 |
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
r1,r2 are the starting/ending radii
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
|
|
|
|
|
|
