render.AddBeam questions

[etcetc]

So, I am trying to make a gun which shoots out a double helix effect like DNA. I figured to try and use the render.AddBeam function in order to do this.

I have a few questions for render.AddBeam:

render.AddBeam( point, width, texture coordinate, color )

I am confused about the third argument (texture coordinate) and what it does. In the example script, it is defined to be "tcoord", which basically is

local tcoord = CurTime() + ( 1 / 12 ) * i;

I have no idea why the argument would be the current time. Can anyone help explain?

One more thing, how do I draw the beams?