Improve display in gepetto-viewer and create function for recording videos

[wxmerkt]

In GitLab by @cmastalli on Apr 18, 2019, 10:18

There is a list of things that we should improve:

1. Changed background from blue to white.
2. Create a function that saves properly the frame and make a video. Using the record button in GV gui renders videos that aren't consistent with time.
3. displayTrajectory might be use a stack of robots. This will render multiple robots and trajectories.

[wxmerkt]

In GitLab by @nmansard on Apr 18, 2019, 10:53

1. should be discussed in GV, not here. We should not impose a particular image style atop GV in crocoddyl.
2. good point. Do you now that Steve did some work to automatically produce Blender videos?
3. I don't understand.

[wxmerkt]

In GitLab by @cmastalli on Apr 18, 2019, 11:03

displayTrajectory can only display one robot. It displays the entire motion for a single robot. If you want to display more than one robot you need to do something like this:

def displayTrajectory(robots, Xs, dt=0.1):
    """  Display a robot trajectory xs using Gepetto-viewer gui.

    :param robots: set of Robot wrappers
    :param xs: set of state trajectory
    :param dt: step duration
    :param rate: visualization rate
    :param cameraTF: camera transform
    """
    if not hasattr(robot, 'viewer'):
        for r in robots:
            r.initDisplay(loadModel=True)
    import numpy as np

    def a2m(a):
        return np.matrix(a).T

    import time
    length_traj = len(Xs[0]) # assert this for each case
    for i in range(length_traj):
        for r, robot in enumerate(robots):
            x = Xs[r][i]
            robot.display(a2m(x[:robot.nq]))
        time.sleep(dt)

This kind of code is needed if you want to do something like this: https://youtu.be/C0h-NLdMVuc

[wxmerkt]

In GitLab by @cmastalli on Apr 18, 2019, 11:08

I forgot to include an option to add a floor.

Do you think we need to request this stuff in GV? I was thinking that Crocoddyl should have its own GUI wrapper that displays the robot (and sets up background and floor) and remove RobotWrapper dependency.