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gluLookAt()
NAME
  gluLookAt - define a viewing transformation

SYNOPSIS
  void gluLookAt(
	  GLdouble eyeX,
	  GLdouble eyeY,
	  GLdouble eyeZ,
	  GLdouble centerX,
	  GLdouble centerY,
	  GLdouble centerZ,
	  GLdouble upX,
	  GLdouble upY,
	  GLdouble upZ );

PARAMETERS
  eyeX, eyeY, eyeZ
      Specifies the position of the eye point.

  centerX, centerY, centerZ
      Specifies the position of the reference point.

  upX, upY, upZ
      Specifies the direction of the up vector.

DESCRIPTION
  gluLookAt() creates a viewing matrix derived from an eye point, a reference
  point indicating the center of the scene, and an UP vector.

  The matrix maps the reference point to the negative z axis and the eye
  point to the origin. When a typical projection matrix is used, the center
  of the scene therefore maps to the center of the viewport.  Similarly, the
  direction described by the UP vector projected onto the viewing plane is
  mapped to the positive y axis so that it points upward in the viewport. The
  UP vector must not be parallel to the line of sight from the eye point to
  the reference point.

  Let

	    centerX - eyeX
       F =  centerY - eyeY
	    centerZ - eyeZ

  Let UP be the vector (upX, upY, upZ).

  Then normalize as follows:

       f = F / ||F||
       UP^prime = UP  ||UP||

  Finally, let s = f times UP^prime, and u = s times f.

  M is then constructed as follows:

	    s[0]    s[1]    s[2]    0

	    u[0]    u[1]    u[2]    0
       M =

	    -f[0]  -f[1]   -f[2]    0

	      0	     0	     0	    0

  and gluLookAt() is equivalent to

       glMultMatrixf(M);
       glTranslated (-eyex, -eyey, -eyez);

SEE ALSO
  glFrustum(3), gluPerspective(3)

Index for Section 3

Alphabetical listing for G

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