Issue Description

When visualizing a model with many links, I was seeing that meshcat was slowing down the simulator significantly and the drake visualizer doesn't. It would be nice if this were at least documented if in fact meshcat is just slower than Drake Visualizer.

Example test script and model here to replicate:

https://gist.github.com/mntan3/be02a1c410a0830f2ddb656aaf6403e2
After running the script for 10 seconds, it should print out the simulator rate. I was observing something like a rate of 0.8 for drake visualizer and 0.6 for meshcat on my computer

Initial discussions from slack:

https://drakedevelopers.slack.com/archives/C43KX47A9/p1586538504017800
sean.curtis 2 hours ago
I think you may just be victim of python loops vs C++ loops.

mntan 2 hours ago
Just to clarify, so you're saying that meshcat is written in python and drake_vis is written in c++, so that's why meshcat is going to be slower?

sean.curtis 2 hours ago
Essentially -- there may be other reasons, but that will be one wall you won't be able to get around. And the key, particularly, is the work that has to be done in a Drake System to translate Drake state to be consumed by the visualizer.
You might try collecting timing on the publish method of the mesh cat visualizer -- easy enough to do in python. I bet most of the time lost is spent right there.

eric.cousineau 1 hour ago
I think this may be good to track in an issue. @mntan Do you feel comfortable porting this to a Drake issue?

eric.cousineau 1 hour ago
My guess is it might be slow due to mesh conversion for sending it over the wire?