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Creating A Constant Pitch Helical Line In Gridgen

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Old   July 31, 2007, 00:13
Default Creating A Constant Pitch Helical Line In Gridgen
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John Hinkey
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I'm trying to create a constant pitch helical line on the surface of a database cylinder using Gridgen. I've tried several ways of doing this, but none of them give a true constant pitch helix - close, but not close enough for griding. Anyone out there have any experience doing this type of thing in Gridgen?

Thanks - John
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Old   August 4, 2007, 13:58
Default Re: Creating A Constant Pitch Helical Line In Grid
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John Chawner
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John,

One way to do this is as follows. All the steps can be done in a Glyph script or you can just generate the points in the script and do the rest interactively.

1. Using a Glyph script, compute points on the helix using the standard analytical definition of the helix (e.g. Wikipedia). Either create a db line from these points or export them to a segment file. Use a large number of points.

2. Create a 360 degree surface of revolution of the desired radius and length.

3. Use cylindrical projection (from the cylinder's axis) to project the helix onto the cylinder.

There also is probably a way to do this analytically. That is, create a surface of revolution and then create a line directly on the surface by computing the points on the helix in the surface's (u,v) space.

Hope this helps. If not, please contact our Tech Support at support@pointwise.com.
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Old   August 5, 2007, 00:01
Default Re: Creating A Constant Pitch Helical Line In Grid
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John Hinkey
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Thanks John -

Your good folks at Pointwise have already found some work-arounds for me. If anybody wants the details of these let me know.

- John
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