Tackling the 3D Simulation League: an interview with Klaus Dorer and Stefan Glaser

A screenshot from the brand new simulator that might be trialled for a particular problem at RoboCup2025.

The annual RoboCup occasion, the place groups collect from throughout the globe to participate in competitions throughout various leagues, will this yr happen in Brazil, from 15-21 July. Upfront of kick-off, we spoke to 2 members of the RoboCup Soccer 3D Simulation League: Government Committee Member Klaus Dorer, and Stefan Glaser, who’s on the Upkeep Committee and who has been lately growing a brand new simulator for the League.

Might begin by simply giving us a fast introduction to the Simulation League?
Klaus Dorer: There are two Simulation Leagues in Soccer: the 2D Simulation League and the 3D Simulation League. The 2D Simulation League, because the identify suggests, is a flat league the place the gamers and ball are simulated with simplified physics and the primary focus is on staff technique. The 3D Simulation League is far nearer to actual robots; it simulates 11 versus 11 Nao robots. The extent of management is like with actual robots, the place you progress every motor of the legs and the arms and so forth to realize motion.

I perceive that you’ve been engaged on a brand new simulator for the 3D League. What was the thought behind this new simulator?
Klaus: The intention is to deliver us nearer to the {hardware} leagues in order that the simulator will be extra helpful. The present simulator that we use within the 3D Simulation League is known as SimSpark. It was created within the early 2000s with the intention of constructing it attainable to play 11 vs 11 gamers. With the {hardware} constraints of that point, there needed to be some compromises on the physics to have the ability to simulate 22 gamers on the identical time. So the simulation is bodily considerably life like, however not within the sense that it’s simple to transpose it to an actual Nao robotic.

Stefan Glaser: The thought for growing a brand new simulator has been round for a couple of years. SimSpark is a really highly effective simulation framework. The bottom framework is area impartial (not soccer particular) and particular simulations are realized through plugins. It helps a number of physics engines within the backend and offers a versatile scripting interface for configuration and variations of the simulation. Nevertheless, all this flexibility comes with the worth of complexity. Along with that, SimSpark makes use of customized robotic mannequin specs and communication protocols, limiting the quantity of accessible robotic fashions and requiring groups to develop customized communication layers just for speaking with SimSpark. Because of this, SimSpark has not been broadly adopted within the RoboCup group.

With the brand new simulator, I wish to tackle these two main points: complexity and standardization. Within the ML group, the MuJoCo physics engine has turn into a extremely popular selection for studying environments after Google DeepMind acquired it and launched it open supply. Its requirements for world and robotic mannequin specs are broadly adopted locally and there exist numerous ready-to-use robotic mannequin specs for all kinds of digital in addition to real-world robots. In the midst of final yr, they (MuJoCo) added a characteristic which lets you manipulate the world illustration throughout simulation (including and eradicating objects to / from the simulation whereas preserving the simulation state). That is one important requirement we have now within the simulation league, the place we begin with an empty subject after which the brokers join on demand and type the groups. When this characteristic has been added, I made a decision to make a step ahead and attempt to implement a brand new simulator for the 3D Simulation League primarily based on MuJoCo. Initially, I wished to start out growth in C/C++ to realize most efficiency, however then determined to start out in Python to cut back complexity and make it extra accessible for different builders. I began growth on Easter Monday so it’s not even three months previous!

I believe it may be helpful to clarify somewhat bit extra in regards to the setup of our league and the necessities of the simulator. If we take the FIFA sport (in your favourite gaming system) for instance, there’s one simulation taking place which simulates 22 gamers and the choice making is a part of the simulation having full entry to the state of the world. Within the 3D Simulation League we have now two groups with 11 robots on the sphere, however we even have 22 particular person agent softwares that are related to the simulation server, every controlling one single robotic. Every related agent solely receives sensor info associated to their robotic within the simulation. They’re additionally solely allowed to speak through the server – there is no such thing as a direct communication between the brokers allowed in Simulation League. So we have now a basic setup the place the simulation server has to have the ability to settle for as much as 22 connections and handle the state of affairs there. This performance has been the key focus for me for the final couple of months and this half is already working effectively. Groups can join their brokers, which is able to obtain sensor info and may actuate joints of the robotic within the simulation and so forth. They’re additionally capable of choose completely different robotic fashions in the event that they like.

An illustration of the simulator set-up.

