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DCL:GRPH1:STPACK: Transformation Functions:Explanation of Subroutines: Coordinate Transformation

6.3.4 STFPR3/STIPR3/STSPR3

1.

Function

Performs 3-D perspective transformation.

2.

Call

CALL STFPR3(UX,UY,UZ,RX,RY)
CALL STSPR3(XFC,YFC,ZFC,THETA,PHI,PSI,FAC,ZVIEW,RXOFF,RYOFF)

3.

Explanation of Arguments

UX,UY,UZ	(R)	The coordinates in UC.
RX,RY	(R)	The coordinates in RC.
ITR3	(I)	Transformation function number
XFC,YFC,ZFC	(R)	The coordinates of the center of focus
THETA,PHI,PSI	(R)	The angle of rotation
FAC	(R)	The scaling factor
ZVIEW	(R)	The Z coordinate of the eye point
RXOFF,RYOFF	(R)	The offset

4.

Notes

(a)

These functions perform the following operations.

• Parallel transformation with the center of focus as the origin.
• Rotation of (THETA,PHI,PSI) around the origin..
• Multiplies the coordinate values by a factor of FAC.
• With the eye point at (0,0,ZVIEW), projects a point onto the X-Y plane.
• Adds an offset of (RXOFF,RYOFF) to the projected coordinate value.