Reimagining Flight Simulator: Then and Now

The first version of Flight Simulator shipped in 1980 for the Apple II and, amazingly, it was in 3D! That was a remarkable achievement. It’s even more amazing when you consider that all of the 3D was done by hand, the result of meticulous calculations and low-level pixel commands. When Bruce Atwick tackled the early versions of Flight Simulator, not only were there no 3D frameworks, but there were no frameworks at all! Those versions of the game were mostly written in assembly, just a single step away from ones and zeroes that flow through a CPU.

When we set out to reimagine Flight Simulator (or Flight Arcade as we call it) for the web and to demonstrate what’s possible in the new Microsoft Edge browser and EdgeHTML rendering engine, we couldn’t help but think about the contrast of creating 3D then and now – old Flight Sim, new Flight Sim, old Internet Explorer, new Microsoft Edge. Modern coding seems almost luxurious as we sculpt 3D worlds in WebGL with great frameworks like Babylon.js. It lets us focus on very high level problems. In this article, we’ll share our approach to one of these fun challenges: a simple way to create realistic looking large-scale terrain.

Note: Interactive code and examples for this article are also located at: http://ift.tt/1GMoy7c

Modeling and 3D Terrain

Most 3D objects are created with modeling tools, and for good reason. Creating complex objects (like an airplane or even a building) is hard to do in code. Modeling tools almost always make sense, but there are exceptions! One of those might be cases like the rolling hills of the Flight Arcade island. We ended up using a technique that we found to be simpler and possibly even more intuitive: a heightmap.

A heightmap is a way to use a regular two-dimensional image to describe the elevation relief of a surface like an island or other terrain. It’s a pretty common way to work with elevation data, not only in games but also in geographic information systems (GIS) used by cartographers and geologists.

To help you get an idea for how this works, check out the interactive heightmap below. Try drawing in the image editor and then check out the resulting terrain.

Try the interactive demo here.

The concept behind a heightmap is pretty straightforward. In an image like the one above, pure black is the “floor” and pure white is the tallest peak. The grayscale colors in-between represent corresponding elevations. This gives us 256 levels of elevation which is plenty of detail for our game. Real-life applications might use the full color spectrum to store significantly more levels of detail (256⁴ = 4,294,967,296 levels of detail if you include an alpha channel).

A heightmap has a few advantages over a traditional polygonal mesh:

First, heightmaps are a lot more compact. Only the most significant data (the elevation) gets stored. It will need to be turned into a 3D object programatically, but this is the classic trade: you save space now and pay later with computation. By storing the data as an image you get another space advantage: you can leverage standard image compression techniques and make the data tiny (by comparison)!

Second, heightmaps are a convenient way to generate, visualize and edit terrain. It's pretty intuitive when you see one. It feels a little like looking at a map. This proved to be particularly useful for Flight Arcade. We designed and edited our island right in Photoshop! This made it very simple to make small adjustments as needed. When, for example, we wanted to make sure that the runway was completely flat, we just made sure to paint over that area in a single color.

You can see the heightmap for Flight Arcade below. See if you can spot the “flat” areas we created for the runway and the village.

The heightmap for the Flight Arcade island. It was created in Photoshop and it's based on the "big island" in a famous Pacific Ocean island chain. Any guesses?

A texture that gets mapped onto the resulting 3D mesh after the heightmap is decoded. More on that below.

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by Robby Ingebretsen via SitePoint