Presumably the brand new simulator has a greater illustration of the physics of an actual robotic.
Klaus: Precisely. For instance, how the motors are managed is now a bit completely different and far nearer to actual robots. So after I did my first experiments, I noticed the robotic collapse and I assumed it was precisely how an actual robotic would collapse! In SimSpark we additionally had falling robots however the motor management within the new simulator is completely different. Now you’ll be able to management the motors by velocity, by pressure, by place, which is rather more versatile – it’s nearer to what we all know from actual robots.

I believe that, not less than initially, it is going to be harder for the Simulation League groups to get the robots to do what they need them to do, as a result of it’s extra life like. For instance, in SimSpark the bottom contact was rather more forgiving. So in case you step onerous on the bottom, you don’t fall instantly with a SimSpark robotic however with a MuJoCo robotic this might be rather more life like. Certainly, in actual robots floor contact is considerably much less forgiving.

I had a query in regards to the imaginative and prescient side – how do the person brokers “see” the place of the opposite brokers on the sphere?
Stefan: We simulate a digital imaginative and prescient pipeline on the server aspect. You’ve gotten a restricted subject of view of ±60° horizontally and vertically. Inside that subject of view you’ll detect the pinnacle, the arms, the toes of different gamers, or the ball, for instance, or completely different options of the sphere. Just like frequent real-world imaginative and prescient pipelines, every detection consists of a label, a course vector and the space info. The knowledge has some noise on it like actual robots have, too, however groups don’t have to course of digicam photos. They get the detections immediately from the simulation server.

We’ve beforehand had a dialogue about transferring in direction of getting digicam photos of the simulation to combine into the imaginative and prescient pipeline on the agent aspect. This was by no means actually life like in SimSpark with the implementation we had there. Nevertheless, it must be attainable with MuJoCo. Nevertheless, for the primary model, I used the identical means the normal simulator handled the imaginative and prescient. Which means that groups don’t want to coach a imaginative and prescient mannequin, and don’t have to deal with digicam photos to get began. This reduces the load considerably and in addition shifts the main target of the issue in direction of movement and choice making.

Will the simulator be used at RoboCup 2025?
Stefan: We plan to have a problem with a brand new simulator and I’ll attempt to present some demo video games. In the meanwhile it’s not likely in a state the place you’ll be able to play an entire competitors.

Klaus: That’s often how we proceed with new simulators. We’d not transfer from one to the opposite with none intermediate step. We can have a problem this yr at RoboCup 2025 with the brand new MuJoCo simulator the place every taking part staff will attempt to educate the robotic to kick so far as attainable. So, we won’t be enjoying an entire sport, we received’t have a number of robots, only a single robotic stepping in entrance of the ball and kicking the ball. That’s the technical problem for this yr. Groups will get an concept of how the simulator works, and we’ll get an concept of what needs to be modified within the simulator to proceed.

This new problem might be voluntary, so we aren’t positive what number of groups will take part. Our staff (MagmaOffenburg) will definitely participate. It is going to be fascinating to see how effectively the groups carry out as a result of nobody is aware of how far a very good kick is on this simulator. It’s a bit like in Formulation One when the foundations change and nobody is aware of which staff would be the main staff.

Do you’ve gotten an concept of how a lot adaptation groups must make if and while you transfer to the brand new simulator for the complete matches?
Stefan: As a long-term member of 3D Simulation League, I do know the previous simulator SimSpark fairly effectively, and know the protocols concerned and the way the processes work. So the primary model of the brand new simulator is designed to make use of the identical fundamental protocol, the identical sensor info, and so forth. The thought is that the groups can use the brand new simulator with minimal effort in adapting their present agent software program. So they need to have the ability to get began fairly quick.

Though, when designing a brand new platform, I wish to take the chance to make a step ahead when it comes to protocols, as a result of I additionally need to combine different Leagues within the long-term. They often produce other management mechanisms, and so they don’t use the identical protocol that’s distinguished in 3D Simulation. Subsequently there needs to be some flexibility sooner or later. However for the primary model, the thought was to get the Simulation League prepared with minimal effort.

Klaus: The large concept is that this isn’t simply used within the 3D Simulation league, but in addition as a helpful simulator for the Humanoid League and in addition for the Customary Platform League (SPL). So if that seems to be true, then it is going to be utterly profitable. For the Kick Problem this yr, for instance, we use a T1 robotic that may be a Humanoid League robotic.

Might you say one thing about this simulation to actual world (Sim2Real) side?
Stefan: We’d prefer it to be attainable for the motions and behaviors within the simulator to be ported to actual robots. From my standpoint, it will be helpful the opposite means spherical too.

