X-Plane 10 Weather

Tyler Young

OK, I have given you the rundown on the plausible, scalable, dynamic world for X-Plane 10. If you haven’t read it yet, see the post from 15 September.

I have given you the run-down on the system requirements: lower than X-Plane 9, because of it’s more efficient use of RAM and CPU, but desiring all the RAM and CPUs you can throw at it (4 GB of RAM, 16 cores, is what I have, and recommend, to run this incredible world at high detail).

Now lets talk about the weather and airplanes.

First, check out this video of Javier Rollon’s latest airplanes. This video does not show X-Plane 10 (it was shot in X-Plane 9, in fact), but shows some of the airplanes of version 10. The 747, KC-10, X-15, B-2, and Space Shuttle are a sampling of what we have done so far. And there is more in store.

Now the weather:

X-Plane 10 will have weather systems that are unlike anything I have ever seen in any simulator, and I have the prototypes of these systems running now. Here is a word on detail: The weather is far, far, far more detailed than the 2048×2048 radar texture I can use to visualize it, but let’s just assume for a moment that the weather was only detailed to a resolution of 2048×2048 pixels. Since of course the weather is 3-D, assuming equal vertical detail, the weather would be 2048x2048x2048 pixels. That is 8.6 GIG. To give you an idea of how much RAM that is, a 32-bit operating systems can only ACCESS 3 GIG! In other words, if the weather was only 2048x2048x2048 data-points, it alone would use 3 times more RAM than all of the memory we have for the entire sim… and in fact the weather is much, much more detailed than that.

So, how do we do it?

The answer is: We use procedural weather. Rather than trying to memorize each bit of air and cloud, we instead develop a fiendishly complex little algorithm that tells us what the turbulence, cloud, precip, etc., will be for any given bit of air.. and then promptly forget what it told us… one-millionth of a second after we used that data to jostle the plane, paint color on a radar texture, or draw a bit of cloud or rain. Using this procedural approach to weather, there is no limit to how far out the weather can go, and how detailed the weather can be in close around the airplane. You will see this when you fly through clouds that have detailed shapes right in close to your airplane, and then zoom the camera out to orbit to see that the weather can encompass a sizable flying area (bigger than the entire map region you are used to seeing in X-Plane 9) with no repetition. With the complexity of the algorithm (based on Perlin noise and other things) the weather looks really realistic… In X-Plane 10, I have seen fronts and cells and cloud patterns that look just like what I have seen in reality. This weather is plausible. As well, because it is procedural and can be evaluated at any scale, it is totally scalable.

For the final little bit of icing on the cake, we now have the new weather system connected to the real-weather downloads so that X-Plane 10 sets up region-wide weather that follows the real world. Unlike X-Plane 9, which set the whole world to the weather of the nearest airport, X-Plane 10 reads in all the airports in the flying region and sets the weather at each airport with a real-world weather-reporting station… and then interpolates the simulated weather between these airports. You can see real weather fronts moving across the real world in X-Plane 10… as it happens in reality, with the real-weather download on. The math gets a little tricky, but the results are simply stunning… and you will be very hard-pressed to ever see the same thing happen twice.

Click on the image to the right of this post and you will understand what I mean by ‘plausible.’ If your monitor has a very high resolution, click here (careful–it’s a 3.5 MB file!) to see the full resolution, high quality version. You will see what I mean by ‘scalable.’

The terms are pretty simple, but what we are doing with them in X-Plane 10 is just amazing.

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