.. note:: :class: sphx-glr-download-link-note Click :ref:`here ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_auto_tutorials_05_physics_viz_chain.py: ===================== Chain Simulation ===================== This example simulation shows how to use pybullet to render physics simulations in fury. In this example we specifically render a Chain oscillating to and fro. First some imports. .. code-block:: default import numpy as np from fury import window, actor, ui, utils import itertools import pybullet as p Setup pybullet and add gravity. .. code-block:: default p.connect(p.DIRECT) # Apply gravity to the scene. p.setGravity(0, 0, -10) Now we render the Chain using the following parameters and definations. .. code-block:: default # Parameters n_links = 20 dx_link = 0.1 # Size of segments link_mass = 0.5 base_mass = 0.1 radii = 0.5 joint_friction = 0.0005 # rotational joint friction [N/(rad/s)] link_shape = p.createCollisionShape(p.GEOM_CYLINDER, radius=radii, height=dx_link, collisionFramePosition=[0, 0, -dx_link/2]) base_shape = p.createCollisionShape(p.GEOM_BOX, halfExtents=[0.01, 0.01, 0.01]) visualShapeId = -1 link_Masses = np.zeros(n_links) link_Masses[:] = link_mass linkCollisionShapeIndices = np.zeros(n_links) linkCollisionShapeIndices[:] = np.array(link_shape) linkVisualShapeIndices = -1 * np.ones(n_links) linkPositions = np.zeros((n_links, 3)) linkPositions[:] = np.array([0, 0, -dx_link]) linkOrientations = np.zeros((n_links, 4)) linkOrientations[:] = np.array([0, 0, 0, 1]) linkInertialFramePositions = np.zeros((n_links, 3)) linkInertialFrameOrns = np.zeros((n_links, 4)) linkInertialFrameOrns[:] = np.array([0, 0, 0, 1]) indices = np.arange(n_links) jointTypes = np.zeros(n_links) jointTypes[:] = np.array(p.JOINT_SPHERICAL) axis = np.zeros((n_links, 3)) axis[:] = np.array([1, 0, 0]) linkDirections = np.zeros((n_links, 3)) linkDirections[:] = np.array([1, 1, 1]) link_radii = np.zeros(n_links) link_radii[:] = radii link_heights = np.zeros(n_links) link_heights[:] = dx_link rope_actor = actor.cylinder(centers=linkPositions, directions=linkDirections, colors=np.random.rand(n_links, 3), radius=radii, heights=link_heights, capped=True) basePosition = [0, 0, 2] baseOrientation = [0, 0, 0, 1] rope = p.createMultiBody(base_mass, base_shape, visualShapeId, basePosition, baseOrientation, linkMasses=link_Masses, linkCollisionShapeIndices=linkCollisionShapeIndices, linkVisualShapeIndices=linkVisualShapeIndices, linkPositions=linkPositions, linkOrientations=linkOrientations, linkInertialFramePositions=linkInertialFramePositions, linkInertialFrameOrientations=linkInertialFrameOrns, linkParentIndices=indices, linkJointTypes=jointTypes, linkJointAxis=axis) We remove stiffness among the joints by adding friction to them. .. code-block:: default friction_vec = [joint_friction]*3 # same all axis control_mode = p.POSITION_CONTROL # set pos control mode for j in range(p.getNumJoints(rope)): p.setJointMotorControlMultiDof(rope, j, control_mode, targetPosition=[0, 0, 0, 1], targetVelocity=[0, 0, 0], positionGain=0, velocityGain=1, force=friction_vec) Next, we define a constraint base that will help us in the oscillation of the chain. .. code-block:: default root_robe_c = p.createConstraint(rope, -1, -1, -1, p.JOINT_FIXED, [0, 0, 0], [0, 0, 0], [0, 0, 2]) # some traj to inject motion amplitude_x = 0.3 amplitude_y = 0.0 freq = 0.6 base_actor = actor.box(centers=np.array([[0, 0, 0]]), directions=np.array([[0, 0, 0]]), scales=(0.02, 0.02, 0.02), colors=np.array([[1, 0, 0]])) We