Free Form Friday: Lights, Water, Frost

First, I appreciate everyone’s cooperation with the RFC on scenery; we’ve had an ongoing discussion in our developer Slack as well as the comment section, and I don’t think I had to nuke any off-topic comments. The feedback was wide-ranging and there’s no one clear answer but it does give us a really good picture of how the scenery system is working (and isn’t working).

It’s Friday, so let’s do something completely different – her’s some show and tell from a few things people have been working on things week.

Light It Up

Alex has been recalibrating the runway and airport lights for the new photometric lighting engine. This spurred an internal discussion about how best to calibrate artificial light sources. Does the author specify the luminance of the bulb before a tinted plastic housing goes on top (this way is good if you have the bulb specs from the internet) or based on what you’d measure when the finished light is tested? (This way matches FAA specs for airport lights.)

After going back and forth a few times, our answer is “well, both”, and we have a system that now allows this, which should solve use cases for both aircraft (where often the bulb properties are known because you can look up replacement parts) and for airports (where the FAA has standards for the light’s final results).

Something to keep in mind: urban airports are quite dark compared to their surroundings. Ther are very few light sources near the runway that aren’t tightly controlled for brightness and direction. I used to fly over KLAX on a regular basis at cruise altitudes (commuting from San Diego to San Francisco for work) and KLAX was always an inky black void in the sea of lights that is the LA basin; at 34,000 feet no runway lights are pointed up at us.

Wet Surfaces

Petr and Sidney have been working on the weather surface shader, which applies water and other weather effects to surfaces. This is how we dynamically make the pavement wet when it rains.

The shader is tricky because the effect of a surface being wet changes a lot once the water forms a real puddle. When I took my kids to their swim lesson, I couldn’t help but notice the useful reference material all over the place.

A rough wet material – reflections change with angle in X-Plane and real life

Stop Writing on the Windows

I must be a dad, because I get annoyed when my kids get finger prints all over the windows when they “write” things in the frost on a cold day.

Turns out Sidney does the same thing.

What you’re seeing there is programmer art. Programmer art is when the programmers make their own texture files to test code. In this case, Sidney is testing the defrosting system for windscreens, which use a special texture to specify the pattern of defrosting. This lets artists control the defrosting effect and get faster defrosting near vents.

Another “behind the scenes” thing you can see here: that popup window is a set of internal controls for testing, debugging and developing the windscreen effects. The parts of these internal controls that are generally useful will become third party developer tools (like the texture browser and particle system editor in X-Plane 11).

Cessna In Spaaaaaaaace

Daniel rewrote the planet shader. In X-Plane 12, water is treated separately from land (so that it can be 3-d). The new planet shader shows a far view of water and a far view of land at the same time and correctly shows atmospheric scattering, which is normally pre-calculated in a special “froxel cache” for regular scenery.

If you haven’t noticed the pattern, it’s that the art team’s screenshots all tend to look good enough to ship, and the programmer’s screen shots tend to be very, very silly. In this case, the Cessna in space is pretty silly, but what we were looking for was the smooth atmospheric effects all the way out to the horizon.

Here’s one more goofy programmer screenshot:

I was calibrating the runway lights according to Alex’s spec, and typed an extra 0 into one of the internal art controls by accident. The result was this fantastic screen shot.

What you’re seeing is: the billboards for the runway environment are accidentally huge and are filling up the entire reflection cube map. The reflective underside of the Cessna wing picks up this blue lights and it looks like a rave.