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Labyrinth Data

Amberstar refers to first-person map resources as "Lab" resources, so we here adopt the terms "Labyrinth" to refer to them.

Here block types are mentioned as Solid, Decoration and Furniture/NPC. In the original they are referred to as Underlay (mostly walls), Overlay and Object.

LabData

A LabData resource collects all indices needed for drawing a particular type of Labyrinth, including background images and palette information. These resources are stored in LAB_DATA.AMB.

offset name size meaning
0x0 magic_0 u8 = 0x00
0x1 num_pixmaps u8 Total number of pixmaps (not including bg images)
0x2 num_labblock_refs u8 Number of LabBlock references
0x3..0x3+num_labblock_refs labblock_ref[i] + 1 u8 Reference to LabBlock resource, with 1 referencing resource 0
0x4 + num_labblock_refs magic_0 u8 = 0x00
0x5 + num_labblock_refs outdoors u8 0x03 for outdoors map (don't flip ceiling when moving forward), 0x02 for indoors
0x6 + num_labblock_refs magic_2 u8 = 0x02
0x7 + num_labblock_refs ceiling u8 Ceiling image: index into the BACKGRND.AMB resources, plus 1
0x8 + num_labblock_refs floor u8 Floor image: index into the BACKGRND.AMB resources, plus 1
0x9 + num_labblock_refs magic_1 u8 = 0x01
0xa + num_labblock_refs palette + 1 u8 Index into the list of Palettes, plus 1
  • Ceiling and floor images, as well as all indexed LabBlock resources, use the specified palette.
  • For 3D city views, the colour 11/0x0b has a special meaning: transparency relative to the day/night sky gradient (see below)
  • When moving around in a Labyrinth, the floor and ceiling images are flipped after every step, except for outdoors images, where the ceiling image is flipped only when rotating.
  • When rotating, the ceiling image is also flipped (UNKNOWN: outdoors only or also in dungeons?)
  • When rotating, the floor images is not flipped outdoors (UNKNOWN: how about in dungeons?)
  • For outdoor maps the ceiling is mirrored if the view direction is north or south, otherwise it iy normally drawn. The floor is mirrored if (mapX ^ mapY) & 0x1 is 1. So basically if the mapX is odd and the mapY is even or vice versa.

LabBlock

These resources are stored in LABBLOCK.AMB.

offset name size meaning
0x00 magic_0 u8 = 0x00
0x01 format u8 Format specifier. 1 = Solid, 2 = Decoration, 3 = Furniture/NPC
0x02 num_perspectives u8 Number of perspectives for this block. For Solid: 13 decimal, for Decoration: 17 decimal, for Furniture/NPC: 4
0x03 num_frames u8 Number of animation frames (same for all perspectives, but see note about Furniture/NPC below
0x04..0x26 xoffset[i] u16[17] x offsets for drawing
0x26..0x48 yoffset[i] u16[17] y offsets for drawing
0x48 specialXOffset u16 special x offset (exists for NPCs only, see below)
0x4a specialYOffset u16 special y offset (exists for NPCs only, see below)
0x48/0x4c sized_pixmap[i] see below Pixmaps for each (frame, perspective) combination

The sized_pixmap entries have the following structure:

  • size : u32 : Number of bytes (excluding size) of the pixmap
  • pixmap: A Pixmap with Header

Notes:

  • The pixmap are ordered first by animation frames, and then by perspectives. E.g., with two animation frames, the file first lists all perspectives for frame 0, then all for frame 1.
  • The xoffset, yoffset information indicates where the upper left corner of the pixmap should be drawn, relative to the background image, with one exception for Furniture/NPC.
  • For Furniture/NPC, the last perspective (index 3) follows a special rule:
    • All animation frames other than frame 0 are drawn on top of frame 0
    • Frame 0 itself is not a complete animation frame, so Furniture/NPC has de facto one animation frame less than the other perspectives in the same resource
    • The offsets for frames 1 and later use specialXOffset and specialYOffset for screen positioning
    • The special offset is only present for Furniture/NPC, otherwise the pixmap data directly follows the 17 other offsets. Please note that you can't just read 18 offsets instead as you would read 18 x-values, then 18 y-values but it is stored as 17 x-values, 17 y-values, special-x and then special-y which is different.
  • Perspectives must be drawn in order, i.e., lower-indexed perspectives are drawn first.

Perspectives

The perspectives have different for the different formats. Each perspective describes a different view on the same entity, depending on where it is positioned relative to the player's view port. In the following, we will describe this using tables that assume a right-facing player/party, marked as @>:
2
@> 3 0 1

This table would mean that:

  • perspective 0 is "one step ahead of the player" (in the direction the player is facing)
  • perspective 1 is "two steps ahead of the player"
  • perspective 2 is "two steps ahead of the player and one to the left"
  • perspective 3 is "same tile as the player"

Perspectives for Solid blocks
0
9 6 3 0
@> 8 5 2
A 7 4 1
1

Note:

  • perspectives 0 and 1 are drawn if either of the blocks indicated in the table contains the block in question.
    • This does mean that they are somewhat inaccurate. The game seems to avoid this by mostly using narrow corridors / obstacles to hide this property
  • *UNKNOWN: what happens if there are two blocks with this property and they overlap? Who wins?

Perspectives for Decoration blocks

Decoration blocks are drawn over a Solid block and decorate it. If the decoration is visible from more than one side, it may have to be drawn multiple times.

The table below is used for decorations that are facing towards the player/party:
6 3 0
@> 8 5 2
7 4 1

The table below is used for decorations that

  • are to the left of the player, facing right (9, F, D, B)
  • are to the right of the player, facing left (A, 10, E, C)
9 F D B
@>
A 10 E C

Perspectives for Furniture/NPC blocks

Furniture/decoration blocks are the only blocks that are drawn when on the same tile as the player.
2 1 0
@> 3 2 1 0
2 1 0

The blocks in the left and right rows (from player's view) are drawn with an offset. The left ones are drawn at x=mapViewArea.Left, the center ones as given as x=mapViewArea.Left + renderX and the right ones at x=mapViewArea.Right - imageWidth/2.

Ceiling and floor

Ceiling and floor use a graphic from the file BACKGRND.AMB. Each subfile stores a Pixmap List. There should be only one pixmap per subfile though. Usually the pixmaps have a width of 144 pixels (full map view area) but the height is arbitrary. Ceilings are displayed at the top of the map view area and floors at the bottom of that area minus the pixmap height.

Sky Gradient

Cities have a background sky gradient. This gradient is stored in AMBERDEV.UDO and consists of three Compact palettes, in order:

  • Day gradient
  • Night gradient
  • Twilight gradient (dawn/dusk)

Each gradient has 83 palette entries. The gradients are stored without any intervening separator. Each palette entry specifies the sky colour for the corresponding scanline in the first-person view, going downwards. The game selects the gradients based on the time of day:

Time of day Gradient
06:00-07:59 Twilight
08:00-17:59 Day
18:00-19:59 Twilight
20:00-05:59 Night

During twilight hours, there is some blending between the gradients; details tbd.