✔️ NEW FEATURE: Curved Horizon

[Krishty]

There is an issue with both ADF/TAW and AC3 levels.

UAW’s world is always flat, and its sky assumes the horizon is at 0°. As a result, there is always a band above terrain. The higher one gets (and the shorter the terrain rendering range), the more obvious it is:

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It’s called The Gray Wall in Falcon 4.0 because that game has the same issue.

One way to resolve it is using spherical terrain (which UAW won’t do due to complexity) and physically-based atmospheric scattering simulation instead of fog (which UAW won’t due before the Direct3D 9 renderer is replaced with something modern).

The other way is … cheating your way out of it. That sphere that draws the sky and horizon around the viewer? Just move it down when the viewer gets higher. If you move it down by the right amount – which can be calculated from the terrain rendering range and the viewer’s altitude – then the horizon will start rendering exactly where the terrain ends.

Some results:

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2024-01-19 horizon curvature 3.png (2.41 MiB) Viewed 1344 times

In these AC3 screenshots, the horizon starts ~10° below the actual horizon (as indicated by the HUD). It’s only 3° for real pilots, but it reduces the gray wall quite a lot. And it feels so much more natural, too!

F22’s wall is greatly reduced at short viewing range:

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We never had a problem with it at far viewing range, but the horizon is also slightly curved there now. It’s only clearly visible from heights around 100k ft, which is at least not totally unrealistic.

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This was another low-hanging fruit. It seems to work; I’ll do some minor cleanup and it will be in the next update.

[Krishty]

Has landed.

[Krishty]

The next source update will bring slight changes to curvature and color.

Most important, the extinction/scattering coefficients of the atmosphere are now less skewed towards blue. Thus, the color of terrain far away will stay more true to what has been defined as horizon color.

Furthermore, the intensity of scattering has been adjusted slightly so that pop-up at the terrain edges is no longer visible. It was very hard to spot anyway, but AC3 brings snow levels, and the problem was really sticking out there.

[Krishty]

Adjustments have landed.