Is there a way to spawn multiple instances of Panda3D, or at least the Bullet phyics?

Scripting Issues
1

I’m using Panda3D with Bullet as a 6DOF environment for Reinforcement Learning with Stable Baselines. In order to effectively train agents I want to execute multiple instances in parallel. Showbase doesn’t allow multiple instances to be spawned, but I never need to visualize more than one instance at a time.

So I’m trying to make ShowBase optional. But without Showbase, I don’t have the render nodepath to which all my phyics objects attach. Is there a way to run only bullet without Showbase? Or is there a way to get multiple Showbase instances after all? Or a different solution entirely?

Thank you.

2

Unless Bullet prohibits this, it seems to me that you could simply keep multiple BulletWorlds, updated in some task or other. These could be associated with separate scene-graphs disconnected from “render”, attached there only when you want to visualise one or another scene.

Something like this (in sketch):

class MySim(ShowBase):
    def __init__(self):
        # All the usual ShowBase and app-startup stuff here,
        # omitted for brevity

        self.worlds = []
        for i in range(NUM_WORLDS):
           world = BulletWorld()
           root = NodePath(PandaNode("world root"))
           self.worlds.append((world, root))

           # More initialisation here...

    # This may not be the ideal way to do the following;
    # I'm doing it this way for simplicity and example
    def addCollisionNPToWorld(self, worldIndex, nodePath):
        world, root = self.worlds[worldIndex]
        nodePath.reparentTo(root)
        world.attach(nodePath.node())

    def update(self, task):
        for world, root in self.worlds:
            world.doPhysics('''<Whatever parameters you intend>''')
        return task.cont

There might be more work to be done if any sort of culling of visible geometry is required, but that may be soluble in some way, I think.

3

Thank you for the pitch, that helped me a great deal. I ended up implementing it a bit differently because I need the instances to be created as individual classes. If rendering is needed I create my showbase class normally and if not, I just never call showbase.init() and the bullet nodes will be attached to a root node.

Again thanks!

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