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<STRONG>NAME</STRONG>
<STRONG>gluLookAt</STRONG> - define a viewing transformation
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>gluLookAt</STRONG>( GLdouble <EM>eyeX</EM>,
GLdouble <EM>eyeY</EM>,
GLdouble <EM>eyeZ</EM>,
GLdouble <EM>centerX</EM>,
GLdouble <EM>centerY</EM>,
GLdouble <EM>centerZ</EM>,
GLdouble <EM>upX</EM>,
GLdouble <EM>upY</EM>,
GLdouble <EM>upZ</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>eyeX</EM>, <EM>eyeY</EM>, <EM>eyeZ</EM>
Specifies the position of the eye point.
<EM>centerX</EM>, <EM>centerY</EM>, <EM>centerZ</EM>
Specifies the position of the reference
point.
<EM>upX</EM>, <EM>upY</EM>, <EM>upZ</EM> Specifies the direction of the <EM>up</EM> vector.
<STRONG>DESCRIPTION</STRONG>
<STRONG>gluLookAt</STRONG> creates a viewing matrix derived from an eye
point, a reference point indicating the center of the scene,
and an <EM>UP</EM> vector.
The matrix maps the reference point to the negative <EM>z</EM> 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 <EM>UP</EM> vector projected onto the viewing plane
is mapped to the positive <EM>y</EM> axis so that it points upward in
the viewport. The <EM>UP</EM> 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 <EM>UP</EM> be the vector (upX,upY,upZ).
Then normalize as follows: f = __<STRONG>_</STRONG>__
||F||
UP' = __<STRONG>__</STRONG>__
||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 <STRONG>gluLookAt</STRONG> is equivalent to glMultMatrixf(M);
glTranslated (-eyex, -eyey, -eyez);
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glFrustum</STRONG>, <STRONG>gluPerspective</STRONG>
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