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Plane equation

Started by boxdot3 Jul 27, 2002 at 9:32 PM 2 replies 800+ views

Original Post

Jul 27, 2002 at 9:32 PM

I am still trying to figure out the plane equation, and i have a few questions... From what i understand, its: ax + by + cz - d = 0 where abc is the plane normal, d is the distance to the origin, and xyz is a point on the plane. Please correct me if im wrong so far. Now for my terrain engine, I want to be able to follow the terrain, so I figured create a plane with the triangle the point is in, and then plug the point into the plain equation. Now, since i dont know the Y value of the point, how do i calculate D and y? Am i just way off on this one? Thank you for your time! Simon

Cedric

Jul 27, 2002 at 9:57 PM

Sorry if this is not an informative post, but plane equation questions are the second most commonly asked question around here, right after "How to find the angle between two vectors?".

Do a search for ''Plane equation'' in the forum archive, and you will find plenty of answers to your question.

Cédric

Dobbs

Jul 27, 2002 at 11:36 PM

This is a very common sort of question but the answer''s pretty short so I''ll tell you. It sounds like you already know how to find A, B, and C. You also know at least 3 points (x,y,z) that are in the plane (the vertices of the triangle). Plug A, B, C and one of the 3 (x,y,z) points into the plane equation and solve for the only unknown, D. You now know A, B, C, and D. Plug in a pair (x,z) and you get the corresponding y.

boxdot3

Jul 28, 2002 at 1:29 AM

Ok, thank you very much! Im sorry for not searching, ill remember next time!

later

Simon

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