[OpenSCAD] Can you give me any rendering advice...?

Marius Kintel marius at kintel.net
Sat Dec 25 22:57:09 CET 2010

On Dec 10, 2010, at 12:56 PM, Dan Zuras 3D wrote:

> 	The fly in the ointment is that CGAL increases the
> 	rendering time by a lot for each object I add.  And
> 	I am no where near the number of objects I need.

I took a look at this and the reason why the F5 preview has issues is that the intersection operation causes the number of evaluated objects for OpenCSG to increase dramatically. We have implemented a safety measure where we don't render this preview if the number of objects after CSG normalization exceeds 1000. This could be made configurable in the GUI, but it would quickly become extremely slow to render the resulting CSG trees.
I'm not 100% familiar with the inner workings of the OpenCSG library, so it hard to say if it's possible to optimize this.

Also, the CGAL library used for geometric evaluation (F6) is extremely slow. This is a long-standing issue which I'm hoping to be able to address in the future, although it's not too trivial. I'm painfully aware of that this significantly limits the usefulness of OpenSCAD for large designs, or even certain types of smaller designs. In the next version of OpenSCAD, CGAL will be isolated into components which could be rewritten to other libraries, which would open for easier experimentation in case someone feels like picking up this issue.


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