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Elite on the BBC Micro

Missile ship blueprint [Disc version]

DISC ELITE MISSILE SHIP BLUEPRINT FILE Elite was written by Ian Bell and David Braben and is copyright Acornsoft 1984 The code on this site has been disassembled from the version released on Ian Bell's personal website at http://www.elitehomepage.org/ The commentary is copyright Mark Moxon, and any misunderstandings or mistakes in the documentation are entirely my fault The terminology and notations used in this commentary are explained at https://www.bbcelite.com/about_site/terminology_used_in_this_commentary.html The deep dive articles referred to in this commentary can be found at https://www.bbcelite.com/deep_dives
This source file produces the following binary file: * MISSILE.bin This gets loaded as part of elite-loader3.asm and gets moved to &7F00 during the loading process.
INCLUDE "1-source-files/main-sources/elite-header.h.asm" _IB_DISC = (_RELEASE = 1) _STH_DISC = (_RELEASE = 2) GUARD &6000 \ Guard against assembling over screen memory
Configuration variables
CODE% = &7F00 LOAD% = &244B ORG CODE%
Name: VERTEX [Show more] Type: Macro Category: Drawing ships Summary: Macro definition for adding vertices to ship blueprints Deep dive: Ship blueprints
Context: See this macro on its own page References: No direct references to this macro in this source file

The following macro is used to build the ship blueprints: VERTEX x, y, z, face1, face2, face3, face4, visibility See the deep dive on "Ship blueprints" for details of how vertices are stored in the ship blueprints, and the deep dive on "Drawing ships" for information on how vertices are used to draw 3D wiremesh ships. Arguments: x The vertex's x-coordinate y The vertex's y-coordinate z The vertex's z-coordinate face1 The number of face 1 associated with this vertex face2 The number of face 2 associated with this vertex face3 The number of face 3 associated with this vertex face4 The number of face 4 associated with this vertex visibility The visibility distance, beyond which the vertex is not shown
MACRO VERTEX x, y, z, face1, face2, face3, face4, visibility IF x < 0 s_x = 1 << 7 ELSE s_x = 0 ENDIF IF y < 0 s_y = 1 << 6 ELSE s_y = 0 ENDIF IF z < 0 s_z = 1 << 5 ELSE s_z = 0 ENDIF s = s_x + s_y + s_z + visibility f1 = face1 + (face2 << 4) f2 = face3 + (face4 << 4) ax = ABS(x) ay = ABS(y) az = ABS(z) EQUB ax, ay, az, s, f1, f2 ENDMACRO
Name: EDGE [Show more] Type: Macro Category: Drawing ships Summary: Macro definition for adding edges to ship blueprints Deep dive: Ship blueprints
Context: See this macro on its own page References: No direct references to this macro in this source file

The following macro is used to build the ship blueprints: EDGE vertex1, vertex2, face1, face2, visibility See the deep dive on "Ship blueprints" for details of how edges are stored in the ship blueprints, and the deep dive on "Drawing ships" for information on how edges are used to draw 3D wiremesh ships. Arguments: vertex1 The number of the vertex at the start of the edge vertex1 The number of the vertex at the end of the edge face1 The number of face 1 associated with this edge face2 The number of face 2 associated with this edge visibility The visibility distance, beyond which the edge is not shown
MACRO EDGE vertex1, vertex2, face1, face2, visibility f = face1 + (face2 << 4) EQUB visibility, f, vertex1 << 2, vertex2 << 2 ENDMACRO
Name: FACE [Show more] Type: Macro Category: Drawing ships Summary: Macro definition for adding faces to ship blueprints Deep dive: Ship blueprints
Context: See this macro on its own page References: No direct references to this macro in this source file

