GPHIGS C FUNCTIONS - EVALUATE VIEW ORIENTATION MATRIX

EVALUATE VIEW ORIENTATION MATRIX

PEVAL_VIEW_ORI_MATRIX

CALL SEQUENCE

void peval_view_ori_matrix(

const Ppoint	*view_ref	/* view reference point in WC	*/
const Pvec	*view_up	/* view up vector	*/
Pint	*error_ind	/* (out) error indicator	*/
Pmatrix	result	/* (out) view orientation matrix	*/

TYPES

typedef struct {
	Pfloat 	x;	/* x coordinate	*/
	Pfloat 	y;	/* y coordinate	*/
} Ppoint;

typedef struct {
	Pfloat 	delta_x;	/* delta x	*/	Pfloat 	delta_y;	/* delta y	*/
} Pvec;

typedef Pfloat Pmatrix[3][3];

PHIGS STATE

(PHOP, *, *, *).

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 view_ref 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 view_up 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