<p>The abbreviations <em>sim2sim, sim2real</em> and <em>real2real</em> refer to techniques that can be used to transfer knowledge from one environment (e.g. in simulation) to another one (e.g. in the real world).</p>

<ul>
<li>sim2sim stands for simulation-to-simulation,</li>
<li>sim2real stands for simulation-to-real, and </li>
<li>real2real stands for real-to-real. </li>
</ul>

<p>In sim2sim, knowledge acquired during one simulation is transferred to an agent (or robot) in another simulation. Similarly, in sim2real, knowledge acquired during the simulation is used in a real-world problem (or environment). Finally, in real2real, knowledge acquired in a real-world problem can be transferred to another agent in another real-world problem.</p>

<p>The main challenges are related to the differences that exist between one environment and the other (either in simulation or in the real-world). For example, in <a href="https://arxiv.org/pdf/1812.07252.pdf" rel="nofollow noreferrer">sim2real</a>, the simulation is almost never a perfect model of the real-world environment, so an agent trained in a simulation will probably not behave optimally in the real-world environment, which is often a lot more complex than the simulated environment. However, it is often the case that a robot needs to be trained in simulation, given that a robot trained in a real-world environment is subject to crashes.</p>

CC BY-SA 4.0
2019-10-14T12:06:08.883Z
I defined _real2real_ based on the concepts of *sim2sim* and _sim2real_ as used in [Sim-to-Real via Sim-to-Sim: Data-efficient Robotic Grasping via
Randomized-to-Canonical Adaptation Networks](https://arxiv.org/pdf/1812.07252.pdf) (2019) by Stephen James et al., given that I've not found any paper that uses the expression real2real.
nbro
CC BY-SA 4.0
2019-10-14T12:04:23.167Z
2019-10-14T12:10:01.993Z
2019-10-14T12:10:01.993Z
nbro
<p>Recently, I always hear about the terms sim2sim, sim2real and real2real. Will anyone explain the meaning/motivation of these terms (in DL/RL research community)?</p>

<p>What are the challenges in this research area?</p>

<p>Anything intuitive would be appreciated!</p>

<deep-learning><reinforcement-learning><computer-vision><terminology><robotics>
What are sim2sim, sim2real and real2real?
wcc
# What are sim2sim, sim2real and real2real?

(Asked by: username_0 on 2019-10-14)

Recently, I always hear about the terms sim2sim, sim2real and real2real. Will anyone explain the meaning/motivation of these terms (in DL/RL research community)?

What are the challenges in this research area?

Anything intuitive would be appreciated!

**Tags:** deep-learning, reinforcement-learning, computer-vision, terminology, robotics


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## 1 answers

### Answer by username_1 on 2019-10-14. Score: 4

The abbreviations *sim2sim, sim2real* and *real2real* refer to techniques that can be used to transfer knowledge from one environment (e.g. in simulation) to another one (e.g. in the real world).

* sim2sim stands for simulation-to-simulation,
* sim2real stands for simulation-to-real, and
* real2real stands for real-to-real.

In sim2sim, knowledge acquired during one simulation is transferred to an agent (or robot) in another simulation. Similarly, in sim2real, knowledge acquired during the simulation is used in a real-world problem (or environment). Finally, in real2real, knowledge acquired in a real-world problem can be transferred to another agent in another real-world problem.

The main challenges are related to the differences that exist between one environment and the other (either in simulation or in the real-world). For example, in [sim2real](https://arxiv.org/pdf/1812.07252.pdf), the simulation is almost never a perfect model of the real-world environment, so an agent trained in a simulation will probably not behave optimally in the real-world environment, which is often a lot more complex than the simulated environment. However, it is often the case that a robot needs to be trained in simulation, given that a robot trained in a real-world environment is subject to crashes.

> **Comments:**
> **username_1**: I defined _real2real_ based on the concepts of *sim2sim* and _sim2real_ as used in [Sim-to-Real via Sim-to-Sim: Data-efficient Robotic Grasping via Randomized-to-Canonical Adaptation Networks](https://arxiv.org/pdf/1812.07252.pdf) (2019) by Stephen James et al., given that I've not found any paper that uses the expression real2real.  

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