Generate the plane from the 3 vertices. You can easily find the code somewhere on google.

The equation of a plane is made from 4 components. The last one is the distance from the origin to the plane. Luckily, the three first ones are the coefficients of a normal of that plane. Get that vector. Normalize it.

Make a dot product between this vector and the vertical axis (0, 1, 0). This will give you the cosinus of the angle of the slope, which is what you’re seeking…

Hope that helps…

Y.

[This message has been edited by Ysaneya (edited 10-23-2002).]