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 Processing 1.0 _ALPHA_    Programming Questions & Help    Programs (Moderators: fry, REAS)    Helix Example « Previous topic | Next topic »

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 Author Topic: Helix Example  (Read 388 times)
fabsina

 Helix Example « on: May 31st, 2004, 11:51pm »

Hey!

I'm working with the Helix Typography Example of the Example Section and I don't really catch on some parts of the code responsible for moving the helix. What exactly is the offset value used for? I skippede the whole scrollbar-part and just want to make helixes move up and down and make them turn back at a certain point. I tried to use the offset value to control that but it doesn't seem to be the right parameter to use. I guess there is no documented version of this code available, is there? Do you have any advice?

m.
arielm

 Re: Helix Example « Reply #1 on: Jun 1st, 2004, 11:36am »

used to be friend with them (the helices!)

the good news with them is that they are linear (i.e. it's possible to predict the xyz location of any point, given a distance), unlike sinewaves or bezier curves...

all this makes continous movement (or writing) on helices relatively simple.

what you need to trace a given helix point at distance D is like:

Code:
 l = TWO_PI * turns; L = PI * turns * (r1 + r2); dz = h / l;   if (conical) {   r = sqrt(r1 * r1 + 2 * dr * D);   d = (r - r1) / dr; } else {   d = D / r; }   point(x - sin(d) * r, y + cos(d) * r, z + d * dz);

where:

x,y,z are the center point of the helix
h is the total height
turns is... the number of turns

the "conical" boolean value is here to avoid division-by-zero problems when an helix has a cylindrical shape (r1 = r2), it is computed this way:

conical = (abs(r1 - r2) > 0.5);

anyway, the Helix Typography example is not the simplier, you may be interested by these ones first:

http://www.chronotext.org/bits/014/

http://www.chronotext.org/bits/015/

http://www.chronotext.org/bits/016/

http://www.chronotext.org/bits/025/

a+

Ariel Malka | www.chronotext.org
fabsina

 Re: Helix Example « Reply #2 on: Jun 2nd, 2004, 12:22pm »

Thanks! I think I have them pretty much under control now!

Martina
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