# [Chimera-users] axis - length

Elaine Meng meng at cgl.ucsf.edu
Fri Jul 14 16:28:24 PDT 2017

```Hi Catherine,
It’s just standard geometry to find the second point farther away on the same line.  First you would need to know how much longer you want the line (cylinder).  If the two points that you have now are are x1,y1,z1 and x2,y2,z2, find

a = x2 - x1
b = y2 - y1
c = z2 - z1

Then multiply a,b,c by the factor (if you want 2x as long, multiply by two) and add them back to x1,y1,z1 to get the new other end of the cylinder.

BILD format:
<http://plato.cgl.ucsf.edu/chimera/docs/UsersGuide/bild.html>

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Jul 14, 2017, at 2:37 PM, Catherine Jenifer Rajam Rajendran <catrajen at umail.iu.edu> wrote:
>
> Hi,
> I am trying to display an axis in chimera. I have one point - x,y,z co-ordinates and centroid's x,y,z co-ordinates. I want to extend the length of the axis generated using this two points. I tried to create a bild format file.
>
> .cylinder 0.584 0.048 0.810 20.912 5.823 19.703 1
>
> where, second 3 co-ordinates are centroid. It creates an axis but i want to extend the length from centroid point to the other end too. Or, Is there any other way to define it? Please help me.
> Thanks,
> Catherine

```