Do some more file format spelunking

`WarHammer.ani` turns out to be a regular `obj` file; `WarHammer.idx`
is partially decoded, but I'm struggling to link it to the former in
a reasonable way at the moment.

doc/formats/obj.md

@@ -206,8 +206,8 @@ in the CENTER position. Interesting.
 | 0x0004 | x,y size (16 bits each) |
 | 0x0008 | ? (blank in all cases so far)
 | 0x000c | Size of remaining pixeldata |
-| 0x0010 | Padding? |
-| 0x0014 | Padding? |
+| 0x0010 | Set in `WarHammer.ani` |
+| 0x0014 | ? (blank in all cases so far) |
 
 The volume represented by a cell is a little odd. We see three faces of a fake
 3D volume of size 64x64x32(ish). This is presented in an isomorphic fashion, so
@@ -512,3 +512,60 @@ break *0x41DD10
 This lets me focus very narrowly on what happens when loading sprites, and
 might give clues.
 
+## WarHammer.ani
+
+This 400MiB file appears to be a standard object file, it's just very large.
+The directory contains 188,286 sprites!
+
+The first 1,064 sprites are all of the same Ultramarine, carryng a bolter. There
+are eight "facing" orientations:
+
+* North
+* Northeast
+* East
+* Southeast
+* South
+* Southwest
+* West
+* Northwest
+
+For each orientation, an action is pictured in a variable number of frames. The
+final frame appears to be "stationary".
+
+* Walk (13 frames)
+* Run (9 frames)
+* Crouch down (8 frames)
+* Stand up (8 frames)
+* Take aim (standing) (6 frames)
+* Fire (standing) (6 frames)
+* Relax aim (standing) (6 frames) 
+* Throw grenade (standing) (18 frames)
+* Take aim (crouched) (5 frames)
+* Fire (crouched) (5 frames)
+* Relax aim (crouched) (5 frames)
+* Throw grenade (crouched) (17 frames)
+* Draw melee weapon (standing) (10 frames)
+* Strike down with melee weapon (standing) (8 frames)
+* Stab with melee weapon (standing) (9 frames)
+
+Added together and multiplied by 87, that's 1064.
+
+The next sprite is a walking-north action for an ultramarine with a flamer. The
+total number of frames for this character is 1120 - 56 additional frames, or 7
+per orientation. Could be an extra action, or an extra frame per action.
+
+Also notable is that while the bolter showed muzzle flash in the animation, the
+flamer only showed a tiny hint of fire. I think the animation for spewing flame
+is held elsewhere.
+
+I strongly suspect the actions and the number of frames in each action are
+configurable. But where?
+
+The field at 0x10 in the sprite header is set in `WarHammer.ani`, but not in
+the other object files encountered so far. However, it seems to be
+set statically to the bytes `[212 113 59 1]` for all of them.
+
+Assuming ~1000 sprites per character, `WarHammer.ani` contains 188 characters.
+
+Two other files have been implicated in animation - `Data/AniObDefs.dat` and
+`Idx/WarHammer.idx`. More on those in `ani.md`.