Turbobasic.bas

' Turbo Basic (Borland 1987) version of rotating cube
' ESC to quit

W% = 320
H% = 200
NBPOINTS% = 8

SCREEN 1
CLS

DIM lines%(1:6, 1:4)
DIM linelen%(1:6)

DIM px!(1:NBPOINTS%)
DIM py!(1:NBPOINTS%)
DIM pz!(1:NBPOINTS%)

' Cube points
DATA  0.25,  0.25,  0.25
DATA -0.25,  0.25,  0.25
DATA -0.25, -0.25,  0.25
DATA  0.25, -0.25,  0.25
DATA  0.25,  0.25, -0.25
DATA -0.25,  0.25, -0.25
DATA -0.25, -0.25, -0.25
DATA  0.25, -0.25, -0.25

FOR i% = 1 TO NBPOINTS%
    READ px!(i%)
    READ py!(i%)
    READ pz!(i%)
NEXT i%

' Faces/edges as loops: count then indices (0-based in data, we +1 after read)
DATA 4, 0,1,2,3
DATA 4, 4,5,6,7
DATA 2, 0,4
DATA 2, 1,5
DATA 2, 2,6
DATA 2, 3,7

FOR i% = 1 TO 6
    READ linelen%(i%)
    FOR j% = 1 TO linelen%(i%)
        READ lines%(i%, j%)
        lines%(i%, j%) = lines%(i%, j%) + 1
    NEXT j%
NEXT i%

dt! = 1! / 60!
dz! = .75!
angle! = 0!

done% = 0

DO WHILE done% = 0
    IF INKEY$ = CHR$(27) THEN done% = 1

    CLS
    PRINT "Turbo Basic - CGA (ESC to quit)"

    angle! = angle! + 3.1415! * dt!
    mcos! = COS(angle!)
    msin! = SIN(angle!)

    FOR i% = 1 TO 6
        FOR j% = 1 TO linelen%(i%)

            l1% = lines%(i%, j%)

            j2% = j% + 1
            IF j2% > linelen%(i%) THEN j2% = 1
            l2% = lines%(i%, j2%)

            ax! = px!(l1%) : ay! = py!(l1%) : az! = pz!(l1%)
            bx! = px!(l2%) : by! = py!(l2%) : bz! = pz!(l2%)

            GOSUB RotTransProjA
            x1! = sx! : y1! = sy!

            GOSUB RotTransProjB
            x2! = sx! : y2! = sy!

            LINE (x1!, y1!)-(x2!, y2!), 3

        NEXT j%
    NEXT i%

    ' Use DELAY instead of busy-wait
    DELAY 0.02
LOOP

END

' --- Subroutines implemented as GOSUB blocks for max TB compatibility ---

RotTransProjA:
    x! = ax! : y! = ay! : z! = az!
    GOSUB RotateXZ
    z! = z! + dz!
    x! = x! / z!
    y! = y! / z!
    sx! = ((x! + 1!) / 2!) * W%
    sy! = (1! - (y! + 1!) / 2!) * H%
RETURN

RotTransProjB:
    x! = bx! : y! = by! : z! = bz!
    GOSUB RotateXZ
    z! = z! + dz!
    x! = x! / z!
    y! = y! / z!
    sx! = ((x! + 1!) / 2!) * W%
    sy! = (1! - (y! + 1!) / 2!) * H%
RETURN

RotateXZ:
    tx! = x!
    tz! = z!
    x! = tx! * mcos! - tz! * msin!
    z! = tx! * msin! + tz! * mcos!
RETURN