"""Hello world for Sapien.
Concepts:
- Engine and scene
- Renderer, viewer, lighting
- Run a simulation loop
Notes:
- For one process, you can only create one engine and one renderer.
"""
import sapien.core as sapien
from sapien.utils import Viewer
import numpy as np
[docs]def main():
engine = sapien.Engine() # Create a physical simulation engine
renderer = sapien.SapienRenderer() # Create a renderer
engine.set_renderer(renderer) # Bind the renderer and the engine
scene = engine.create_scene() # Create an instance of simulation world (aka scene)
scene.set_timestep(1 / 100.0) # Set the simulation frequency
# NOTE: How to build actors (rigid bodies) is elaborated in create_actors.py
scene.add_ground(altitude=0) # Add a ground
actor_builder = scene.create_actor_builder()
actor_builder.add_box_collision(half_size=[0.5, 0.5, 0.5])
actor_builder.add_box_visual(half_size=[0.5, 0.5, 0.5], color=[1., 0., 0.])
box = actor_builder.build(name='box') # Add a box
box.set_pose(sapien.Pose(p=[0, 0, 0.5]))
# Add some lights so that you can observe the scene
scene.set_ambient_light([0.5, 0.5, 0.5])
scene.add_directional_light([0, 1, -1], [0.5, 0.5, 0.5])
viewer = Viewer(renderer) # Create a viewer (window)
viewer.set_scene(scene) # Bind the viewer and the scene
# The coordinate frame in Sapien is: x(forward), y(left), z(upward)
# The principle axis of the camera is the x-axis
viewer.set_camera_xyz(x=-4, y=0, z=2)
# The rotation of the free camera is represented as [roll(x), pitch(-y), yaw(-z)]
# The camera now looks at the origin
viewer.set_camera_rpy(r=0, p=-np.arctan2(2, 4), y=0)
viewer.window.set_camera_parameters(near=0.05, far=100, fovy=1)
while not viewer.closed: # Press key q to quit
scene.step() # Simulate the world
scene.update_render() # Update the world to the renderer
viewer.render()
if __name__ == '__main__':
main()