a is the place vector of the line, b the direction vector.
DOUBLE_EQ checks wether two doubles are about the same (with a little delta due to imprecision).
Returns LPI_INSIDE if the line is inside the plane. LPI_PARALLEL if the line is parallel to the plane. LPI_CUT otherwise.

I have a vector class, that’s why I can simply calculate with these vectors. The theory stays the same however, even if you haven’t it (yeah… sorry.)

[This message has been edited by Michael Steinberg (edited 04-15-2001).]

actually I feel stupid that I didn’t come back and close the discussion; about 5 minutes after I posted that I figured it out, so though I didn’t end up using your code, I’m sure that its good, however given my own datatypes and such and the fact that I figured it out before I had a chance to read your post, I didn’t end up using them. Sorry, but thanks.