Function GraRotate() Foundation
Calculates a rotational transformation for a matrix.
GraRotate( [<oPS>], <aMatrix>, <nAngle>, ;
<aPoint> , [<nMode>] ) > lSuccess
Constant  Description 

GRA_TRANSFORM_REPLACE  Replaces the existing <aMatrix> transformation after the transformation 
GRA_TRANSFORM_ADD  Keeps the existing <aMatrix> transformation and calculates an additional transformation 

The return value of GraRotate() is .T. (true) when the rotational transformation was calculated, otherwise it is .F. (false). If the return value equals .F., the cause of error can be determined by GraError().
The function GraRotate() performs the matrix calculations required for rotating graphic segments. A matrix must be passed to the function to hold the values resulting from the calculation. This matrix is a three dimensional array which must be generated by GraInitMatrix() before it is used for matrix calculations.
Graphic segments which are rotated (turned) at a specific angle must be previously generated from graphic primitives. The functions GraSegOpen() and GraSegClose() are used to define a graphic segment. GraRotate() calculates the rotation and the function GraSegDraw() makes the rotation visible.
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