Math..

A much simpler solution than the perspective projection suggested in the
comment below, and arguably a more attractive one, is the orthographic
projection. I shall give you the formulas to convert (x, y, z) coordinates
into (x, y) coordinates after rotation about the axes.

Suppose that we rotate the cube by Rx degrees about the x axis, by Ry
degrees about the y axis, and by Rz degrees about the z axis.

First, apply the x-axis rotation to transform coordinates (x, y, z)
into coordinates (x0, y0, z0).

x0 = x

y0 = y*cos(Rx) + z*sin(Rx)

z0 = z*cos(Rx) - y*sin(Rx)

Then apply the y-axis rotation to (x0, y0, z0) to obtain (x1, y1, z1).

x1 = x0*cos(Ry) - z0*sin(Ry)

y1 = y0

z1 = z0*cos(Ry) + x0*sin(Ry)

Finally, apply the z-axis rotation to obtain the point (x2, y2).

x2 = x1*cos(Rz) + y1*sin(Rz)

y2 = y1*cos(Rz) - x1*sin(Rz)

Hey presto, you can now plot (x2, y2) in two dimensions.

Regards,

leapinglizard