Developer Month 2019: Arno Gerretsen

Welcome to Developer Month 2019. Between April 8th and May 8th 2019, we will feature a variety of developers, publishers, community personalities and more who will tell us their story. From written interviews and blog…

Posted: 06-May-2019 @ 18:00z
Developer Month 2019: Arno Gerretsen

Welcome to Developer Month 2019. Between April 8th and May 8th 2019, we will feature a variety of developers, publishers, community personalities and more who will tell us their story. From written interviews and blog posts to video interviews and more, we have curated a range of interesting content to maybe even inspire you to be one of these developers in future years. Please enjoy Developer Month 2019 as much as we enjoyed putting it together for you.

We couldn’t have put together Developer Month without the support of all the developers & publishers involved. Also, huge thanks to Thrustmaster for their assistance in sponsoring Developer Month.

May 6th – Arno Gerretsen

Perhaps a name many of you aren’t familiar with, but Arno Gerretsen is one of the most prominent names in the progress of Scenery design. Much of Arno’s work focuses on new tools and assisting with many of the developers featured during Developer Month to craft wonderful products. As the founder of the FSDeveloper, Arno has been instrumental for many of the products you use today. It is with great pleasure that Arno has decided to take part in Developer Month.

Tell us who are you and a little about what you presently do?

I’m Arno Gerretsen and I’m probably not a well-known developer for FS users since most of the things I make are focussed on fellow developers and not directly at end users of add-ons. I mainly focus on making tools that developers can use to make their add-ons. My two main tools, although I have more, are ModelConverterX and scenProc.

ModelConverterX is a tool that can convert objects between different formats, for example from COLLADA to FS MDL file so that people can use SketchUp to model. Besides that the tool allows developers to make changes to their objects, like tweaking material settings or adding night textures.

ScenProc is a tool that is used to make autogen for photoreal scenery based on geographical (GIS) data. This way autogen for big areas can be generated in a data-driven way, without having to do it manually in Annotator.

Besides developing these tools, I am also the founder and one of the administrators of the FSDeveloper website. This is a community for FS developers where they can ask for help, share tips or just hang around with other developers.

When did you first start flight simulation development?

That’s quite some time ago. I started flying with FS with Flight Simulator 5 around 1996 or so. Quite soon I got bored with only flying, so I wanted to try to make an aircraft or airport for the sim. So it must have been around 1997 or so that I tried to make my first aircraft. Later I switched to making scenery and I made some airport for the Netherlands for FS5.

In 1999 I joined the freeware Netherlands 2000 scenery design team and I have been a member of that team for around 10 years. In that period I made various airports in the Netherlands, including Amsterdam Schiphol Airport.

In early 2000, I started to develop tools for scenery developers as well, as I found ways to optimize the workflow of scenery development. In the end, I enjoy finding new ways to do things more than actually developing sceneries, so at the moment my main focus is the development of tools.

Developer Month 2019: Arno Gerretsen

What is your background outside of flight simulation development?

I have studied Aeronautical Engineering and I have graduated in the direction of Control and Simulation. After my study, I started to work at the Netherlands Aerospace Centre, which is a research institute in the Netherlands for aerospace. There I am involved in research on simulation technologies and we use research flight simulators in our projects. So you can say that hobby and work have really blended for me.

An interesting observation is that in some areas the Flight Simulator games we are using are more advanced than the professional flight simulators that are used to train pilots. For example, making new scenery or modifying an airport probably goes quicker and more efficient in the games we use. For example, the way the terrain is procedurally generated in FSX was quite ahead of how professional simulators do it, those kinds of technologies only appear their recently. Of course, that is partly because professional usage and gaming have different requirements.

It is also possible to share content between FS and the professional simulators. Using my tools I have for example converted multiple airports to the OpenFlight format that is used in many professional simulators. That way the airports made for FS could be imported in those sims as well and this was the quickest way to add a realistic airport in them since the quality of the FS addons is very high in general.

You have a blog called Your first post was back in 2005 and you have since updated it with useful information for scenery development. Do you often get feedback from the community about how help it is for them? Why did you decide to start the blog?

Actually, the website started as a community for scenery developers. I started this because before that we used the scenery design forum at Avsim for our discussions, but everything was combined in one forum there. I thought it would be better to have a forum focussed on scenery developers and be able to have sub-forums for the specific tools and areas of scenery development. Later we decided that this community should not focus on scenery only and we renamed it to FSDeveloper.

Since I still had the domain and in my tools, I still used the logo as an icon, I decided to revive the website as a blog where I could share information about my tools and other interesting findings for fellow developers.

I do not get feedback on the blog so often, but for my tools, I often get feedback that they are very helpful for other developers. Of course, that is always nice to hear and the interaction with other developers on how they use the tools always inspires me to add new features or improve things.

You also created the FSDeveloper forums. Why was this? How do you think this has helped sim developers?

I already explained the history of FSDeveloper above. Having such a community and knowledge base is a big help to developers, especially for those that just started to make their own add-ons. Because they can find tutorials and solutions for common problems in the community.

Over the years to the quality of FS add-ons has increased a lot. Just compare some airport from FS2000 with what we have now in P3D. For a developer this means that the bar is put a lot higher when you want to make your first addon, everybody expects the level of quality of the commercial add-ons. This means that for developers it is probably harder to get started now than it was 15 years ago or so. So having a community of fellow developers to help you get going is very helpful in that case.

