atan2 problem

[PGUp]

hi, so i have a problem with atan2, i want to make my rectangle to face mouse and rotate towards it, i try to use atan2, but it didnt work, it shows a very weird movement instead,

(in the update function)
angle = angle + math.atan2(y - love.mouse.getY, love.mouse.getX() - x) * dt
end

the rotation is uncontrollable

[raidho36]

That's because you're adding up to rotation angle every frame. What you need to do is to apply it as is.

[ivan]

Yes, like raidho said, it should be:

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target_angle = math.atan2(y - love.mouse.getY, love.mouse.getX() - x)

If you're looking for gradual rotation they you need the find the arc between the "current" and "target" angle.

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arc = (current_angle - target_angle + math.pi)%(2*math.pi) - math.pi

Just make sure to check if the "current angle" is near the target to avoid jitter (and division by 0):

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if math.abs(arc) < rotation_speed*dt then
  -- already facing the target!
  return
end

Then you can normalize the arc and use that to rotate at a constant speed:

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direction = arc/math.abs(arc)
current_angle = current_angle + direction*rotation_speed*dt