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'\" te
'\"! tbl|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 mapgrid.g
.ds Xs 53033 5 mapgrid.gl
.TH GLMAPGRID 3G
.SH NAME
.B "glMapGrid1d, glMapGrid1f, glMapGrid2d, glMapGrid2f
\- define a one- or two-dimensional mesh
.SH C SPECIFICATION
void \f3glMapGrid1d\fP(
GLint \fIun\fP,
.nf
.ta \w'\f3void \fPglMapGrid1d( 'u
GLdouble \fIu1\fP,
GLdouble \fIu2\fP )
.fi
void \f3glMapGrid1f\fP(
GLint \fIun\fP,
.nf
.ta \w'\f3void \fPglMapGrid1f( 'u
GLfloat \fIu1\fP,
GLfloat \fIu2\fP )
.fi
void \f3glMapGrid2d\fP(
GLint \fIun\fP,
.nf
.ta \w'\f3void \fPglMapGrid2d( 'u
GLdouble \fIu1\fP,
GLdouble \fIu2\fP,
GLint \fIvn\fP,
GLdouble \fIv1\fP,
GLdouble \fIv2\fP )
.fi
void \f3glMapGrid2f\fP(
GLint \fIun\fP,
.nf
.ta \w'\f3void \fPglMapGrid2f( 'u
GLfloat \fIu1\fP,
GLfloat \fIu2\fP,
GLint \fIvn\fP,
GLfloat \fIv1\fP,
GLfloat \fIv2\fP )
.fi
.EQ
delim $$
.EN
.SH PARAMETERS
.TP \w'\f2un\fP\ \ 'u
\f2un\fP
Specifies the number of partitions in the grid range interval
[\f2u1\fP, \f2u2\fP].
Must be positive.
.TP
\f2u1\fP, \f2u2\fP
Specify the mappings for integer grid domain values $i~=~0$ and $i~=~"un"$.
.TP
\f2vn\fP
Specifies the number of partitions in the grid range interval
[\f2v1\fP, \f2v2\fP]
.br
(\%\f3glMapGrid2\fP only).
.TP
\f2v1\fP, \f2v2\fP
Specify the mappings for integer grid domain values $j~=~0$ and $j~=~"vn"$
.br
(\%\f3glMapGrid2\fP only).
.SH DESCRIPTION
\%\f3glMapGrid\fP and \%\f3glEvalMesh\fP are used together to efficiently
generate and evaluate a series of evenly-spaced map domain values.
\%\f3glEvalMesh\fP steps through the integer domain
of a one- or two-dimensional grid,
whose range is the domain of the evaluation maps specified by
\%\f3glMap1\fP and \%\f3glMap2\fP.
.P
\%\f3glMapGrid1\fP and \%\f3glMapGrid2\fP specify the linear grid mappings
between the $i$
(or $i$ and $j$)
integer grid coordinates,
to the $u$
(or $u$ and $v$)
floating-point evaluation map coordinates.
See \%\f3glMap1\fP and \%\f3glMap2\fP for details of how $u$ and $v$ coordinates
are evaluated.
.P
\%\f3glMapGrid1\fP specifies a single linear mapping
such that integer grid coordinate 0 maps exactly to \f2u1\fP,
and integer grid coordinate \f2un\fP maps exactly to \f2u2\fP.
All other integer grid coordinates $i$ are mapped so that
.sp
.ce
.EQ
u ~=~ i ("u2" - "u1") / "un" ~+~ "u1"
.EN
.sp
\%\f3glMapGrid2\fP specifies two such linear mappings.
One maps integer grid coordinate $i~=~0$ exactly to \f2u1\fP,
and integer grid coordinate $i~=~"un"$ exactly to \f2u2\fP.
The other maps integer grid coordinate $j~=~0$ exactly to \f2v1\fP,
and integer grid coordinate $j~=~"vn"$ exactly to \f2v2\fP.
Other integer grid coordinates $i$ and $j$ are mapped such that
.P
.ce
.EQ
u ~=~ i ("u2" - "u1") / "un" ~+~ "u1"
.EN
.P
.ce
.EQ
v ~=~ j ("v2" - "v1") / "vn" ~+~ "v1"
.EN
.P
The mappings specified by \%\f3glMapGrid\fP are used identically by
\%\f3glEvalMesh\fP and \%\f3glEvalPoint\fP.
.SH ERRORS
\%\f3GL_INVALID_VALUE\fP is generated if either \f2un\fP or \f2vn\fP is not
positive.
.P
\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glMapGrid\fP
is executed between the execution of \%\f3glBegin\fP
and the corresponding execution of \%\f3glEnd\fP.
.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,
\%\f3glEvalPoint(3G)\fP,
\%\f3glMap1(3G)\fP,
\%\f3glMap2(3G)\fP
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