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NEWS FLASH: taper extruding rounded rectangles with Zero cm radius corners crashes VW, too.

I'm just baffled by the fact that anyone:

a) is attempting to taper extrude a ROUNDED RECTANGLE with a corner radius of zero;

b) is surprised that creating an object that requires dividing by zero crashes VW; and

c) would fault Nemetschek for not forseeing someone would be dumb enough to try to create a ROUNDED RECTANGLE with a corner radius of Zero and try to taper extrude it.

Sorry, but in my book, this one gets filed in the category of "It's impossible to make something idiot-proof, because the universe keeps making better idiots."

So what about people who design molds for thermoformed and injection molded plastic parts? Are you saying that they are all idiots? Or dumb enough to create a mold profile with rounded corners and a 2 degree taper, and running what-if scenarios for molds with corner radii ranging from 1" radius down to square corners? Are you saying they are idiots for trying to reproduce a number of possible toolpaths quickly for a CNC mill cutting with a 2 degree taper end mill? Dumb enough to try something that is faster than editing polyline vertices?

If we are designing an injection mold or a thermoforming mold, we are working with tapered extrusions, almost always. And we are working with rounded corners on rectangular shapes, almost always. But sometimes we have to visuallize the difference between a mold with rounded corners and a mold with sharp corners.

In Solidworks or Inventor (or most any parametric modeling app), you can drive the corner radii of the profile with one common radius parameter. You can then change that radius parameter to 0 or any other value within reason, and Solidworks or Inventor will update the geometry accordingly.

Perhaps you should find out what designers are trying to accomplish before you say we are idiots who are dumb enough to try to do something a certain way.

Also, please explain how this is a divide by zero crash.

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Rick, I think what Fsung is trying to point out is that division by zero gives a result of infinity which the program then can't deal with - hence the crash.

Dividing by zero causing problems is an issue which is almost as old as computer programming and it should not cause VW to crash.

I think the points you make that it should be possible to have a tapered extrude with a directly variable radius parameter (ie not having to go back and edit the 2D geometry) is very relevant. That would be a great addition of capability, and as you state the radii must be variable from zero upwards.

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Simply stated... divide by zero is a valid event and therefore requires a valid response.

In this limited instance VW crashes for the lack of a valid response not because of an invalid event.

I would argue that any event for which the result is indeterminate, as is the case of divide by zero, is NOT a valid event(NB: the quotient of divide by zero is NOT infinity; it is indeterminable) but the philosophical issue aside, I DO get a valid response when in this limited instance (see screenshot above).

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While the situation you describe is a common one, it is not the one specified by the OP.

Go back and re-read the conditions specified by the OP again carefully. The conditions do NOT specify a rounded corner of radius > 0 tapering down to a square corner: they specify a Zero radius corner as the initial condition tapering down to a zero radius corner, i.e., rectangle to rectangle, not rounded rectangle to rectangle.

Are there situations in which a designer might want or need to taper an extrued from a right angle corner to a radius > 0 corner? Possibly; so the capability you describe would indeed be nice addition. But the fact that the conditions specified in the OP crash every version of VW going back to 8.0 (not simply 9.0, as fsung observed), regardless of OS, suggests how rarely that situation arises, and how non-obvious those situations would be to identify for someone who does NOT need to do that as a matter of routine.

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