DECLARE FUNCTION arctan! (s1!, s2!)

edit:
SCREEN 9, , 1, 1
COLOR 2
CLS
PRINT "                    Cool 3D Stuff by John": PRINT : PRINT
PRINT "1     load built in cube": PRINT
PRINT "2     load a shape from   'c:\qbasic71\3dtest2.txt'": PRINT
PRINT "3     quit": PRINT
DO
button$ = INKEY$
LOOP UNTIL button$ <> ""
IF button$ = "2" THEN
        OPEN "c:\qbasic71\3dtest2.txt" FOR INPUT AS 1
        INPUT #1, numberoflines
        REDIM threeDdat(numberoflines, 7)
        FOR l = 1 TO numberoflines
                FOR c = 1 TO 7
                        INPUT #1, threeDdat(l, c)
                NEXT c
        NEXT l
        CLOSE
        GOSUB display
END IF
IF button$ = "1" THEN
        REDIM threeDdat(12, 7)
        numberoflines = 12
        RESTORE
        FOR p = 1 TO numberoflines
                FOR c = 1 TO 7          'read into array
                        READ threeDdat(p, c)
                NEXT c
        NEXT p
        GOSUB display
END IF
IF button$ = "3" THEN END
GOTO edit

                     
'OPEN "c:\qbasic71\3dtest2.txt" FOR OUTPUT AS 1
'FOR l = 1 TO numberoflines
'        WRITE #1, threedDat(l, 1), threedDat(l, 2), threedDat(l, 3), threedDat(l, 4), threedDat(l, 5), threedDat(l, 6), threedDat(l, 7)
'NEXT l
'CLOSE
                     
                     
display:
KEY 15, CHR$(0) + CHR$(72)
KEY 16, CHR$(0) + CHR$(75)
KEY 17, CHR$(0) + CHR$(77)
KEY 18, CHR$(0) + CHR$(80)
KEY 19, CHR$(0) + CHR$(1)
KEY 20, CHR$(0) + CHR$(71)
KEY 21, CHR$(0) + CHR$(73)
KEY 22, CHR$(0) + CHR$(30)
KEY 23, CHR$(0) + CHR$(44)
ON KEY(15) GOSUB up
ON KEY(16) GOSUB left
ON KEY(17) GOSUB right
ON KEY(18) GOSUB down
ON KEY(19) GOSUB quit
ON KEY(20) GOSUB yawleft
ON KEY(21) GOSUB yawright
ON KEY(22) GOSUB zoomin
ON KEY(23) GOSUB zoomout
FOR i = 15 TO 23
        KEY(i) ON
NEXT i
depth = 200
CONST pi = 3.141593
SCREEN 9, , 0, 1 '640*350, writing page 0, seeing page 1
CLS
COLOR 2
top:
DO
frame = frame + 1: IF frame > 10 THEN frame = 1
IF frame = 1 THEN timestartrender = TIMER
IF rotx <> 0 THEN
        FOR l = 1 TO numberoflines
                y1a = threeDdat(l, 2)
                z1a = threeDdat(l, 3)
                y2a = threeDdat(l, 5)
                z2a = threeDdat(l, 6)
                y1b = SQR(y1a ^ 2 + z1a ^ 2) * SIN(arctan(y1a, z1a) + rotx)
                z1b = SQR(y1a ^ 2 + z1a ^ 2) * COS(arctan(y1a, z1a) + rotx)
                y2b = SQR(y2a ^ 2 + z2a ^ 2) * SIN(arctan(y2a, z2a) + rotx)
                z2b = SQR(y2a ^ 2 + z2a ^ 2) * COS(arctan(y2a, z2a) + rotx)
                threeDdat(l, 2) = y1b
                threeDdat(l, 3) = z1b
                threeDdat(l, 5) = y2b
                threeDdat(l, 6) = z2b
        NEXT l
        'rotx = 0
END IF
IF roty <> 0 THEN
        FOR l = 1 TO numberoflines
                x1a = threeDdat(l, 1)
                z1a = threeDdat(l, 3)
                x2a = threeDdat(l, 4)
                z2a = threeDdat(l, 6)
                x1b = SQR(x1a ^ 2 + z1a ^ 2) * COS(arctan(z1a, x1a) + roty)
                z1b = SQR(x1a ^ 2 + z1a ^ 2) * SIN(arctan(z1a, x1a) + roty)
                x2b = SQR(x2a ^ 2 + z2a ^ 2) * COS(arctan(z2a, x2a) + roty)
                z2b = SQR(x2a ^ 2 + z2a ^ 2) * SIN(arctan(z2a, x2a) + roty)
                threeDdat(l, 1) = x1b
                threeDdat(l, 3) = z1b
                threeDdat(l, 4) = x2b
                threeDdat(l, 6) = z2b
        NEXT l
        'roty = 0
END IF
IF rotz <> 0 THEN
        FOR l = 1 TO numberoflines
                x1a = threeDdat(l, 1)
                y1a = threeDdat(l, 2)
                x2a = threeDdat(l, 4)
                y2a = threeDdat(l, 5)
                x1b = SQR(x1a ^ 2 + y1a ^ 2) * SIN(arctan(x1a, y1a) + rotz)
                y1b = SQR(x1a ^ 2 + y1a ^ 2) * COS(arctan(x1a, y1a) + rotz)
                x2b = SQR(x2a ^ 2 + y2a ^ 2) * SIN(arctan(x2a, y2a) + rotz)
                y2b = SQR(x2a ^ 2 + y2a ^ 2) * COS(arctan(x2a, y2a) + rotz)
                threeDdat(l, 1) = x1b
                threeDdat(l, 2) = y1b
                threeDdat(l, 4) = x2b
                threeDdat(l, 5) = y2b
        NEXT l
        'rotz = 0
END IF

