Night over Hamburg now looks like night
The Hamburg Airport live stream has been running around the clock for a few days now, and the first night on it showed a problem we had never noticed in the sim: the sky went black with stars, and the ground stayed bright green underneath it. It looked like someone had pasted a night sky over a daytime photo.
There were two separate faults behind it.
The ground barely got darker. At night we tint the satellite imagery down, and the code asked for 16% brightness. That number is in linear colour, though, and after it goes through the conversion to what your screen shows it lands at about 44%. Half-bright grass under a black sky reads as day. The night floor is now 5% linear, which is roughly a quarter of daytime brightness on screen. You can still see fields, rivers and the runway outline, but it is clearly night.
Some camera panes had a daytime sky. The sky is a small sphere that travels with the main camera. The stream shows up to four cameras at once, placed kilometres apart around the airport, and every camera except the first one was standing outside that sphere. They saw the scene's default background colour instead, which is a pale beige meant for daytime. So one pane showed stars and the pane next to it showed a cloudy afternoon. Each camera now gets the sky moved to it before its pane is drawn.
Street lamps after dusk. With the ground dark, the city needed something to see by. Every road from the Overture map now carries a row of lamps, one every 30 to 55 metres depending on the road, and the road surface itself gets a faint warm tint. Motorways and trunk roads get whiter lamps, smaller streets the orange of old sodium lights. Fly low and you see individual lamps strung along the streets; climb and they merge into glowing lines that trace the city. They fade in on the same curve that darkens the ground, so at sunset you watch the street grid appear as the fields disappear. During the day there are no lamps and roads keep the same flat asphalt grey as before.
This is the same layer in the flight sim and on the stream, so if you fly at night with the day/night cycle switched on, you get it too. Turn the cycle off in settings and the world stays in its fixed afternoon light.
The stream's map goes dark too. The software renderer on the streaming server can't draw the 3D world at a watchable frame rate without a graphics card, so for now the stream shows the overview map instead of the 3D cameras. That map now has its own night look: after sunset the land turns dark blue and the roads light up, motorways almost white and streets orange, with aircraft and ships drawn bright on top. The 3D cameras come back when the stream moves to a machine with a GPU.
What is not done yet: buildings still use the old lighting, so in some places white walls look brighter than they should at night, and runways have no edge lights. Both are on the list. If something looks wrong over your city after dark, the Discord is the fastest place to tell us, ideally with a screenshot.
You can watch the Hamburg stream on our YouTube channel, or fly the same airspace yourself at skydex.online.