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*On 21/05/2010 at 04:47, ***xxxxxxxx** wrote:

A plane is defined in Cinema as a plane through the planes global matrix.

The orientation parameter of the plane (+/-x, y, or z respectively) defines how the plane is oriented in this matrix.

While a plane mathematically could be defined by a point and a normal only as Franz suggested, this leaves the orientation of the other two matrix vectors undefined.

So, to construct a plane, you need to construct an orthogonal matrix with the offset vector off [= any point on the plane], the normal vector and two new vectors for v1-v3. V1-v3 should be perpendicular to each other = orthogonal.

Depending which of v1-v3 carries your normal vector, set the orientation parameter of plane accordingly.

Hope it helps

Kabe