XANSYS Message: 16526 [Go back to message list] [bookmark on del.icio.us]
No rating yet Subject: Re: IGES import with subsequent creation of a Solid model Author: Mitch Voehl Date: 2000-10-12 00:05:00John Crawford wrote:
> I seem to remember that XOX entered the ANSYS universe when 5.0 hit the > streets in 1991 or 1992. ANSYS wanted a smarter modeler than the one they > had in 4.X and instead of starting over they obtained the XOX engine and > integrated it's boolean functionality within ANSYS.
That's my recollection as well, but then my recollection is getting a little fuzzy...
> The big problem is that > native ANSYS geometry is in one form (b-spline, nurb, whatever...) and XOX > wants something else, so every time ANSYS performs a boolean it has to > translate native ANSYS geometry into XOXese (for lack of a better term), > have XOX import it and do the boolean, then export the booleaned entities > and translate them back into ANSYSese. It doesn't take a rocket scientist > (although I'm sure several are reading this) to see that there are 3 places > for failure to occur in this process; the first translation, the boolean > operation itself, and the second translation. After you consider all that > goes on beneath the sheets, it's not suprising that we see "Change BTOL and > try again" as often as we do. I sometimes find it hard to believe that > we've been having this kind of fun for 8 or9 years now.
My how the time flies when we are having fun...
Sheldon Imaoka wrote:
> > Hmmm, if the ANSYS standard modeler has its own set of Boolean > > operations, what purpose has the XOX modeler served over all of these > > past years? It is my impression that ANSYS started using XOX many years > > ago, perhaps in the late 4.x revs or at least in the early 5.x revs.
> As a stab in the dark, I think there is a difference between "SHAPES" > and "SHAPES MT" from XOX Corp. The latter is what I've been referring to in > my previous posting and what I call the "Shapes modeler", although I guess I > should call it by its official name, SHAPES MT (Shapes MicroTopology). > Since SHAPES MT is an extension (?) of SHAPES, maybe ANSYS had the SHAPES > engine long ago, then added the SHAPES MT kernel for default IGES/CK w/ > defeaturing.
Interesting, I was unaware of the distinction between SHAPES and SHAPES MT. I appreciate the clarification.
Now, after having perused the XOX web page at the kind suggestion of John and Sheldon, I have yet another question for the folks at ANSYS, Inc. The XOX description of SHAPES MicroTopology states:
"Highly Efficient and Robust Booleans:
One of the most problematic aspects of geometric modeling systems is their proclivity to fail when intersecting surfaces with "touchy" configurations. SHAPES MicroTopology allows the Boolean algorithms to treat patches as flat triangles and rectangles since data is frequently in that form anyway. The Boolean algorithms for web-surfaces then exploit the simplicity of the flat triangles and rectangles and result in robust and fast Boolean algorithms."
So, if SHAPES MicroTopology has the ability to perform Booleans ("robust and fast", no less), and if the "allow defeaturing" geometry import option is storing the geometry in the SHAPES MicroTopology format, why can't we do boolean operations on the imported "defeaturable" geometry?
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