How do I determine a value from an angle (radio tuner simulation) ?

Hello,

I'm trying to simulate a radio receiver.

Here's how it works : the needle rotates around its axis. In the following image, theres a network broadcasting from the position where the red dot is (90°). When needle angle is 90°, volume is at its max (0 db). When needle moves away from 90° (ie to 85° or 95°, ie 90°±5°), volume decreases and reaches silence (-20) when 85° or 95° is reached.

How can I do that ? I knwo angle math is involved but I have issues dealing with the "90°±5°" part.

I even tried an approach using positionning sounds (using the blue dot as a receiver and red dot as a emitter) but it is not very flexible.

Well in construct the red dot is at angle 0 from the center of the needle. You can then use the anglediff() expression to get the difference between two angles. And to make it -20 at five just multiply by -4

Volume =-4* anglediff(0, needle.angle)

Or if you just want to use the position of the red dot instead of an angle

Volume = -4*anglediff(angle(needle.x,needle.y,red.x,red.y), needle.angle)

Wonderful ! Thank you very much.

the first solution works very well but there seem to have a problem with the second where the comparison should maybe be made with angle between blue dot and red dot from the rotation center of the needle. What do you think ?

It should be the same.