Experimentation with 3d formulae in DOS.

3dexperiment is an experiment with 3D formulae in QuckBASIC, DOS.
The program demonstrates a cuboid which can be rotated and translated using
mentioned keys. The 3d formulae used are:

Symbols	Meaning
objectx, objecty, objectz	point of rotation of object
camerax, cameray, cameraz	point of camera looking at the world you make
xpos, ypos, zpos	position of pixel in the world coords
a, b, c	angles around x, y, z axes
xscale, yscale	scale factors for x, y axes
xcentre, ycentre	centre of vision on the screen
x, y	position of pixel on screen

x1 = xpos - objectx
y1 = ypos - objecty
z1 = zpos - objectz
y2 = y1*cos(a) + z1*sin(a)
z2 = z1*cos(a) - y1*sin(a)
x2 = x1*cos(b) + z2*sin(b)
z3 = z2*cos(b) - x1*sin(b)
y3 = y2*cos(c) + x2*sin(c)
x3 = x2*cos(c) - y2*sin(c)
rx = objectx - camerax
ry = objectx - cameray
rz = objectz - cameraz
xf = rx + (xscale*x3) / (rz+z3)
yf = ry + (perspy*y3) / (rz+z3)
x = xf + xcentre
y = yf + ycentre

Cuboid in default position (keeps rotating).

Cuboid in moved position (translated, rotated).