Animate a loft

[jeremy.cui]

Hi, does anyone know the easiest way to achive this:

I have a cut view of a device, within the device I want to show an animation of the path a laser will take through the device bouncing off of mirrors.

Right now there is a complex path in which I lofted a circle onto to represent the beam. I tried animating the slice tool, however since the cut plane expands the entire model, it cuts off the beam in places I don't want.

I saw a tutorial on animating the scale deformation, but there is probably another simple way that I am overlooking. Can anyone help with this and explain what I can do?

Thanks!

[CAMedeck]

I'd animate the opacity of the material.  If this is created as a Loft, than it can generate UVW coordinates that follow the shape.  You could use a Gradient Ramp that has an animated color that moves from Black to White, making the material opacity change along the Loft as the gradient changes.

[BenBisares]

Alternately you can animate a path deform. Basically you make a straight cylinder and a path in the intended shape. You then apply the "Path Deform (WSM)" modifier on the cylinder and then pick the path from the modifier's attributes. Last thing would be to animate the percentage attribute. See my attachement (Saved as a 2013 scene).

Since the object is being deformed along the path and not extruded you'll have to do something about the start of the animation but there are a couple of simple ways to handle that.