227 lines
6.3 KiB
Plaintext
227 lines
6.3 KiB
Plaintext
'\" te
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'\"! tbl|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 evalcoord
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.ds Xs 42414 8 evalcoord.gl
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.TH GLEVALCOORD 3G
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.SH NAME
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.B "glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv
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\- evaluate enabled one- and two-dimensional maps
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.EQ
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delim $$
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.EN
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.SH C SPECIFICATION
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void \f3glEvalCoord1d\fP(
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GLdouble \fIu\fP )
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.nf
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.fi
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void \f3glEvalCoord1f\fP(
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GLfloat \fIu\fP )
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.nf
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.fi
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void \f3glEvalCoord2d\fP(
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GLdouble \fIu\fP,
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.nf
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.ta \w'\f3void \fPglEvalCoord2d( 'u
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GLdouble \fIv\fP )
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.fi
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void \f3glEvalCoord2f\fP(
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GLfloat \fIu\fP,
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.nf
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.ta \w'\f3void \fPglEvalCoord2f( 'u
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GLfloat \fIv\fP )
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.fi
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.SH PARAMETERS
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.TP \w'\f2u\fP\ \ 'u
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\f2u\fP
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Specifies a value that is the domain coordinate $u$ to the basis function
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defined in a previous \%\f3glMap1\fP or \%\f3glMap2\fP command.
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.TP
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\f2v\fP
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Specifies a value that is the domain coordinate $v$ to the basis function
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defined in a previous \%\f3glMap2\fP command.
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This argument is not present in a \%\f3glEvalCoord1\fP command.
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.SH C SPECIFICATION
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void \f3glEvalCoord1dv\fP(
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const GLdouble \fI*u\fP )
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.nf
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.fi
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void \f3glEvalCoord1fv\fP(
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const GLfloat \fI*u\fP )
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.nf
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.fi
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void \f3glEvalCoord2dv\fP(
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const GLdouble \fI*u\fP )
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.nf
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.fi
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void \f3glEvalCoord2fv\fP(
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const GLfloat \fI*u\fP )
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.nf
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.fi
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.SH PARAMETERS
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.TP
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\f2u\fP
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Specifies a pointer to an array containing
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either one or two domain coordinates.
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The first coordinate is $u$.
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The second coordinate is $v$,
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which is present only in \%\f3glEvalCoord2\fP versions.
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.SH DESCRIPTION
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\%\f3glEvalCoord1\fP evaluates enabled one-dimensional maps at argument
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\f2u\fP.
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\%\f3glEvalCoord2\fP does the same for two-dimensional maps using
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two domain values,
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\f2u\fP and \f2v\fP.
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To define a map, call \%\f3glMap1\fP and \%\f3glMap2\fP; to enable and
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disable it, call \%\f3glEnable\fP and \%\f3glDisable\fP.
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.P
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When one of the \%\f3glEvalCoord\fP commands is issued,
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all currently enabled maps of the indicated dimension are evaluated.
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Then,
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for each enabled map,
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it is as if the corresponding GL command had been issued with the
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computed value.
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That is,
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if \%\f3GL_MAP1_INDEX\fP or
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\%\f3GL_MAP2_INDEX\fP is enabled,
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a \%\f3glIndex\fP command is simulated.
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If \%\f3GL_MAP1_COLOR_4\fP or
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\%\f3GL_MAP2_COLOR_4\fP is enabled,
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a \%\f3glColor\fP command is simulated.
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If \%\f3GL_MAP1_NORMAL\fP or \%\f3GL_MAP2_NORMAL\fP is enabled,
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a normal vector is produced,
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and if any of
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\%\f3GL_MAP1_TEXTURE_COORD_1\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_2\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_3\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_4\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_1\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_2\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_3\fP, or
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\%\f3GL_MAP2_TEXTURE_COORD_4\fP is enabled, then an appropriate \%\f3glTexCoord\fP command is simulated.
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.P
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For color,
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color index,
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normal,
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and texture coordinates the GL uses evaluated values instead of current values for those evaluations
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that are enabled,
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and current values otherwise,
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However,
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the evaluated values do not update the current values.
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Thus, if \%\f3glVertex\fP commands are interspersed with \%\f3glEvalCoord\fP
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commands, the color,
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normal,
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and texture coordinates associated with the \%\f3glVertex\fP commands are not
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affected by the values generated by the \%\f3glEvalCoord\fP commands,
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but only by the most recent
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\%\f3glColor\fP,
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\%\f3glIndex\fP,
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\%\f3glNormal\fP, and
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\%\f3glTexCoord\fP commands.
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.P
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No commands are issued for maps that are not enabled.
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If more than one texture evaluation is enabled for a particular dimension
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(for example, \%\f3GL_MAP2_TEXTURE_COORD_1\fP and
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\%\f3GL_MAP2_TEXTURE_COORD_2\fP),
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then only the evaluation of the map that produces the larger
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number of coordinates
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(in this case, \%\f3GL_MAP2_TEXTURE_COORD_2\fP)
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is carried out.
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\%\f3GL_MAP1_VERTEX_4\fP overrides \%\f3GL_MAP1_VERTEX_3\fP,
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and
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\%\f3GL_MAP2_VERTEX_4\fP overrides \%\f3GL_MAP2_VERTEX_3\fP,
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in the same manner.
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If neither a three- nor a four-component vertex map is enabled for the
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specified dimension,
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the \%\f3glEvalCoord\fP command is ignored.
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.P
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If you have enabled automatic normal generation,
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by calling \%\f3glEnable\fP with argument \%\f3GL_AUTO_NORMAL\fP,
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\%\f3glEvalCoord2\fP generates surface normals analytically,
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regardless of the contents or enabling of the \%\f3GL_MAP2_NORMAL\fP map.
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Let
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.sp
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.ce
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.EQ
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bold m ~=~ {partial bold p} over {partial u} ~times~
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{partial bold p} over {partial v}
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.EN
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.ce 0
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.sp
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.br
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Then the generated normal $ bold n $ is
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.br
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.ce
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$bold n ~=~ bold m over { || bold m || }$
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.ce 0
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.sp
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.br
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If automatic normal generation is disabled,
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the corresponding normal map \%\f3GL_MAP2_NORMAL\fP,
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if enabled,
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is used to produce a normal.
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If neither automatic normal generation nor a normal map is enabled,
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no normal is generated for
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\%\f3glEvalCoord2\fP commands.
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.SH ASSOCIATED GETS
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.nf
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_VERTEX_3\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_VERTEX_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_INDEX\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_COLOR_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_NORMAL\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_TEXTURE_COORD_1\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_TEXTURE_COORD_2\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_TEXTURE_COORD_3\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP1_TEXTURE_COORD_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_VERTEX_3\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_VERTEX_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_INDEX\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_COLOR_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_NORMAL\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_TEXTURE_COORD_1\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_TEXTURE_COORD_2\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_TEXTURE_COORD_3\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_MAP2_TEXTURE_COORD_4\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_AUTO_NORMAL\fP
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.br
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\%\f3glGetMap\fP
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.SH SEE ALSO
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\%\f3glBegin(3G)\fP,
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\%\f3glColor(3G)\fP,
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\%\f3glEnable(3G)\fP,
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\%\f3glEvalMesh(3G)\fP,
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\%\f3glEvalPoint(3G)\fP,
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\%\f3glIndex(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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\%\f3glNormal(3G)\fP,
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\%\f3glTexCoord(3G)\fP,
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\%\f3glVertex(3G)\fP
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