I can find the line-plane intersection condition easily enough as discussed
above. But, I also need to satisfy the condition that the point be bounded
within the 4 vertices of the quad as well.
I was thinking of a couple of possible solutions, but all untested. After
I got the point on the plane, I could find the min-max values of all 4 vertices
of the quad and test them against the point. But I really don''t know if this
is a good idea that works every time.
What I was really hoping for is a equation that I could plug my point values
in to test for this bounded condition.