World: add prop tint and fog override

- World tint now also colours prop materials (models/props*) with their own
  colour, covering static props and prop_physics while leaving NPC, player and
  weapon materials untouched.
- New Fog card: fog_override colour/start/end via ClientCmd, optional skybox
  fog, and a Remove fog mode. Restores the map fog (fog_override 0) when
  disabled and re-applies after level changes.
- Config sections [worldtint] prop/colour keys and [fog].

1 files changed, 23 insertions, 3 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index b48100b..1d365e8 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -316,8 +316,11 @@ vocabulary / decisions.
   already-loaded `materialsystem.so` and walk every material with
   `FirstMaterial` / `NextMaterial` / `GetMaterial`.
 - `IMaterial::ColorModulate(r,g,b)` is applied to materials whose
-  `GetTextureGroupName()` is `World textures` (sky names excluded) and to
-  `SkyBox textures` (or names containing `sky`). Lightmaps are not touched.
+  `GetTextureGroupName()` is `World textures` (sky names excluded), to
+  `SkyBox textures` (or names containing `sky`), and to prop materials whose
+  name starts with `models/props` (static props and prop_physics share those
+  model materials; NPC/player/weapon materials are excluded). Lightmaps are
+  not touched.
 - Slot map (2013 SDK layout, registered under `VMaterialSystem080`):
   `IMaterialSystem` 73/74/75/76/77 = First/Next/Invalid/Get/GetNumMaterials;
   `IMaterial` 0/1/28 = GetName/GetTextureGroupName/ColorModulate.
@@ -327,7 +330,24 @@ vocabulary / decisions.
 - Validation before any walk: `GetNumMaterials()` must return 1..200000; the
   first material's name/group must be printable strings. A mismatch logs and
   toasts instead of poking garbage.
-- Saved as `[worldtint] active/bind/world/sky/wr..wb/sr..sb`.
+- Saved as `[worldtint] active/bind/world/sky/prop/wr..pb`.
+- Particle tint is deliberately not implemented: HL2's old particle manager
+  draws per-vertex coloured IMesh quads, and SpriteCard/TF2-style particles
+  take colour from per-particle vertex data, so `IMaterial::ColorModulate`
+  does nothing for them. It needs a hook in the client particle render path.
+
+### Fog
+
+- `src/world.cpp` `fog_update()`, driven by the `fog_override` engine command
+  family through `IVEngineClient::ClientCmd` (same safe path as fullbright).
+  No render hooks.
+- Enabled: `fog_override 1`, `fog_enable 1`, `fog_color`, `fog_start`,
+  `fog_end`, plus `fog_enableskybox` / `fog_colorskybox` /
+  `fog_startskybox` / `fog_endskybox` when skybox fog is on.
+  "Remove fog" issues `fog_enable 0` instead.
+- Disabled: `fog_override 0` restores the map's own fog controller.
+- End is clamped above Start. Re-applied on level change via
+  `fog_invalidate()`. Saved as `[fog] active/bind/r/g/b/start/end/skybox/disable`.
 
 ## Logging