First to base everything on sphere1 S(x1,y1,z1) as the origin and transalate later.

that means S2 is centered on (x2-x1,y2-y1,z2-z1) which is also the direction and length of the cylinder. (So I get a length of 2 2 2 sqrt( (x2-x1) + (y2-y1) + (z2-z1) )

How you get your length formula is interesting, it looks like using the in-product without the angle component.

angle with respect to the xy plane: arctan((y2-y1)/(x2-x1)) xz plane arctan ((z2-z1)/(x2-x1)).

This is what is needed to calculate the angles. And transalate over (x1,x2,x3) when you are done.

Or you can use [rotate] with the (x2-x1, y2-y1,z2-z1) vector. No need to calculate the angles. And then translate to S1.

Hope this helps

Gerard

Hi,

I'm having a little trouble conceptually with trigonometric concepts in gem. Any hints of tutorials or examples that could help me with the following problem would be really useful.

Imagine that I have two spheres, translated in XYZ to random positions (let's assume (x1,y1,x1) and (x2,y2,z2).

I want to put a cylinder to join the two, and make the cylinder move with the spheres (in other words, imagine the cylinder is a rubber band stretched between the two spheres.)

Calculating the length of the cylinder (which I change with scaleXYZ) is not very difficult, I can obtain it with sqrt (x2 * x1 + y2 * y1 + z2 * z1).

The tricky part, on the other hand is finding the correct amount of rotation in xyz for the cylinder, and the correct displacement.

Thanks in advance.

• martin

---

PD-list mailing list PD-list@iem.at http://iem.at/cgi-bin/mailman/listinfo/pd-list