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Code Issues 157 Wiki Activity

Shade the sky and the sun by the scenery around the camera instead of the track environment flags

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Hirek
2026-10-27 16:02:36 +01:00
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@@ -269,6 +269,54 @@ the reflections of the cab.
| `gfx.cabprobe.bounce` | `1.0` | 0..4: share of the light of the lamp the cab reflects which lights it again |
| `gfx.cabprobe.reflections yes/no` | `yes` | the cab reflects itself where the screen space reflections find nothing; `no`: the sky, as before |
### Tunnels, bridges and roofs: the occlusion of the sky
The light of the sky and of the sun is held back by the geometry around, not by the environment flags of the tracks
(`tunnel`, `canyon`): the tracks and the vehicles on them are drawn alike wherever they are, and a tunnel is dark because the
hill and the vault over it hide the sky. A track with the `tunnel` flag and nothing built over it is lit as in the open; the
flag stays in the scenery files (the sound in the tunnel, the driver turning the lights on). `gfx.tunnelflags yes` brings the
old darkening by the flags back.
The scenery around the camera is laid out seen from above, in tiles, in the background (a thread of its own): for each texel
the height of the highest surface (the top) and of the lowest one facing down (the ceiling: the vault of a tunnel, the deck of a
bridge seen from below, a roof). Taken are the shapes (the terrain, the heightmap terrain, roads, platforms) and the opaque parts
of the models at their nearest level of detail; not the vehicles, the tracks, the catenary, nor what is see-through (trees).
Things narrower than about three texels (poles, masts, fences) are left out. From the heights around, each texel gets:
- the share of the sky a surface facing up sees above the top, and under the ceiling (light comes in under the vault from the
portal, along the tunnel);
- the heights between which the sun (the moon at night) comes in: above the top what is higher than the shadow of the hills
and buildings towards it, under the ceiling what the rays reach under the vault from the portal (a low sun shines a little way
into a tunnel).
The shading takes the ambient light, the reflection of the sky and the sun by them, wherever a surface is (the half of a train
in the tunnel is dark, the other half in the light, with the passage over a few metres at the portal). The headlights, the lamps
and the light of the cab are direct light and are not held back; the headlights fade in daylight by the light around the
vehicle, which is read from the same maps, so in a tunnel they light by day as by night. The rain and the snow don't fall under
the roofs, bridges and in tunnels, and the light of the volumetric fog and of the smoke is held back as well. A tile is laid out
once, when it comes into the square around the camera, and again only when its scenery changes (the editor, the streamed
terrain, models shown or hidden by events); the sun is followed every quarter of a degree.
| Level | Square around the camera | Texel | Searched around a texel (sky / sun) |
|---|---|---|---|
| `low` (1) | 256 m (at least 96 m on each side) | 1 m | 32 m in 8 directions / 64 m |
| `medium` (2) | 512 m (at least 192 m) | 1 m | 48 m in 12 directions / 128 m |
| `high` (3) | 512 m (at least 192 m) | 0.5 m | 64 m in 16 directions / 128 m |
Cost: on the main thread, the triangles of a tile gathered when it comes in (one tile a frame, more at the start), a fraction
of a millisecond; in the background, a few to some tens of milliseconds per tile, which doesn't hold the frame up. On the GPU,
two textures (`medium`: 3 MB, `high`: 12 MB) and five texture reads per pixel in the shading. With `no` nothing of it is made
and the scenery is lit as in the open everywhere.
| Entry | Default | Meaning |
|---|---|---|
| `gfx.skyvisibility` | `medium` | `no`/`low`/`medium`/`high` (or 0..3), see above |
| `gfx.skyvisibility.sun yes/no` | `yes` | the sun is held back too (beyond the reach of the shadow map, and in the tunnels whatever the shadow map holds); `no`: the sun only by the shadow map |
| `gfx.skyvisibility.fog yes/no` | `yes` | the light of the volumetric fog is held back too |
| `gfx.tunnelflags yes/no` | `no` | `yes`: the flags `tunnel`/`canyon` of the tracks darken the tracks and the vehicles on them, as before (on top of the occlusion) |
All of them can be changed while the simulator runs, in the **Sky and exposure** debug window, which also shows views of the
maps around the camera (the share of the sky above the top and under the ceilings, the sun, the heights).
### Contact shadows
Short shadows where things touch or nearly touch: the rails on the sleepers, bolts and edges of panels, a wheel on the rail,