Create a radial wipe on a plane

Question

I have a plane with the following material on it

But, I wish to create a radial wipe kinda effect on the plane. Any idea how I can go about doing so?

Answer 1

You can split the generated coordinates to get the X position:

And Y position:

Based on those you can calculate an angle:

As you can probably see, it's an angle around the bottom left corner, because that corner has coordinates X:0; Y:0. In order to fix that, you have to convert the ranges of the coordinates from 0..1 to -1..1 (- 0.5 = -0.5..0.5 *2 = -1..1) or using Object coordinate instead, since the origin point of your plane is in the center:

Half of it is black, because the result of the Arctan2 node is in range of all possible angles expressed in radians, so from roughly -3.14 rad (-180°) to roughly +3.14 rad (+180°). You could use the Math node in "To Degrees" mode to get -180..180 range, divide by 360 for -0.5..0.5 and add 0.5 for 0..1 And then scale it down (so divide again) to the actual size of the transition you want to achieve and add an offset based on the frame (or custom property), but it would be a little redundant and you can get away with much less nodes:

Multiply image alpha by it and you're done.