Add the view-map command and some exploration of results

doc/formats/maps.md

@@ -293,6 +293,8 @@ Total number of possible coordinates is 100x130x7 = 91,000 = 1,456,000 bytes.
 Uncompressed file size is always 1,458,915 bytes, leaving 2,915 bytes over for
 header and any trailing data.
 
+How are the rows structured? `[z][y][x]`?
+
 Looking at the data around 0x163890, we see:
 
 ```
@@ -328,6 +330,67 @@ So this looks like a good working theory.
 Wherever they start, these rows must refer to the object sets somehow. We also
 need to work out how they're arranged.
 
+Disassembly of WH40K_TD.EXE suggests a file `Engine::CellInfo` at 0x4226F0. It
+dumps the following information:
+
+* Mission exit: true / false
+* Smoke: true / false
+* Sprite: true / false
+* Vehicle: true / false
+* Net start: true / false
+* Spell: true / false
+* Trigger: true / false
+* Breadcrumb: true / false
+* Door: true / false
+* Lock: true / false
+* Reactor: true / false
+* Objective: true / false
+* Canister number %d
+* Cell visible %d
+* Tile visible %d
+* N0 - N7: true / false (seems to be a bitfield)
+* Object 0 SURFACE: true / false
+* Object area %d
+* Curr sprite %d
+* Object 1 LEFT: true / false
+* Object area %d
+* Curr sprite %d
+* Object 2 RIGHT: true / false
+* Object area %d
+* Curr sprite %d
+* Object 3 CENTRE: true / false
+* Object area %d
+* Curr sprite %d
+
+Presumably at least some of these attributes come from the records identified
+above. Will need to experiment to establish correlations. Items of interest:
+
+* A cell can have 4 objects in it - a surface, a left, a right, and a centre.
+* Presumably a surface is what we show on the ground, and it will be set for
+  "ground level" data.
+
+Press "U" to get to the screen!
+
+![Debug screen](img/cell-information-debug.png)
+
+I've added a `view-map` command to explore the data graphically. Each of the 16
+bytes in a cell row must have a function; comparing a known map to how it looks
+in WH40K_TD.exe can help me to unravel that function.
+
+Here's a side-by-side comparison of Chapter3.MAP, investigating CellIndex=3 and
+Z index = 0
+
+![Map comparison](img/chapter_01_cell_index_3.png)
+
+Incrementing the Z index shows the building and terrain progressively changing
+as expected, so this is a good hint that the data is actually arranged in
+`[z][y][x][16]` blocks and that I either have the right offset, or I'm out by a
+well-aligned amount.
+
+Trying to constrict to the viewport currently cuts off much of this displayed
+map, suggesting that I've got something wrong in the calculation somewhere. Need
+to dig into that more.
+
 ## Trailer
 
 Assuming the theory above is correct, we have trailer data starting at