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. 

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