EVALUATE VIEW ORIENTATION MATRIX 3

PEVOM3

CALL SEQUENCE

CALL PEVOM3	(VWRX, VWRY, VWRZ, VPNX, VPNY, VPNZ, VUPX, VUPY, VUPZ, ERRIND, VWORMT)

INPUT PARAMETERS

REAL VWRX, VWRY, VWRZ

View reference point coordinates in World Coordinates.

REAL VPNX, VPNY, VPNZ

Components normal to the view plane in WC.

REAL VUPX, VUPY, VUPZ

View up vector components .

OUTPUT PARAMETERS

INTEGER ERRIND

Error indicator

REAL VWORMT(4,4)

Resulting homogeneous (4 x 4) 3D matrix.

PHIGS STATE

EFFECT

Returns a matrix allowing passage from world coordinates (WC) to view reference coordinates (VRC). This matrix is calculated from: - view reference point - view plane normal

- view up vector.

This matrix is used in the SET VIEW REPRESENTATION 3 function to define the WC transformation (see SET VIEW REPRESENTATION 3 function).

The 3D point VWRX,VWRY,VWRZ defines the view reference point in WC. This point becomes the VRC origin. Generally, it is near the object to be displayed. Moving this point is equivalent to moving the object with respect to the display surface.

The vector specified by VPNX,VPNY,VPN,Z is the view plane normal; it is defined in WC. It defines the VRC N axis. This axis defines the view front-back orientation. The WC plane containing the view reference point and orthogonal to N, defines the view reference plane.

The vector specified by VUPX,VUPY,VUPZ is the view up vector; it is defined in WC. The vector is projected on the view reference plane parallel to the view plane normal. This vector defines the VRC V axis and the top-bottom orientation of the view.

The third axis, U, defining the VRC is defined in such a way that UVN is a direct reference.

ERRORS

2

Ignoring function, function requires state (PHOP, *,*,*)

SEE ALSO

set view representation 3, evaluate view mapping matrix 3