We, as a Simulation League, often develop for the Simulation League and due to this fact wish to get the behaviors working on an actual robotic. However the {hardware} groups often have the same situation after they need to check high-level choice making. They may have two to 5 robots on the sphere, and in the event that they need to play a high-level decision-making match and prepare in that regard, they all the time must deploy numerous robots. If additionally they need to have an opponent, they must double the quantity of robots in an effort to play a sport to see how the technique would prove. The Sim2Real side can be fascinating for these groups, as a result of they need to have the ability to take what they deployed on the actual robotic and it must also work within the simulation. They’ll then use the simulation to coach high-level expertise like staff play, participant positioning and so forth, which is a difficult side for the actual robotic leagues like SPL or the Humanoid Leagues.

Klaus: And the rationale we all know it’s because we have now a staff within the Simulation League and we have now a staff within the Humanoid League. In order that’s another excuse why we’re eager to deliver these items nearer collectively.

How does the refereeing work within the Simulation League?
Klaus: A pleasant factor about Simulation Leagues is that there’s a program which is aware of the actual state of the world so we are able to construct within the referee contained in the simulator and it’ll not fail. For issues like offside, whether or not the ball handed the aim line, that’s fail protected. All of the referee choices are taken by the system itself. We’ve got a human referee however they by no means have to intervene. Nevertheless, there are conditions the place we wish synthetic intelligence to play a job. This isn’t presently the case in SimSpark as a result of the foundations are all onerous coded. We’ve got numerous fouls which can be debatable. For instance, there are lots of fouls that groups agree shouldn’t have been a foul, and different fouls that aren’t known as that ought to have been. It might be a pleasant AI studying job to get some conditions judged by human referees after which prepare an AI mannequin to raised decide the foundations for what’s a foul and what isn’t a foul. However that is presently not the case.

Stefan: On the brand new simulator I’m not that far into the event that I’ve applied the automated referee but. I’ve some fundamental algorithm which progress the sport as such, however judging fouls and deciding on particular conditions just isn’t but applied within the new simulator.

What are the following steps for growing the simulator?
Stefan: One of many subsequent main steps might be to refine the physics simulation. As an illustration, although there exists a ball within the simulation, it’s not but very well refined. There are numerous physics parameters which we have now to resolve on to replicate the actual world pretty much as good as attainable. This may seemingly require a collection of experiments in an effort to get to the proper values for varied elements. On this side I’m hoping for some engagement of the group, as it’s a nice analysis alternative and I personally would like the group to resolve on a generally accepted parameter set primarily based on a stage of proof that I can’t simply present all on my own. So in case somebody is desirous about refining the physics of the simulation such that it greatest displays the actual world, you might be welcome to affix!

One other main subsequent step would be the growth of the automated referee of the soccer simulation, deciding on fouls, dealing with misbehaving brokers and so forth. Within the first model, foul situations will seemingly be judged by an professional system particularly designed for this objective. The simulation league has developed a set of foul situation specs which I plan to adapt. In a second step, I wish to combine and assist the event of AI primarily based foul detection fashions. However yeah, one step after the opposite.

What are you notably trying ahead to at RoboCup2025?
Klaus: Nicely, with our staff we have now been vice world champion seven occasions in a row. This yr we’re actually hoping to make it to world champion. We’re very skilled in getting losses in finals and this yr we’re trying ahead to altering that, from a staff perspective.

Stefan: I’m going to Brazil in an effort to promote the simulator, not only for the Simulation League, but in addition throughout the boundaries for the Humanoid Leagues and the SPL Leagues. I believe that this simulator is a superb probability to deliver individuals from all of the leagues collectively. I’m notably within the particular necessities of all of the groups of the completely different leagues. This understanding will assist me tailor the brand new simulator in direction of their wants. That is one in every of my main highlights for this yr, I’d say.

You’ll find out extra in regards to the new simulator on the undertaking webpage, and from the documentation.

Klaus Dorer is professor for synthetic intelligence, autonomous programs and software program engineering at Offenburg College, Germany. He’s additionally a member of the Institute for Machine Studying and Analytics IMLA. He has been staff chief of the RoboCup simulation league groups magmaFreiburg (since 1999), dwelling programs, magmaFurtwangen and is now staff chief of magmaOffenburg since 2009. Since 2014, he has additionally been a part of the humanoid grownup measurement league staff Sweaty.

Stefan Glaser is educating assistant for synthetic intelligence and clever autonomous programs on the Offenburg College, Germany. He has been a part of the RoboCup simulation league staff magmaOffenburg since 2009 and the RoboCup humanoid grownup measurement league staff Sweaty since 2014.