Python script lagging?

Question

I have a script that is attached to player it makes an empty follow to position of the character but when I run the game the empty is always deviating from the objects current position how do I fix that?

This is the script:

import bge
import mathutils

cont = bge.logic.getCurrentController()
soul = cont.owner

def main():

    scene = bge.logic.getCurrentScene()
    body = scene.objects['Player']
    sens = cont.sensors['always']
    bodRot = body.worldOrientation.to_euler().z
    solRotList = [soul.worldOrientation.to_euler().x, soul.worldOrientation.to_euler().y, bodRot]
    solRot = mathutils.Euler(solRotList).to_matrix()

    if sens.positive:
        soul.worldPosition = body.worldPosition
        soul.worldOrientation = solRot
    else:
        None

main()  

...

It works, but 'soul' takes time to follow the body (hence the 'delay' or 'lag'). The script is attached to an always sensor with True level triggering. I believe the lag is due to less frequency per frame of the script. How do I increase it?

Answer 1

That is impossible.

Process flow

Logic

You copy the position of the "master" object to a "slave" object. At that moment the positions matches.

Then the logic is done and the physics gets calculated.

Physics

It calculates a new position of the master object ... which is now different to the slave as this is not considered by the physics (otherwise your slave object or the master object or both would fly away as they occupy the same space).

Render

Due to the different positional changes (one from logic one from physics) both objects are rendered at two different positions (unless the master was not moving at all).

This is pretty good to see when you do that with cameras (Sky background scene), or objects that occupy nearly the same space (aura). You always get a noticeable one frame delay.

Solution

Hide the master object. Use two visible slaves. This way you still have the delay, but it is not visible anymore.

Answer 2

If you're trying to join two objects, have you considered parenting them? If you don't want to copy rotation, vertex parenting?

Normal parenting can be modified at run-time as well.

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Another possible solution is to stick the code moving the objects into a pre-draw callback. This way the code is executed just before the frame is drawn. However the game state in the pre-draw callback is a little weird. There is no bge.logic.getCurrentScene() or bge.logic.getCurrentController(), so you have to store nearly everything somewhere in your python module to be able to access it.