Panda3D Game Loop

General Discussion
1

Can anyone point me towards documentation about how the Panda3D game loop works internally? I know about extending DirectObject and calling .run() which runs the taskMgr. However, I’d like to find out everything that happens in a given Panda3D loop.

Thanks.

Matt

2

I dunno for sure, perhaps this page is of help for you?

~powerpup118

3

Hey, welcome to the forums! :slight_smile:

Basically, run() invokes base.taskMgr.run(), which polls the task manager in a continuous loop.

If you want to see what exactly happens inside it, you should look at which tasks are registered. I think you can do so by simply typing “print base.taskMgr”.

4

powerpup118 and rdb, thank you for your timely responses - they were both helpful.

I did go ahead and try printing out the TaskManager info and received the following details:

Task sort

resetPrevTransform -51
dataLoop -50
eventManager 0
ivalLoop 20
collisionLoop 30
igLoop 50
audioLoop 60

I really don’t know what tasks 1,2,4,6 and do. I would guess resetPrevTransform is simply acting on the graphics state to bring the rendering system back to the origin…but who knows. Maybe dataLoop repopulates the vertex/shader information? Just out of curiosity, anyone actually know those 4 tasks are responsible for?

Thanks.

Matt

5

You can look in direct/showbase/ShowBase.py and see for yourself how the tasks work and what they do.

6

For any future passerby of this thread who is also curious about these tasks, here are the descriptions of the tasks:

def __resetPrevTransform(self, state):
# Clear out the previous velocity deltas now, after we have
# rendered (the previous frame).  We do this after the render,
# so that we have a chance to draw a representation of spheres
# along with their velocities.  At the beginning of the frame
# really means after the command prompt, which allows the user
# to interactively query these deltas meaningfully.


def __dataLoop(self, state):
# traverse the data graph.  This reads all the control
# inputs (from the mouse and keyboard, for instance) and also
# directly acts upon them (for instance, to move the avatar).

def __ivalLoop(self, state):
# Execute all intervals in the global ivalMgr.

def __shadowCollisionLoop(self, state):
# run the collision traversal if we have a
# CollisionTraverser set.

def __collisionLoop(self, state):
# run the collision traversal if we have a
# CollisionTraverser set.

def __audioLoop(self, state):
    if (self.musicManager != None):
        self.musicManager.update()
    for x in self.sfxManagerList:
        x.update()
    return Task.cont

def __igLoop(self, state):
# We render the watch variables for the onScreenDebug as soon
# as we reasonably can before the renderFrame().