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6502bench/SourceGen/SGTestData/Visualization/wireframe-test.S
Andy McFadden b3dacc2613 Switch to left-handed coordinate system
There's no "standard" coordinate system, so the choice is arbitrary.
However, an examination of the Transporter mesh in Elite revealed
that the mesh was designed for a left-handed coordinate system.  We
can compensate for that trivially in the Elite visualizer, but we
might as well match what they're doing.  (The only change required
in the code is a couple of sign changes on the Z coordinate, and an
update to the rotation matrix.)

This also downsizes Matrix44 to Matrix33, exposes the rotation mode
enum, and adds a left-handed ZYX rotation mode.

This does mean that meshes that put the front at +Z will show their
backsides initially, since we're now oriented as if we're flying
the ships rather than facing them.  I considered adding a 180-degree
Y rotation (with a tweak to the rotation matrix handedness to correct
the first rotation axis) to have them facing by default, but figured
that might be confusing since +Z is supposed to be away.

Anybody who really wants it to be the other way can trivially flip
the coordinates in their visualizer (negate xc/zc).

The Z coordinates in the visualization test project were flipped so
that the design is still facing the viewer at rotation (0,0,0).
2020-03-14 13:59:08 -07:00

62 lines
1.7 KiB
ArmAsm

; Copyright 2020 faddenSoft. All Rights Reserved.
; See the LICENSE.txt file for distribution terms (Apache 2.0).
;
; Assembler: Merlin 32
; Cube with a decoration on the front (should look like a "7").
; Defined in a left-handed coordinate system (+Z away from viewer).
org $1000
lda vertices
lda edges
lda faces
rts
; List of vertices (X,Y,Z).
vertices
dfb -32,32,-32 ;0
dfb -32,-32,-32 ;1
dfb 32,-32,-32 ;2
dfb 32,32,-32 ;3
dfb -32,32,32 ;4
dfb -32,-32,32 ;5
dfb 32,-32,32 ;6
dfb 32,32,32 ;7
; Put a decoration on the front face.
dfb -20,-20,-32 ;8
dfb 20,20,-32 ;9
dfb 10,20,-32 ;10
dfb $80
; List of edges (vertex0, vertex1, face0, face1).
edges
dfb 0,1, 0,5 ;0
dfb 1,2, 0,3 ;1
dfb 2,3, 0,4 ;2
dfb 3,0, 0,2 ;3
dfb 4,5, 1,5 ;4
dfb 5,6, 1,3 ;5
dfb 6,7, 1,4 ;6
dfb 7,4, 1,2 ;7
dfb 0,4, 2,5 ;8
dfb 1,5, 3,5 ;9
dfb 2,6, 3,4 ;10
dfb 3,7, 2,4 ;11
dfb 8,9, 0,0 ;12
dfb 9,10, 0,0 ;13
dfb $80
; List of faces (surface normal X,Y,Z).
faces
dfb 0,0,-1 ;0 front
dfb 0,0,1 ;1 back
dfb 0,1,0 ;2 top
dfb 0,-1,0 ;3 bottom
dfb 1,0,0 ;4 right
dfb -1,0,0 ;5 left
dfb $80