Developer Month 2019: Arno Gerretsen
Arno’s first scenery

Have you ever created any products in the past? If so, what are they? (if not, why not?)

Yes, like I mentioned before I made some add-ons in the past. Most of them were freeware, as I was a member of the Netherlands 2000 scenery design team. I have also supported some commercial developers over the years, for example, the LunarPilot product by Things-To-Come. Making all those advanced animations for their scenery was a lot of fun.

Like I mentioned before my motivation is mainly on exploring how things can be done and trying to find the limits of what we can do with the sim. So once I have found out or made a tool for that, in general, I have less interest to do it again. That’s why I mainly focus on making tools and less on actual products for end users. But I guess my fellow developers are more than happy that I focus on those tools.

Having said that, at the moment I’m working with another developer on a new product. We are trying to create photorealistic sceneries with realistic autogen for large areas. This means we try to combine all the high-resolution geographical data that is currently available to create a more realistic environment. This is a lot of fun to work on, as I can explore ideas that I have to improve scenery development, work on my scenProc tool and also create a product in the end (hopefully).

With the simulators in a state of active development – is this exciting or scary for developers (with the always changing code base)

For many years that was the situation, we were used to. Every few years Microsoft would release a new version of Flight Simulator. On one hand, this was always very exciting for developers, as the new versions would typically include some new features that we were hoping for and that we could use to make our addons even better.

On the other hand, it was also scary, because with each new version things would also change. So that would mean that parts of the addon have to be re-developed or that we had to learn again how to develop our addons for the new sim. Remember that at that time the SDK was also not as detailed as we now have for FSX or P3D. For earlier versions, the SDK was much less detailed and often released long after the sim. So most things we had to learn by trial and error.

For developers, the current situation with less frequent changes is probably better, as they don’t have to redo their addon for new versions all the time. Although in the long run we also want improved features and new technologies of course. The way P3D is currently developed works quite well since most version updates are gradual changes and not big sudden changes.

What tools or guides out there do you think would be most helpful to those starting out on development?

That is a very difficult question to answer. We often see such question on the forum as well, they go like: “Hey, can you tell me how to make a scenery with the quality of (…insert well know developer…)?”

The main problem is that there is not one single tool to make your addon. If you take a scenery as example you need one tool to make your 3D objects, another tool to model the airport AFCAD file and yet another tool to modify the terrain surrounding the airport.

This means that a developer needs to learn various tools and also needs to “find” his own workflow on how to combine these different tools. Of course, FSDeveloper has a lot of knowledge to get you started.

So I would advise people to start small and learn the tools that way. Don’t start with trying to make a big international airport directly at payware quality, but just start to model that character building in your town or your local airport. I think it is more important and more fun to work on something that you can oversee at the beginning and you also get rewarded for your work more quickly. Once you know the tools and the workflows, you can start with those more ambitious and bigger projects.

Developer Month 2019: Arno Gerretsen
Some of Arno’s latest in-sim work

What are you most excited for in the future of flight sim development?

I think what is most exciting is that with the current computer power, the amount of available geographical data and the virtual reality technologies, we are getting at a point that the simulation will be able to reach the level of realism of the real world. In the near future, we can have such a realistic flight experience just at home.

What keeps you motivated to provide tools and tutorials for developers?

I already mentioned this above a bit as well, but what I find interesting is to explore how we can do things and then try to optimize and develop a tool to be able to do these things. So since that is my motivation, it is not hard for me to keep providing tools. There are always things that we would like to improve in our add-ons, so that means there is always something to explore or optimize.
The last few years I have less time to write tutorials, so that is something I do less at the moment. But I try to make video tutorials now if I have new features in my tools. That is an easier and quicker way to show how things work. And I think other developers in general also like to watch them.

We started Developer Month to hopefully inspire the next generation of developers out there. With your knowledge and experience, what advice would you give to them?

That is a very good objective, it seems like we have less young people active in the FS community and in the developer community than when I started around 20 years ago. Like I mentioned above my advice would be to start making some small addon for something you really like. A repaint of your favourite aircraft, some new hangar at your local airport, or whatever. Just start with something you like and care for so that you have enough motivation to learn all the tools and techniques that you need to master to get it in FS.

And once you have done one addon more will follow, since it is very addictive (I have warned you now). Most developers probably spend more time slewing to look at their addon than actually flying in the simulator. But it is loads of fun to develop your own add-ons.

Is there anything else you would like to say to the community?

Geeh, haven’t I said enough yet?

If there is one more thing I would like to say to the community I think it is that we should help each other. And remember that we all started small by making a freeware addon one day because we just missed something our simulator. Even though we today all expect the payware quality add-ons and might be disappointed if some addon doesn’t meet that standard, we need to remember every developer needs to start somewhere. And if we help and encourage each other we can create some many beautiful add-ons for our simulators. And we need to keep that freeware community around our simulators alive as well, as else there is no place anymore where the top payware developers of tomorrow can learn their skills.


Head over to the FSDeveloper forum to get inspired by other developers working out solutions together.

Thank you once again to Arno for taking part.

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Stay tuned as Developer Month continues tomorrow with TFDi Designs.

Content sponsored by Thrustmaster. Read our review on the TPR Pedal Set. | Read our review on the Air-Force Edition Headset.

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Calum Martin
Calum has been an avid fan of Flight Sim since the release of FS2000 and has developed his love for aviation ever since.
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