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