Since -180 and 180 have the same effect, just go directly from 179 to -180 (or, more simply, from 359 to 0). Get rid of the slide object in your patch. Also note that you should really count 0 to 359, not 0 to 360, in order to get a smooth cyclic effect.

I suggest using a [counter 0 359] object, or applying a [% 360] object to any constantly increasing or decreasing series of rotation values. Here's an example:Example 37: Display a video on a plane in OpenGL

thanks a lot christopher (nice site)

i've tried to convert polar coord to cartesian coordinates, and it's works well