Collectible Card Game Headquarters

I'm writing a script for our Photoshoppers to use. I'm stuck on some perspective transformation mathematics. Can anybody help?

Basically I need a function to calculate screen corrdinates for an object in perspective using a cross ratio like this.

Code: Select all

function crossRatio(a_2D, b_2D, c_2D, b_3D, c_3D, d_3D)
{
    return d_2D;
}

Actually I think I figured it out. But if anybody is interested in helping, just send me a PM.