This topic is now archived and is closed to further replies.

normal of a plane

This topic is 5047 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Pick three.

Form two vectors:

V1 = P2 - P1
V2 = P3 - P1

The normal is the cross product of the vectors:

N = V1 X V2

(normalized is usually most useful)

If you know something about the points which will give you a particular ''sidedness'' to the plane then you may want the negation of the cross product above.

Share this post

Link to post
Share on other sites
I assume that when you look at the polygon from the front, your verts go counter clockwise. Subsequently you have at least 3 verts (even if you have more than 3 verts, you ignore the rest) v0,v1, and v2. To calculate the normal:

Vector1 = v1 - v0;

Vector2 = v2 - v0;

//Crossproduct(hand,palm) returns the direction of ''thumb''
Normal = CrossProduct(Vector1,Vector2);

Normal.Normalize(); //The length of the normal is ||Vector1|| * ||Vector2|| * sine of the angle between the two

Share this post

Link to post
Share on other sites