gluLookAt(3G) OpenGL Reference gluLookAt(3G)
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).
__F__
Then normalize as follows: f =
||F||
' __UP__
UP =
||UP||
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gluLookAt(3G) OpenGL Reference gluLookAt(3G)
'
Finally, let s = f x UP , and u = s x f.
( s[0] s[1] s[2] 0 )
| |
u[0] u[1] u[2] 0
| |
M is then constructed as follows: 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
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