Fire propagation script errors

Game Engine Game Engine Support and Discussion
1

I’m trying to develop a method for spreading fire along a ground plane, like so:

  • A “fireball” is launched
  • When it hits the ground, it spawns a piece of “firewood”
  • After a pause, the firewood spreads in a grid fashion, to adjacent squares
  • These new pieces of firewood will again spread in similar fashion

However, the python script for my blocks of firewood creates errors after spawning the second generation of firewood.

I wrote a finite state machine within a class called Firewood, with this basic structure:

class Firewood(types.KX_GameObject):

	def __init__(self, own):
		self.main = self.state_idle
		
	def state_idle(self):
		foo

...

def main(cont):
	own = cont.owner

	if not "init" in own:
		own["init"] = True
		own = Firewood(own)

	own.main()

However, the second generation of firewood spawns and gives this attribute error:

Python script error - object 'firewood', controller 'Python':
Traceback (most recent call last):
  File "C:\...\fire_propogation\firewood.py", line 94, in main
    own.main()
AttributeError: 'KX_GameObject' object has no attribute 'main'

Does the game engine not play nicely when objects use the same code? Am I making a logic error in how I control the firewood’s state changes?

Attachments

fire_prop.zip (90.8 KB)

2

Don’t use the instantAddObject actuator method (actually, you can get rid of the actuator completely) - It seems to do some really bizarre property copy tricks, so when you create a new instance, it already carries the “init” property, meaning that the Firewood re-instance doesn’t happen, and that’s why main doesn’t exist.

It might be a bug, but I’m not sure.

Use scene.addObject instead:


# Add a firewood
scene = logic.getCurrentScene()
fire_obj = scene.addObject("firewood", self)

That should work properly.

*Edit

Try to avoid posting .zip files in the future. Make your scripts internal, and just post the .blend.

Make it as easy as possible for us.

3

Thanks for the help and advice! Problem solved.

4

I suggest to improve your Python code:


class Firewood(types.KX_GameObject):

	def __init__(self, own):
		self.main = self.state_idle
		
	def state_idle(self):
		foo
...
def init(cont):
  Firewood(own)

def performSomething(cont):
  ...
def performSomethingElse(cont):
  ...

Simply trigger the init-EntryPoint first.
This is much better than fiddling around with needless init-properties.