NAME
gluLookAt - define a viewing transformation
C SPECIFICATION
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||
UP' = ______
||UP||
Finally, let s = f x UP', and u = s x 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 1 |
( )
and gluLookAt is equivalent to glMultMatrixf(M);
glTranslated (-eyex, -eyey, -eyez);
SEE ALSO
glFrustum, gluPerspective