mapw(3G)							      mapw(3G)

NAME    [Toc]    [Back]

     mapw - maps a point on the	screen into a line in 3-D world	coordinates

C SPECIFICATION    [Toc]    [Back]

     void mapw(vobj, sx, sy, wx1, wy1, wz1, wx2, wy2, wz2)
     Object vobj;
     Screencoord sx, sy;
     Coord *wx1, *wy1, *wz1, *wx2, *wy2, *wz2;

PARAMETERS    [Toc]    [Back]

     vobj   expects a viewing object containing	the transformations that map
	    the	current	displayed objects to the screen.

     sx	    expects the	x coordinate of	the screen point to be mapped.

     sy	    expects the	y coordinate of	the screen point to be mapped.

     wx1    returns the	x world	coordinate of one endpoint of a	line.

     wy1    returns the	y world	coordinate of one endpoint of a	line.

     wz1    returns the	z world	coordinate of one endpoint of a	line.

     wx2    returns the	x world	coordinate of the remaining endpoint of	a
	    line.

     wy2    returns the	y world	coordinate of the remaining endpoint of	a
	    line.

     wz2    returns the	z world	coordinate of the remaining endpoint of	a
	    line.

DESCRIPTION    [Toc]    [Back]

     mapw takes	a pair of 2-D screen coordinates and maps them into 3-D	world
     coordinates.  Since the z coordinate is missing from the screen
     coordinate	system,	the point becomes a line in world space.  mapw
     computes the inverse mapping from the viewing object, vobj.

     A viewing object is a graphical object that contains only routines	that
     affect the	model-view matrix, the projection matrix, or the viewport
     specification.  A correct mapping from screen coordinate to world
     coordinates requires that the viewing object contain the projection and
     viewing transformations that mapped the displayed object from world to
     screen coordinates.

     The system	returns	a world	space line, which is computed from (sx,	sy)
     and vobj, as two points and stores	them in	the locations addressed	by
     wx1, wy1, wz1 and wx2, wy2, wz2.






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mapw(3G)							      mapw(3G)

SEE ALSO    [Toc]    [Back]

     mapw2

NOTE    [Toc]    [Back]

     This routine is available only in immediate mode.


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