gluLookAt - define a viewing transformation
GLdouble upZ );
Specifies the position of the eye point. Specifies the
position of the reference point. Specifies the direction
of the up vector.
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
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
Finally, let s = f times UP^prime, and u = s times f.
M is then constructed as follows:
s s s 0
u u u 0 M =
-f -f -f 0
0 0 0 0
and gluLookAt() is equivalent to glMultMatrixf(M);
glTranslated (-eyex, -eyey, -eyez);
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