EVALUATE VIEW ORIENTATION MATRIX

PEVOM

CALL SEQUENCE

CALL PEVOM (VWRX, VWRY, VUPX, VUPY, ERRIND, VWORMT)

INPUT PARAMETERS

REAL VWRX, VWRY

View reference point coordinates in World Coordinates (Viewing Reference Point).

REAL VUPX, VUPY

View up vector components.

OUTPUT PARAMETERS

INTEGER ERRIND

Error indicator (see ERRORS).

REAL VWORMT(3,3)

Resulting homogeneous (3 x 3) 2D 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 up vector.

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

The 2D point VWRX,VWRY 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 VUPX,VUPY is the view up vector; it is defined in WC. This vector defines the VRC V axis and the top-bottom orientation of the view.

The U axis is defined in such a way that UV is a direct reference.

ERRORS

2

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

160

Ignoring function, the view up vector has length zero

SEE ALSO

set view representation, evaluate view mapping matrix