The following macro is used to build the ship blueprints: FACE normal_x, normal_y, normal_z, visibility See the deep dive on "Ship blueprints" for details of how faces are stored in the ship blueprints, and the deep dive on "Drawing ships" for information on how faces are used to draw 3D wiremesh ships. Arguments: normal_x The face normal's x-coordinate normal_y The face normal's y-coordinate normal_z The face normal's z-coordinate visibility The visibility distance, beyond which the edge is always shown
MACRO FACE normal_x, normal_y, normal_z, visibility IF normal_x < 0 s_x = 1 << 7 ELSE s_x = 0 ENDIF IF normal_y < 0 s_y = 1 << 6 ELSE s_y = 0 ENDIF IF normal_z < 0 s_z = 1 << 5 ELSE s_z = 0 ENDIF s = s_x + s_y + s_z + visibility ax = ABS(normal_x) ay = ABS(normal_y) az = ABS(normal_z) EQUB s, ax, ay, az ENDMACRO
Name: SHIP_MISSILE [Show more] Type: Variable Category: Drawing ships Summary: Ship blueprint for a missile Deep dive: Ship blueprints
Context: See this variable on its own page References: No direct references to this variable in this source file
.SHIP_MISSILE EQUB 0 \ Max. canisters on demise = 0 EQUW 40 * 40 \ Targetable area = 40 * 40 EQUB LO(SHIP_MISSILE_EDGES - SHIP_MISSILE) \ Edges data offset (low) EQUB LO(SHIP_MISSILE_FACES - SHIP_MISSILE) \ Faces data offset (low) EQUB 81 \ Max. edge count = (81 - 1) / 4 = 20 EQUB 0 \ Gun vertex = 0 EQUB 10 \ Explosion count = 1, as (4 * n) + 6 = 10 EQUB 102 \ Number of vertices = 102 / 6 = 17 EQUB 24 \ Number of edges = 24 EQUW 0 \ Bounty = 0 EQUB 36 \ Number of faces = 36 / 4 = 9 EQUB 14 \ Visibility distance = 14 EQUB 2 \ Max. energy = 2 EQUB 44 \ Max. speed = 44 EQUB HI(SHIP_MISSILE_EDGES - SHIP_MISSILE) \ Edges data offset (high) EQUB HI(SHIP_MISSILE_FACES - SHIP_MISSILE) \ Faces data offset (high) EQUB 2 \ Normals are scaled by = 2^2 = 4 EQUB %00000000 \ Laser power = 0 \ Missiles = 0 \VERTEX x, y, z, face1, face2, face3, face4, visibility VERTEX 0, 0, 68, 0, 1, 2, 3, 31 \ Vertex 0 VERTEX 8, -8, 36, 1, 2, 4, 5, 31 \ Vertex 1 VERTEX 8, 8, 36, 2, 3, 4, 7, 31 \ Vertex 2 VERTEX -8, 8, 36, 0, 3, 6, 7, 31 \ Vertex 3 VERTEX -8, -8, 36, 0, 1, 5, 6, 31 \ Vertex 4 VERTEX 8, 8, -44, 4, 7, 8, 8, 31 \ Vertex 5 VERTEX 8, -8, -44, 4, 5, 8, 8, 31 \ Vertex 6 VERTEX -8, -8, -44, 5, 6, 8, 8, 31 \ Vertex 7 VERTEX -8, 8, -44, 6, 7, 8, 8, 31 \ Vertex 8 VERTEX 12, 12, -44, 4, 7, 8, 8, 8 \ Vertex 9 VERTEX 12, -12, -44, 4, 5, 8, 8, 8 \ Vertex 10 VERTEX -12, -12, -44, 5, 6, 8, 8, 8 \ Vertex 11 VERTEX -12, 12, -44, 6, 7, 8, 8, 8 \ Vertex 12 VERTEX -8, 8, -12, 6, 7, 7, 7, 8 \ Vertex 13 VERTEX -8, -8, -12, 5, 6, 6, 6, 8 \ Vertex 14 VERTEX 8, 8, -12, 4, 7, 7, 7, 8 \ Vertex 15 VERTEX 8, -8, -12, 4, 5, 5, 5, 8 \ Vertex 16 .SHIP_MISSILE_EDGES \EDGE vertex1, vertex2, face1, face2, visibility EDGE 0, 1, 1, 2, 31 \ Edge 0 EDGE 0, 2, 2, 3, 31 \ Edge 1 EDGE 0, 3, 0, 3, 31 \ Edge 2 EDGE 0, 4, 0, 1, 31 \ Edge 3 EDGE 1, 2, 4, 2, 31 \ Edge 4 EDGE 1, 4, 1, 5, 31 \ Edge 5 EDGE 3, 4, 0, 6, 31 \ Edge 6 EDGE 2, 3, 3, 7, 31 \ Edge 7 EDGE 2, 5, 4, 7, 31 \ Edge 8 EDGE 1, 6, 4, 5, 31 \ Edge 9 EDGE 4, 7, 5, 6, 31 \ Edge 10 EDGE 3, 8, 6, 7, 31 \ Edge 11 EDGE 7, 8, 6, 8, 31 \ Edge 12 EDGE 5, 8, 7, 8, 31 \ Edge 13 EDGE 5, 6, 4, 8, 31 \ Edge 14 EDGE 6, 7, 5, 8, 31 \ Edge 15 EDGE 6, 10, 5, 8, 8 \ Edge 16 EDGE 5, 9, 7, 8, 8 \ Edge 17 EDGE 8, 12, 7, 8, 8 \ Edge 18 EDGE 7, 11, 5, 8, 8 \ Edge 19 EDGE 9, 15, 4, 7, 8 \ Edge 20 EDGE 10, 16, 4, 5, 8 \ Edge 21 EDGE 12, 13, 6, 7, 8 \ Edge 22 EDGE 11, 14, 5, 6, 8 \ Edge 23 .SHIP_MISSILE_FACES \FACE normal_x, normal_y, normal_z, visibility FACE -64, 0, 16, 31 \ Face 0 FACE 0, -64, 16, 31 \ Face 1 FACE 64, 0, 16, 31 \ Face 2 FACE 0, 64, 16, 31 \ Face 3 FACE 32, 0, 0, 31 \ Face 4 FACE 0, -32, 0, 31 \ Face 5 FACE -32, 0, 0, 31 \ Face 6 FACE 0, 160, 110, 31 \ Face 7 FACE 0, 64, 4, 0 \ Face 8
Name: VEC [Show more] Type: Variable Category: Screen mode Summary: The original value of the IRQ1 vector
Context: See this variable on its own page References: No direct references to this variable in this source file
.VEC EQUW &0004 \ VEC = &7FFE \ \ This gets set to the value of the original IRQ1 vector \ by the loading process \ \ This default value is presumably noise included at the \ time of compilation, as it gets overwritten
Save MISSILE.bin
PRINT "MISSILE" PRINT "Assembled at ", ~CODE% PRINT "Ends at ", ~P% PRINT "Code size is ", ~(P% - CODE%) PRINT "Execute at ", ~LOAD% PRINT "Reload at ", ~LOAD% PRINT "S.MISSILE ",~CODE%," ",~P%," ",~LOAD%," ",~LOAD% SAVE "3-assembled-output/MISSILE.bin", CODE%, P%, LOAD%