Drake Visualizer with multiple robots

I’ve run into an issue that’s pretty hard to get around with the way drake-visualizer is currently set up. Specifically, I would like to:

• load robot A in drake visualizer once
• at each iteration of my function:
  • draw robot A in a configuration
  • load and draw another robot B (whose geometry changes at every iteration)

I can’t currently do that, because loading robot B deletes all robots from the visualizer. I could do:

• at each iteration:
  • load robots A and B
  • draw robot A
  • draw robot B

but it’s computationally wasteful, since it loads robot A every time (which might be expensive, if robot A has fancy meshes), and it’s inconvenient.

@patmarion I think we chatted about whether to have the LOAD_ROBOT command only delete any existing robot with the same robot ID number, rather than all robots. At the time, that seemed like a bad idea, because it leaves additional state in the visualizer. But I’m starting to wonder if it might be the right thing to do. It would certainly fix my immediate problem.

But perhaps someone else has a better idea, or another use case we need to address?

How about it? Is anyone else trying to visualize multiple robots simultaneously in the drake-visualizer?

[rdeits]

@david-german-tri I agree that as far as I know, no one (except me) is currently using drake-visualizer with more than one robot ID number. That’s because we’ve always used the trick that @liangfok mentioned in which we combined multiple robots into a singe rigid body tree/manipulator.

[rdeits]

The benefit of using a channel instead of adding a flag to the message is that it does not break backwards compatibility for users of the old message type.