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stack-of-tasks / pinocchio

A fast and flexible implementation of Rigid Body Dynamics algorithms and their analytical derivatives
http://stack-of-tasks.github.io/pinocchio/
BSD 2-Clause "Simplified" License
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How to add ground collision in pinocchio? #756

Closed littleggghost closed 5 years ago

littleggghost commented 5 years ago

Hi, @cmastalli I have seen your new progress about quadruped through youtube https://www.youtube.com/watch?v=C0h-NLdMVuc. Here I have a question, considering you use gepetto in this video, then is that done by pinocchio? It has been a long time that I tried to add ground collision in pinocchio. Thanks.

cmastalli commented 5 years ago

As you said, I displayed the planned motion using Gepetto viewer (GV). Planned motions are generated by an optimal control solvers that I've working on. And Pinocchio is used to model the robot's dynamics and its derivatives.

On the other hand, we use RobotWrapper from displaying the robot posture. Inside it wraps some GV functionalities. And you can't add other objects with it.

I would suggest to learn more about GV. Unfortunatelu there isn't a tutorial yet for that. Nevertheless it's not too difficult to understand it.

In that video I used the following Python code for adding the floor:

window_id = robot.viewer.gui.getWindowID('python-pinocchio')
robot.viewer.gui.addFloor('hpp-gui/floor')
robot.viewer.gui.setScale('hpp-gui/floor', [0.5, 0.5, 0.5])
robot.viewer.gui.setColor('hpp-gui/floor', [0.7, 0.7, 0.7, 1.])
robot.viewer.gui.setLightingMode('hpp-gui/floor', 'OFF')

and this one for setting the white background

robot.viewer.gui.setBackgroundColor1(window_id, [1., 1., 1., 1.])
robot.viewer.gui.setBackgroundColor2(window_id, [1., 1., 1., 1.])

Feel free to re-open it, if you have further questions.

littleggghost commented 5 years ago

Hello @cmastalli I know how to add the floor in "visual", but here my focus is on the ground collision with foot. For example, I try a box that free drop and plan to contact with ground, and calculate its position through pinocchio dynamic API, but the result is that the box drop "through" the floor, which means no collision happens. I really want to know how to set the collision property of floor. Thanks in advance!

cmastalli commented 5 years ago

I'm not the best person to ask this, you might want to ask @jmirabel.

littleggghost commented 5 years ago

Hi, @jmirabel What is your advice about ground collision? And, I do not have the authority to reopen this issue @cmastalli

jmirabel commented 5 years ago

You can represent the floor with a box of the right shape for collision detection. But it won't make your example work. You have to handle yourself the different phases (free drop and contact with ground) with a suitable contact model.

The practical exercise "Snap your finger" in the doc may help you.

littleggghost commented 5 years ago

Hi, @jmirabel Sorry for my late reply! What I am concern here is only about the collision. The walk phase is not needed, but I want a stick or a box or a boll just contact with ground box. About the exercise you mentioned, I have asked an issue before: https://github.com/stack-of-tasks/pinocchio/issues/731. And, how many collisionPairs should be added? Because the ground box will be huge and don't know where the collision will happen. Hope you can explain it in more detail!

littleggghost commented 5 years ago

Hello @cmastalli I really think this issue should be re-opened.