"Bob Hughes" <omniverse@charter%net> wrote:
> The period (second number after x,y,z) can be negative to turn it the other
> direction. Could also use just one f_helix1 by specifying 2 as the first
> number to double the strand. And... if 2 is used for the 3rd to last number
> (said to be the type) then that will make it square for a ribbon-like
> appearance when using a 45 degree rotation as the last parameter, should
> look much like many illustrations show it.
>
> Bob H

Thanks! I thought I tried putting negatives everywhere, but that certainly
works. The only issue with using the 2 in the fhelix1 function for the two
strand is that there doesn't appear to be a way to change phase of the
strands. For biological correctness, DNA has alternating major and minor
grooves (see my first example). It was simple enough to make two identical
backbones and rotate one 120 degrees to set the proper phase.

Thanks for the help.

--paul

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