How do I get inertia rotation?

Hi, guys!

I have been trying to achieve a rotation with momentum (inertia).

It's about a submarine (top down perspective). Rotating must be smooth (I achieve this) but it's not slowing down until stops when key/stick is not being pressed anymore.

Using anglediff or anglelerp on this code didn't do the trick:

anglelerp(self.Angle,angle(0,0,gamepad.axis(0,2),gamepad.axis(0,3)),1*dt)

OR

anglediff(self.Angle,angle(0,0,gamepad.axis(0,2),gamepad.axis(0,3)))*(dt)

Could you help with this? (It could be keyboard instead of gamepad, of course).

Giving something momentum basically means you give it velocity and instead of changing the position or angle, you’d change the velocity.

It’s pretty popular to use lerp() to do an ease out but I don’t think that’s suitable to use with momentum.

So you’d add a angvel variable to the sprite and then one way you can change the angular velocity is with a damped spring. Diff is the signed angle difference which is like the anglediff() expression but it’s negative if ccw. In the expression that sets the angvel you’ll see 0.1. You can change those in the range of 0-1 to adjust the spring stiffness and the amount of damping.

Var diff=0

Compare: dt>0

— set diff to sprite.angle-angle(0,0,gamepad.axis(0,2),gamepad.axis(0,3))

— set diff to angle(0,0,cos(diff),sin(diff))

— sprite: add -0.1*diff/dt-0.1*self.angvel to angvel

— sprite: rotate self.angvel*dt degrees clockwise.