102 lines
2.3 KiB
Plaintext
102 lines
2.3 KiB
Plaintext
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'\"! eqn | mmdoc
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'\"macro stdmacro
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.ds Vn Version 1.2
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.ds Dt 6 March 1997
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.ds Re Release 1.2.0
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.ds Dp May 02 11:53
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.ds Dm 37 lookat.gl
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.ds Xs 1014 4 lookat.gl
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.TH GLULOOKAT 3G
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.SH NAME
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.B "gluLookAt
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\- define a viewing transformation
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.SH C SPECIFICATION
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void \f3gluLookAt\fP(
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GLdouble \fIeyeX\fP,
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.nf
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.ta \w'\f3void \fPgluLookAt( 'u
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GLdouble \fIeyeY\fP,
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GLdouble \fIeyeZ\fP,
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GLdouble \fIcenterX\fP,
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GLdouble \fIcenterY\fP,
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GLdouble \fIcenterZ\fP,
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GLdouble \fIupX\fP,
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GLdouble \fIupY\fP,
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GLdouble \fIupZ\fP )
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.fi
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.EQ
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delim $$
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.EN
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.SH PARAMETERS
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.TP \w'\f2eyeX\fP\ \f2eyeY\fP\ \f2eyeZ\fP\ \ 'u
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\f2eyeX\fP, \f2eyeY\fP, \f2eyeZ\fP
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Specifies the position of the eye point.
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.TP
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\f2centerX\fP, \f2centerY\fP, \f2centerZ\fP
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Specifies the position of the reference point.
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.TP
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\f2upX\fP, \f2upY\fP, \f2upZ\fP
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Specifies the direction of the \f2up\fP vector.
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.SH DESCRIPTION
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\%\f3gluLookAt\fP creates a viewing matrix derived from an eye point, a reference
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point indicating the center of the scene, and an \f2UP\fP vector.
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.P
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The matrix
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maps the reference point to the negative \f2z\fP axis and the
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eye point to the origin.
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When a typical projection matrix is used,
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the center of the scene therefore maps to the center of the viewport.
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Similarly, the direction described by the \f2UP\fP
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vector projected onto the viewing plane is mapped to the positive \f2y\fP
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axis so that it points upward in the viewport.
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The \f2UP\fP vector must not be parallel to the line of sight from the
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eye point to the reference point.
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.P
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Let
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.sp
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.EQ
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F ~=~ left ( down 20 { ~ matrix {
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ccol {"centerX" above "centerY" above "centerZ"}
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ccol { ~-~ above ~-~ above ~-~}
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ccol {"eyeX" above "eyeY" above "eyeZ"}
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} } ~~ right )
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.EN
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.sp
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Let \f2UP\fP be the vector $("upX", "upY", "upZ")$.
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.P
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Then normalize as follows:
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.EQ
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f ~=~ F over {|| F ||}
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.EN
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.P
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.EQ
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UP sup prime ~=~ UP over {|| UP ||}
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.EN
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.sp
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.P
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Finally, let $s ~=~ f ~times~ UP sup prime$, and $u ~=~ s ~times~ f$.
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.P
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.sp
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M is then constructed as follows:
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.EQ
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M ~=~ left ( matrix {
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ccol { ~s[0] above ~u[0] above -f[0] above 0 }
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ccol { ~s[1] above ~u[1] above -f[1] above 0 }
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ccol { ~s[2] above ~u[2] above -f[2] above 0 }
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ccol { 0 above 0 above 0 above 1 }
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} ~~right )
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.EN
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.P
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and \%\f3gluLookAt\fP is equivalent to
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.Ex
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glMultMatrixf(M);
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glTranslated (-eyex, -eyey, -eyez);
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.Ee
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.SH SEE ALSO
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\f3glFrustum(3G)\fP, \%\f3gluPerspective(3G)\fP
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