fix(render3d): the ground keeps more of its own colour, and the rock keeps all of it

55% of every ground pixel was the orthophotograph, at every distance and on every
material. A survey image records WHERE the forest and the scree are well and what a
steep rock face is coloured badly - it is shot through kilometres of air at an angle no
player stands at. The photograph keeps the meadow and the forest and gives the rock back
to the rock, by material and by elevation and never by distance: a distance fade used to
live here and was removed because the photograph has the day's own shadows baked in, so
grass grew dark patches as you backed away and they slid as you walked.

The far tier's rock fallback is the maroon mean, not a neutral grey - TFAST_3 skips the
rock sample and leaves that constant standing in for a whole mountain.

Ortho-classified snow needs altitude now. Bright and unsaturated is what snow looks like
from a satellite and also what a sunlit rock face looks like. Gully snow is gated on the
snow line rather than two absolute heights.

Distance desaturation eased 1.9 -> 1.15: tuned on a valley whose rock was grey anyway.

NOT FIXED, and I want it recorded rather than implied: the Bells themselves are still
not maroon. The near and middle rock is warmer and measurably so, but the distant peak
does not respond to ANY of this - not the rock tint, not the ortho weight, not the snow
line, not the gully gate. Painting sA bright red left it unchanged, so whatever surface
that is, it is not this shader's snow and not this shader's material blend. Somebody
should find out what draws it before tuning any of these numbers further.

400 frames: GL 7.0 s, VK 7.2 s. Backends agree to 0.62/255.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

changes/the-ground-up-close.md

@@ -0,0 +1,26 @@
+bump: patch
+type: fix
+The ground keeps more of its own colour, and the rock keeps all of it.
+
+55% of every ground pixel was the orthophotograph, at every distance and on every
+material. A survey image is a good record of WHERE the forest and the scree are and a
+poor record of what a steep rock face is coloured: it is shot through kilometres of air
+at an angle no player stands at, and it comes back pale. So the photograph keeps the
+meadow and the forest, where it carries real variation nothing else knows, and gives the
+rock back to the rock - by material and by elevation, never by distance, because a
+distance fade used to live here and was removed for a good reason (the photograph has
+the day's own shadows baked in, so grass grew dark patches as you backed away and they
+slid as you walked). Material and height do not move when the camera does.
+
+The far tier's rock fallback is the maroon mean rather than a neutral grey. TFAST_3 skips
+the rock sample and leaves that constant standing in for it, and the file's own rule says
+the cheap tier must keep the near tier's mean colour or the boundary shows as a ring.
+
+Ortho-classified snow now needs altitude. Bright and unsaturated is what snow looks like
+from a satellite and also what a sunlit rock face looks like, so faces were being painted
+90% white wherever the photograph was pale. Gully snow is gated on the snow line too,
+rather than on two absolute heights five hundred metres below where snow can lie.
+
+And the distance desaturation from `light-air-and-the-hour` is eased from 1.9 to 1.15.
+It was tuned on a valley whose rock was grey anyway; Maroon's air is thin and dry and the
+peaks are two kilometres from the lake.