GLEVALCOORD(3G)

💖 GLEVALCOORD 💖 (that's the 3G one, bestie)

ok so. sit down. hydrate. we're talking about glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, and glEvalCoord2fv — the whole lil squad whose entire job is evaluating enabled one- and two-dimensional maps. no cap. that's the vibe. ✨

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🌸 NAME 🌸

glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv — evaluate enabled one- and two-dimensional maps 💅

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🎀 C SPECIFICATION 🎀

void glEvalCoord1d( GLdouble u )
void glEvalCoord1f( GLfloat u )
void glEvalCoord2d( GLdouble u,
                    GLdouble v )
void glEvalCoord2f( GLfloat u,
                    GLfloat v )

✨ PARAMETERS ✨

• u — a value that is the domain coordinate u to the basis function you defined earlier in a glMap1 or glMap2 command. yes queen, it's literally the input 🫶
• v — a value that is the domain coordinate v to the basis function defined in a previous glMap2 command. heads up bestie: this argument is not present in a glEvalCoord1 command. she simply doesn't show up 💀

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🦋 C SPECIFICATION (the pointer girlies) 🦋

void glEvalCoord1dv( const GLdouble *u )
void glEvalCoord1fv( const GLfloat *u )
void glEvalCoord2dv( const GLdouble *u )
void glEvalCoord2fv( const GLfloat *u )

💜 PARAMETERS 💜

• u — a pointer to an array containing either one or two domain coordinates. the first coordinate is u. the second coordinate is v, and she only exists in the glEvalCoord2 versions. periodt.

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👑 DESCRIPTION 👑

glEvalCoord1 evaluates enabled one-dimensional maps at argument u. glEvalCoord2 does the exact same thing but for two-dimensional maps, using two domain values, u and v. to define a map, call glMap1 and glMap2. to enable and disable it, call glEnable and glDisable. that's the whole friendship group. 🌈

when one of the glEvalCoord commands is issued, all currently enabled maps of the indicated dimension are evaluated. then, for each enabled map, it is as if the corresponding GL command had been issued with the computed value. like, translation:

• if GL_MAP1_INDEX or GL_MAP2_INDEX is enabled, a glIndex command is simulated.
• if GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4 is enabled, a glColor command is simulated.
• if GL_MAP1_NORMAL or GL_MAP2_NORMAL is enabled, a normal vector is produced.
• and if any of GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2, GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4, GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2, GL_MAP2_TEXTURE_COORD_3, or GL_MAP2_TEXTURE_COORD_4 is enabled, then an appropriate glTexCoord command is simulated. the whole alphabet of texture coords, we love her 💅

for color, color index, normal, and texture coordinates, the GL uses evaluated values instead of current values for those evaluations that are enabled, and current values otherwise. However (capital H, she's serious), the evaluated values do not update the current values. so if glVertex commands are interspersed with glEvalCoord commands, the color, normal, and texture coordinates associated with the glVertex commands are not affected by the values generated by the glEvalCoord commands — only by the most recent glColor, glIndex, glNormal, and glTexCoord commands. it's giving "separate friend groups, no crossover." 🙈

no commands are issued for maps that are not enabled. and listen: if more than one texture evaluation is enabled for a particular dimension (for example, GL_MAP2_TEXTURE_COORD_1 and GL_MAP2_TEXTURE_COORD_2), then only the evaluation of the map that produces the larger number of coordinates (in this case, GL_MAP2_TEXTURE_COORD_2) is carried out. main character energy, only one gets the spotlight. 🌟

GL_MAP1_VERTEX_4 overrides GL_MAP1_VERTEX_3, and GL_MAP2_VERTEX_4 overrides GL_MAP2_VERTEX_3, in the same manner. and if neither a three- nor a four-component vertex map is enabled for the specified dimension, the glEvalCoord command is ignored. she said nothing, she's not doing it, moving on 💀

if you have enabled automatic normal generation by calling glEnable with argument GL_AUTO_NORMAL, then glEvalCoord2 generates surface normals analytically, regardless of the contents or enabling of the GL_MAP2_NORMAL map. let

m=__×__

then the generated normal n is

n=_____

if automatic normal generation is disabled, the corresponding normal map GL_MAP2_NORMAL, if enabled, is used to produce a normal. if neither automatic normal generation nor a normal map is enabled, no normal is generated for glEvalCoord2 commands. no normal, no drama. 🎀

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🍓 ASSOCIATED GETS 🍓

the lil "how do I check on her" list, and yes every single one is here:

• glIsEnabled with argument GL_MAP1_VERTEX_3
• glIsEnabled with argument GL_MAP1_VERTEX_4
• glIsEnabled with argument GL_MAP1_INDEX
• glIsEnabled with argument GL_MAP1_COLOR_4
• glIsEnabled with argument GL_MAP1_NORMAL
• glIsEnabled with argument GL_MAP1_TEXTURE_COORD_1
• glIsEnabled with argument GL_MAP1_TEXTURE_COORD_2
• glIsEnabled with argument GL_MAP1_TEXTURE_COORD_3
• glIsEnabled with argument GL_MAP1_TEXTURE_COORD_4
• glIsEnabled with argument GL_MAP2_VERTEX_3
• glIsEnabled with argument GL_MAP2_VERTEX_4
• glIsEnabled with argument GL_MAP2_INDEX
• glIsEnabled with argument GL_MAP2_COLOR_4
• glIsEnabled with argument GL_MAP2_NORMAL
• glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1
• glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2
• glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3
• glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4
• glIsEnabled with argument GL_AUTO_NORMAL
• glGetMap

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🧚 SEE ALSO 🧚

the extended universe, iykyk:

glBegin(3G), glColor(3G), glEnable(3G), glEvalMesh(3G), glEvalPoint(3G), glIndex(3G), glMap1(3G), glMap2(3G), glMapGrid(3G), glNormal(3G), glTexCoord(3G), glVertex(3G)

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ok that's the whole page bestie, go evaluate some maps, you're gonna slay so hard 🔥🫶

this page came to you from GLEVALCOORD(3G) — that's the source and version tag, mwah, and she's dated like a fine little manual. bye pookie 💖🎀✨