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Building a Sailing Simulator

Posted on Jan 28, 2016 by Richard Knol

What does a nerdy sailor without a boat do?
He builds a computer simulation. Ha, ha.

Of course there are quite a few sailing simulators available already. But most of them focus on regattas and don't allow you to sail big journeys across the oceans. This is how the idea for Sailaway.world was formed. A realistic sailing simulator that allows you to travel across the oceans or even around the world.

Earth model

The simulator needs real geographical data and since there is no budget to commercially use services like Google Earth, raw satellite data was combined, filtered and enhanced to create a sailable model of the earth.

When I was reviewing these enormous amounts of data, I found a tiny pixel in the middle of the Indian Ocean and was about to erase it, assuming it to be a data error. But it turned out to be a beautiful island and the habitat of many plants and animals..... A humbling experience. The earth is such a vast place.

Real time, real speed, real size

Most games don't take much longer than a few minutes up to a few hours. But a sailboat traveling from Brest (France) to Aruba (Caribbean) will sail for several weeks. Not even the biggest sailing enthusiast will sit behind a computer screen for that long. So instead of forcing you to be online 24 hours a day, the game continues when the player is not logged in. The boat sails virtually on the server and sends you updates via mail. You can log in when you want, make changes to the sail trim, set a reef, change waypoints and then let the boat continue by itself again.


When your sailboat travels across the ocean, the only thing you will see most of the time is water, which makes the behaviour and appearance of the ocean the most important part of the experience. An ocean that can change from a flat mirror to a violent chaos of water and foam, from blindingly bright to dull grey, from dark blue to bright turquoise to dirty brown. To achieve this, I wrote a massive shader that can do all these things at very high speed.

After months of working on the virtual ocean of Sailaway, me and my family went to the beach to let the dog run. This time I looked at the sea with different eyes, because I had been trying to capture it in code for so long. What I saw took my breath away. The real sea has more details than will ever fit on any 4K, 5K or 10M screen. There is no way I or anyone else will be able to code something that even comes close to this complexity.... Another humbling experience. The ocean is so immense.


The boat will encounter storms, impenetrable fog, calms with no wind at all, showers and freezing blizzards. The system downloads real weather data from NOAA and uses it to simulate light intensity, clouds, fog, rain and snow. Special shaders will make the surface of the boat look wet after a shower or bow spray.

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