How do I convert PyBullet rigidbody position and orientation to something PyGLM/PyOpenGL can use and vice versa?

[Lollio64]

I've been trying for days use PyBullet as a physics engine for my game and I had some trouble displaying PyBullet's physics calculation. With weird rotations and position offsets being displayed in my OpenGL window (in relation to what is displayed in PyBullet's debug viewer). How do I correctly convert position/orientation data from PyBullet (for example getBasePositionAndOrientation()) to something PyOpenGL and PyGLM can use correctly and the opposite?

[Avithohol]

I used GLM math library, and basically created conversion functions in my physics class to return GLM types to see the positions/rotations. If i recall correctly, Bullet is row major in matricies, and GLM is column major by default.

[Lollio64]

How did you do it exactly? As I myself have also been trying to do that with PyGLM, to no usable result.

[ivan-enzhaev]

I use PyOpenGL with PySDL3 (https://pypi.org/project/PySDL3/) (PySDL3 is a lib for window, keyboard/mouse handlers and so on). I have not found a way how to use PyBullet with PyGLM and OpenGL. But Panda3D game framework has the Bullet Physics port to Python. I use Panda3D for Bullet Physics only. I draw graphics using OpenGL. The Panda3D version of Bullet Physics is very close to the original C++ version.

Simple Hello World example that creates a rigid body, the rigid body falls, position/orientation are print in the console:

pip install Panda3D

from panda3d.bullet import BulletWorld, BulletRigidBodyNode, BulletBoxShape
from panda3d.core import Vec3, Point3, Quat, TransformState
import time

# Setup the Physics World
world = BulletWorld()
world.set_gravity(Vec3(0, 0, -9.81))

# Create a Collision Shape (Box with half-extents 0.5)
shape = BulletBoxShape(Vec3(0.5, 0.5, 0.5))

# Create a Rigid Body
node = BulletRigidBodyNode("Box")
node.set_mass(1.0)
node.add_shape(shape)

# Set Initial Position and Orientation
p = Point3(0, 0, 10)     # Position
q = Quat.ident_quat()    # Orientation (No rotation)
s = Vec3(1, 1, 1)        # Scale (100%)

initial_transform = TransformState.make_pos_quat_scale(p, q, s)
node.set_transform(initial_transform)

# Attach to the world
world.attach_rigid_body(node)

print(f"{'Step':<5} | {'Z-Position':<12} | {'Quaternion (W, X, Y, Z)':<30}")
print("-" * 60)

# Physics Loop (Simulate falling for 2 seconds)
dt = 1.0 / 60.0
for i in range(120):
    world.do_physics(dt)
    
    # Get the current transform
    curr_transform = node.get_transform()
    pos = curr_transform.get_pos()
    quat = curr_transform.get_quat()
    
    # Print the coordinates
    # Quaternions are printed as (w, x, y, z) in Panda3D
    print(f"{i:<5} | {pos.get_z():<12.4f} | {quat}")
    
    time.sleep(dt)

This is more advanced example in OpenGL + PySDL3 + Panda3D's Bullet Physics:
box-edges-debug-drawer-bullet-physics-opengl-pysdl3.zip

pip install Panda3D PySDL3 numpy PyOpenGL Pillow PyGLM
py main.py

My examples in OpenGL, PySDL3 and Python: Aermoss/PySDL3#23