Maths for printing isometric projection lines to the screen

I have spent too many hours on the internet trying to locate
some code that will help me do this. There seems to be lots of articals aimed at isometric tile graphics but not on the maths behind it and nothing on plotting lines.

Can any of you 2D guys help me?

Lee.

There is an article by Ed Upton on Blitzcoder if that is any help?

It's not terrible complicated (unless you want to calculate it via a orthagonal projection matrix and even then it's not too bad). If you're going for a 2:1 x:y screen ratio (which is the usual one)

SCREEN_Y = ((X + Y) / 2) - Z
SCREEN_X = (X - Y)

Although it depends on what co-ords system you're using, but here I'm assuming that the X axis heads down-right, the Y axis head down-left and the Z axis heads up.

It is as simple as that!!!.

I should have stuck in more a school.

Thanks.

Lee.