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doc/gl-docs/GL/gl/evalpoint.3gl

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+'\" e
+'\"! eqn | mmdoc
+'\"macro stdmacro
+.ds Vn Version 1.2
+.ds Dt 24 September 1999
+.ds Re Release 1.2.1
+.ds Dp Jan 14 18:30
+.ds Dm 01 evalpoint
+.ds Xs 57169 5 evalpoint.gl
+.TH GLEVALPOINT 3G
+.SH NAME
+.B "glEvalPoint1, glEvalPoint2
+\- generate and evaluate a single point in a mesh
+
+.SH C SPECIFICATION
+void \f3glEvalPoint1\fP(
+GLint \fIi\fP )
+.nf
+.fi
+void \f3glEvalPoint2\fP(
+GLint \fIi\fP,
+.nf
+.ta \w'\f3void \fPglEvalPoint2( 'u
+	GLint \fIj\fP )
+.fi
+
+.EQ
+delim $$
+.EN
+.SH PARAMETERS
+.TP \w'\f2i\fP\ \ 'u 
+\f2i\fP
+Specifies the integer value for grid domain variable $i$.
+.TP
+\f2j\fP
+Specifies the integer value for grid domain variable $j$
+(\%\f3glEvalPoint2\fP only).
+.SH DESCRIPTION
+\%\f3glMapGrid\fP and \%\f3glEvalMesh\fP are used in tandem to efficiently
+generate and evaluate a series of evenly spaced map domain values.
+\%\f3glEvalPoint\fP can be used to evaluate a single grid point in the same gridspace
+that is traversed by \%\f3glEvalMesh\fP.
+Calling \%\f3glEvalPoint1\fP is equivalent to calling
+.nf
+.IP
+\f7
+glEvalCoord1( i$^cdot^DELTA u ~+~ u sub 1$ );
+\fP
+.RE
+.fi
+where
+.sp
+.in
+$DELTA u ~=~ ( u sub 2 - u sub 1 ) ^/^ n$
+.in 0
+.sp
+.P
+and $n$, $u sub 1$, and $u sub 2$
+are the arguments to the most recent \%\f3glMapGrid1\fP command.
+The one absolute numeric requirement is that if $i~=~n$,
+then the value computed from 
+$i ^cdot^ DELTA u ~+~ u sub 1$ is exactly $u sub 2$.
+.P
+In the two-dimensional case, \%\f3glEvalPoint2\fP, let 
+.nf
+.IP
+$DELTA u ~=~ mark ( u sub 2 - u sub 1 ) ^/^ n$
+.sp
+$DELTA v ~=~ mark ( v sub 2 - v sub 1 ) ^/^ m,$
+.RE
+.fi
+.P
+where $n$, $u sub 1$, $u sub 2$, $m$, $v sub 1$, and $v sub 2$
+are the arguments to the most recent \%\f3glMapGrid2\fP command.
+Then the \%\f3glEvalPoint2\fP command is equivalent to calling
+.nf
+.IP
+\f7
+glEvalCoord2( i$^cdot^DELTA u ~+~ u sub 1$, j$^cdot^DELTA v ~+~ v sub 1$ );
+\fP
+.RE
+.fi
+The only absolute numeric requirements are that if $i~=~n$,
+then the value computed from
+$i ^cdot^DELTA u ~+~ u sub 1$ is exactly $u sub 2$,
+and if $j~=~m$, then the value computed from 
+$i ^cdot^DELTA v ~+~ v sub 1$ is exactly $v sub 2$.
+.SH ASSOCIATED GETS
+\%\f3glGet\fP with argument \%\f3GL_MAP1_GRID_DOMAIN\fP
+.br
+\%\f3glGet\fP with argument \%\f3GL_MAP2_GRID_DOMAIN\fP
+.br
+\%\f3glGet\fP with argument \%\f3GL_MAP1_GRID_SEGMENTS\fP
+.br
+\%\f3glGet\fP with argument \%\f3GL_MAP2_GRID_SEGMENTS\fP
+.SH SEE ALSO
+\%\f3glEvalCoord(3G)\fP,
+\%\f3glEvalMesh(3G)\fP,
+\%\f3glMap1(3G)\fP,
+\%\f3glMap2(3G)\fP,
+\%\f3glMapGrid(3G)\fP