Hi
I got several prombles on recent stduy
I read the code in KeyLookDownAction.class (package com.jme.input.action)
public void performAction(InputActionEvent evt) {
incr.fromAngleNormalAxis(speed * evt.getTime(), camera.getLeft());
incr.mult(camera.getLeft(), camera.getLeft());
incr.mult(camera.getDirection(), camera.getDirection());
incr.mult(camera.getUp(), camera.getUp());
camera.normalize();
camera.update();
}
i draw a picture about my understand, here it is:

the incr.fromAngleNormalAxis(speed * evt.getTime(), camera.getLeft()); just initialization the matrix with the angle which should turn down.
incr.mult(camera.getLeft(), camera.getLeft());
incr.mult(camera.getDirection(), camera.getDirection());
incr.mult(camera.getUp(), camera.getUp());
those codes just turn the aix,
ex:
incr.mult(camera.getLeft(), camera.getLeft()); turn the lefe_aix to the new left_aix(in the picture)
here my question:
1`
this action is design for use the Mouse Move Delta(dy---> Mouse.newX-Mouse.oldX) to turn the Camera down
so:
if the action only turn the Camera down
why use incr.mult(camera.getLeft(), camera.getLeft());?
in my theoretics it dosn't change anything.
2`
the fromAngleNormalAxis just used this expressions

why just use this expressions

:? Help me Thanks a lot