NAME

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

SPECIFICATION

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

FORTRAN
subroutine mapw(vobj, sx, sy, wx1,
wy1, wz1, wx2, wy2, wz2)
integer*4 vobj, sx, sy
real wx1, wy1, wz1, wx2, wy2, wz2

Pascal
procedure mapw(vobj: Object; sx sy: longint;
var wx1, wy1, wz1, wx2, wy2,

DESCRIPTION

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 vobj, a viewing object. 

A viewing object is a graphical object that contains only viewport, projection, viewing transformation, and modeling routines.  A correct mapping from screen coordinates to world coordinates requires 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. 

SEE ALSO

mapw2 Programming Guide, Section 9.1, Mapping Screen Coordinates to World Coordinates

NOTE

This routine is available only in immediate mode. 

Version 3.6  —  December 20, 1987