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Elite on the BBC Micro

Version analysis of SHIP_THARGON

This code appears in the following versions (click to see it in the source code):

Code variations between these versions are shown below.

Name: SHIP_THARGON Type: Variable Category: Drawing ships Summary: Ship blueprint for a Thargon Deep dive: Ship blueprints
The ship blueprint for the Thargon reuses the edges data from the cargo canister, so the edges data offset is negative.
.SHIP_THARGON

Code variation 1 of 2Related to an enhanced feature

In the enhanced versions, the Thargon ship blueprint contains the information in the top nibble of byte #0 that scooping Thargons gives us alien items.

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Cassette

Flight, 6502SP, Master

EQUB 0 \ Max. canisters on demise = 0
EQUB 0 + (15 << 4) \ Max. canisters on demise = 0 \ Market item when scooped = 15 + 1 = 16 (alien items)
 EQUW 40 * 40           \ Targetable area          = 40 * 40
 EQUB LO(SHIP_CANISTER_EDGES - SHIP_THARGON)       \ Edges from canister
 EQUB LO(SHIP_THARGON_FACES - SHIP_THARGON)        \ Faces data offset (low)

Code variation 2 of 2Related to an advanced feature

The advanced versions of Elite have an extra edge count for the ship colour; Thargons are shown in "white" (cyan/red stripes).

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Cassette, Flight

6502SP, Master

EQUB 65 \ Max. edge count = (65 - 1) / 4 = 16
EQUB 69 \ Max. edge count = (69 - 1) / 4 = 17
 EQUB 0                 \ Gun vertex               = 0
 EQUB 18                \ Explosion count          = 3, as (4 * n) + 6 = 18
 EQUB 60                \ Number of vertices       = 60 / 6 = 10
 EQUB 15                \ Number of edges          = 15
 EQUW 50                \ Bounty                   = 50
 EQUB 28                \ Number of faces          = 28 / 4 = 7
 EQUB 20                \ Visibility distance      = 20
 EQUB 20                \ Max. energy              = 20
 EQUB 30                \ Max. speed               = 30
 EQUB HI(SHIP_CANISTER_EDGES - SHIP_THARGON)       \ Edges from canister
 EQUB HI(SHIP_THARGON_FACES - SHIP_THARGON)        \ Faces data offset (high)
 EQUB 2                 \ Normals are scaled by    = 2^2 = 4
 EQUB %00010000         \ Laser power              = 2
                        \ Missiles                 = 0

\VERTEX    x,    y,    z, face1, face2, face3, face4, visibility
 VERTEX   -9,    0,   40,     1,      0,    5,     5,         31    \ Vertex 0
 VERTEX   -9,  -38,   12,     1,      0,    2,     2,         31    \ Vertex 1
 VERTEX   -9,  -24,  -32,     2,      0,    3,     3,         31    \ Vertex 2
 VERTEX   -9,   24,  -32,     3,      0,    4,     4,         31    \ Vertex 3
 VERTEX   -9,   38,   12,     4,      0,    5,     5,         31    \ Vertex 4
 VERTEX    9,    0,   -8,     5,      1,    6,     6,         31    \ Vertex 5
 VERTEX    9,  -10,  -15,     2,      1,    6,     6,         31    \ Vertex 6
 VERTEX    9,   -6,  -26,     3,      2,    6,     6,         31    \ Vertex 7
 VERTEX    9,    6,  -26,     4,      3,    6,     6,         31    \ Vertex 8
 VERTEX    9,   10,  -15,     5,      4,    6,     6,         31    \ Vertex 9

.SHIP_THARGON_FACES

\FACE normal_x, normal_y, normal_z, visibility
 FACE      -36,        0,        0,         31    \ Face 0
 FACE       20,       -5,        7,         31    \ Face 1
 FACE       46,      -42,      -14,         31    \ Face 2
 FACE       36,        0,     -104,         31    \ Face 3
 FACE       46,       42,      -14,         31    \ Face 4
 FACE       20,        5,        7,         31    \ Face 5
 FACE       36,        0,        0,         31    \ Face 6

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