# Evolution

Create creatures and let them evolve to see how they master various tasks. · By Keiwan

# How do muscles work?

A topic by brunoschull created Dec 06, 2018 Views: 330 Replies: 3
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Hi.  I'm trying to figure out how muscles work.
In the information, I find three  hints about how muscles work.
1) "Muscles are spring-like, which means that they will always tend to go back into their starting position."

2) "The output is a floating point number between -1 and 1 which determines how far the muscles should expand/contract."

3) "A creature can expand and contract its muscles continuously by applying a different amount of force to them."

So what does the output change?  How far the muscles contract?  How much force the muscles apply?  Or are these two things related?  For example, if the muscles are like springs, it takes more force to stretch them farther, and subsequently they spring back with more force?

During the simulation, do the muscles keep firing at a constant rate?

Thanks for making this amazing simulator!  My students love it.

B

Developer

The muscles work by applying force to the bones that they are connected to. The magnitude and direction (expansion vs contraction) of that force  is determined by the neural network output. Internally they use the Spring Joint component of Unity's physics system, which essentially acts like a real spring. The muscles fire at a constant rate.

Thank you very much for all of your questions! (I've also seen the other batch but haven't had time to appropriately answer them yet) I'm currently  working on not only a big update for Evolution but also a FAQ page on my website where I will try to answer all of these questions and others that I've been getting in more detail, so that I can then just link to those answers when someone asks them again. If you or your students have any more questions, just drop them here in this forum or send me an e-mail and I'll add them to my list of questions for the FAQ.

I'll let you know once that page is ready (I'm a little busy at the moment so it might take a while).

Thanks for your answers!  I really appreciate it.  I answered some of my other questions on my own (I think), but the page of Q and A would be really helpful.  All the best, Bruno.

Developer

Hi Bruno,

I hope you're doing well!

I finally managed to finish the FAQs. If you would like to see me elaborate on any of the answers there, just let me know and I'll add more information.

Best regards,

Keiwan