Fog by view depth again

Fogging by depth buffer value, as Direct3D 9's documentation suggests for IMVU's projections, looks nothing like the client; fogging by view depth matched it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/interface.md

@@ -74,8 +74,8 @@ virtual methods, IMVU's code only uses an engine through helpers that call its v
 - Particles (`drawPointSprites`): a Visual C++ 2010 `std::vector` of 16-byte points (position, color), drawn as
   Direct3D 9 point sprites: squares viewport height / distance pixels across (Direct3D 9's defaults clamp them to
   1 to 64; IMVU sets only the size, 1, and the scale factors 0, 0, 1), textured over the whole square.
-- Fog: linear table fog. Direct3D 9 fogs by eye distance only for projections whose (3, 4) element is +1; IMVU's are
-  right-handed (-1), so it fogs by depth buffer value (0 to 1) against start 1 and end 50: in effect no fog.
+- Fog: linear table fog, start 1 and end 50 in rooms. Fogging by view depth matches the client; by depth buffer
+  value (as Direct3D 9's documentation suggests for projections like IMVU's) doesn't.
 - Still unknown: render targets, `CompoundRegion` (texture update
   regions), `newRenderTexture`'s flags, and what `beginRendering` does with a null target. MSVC orders overloaded
   virtual methods unlike their declaration, so our declarations never overload virtual methods.