add the necessary actors to the scene. .. code-block:: default scene = window.Scene() scene.background((1, 1, 1)) scene.set_camera((2.2, -3.0, 3.0), (-0.3, 0.6, 0.7), (-0.2, 0.2, 1.0)) scene.add(actor.axes(scale=(0.1, 0.1, 0.1))) scene.add(rope_actor) scene.add(base_actor) # Create show manager. showm = window.ShowManager(scene, size=(900, 768), reset_camera=False, order_transparent=True) showm.initialize() # Counter interator for tracking simulation steps. counter = itertools.count() We define a couple of syncing methods for the base and chain. .. code-block:: default # Function for syncing actors with multibodies. def sync_actor(actor, multibody): pos, orn = p.getBasePositionAndOrientation(multibody) actor.SetPosition(*pos) orn_deg = np.degrees(p.getEulerFromQuaternion(orn)) actor.SetOrientation(*orn_deg) vertices = utils.vertices_from_actor(rope_actor) num_vertices = vertices.shape[0] num_objects = linkPositions.shape[0] sec = np.int(num_vertices / num_objects) def sync_joints(actor_list, multibody): for joint in range(p.getNumJoints(multibody)): # `p.getLinkState` offers various information about the joints # as a list and the values in 4th and 5th index refer to the joint's # position and orientation respectively. pos, orn = p.getLinkState(multibody, joint)[4:6] rot_mat = np.reshape( p.getMatrixFromQuaternion( p.getDifferenceQuaternion(orn, linkOrientations[joint])), (3, 3)) vertices[joint * sec: joint * sec + sec] =\ (vertices[joint * sec: joint * sec + sec] - linkPositions[joint])@rot_mat + pos linkPositions[joint] = pos linkOrientations[joint] = orn We define a TextBlock to display the Avg. FPS and Simulation steps. .. code-block:: default fpss = np.array([]) tb = ui.TextBlock2D(position=(0, 680), font_size=30, color=(1, 0.5, 0), text="Avg. FPS: \nSim Steps: ") scene.add(tb) t = 0.0 freq_sim = 240 Timer callback to sync objects, simulate steps and oscillate the base. .. code-block:: default def timer_callback(_obj, _event): cnt = next(counter) global t, fpss showm.render() t += 1./freq_sim if cnt % 1 == 0: fps = scene.frame_rate fpss = np.append(fpss, fps) tb.message = "Avg. FPS: " + str(np.round(np.mean(fpss), 0)) +\ "\nSim Steps: " + str(cnt) # some trajectory ux = amplitude_x*np.sin(2*np.pi*freq*t) uy = amplitude_y*np.cos(2*np.pi*freq*t) # move base arround pivot = [3*ux, uy, 2] orn = p.getQuaternionFromEuler([0, 0, 0]) p.changeConstraint(root_robe_c, pivot, jointChildFrameOrientation=orn, maxForce=500) # Sync base and chain. sync_actor(base_actor, rope) sync_joints(rope_actor, rope) utils.update_actor(rope_actor) # Simulate a step. p.stepSimulation() # Exit after 2000 steps of simulation. if cnt == 130: showm.exit() # Add the timer callback to showmanager. # Increasing the duration value will slow down the simulation. showm.add_timer_callback(True, 1, timer_callback) interactive = False # start simulation if interactive: showm.start() window.record(scene, size=(900, 768), out_path="viz_chain.png") .. image:: /auto_tutorials/05_physics/images/sphx_glr_viz_chain_001.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-timing **Total running time of the script:** ( 0 minutes 0.176 seconds) .. _sphx_glr_download_auto_tutorials_05_physics_viz_chain.py: .. only :: html .. container:: sphx-glr-footer :class: sphx-glr-footer-example .. container:: sphx-glr-download :download:`Download Python source code: viz_chain.py ` .. container:: sphx-glr-download :download:`Download Jupyter notebook: viz_chain.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_