the overall importance of CAD integration to your Visio usage is encouraged.