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Resizing Pyramids?

Posted: Thu Mar 27, 2014 11:18 pm
by Philip
Hi,

I can't figure out how to resize the Johnson Solid - Square Pyramid. What option do I use in the Scale menu?
Non-uniform Scale was the only one that changed the shape. I looked in the GS manual too but couldn't find anything.

I want to create a pyramid with specific base to top edge length ratios.

Any help is appreciated.

Philip

Posted: Fri Mar 28, 2014 5:08 pm
by Peter Kane
Hi Phillip,

In the stretch (Non-uniform Scale) dialog box, I just selected the "Scale by" option and changed the value from 1 to 2. That increased the height of the triangular faces, leaving the base unchanged.

Pete K

Posted: Sun Mar 30, 2014 11:49 am
by robertw
The other options on the scale menu don't make a visual change on the screen, unless you have edge lengths displayed on the net etc, but the scale is changed, which shows up if you print nets or use Measurement Mode.

So start with J1, scale edges to the base length, then use non-uniform scale to get the height you want.

If you're more courageous and want to set the length of edges to the apex directly, try the following. Start with a cube, scale edges to the length you want the edges around the base of the pyramid. Use "Poly->Augment Polyhedron" (or hit "a") and select these options: Pyramid, "Edge Length = 1" for the pyramid height, and set "Scale" to whatever length you want the remaining edges of the pyramid. Choose "Selected face only" and hit OK. Then hit Enter to accept the augmentation preview. Now you have the pyramid you wanted atop a cube. To get rid of the cube at the bottom, select one of the remaining faces of the cube and use augmentation mode again, but this time tell it to excavate, and select either a prism (a square prism is a cube) or just enter "c" (or "cube") in the Built-in Model field.

Rob.