explination on this code pls..

General Discussion
#1

if (self.keyMap[“forward”]!=0):
backward = self.ralph.getNetTransform().getMat().getRow3(1)
backward.setZ(0)
backward.normalize()
self.ralph.setPos(self.ralph.getPos() - backward*(elapsed*5))

can some one explain briefly what this set of code is doing… im totally new to panda, python and programming in general… thxs in advance…

#2

You don’t need to understand this IMHO, the Roaming Ralph sample does it wayy too complicated.
The correct and simpler way to do it is:

if (self.keyMap["forward"]!=0):
  self.ralph.setY(self.ralph, elapsed*5)

This basically moves ralph over a distance of ‘elapsed*5’ over his own Y axis (meaning forward)

#3

It’s not necessary for roaming ralph but for some specific circumstances that code comes in handy, for example if you have a node and you’re interested its direction vector without the pitch.

backward = self.ralph.getNetTransform().getMat().getRow3(1)

getNetTransform().getMat() returns the total transformation of a node as a matrix. getRow3(1) returns the Y axis of the transformation matrix as a vector.

backward.setZ(0)

This ‘flattens’ the vector on the Z axis so that the vector is only applicable to the XY axis

backward.normalize()
self.ralph.setPos(self.ralph.getPos() - backward*(elapsed*5))

The normalize() method sets the length of the vector to 1. This vector is then applied to the position of ralph along with the delta time.

#4

thx…that was helpfull… :slight_smile: