best practice for Panda run()

C++ coding using Panda3D
1

Hi guys,

I’m wondering what’s the best way to implement the equivalent panda3D for python ‘run()’
in a C++ code.

Especially in term of keeping alive the main code while the async tasks are running.

Is a ‘Sleep(time)’ recommended to avoid unecessary CPU load or does it slow Panda execution ??

Is there a smart way to cope with this ?

// simple C++ panda bone
	
#includes ...

PandaFramework	framework;

// ... various functions ...
	
int main(int argc, char *argv[]) { 

	framework.open_framework(argc, argv);	// open a new window framework

	// ...
	// ... whatever application code ...
	// ...
	
// various asynchronous tasks
	taskMgr->add(new GenericAsyncTask("task1", &task1, (void*) NULL));
	// ...
	taskMgr->add(new GenericAsyncTask("taskn", &taskn, (void*) NULL));
	
	// *** execution loop ***
	Thread *current_thread = Thread::get_current_thread();
	while(framework.do_frame(current_thread)) {
		Sleep(20);						// sleep for 20 milliseconds *** ?
	}

	framework.close_framework();			// close the windows framework
	return (0);
}

Is the ‘do_frame()’ blocking ?

2

Hi

Did you know about framework.main_loop(); ?
That’s all you need to do, unless you were planning on doing something fancy and need more control.

example main

int main(int argc, char *argv[]) {

PandaFramework framework;
framework.open_framework(argc, argv);

// stuff

framework.main_loop();

framework.close_framework();

return (0);

}

3

Hi Tah,
Thank you again.

The point is that I’m trying to interleave Panda execution within a Directshow filter, and I’m encountering timing/synchronization issues.

So, I guess my question actually should have been: how to control simulation steps in Panda c++ ?

4

Sorry, I should have known it was something fancy… ha

By any chance did you change your sync_video in the config file to 0 or #f ? By default sync_video is set true so frame rate can’t exceed 60 fps.

Not sure if that’s the problem…

5

Tried it… seems to eat more CPU power for nothing.

I’ll try and dig into how to control a Panda simulation step from an external program.
All this should be tied one way or another to managing a round robin real time event wheel or some sort of stuff.

6

Well, Panda’s task system isn’t meant to be a real-time scheduler. But very few task systems are, really. If you really need real-time scheduling guarantees, you’ll have to provide that scheduler yourself, and call frame->do_frame() once per epoch within that system.

But for most needs, it’s usually sufficient to let Panda run the main loop, and simply add a task to call your DirectShow filter once per frame. Of course, your task will only get called once per frame, which will be every 1/60 sec if you are generating 60fps. You have to be sure your task can handle that kind of timing.

David