I have 2 problems I need some help with. They shouldn''t be giving me trouble but oddly enough they are. First... I need to be able to start with a 3d point (x, y, and z coord) then rotate it around the x, y, and then z axis (in that order) and know what the result x, y, and z coords would be (I have gotten it close but I can''t quite figure it out). Second... I have a triangle, and I need to find the equation (0=x+y+z) for the plane that the triangle lays on. The only information I have is the 3d coords for the 3 vertices. If any one can help thanks ahead of time... Zech

a(x-x0) + by(y - y0) + c(z - z0) = 0

where n is the normal vector for the triangle and n = (a, b, c),
r0 is a vector and r0 = (x0, y0, z0) (ie. a vertex in the plane ; one of your triangle vertices).

If memory serves.


Edited by - MelvinElvin on March 11, 2002 4:26:28 AM

And you can get the normal as a cross product of two vectors, which you get from your vertices (v1-v0 and v2-v0).

As for the rotations, that makes 3 matrix multiply. Write down you original XYZ vector, the rotation matrix around X, multiply, write the Y-rotation matrix, multiply, write the Z-rotation matrix, multiply.

If you can''t write a rotation matrix... you are doomed.