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Elite on the BBC Micro

Version analysis of SHIP_ESCAPE_POD

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_ESCAPE_POD Type: Variable Category: Drawing ships Summary: Ship blueprint for an escape pod Deep dive: Ship blueprints
.SHIP_ESCAPE_POD

Code variation 1 of 4Related to an enhanced feature

In the enhanced versions, the escape pod ship blueprint contains the information in the top nibble of byte #0 that scooping escape pods gives us slaves.

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Cassette, Electron

Flight, 6502SP, Master

EQUB 0 \ Max. canisters on demise = 0
EQUB 0 + (2 << 4) \ Max. canisters on demise = 0 \ Market item when scooped = 2 + 1 = 3 (Slaves)
 EQUW 16 * 16           \ Targetable area          = 16 * 16
 EQUB &2C               \ Edges data offset (low)  = &002C
 EQUB &44               \ Faces data offset (low)  = &0044

Code variation 2 of 4Related to an advanced feature

The advanced versions of Elite have an extra edge count for the ship colour; escape pods are shown in cyan.

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Cassette, Flight, Electron

6502SP, Master

EQUB 25 \ Max. edge count = (25 - 1) / 4 = 6
EQUB 29 \ Max. edge count = (29 - 1) / 4 = 7
 EQUB 0                 \ Gun vertex               = 0
 EQUB 22                \ Explosion count          = 4, as (4 * n) + 6 = 22
 EQUB 24                \ Number of vertices       = 24 / 6 = 4
 EQUB 6                 \ Number of edges          = 6
 EQUW 0                 \ Bounty                   = 0
 EQUB 16                \ Number of faces          = 16 / 4 = 4
 EQUB 8                 \ Visibility distance      = 8
 EQUB 17                \ Max. energy              = 17
 EQUB 8                 \ Max. speed               = 8
 EQUB &00               \ Edges data offset (high) = &002C
 EQUB &00               \ Faces data offset (high) = &0044

Code variation 3 of 4Related to a standard feature

In the cassette version, the escape pod stores its faces with a scale factor of 8, while the other versions store them at a more accurate factor of 16.

See below for more variations related to this code.

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Cassette, Electron

Flight, 6502SP, Master

EQUB 3 \ Normals are scaled by = 2^3 = 8
EQUB 4 \ Normals are scaled by = 2^4 = 16
 EQUB %00000000         \ Laser power              = 0
                        \ Missiles                 = 0

\VERTEX    x,    y,    z, face1, face2, face3, face4, visibility
 VERTEX   -7,    0,   36,     2,      1,    3,     3,         31    \ Vertex 0
 VERTEX   -7,  -14,  -12,     2,      0,    3,     3,         31    \ Vertex 1
 VERTEX   -7,   14,  -12,     1,      0,    3,     3,         31    \ Vertex 2
 VERTEX   21,    0,    0,     1,      0,    2,     2,         31    \ Vertex 3

.SHIP_ESCAPE_POD_EDGES

\EDGE vertex1, vertex2, face1, face2, visibility
 EDGE       0,       1,     3,     2,         31    \ Edge 0
 EDGE       1,       2,     3,     0,         31    \ Edge 1
 EDGE       2,       3,     1,     0,         31    \ Edge 2
 EDGE       3,       0,     2,     1,         31    \ Edge 3
 EDGE       0,       2,     3,     1,         31    \ Edge 4
 EDGE       3,       1,     2,     0,         31    \ Edge 5

Code variation 4 of 4Related to a standard feature

See variation 3 above for details.

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Cassette, Electron

Flight, 6502SP, Master

\FACE normal_x, normal_y, normal_z, visibility FACE 26, 0, -61, 31 \ Face 0 FACE 19, 51, 15, 31 \ Face 1 FACE 19, -51, 15, 31 \ Face 2 FACE -56, 0, 0, 31 \ Face 3
\FACE normal_x, normal_y, normal_z, visibility FACE 52, 0, -122, 31 \ Face 0 FACE 39, 103, 30, 31 \ Face 1 FACE 39, -103, 30, 31 \ Face 2 FACE -112, 0, 0, 31 \ Face 3
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