Hi Everyone! This may seem like a basic question, but in the interest of time, I am going to ask it anyway rather than struggle with it.
All of the sideness tests I have seen in 2D (i.e. the Area() function in triangulate.cpp in libcrystalspace, which is essentially a copy of AreaSide() in http://orion.math.iastate.edu/burkardt/c_src/orourke/tri.c) uses a matrix determinant to find whether a point is on one side or another of a line, (essentially uses cross products). The problem I have is that these are all assuming that the planes in which the vectors lie are parallel to the XY plane. That is, the Z component can essentially be disregarded. Of course, when I take cross products of 3D vectors, I obtain another 3D vector. This happens in 2D of course, but there is a matrix which can be used to obtain a determinant telling the side on which a point lies, given a vector. Now, my question is this: Given two vectors (three points), we know they are all coplanar, so is there a way to utilize a matrix determinant trick similar to in 2D which will give us the side of the line the point lies on (i.e. negative or positive - it doesn't really mean 'right' or 'left', as these don't have meanings in arbitrary 3-dimesions). My initial intuition was to determine the angle the vector makes with the XY plane, in X and Y dimensions, then rotate all points by this, to ensure that we are parallel to the XY plane, then utilize the same method. Would this be too much work? I am wondering if I am overthinking the problem. Any suggestions would be helpful. Thanks! ~Scott ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Crystal-main mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/crystal-main Unsubscribe: mailto:[EMAIL PROTECTED]