LINE (0, 14)-(640, 350), 0, BF     'clear display

FOR l = 1 TO numberoflines               'display figure
        x1 = threeDdat(l, 1)
        y1 = threeDdat(l, 2)
        z1 = threeDdat(l, 3)
        x2 = threeDdat(l, 4)
        y2 = threeDdat(l, 5)
        z2 = threeDdat(l, 6)
        'PALETTE 1, INT((threeDdat(l, 6) + threeDdat(l, 3)) / 2)
         c = 1 'threeDdat(l, 7)
        LINE (320 + x1 * 2 ^ (-z1 / depth), 175 + (35 / 48) * (y1 * 2 ^ (-z1 / depth)))-(320 + x2 * 2 ^ (-z2 / depth), 175 + (35 / 48) * (y2 * 2 ^ (-z2 / depth))), c
NEXT l
IF frame = 10 THEN
        LOCATE 1, 1
        PRINT "fps ", 10 / (TIMER - timestartrender)
END IF
PCOPY 0, 1
LOOP

'horizontal lines, then vertical lines
DATA -50,-50,-50, 50,-50,-50,  1
DATA -50,-50, 50, 50,-50, 50,  2
DATA -50,-50,-50,-50,-50, 50,  3
DATA  50,-50,-50, 50,-50, 50,  4
DATA -50, 50,-50, 50, 50,-50,  5
DATA -50, 50, 50, 50, 50, 50,  6
DATA -50, 50,-50,-50, 50, 50,  7
DATA  50, 50,-50, 50, 50, 50,  8

DATA -50, 50,-50,-50,-50,-50,  9
DATA  50, 50,-50, 50,-50,-50, 10
DATA -50, 50, 50,-50,-50, 50, 11
DATA  50, 50, 50, 50,-50, 50, 12
'     x1  y1  z1  x2  y2  z2  color
'     1   2   3   4   5   6   7
up:
rotx = rotx + .01
RETURN

down:
rotx = rotx - .01
RETURN

left:
roty = roty - .01
RETURN

right:
roty = roty + .01
RETURN

yawleft:
rotz = rotz + .01
RETURN

yawright:
rotz = rotz - .01
RETURN

zoomin:
FOR l = 1 TO numberoflines
threeDdat(l, 3) = threeDdat(l, 3) - 1
threeDdat(l, 6) = threeDdat(l, 6) - 1
NEXT l
RETURN

zoomout:
RETURN

quit:
GOTO edit
RETURN

FUNCTION arctan (s1, s2)
IF s2 = 0 THEN
        IF s1 > 0 THEN arctan = pi / 2 ELSE arctan = 3 * pi / 4
ELSEIF s2 < 0 THEN
        IF s1 > 0 THEN arctan = ATN(s1 / s2) + pi ELSE arctan = ATN(s1 / s2) + pi
ELSEIF s2 > 0 THEN
        IF s1 > 0 THEN arctan = ATN(s1 / s2) ELSE arctan = ATN(s1 / s2) + 2 * pi
END IF
END FUNCTION