1GLTEXENV(3G) GLTEXENV(3G)
2
6 glTexEnvf, glTexEnvi, glTexEnvfv, glTexEnviv - set texture environment
7 parameters
8
11 void glTexEnvf( GLenum target,
12 GLenum pname,
13 GLfloat param )
14 void glTexEnvi( GLenum target,
15 GLenum pname,
16 GLint param )
17
20 target Specifies a texture environment. Must be GL_TEXTURE_ENV.
21 pname Specifies the symbolic name of a single-valued texture environ‐
23 ment parameter. Must be GL_TEXTURE_ENV_MODE.
24 param Specifies a single symbolic constant, one of GL_MODULATE,
26 GL_DECAL, GL_BLEND, or GL_REPLACE.
27
29 void glTexEnvfv( GLenum target,
30 GLenum pname,
31 const GLfloat *params )
32 void glTexEnviv( GLenum target,
33 GLenum pname,
34 const GLint *params )
35
38 target Specifies a texture environment. Must be GL_TEXTURE_ENV.
39 pname Specifies the symbolic name of a texture environment parameter.
41 Accepted values are GL_TEXTURE_ENV_MODE and
42 GL_TEXTURE_ENV_COLOR.
43 params Specifies a pointer to a parameter array that contains either a
45 single symbolic constant or an RGBA color.
46
48 A texture environment specifies how texture values are interpreted when
49 a fragment is textured. target must be GL_TEXTURE_ENV. pname can be
50 either GL_TEXTURE_ENV_MODE or GL_TEXTURE_ENV_COLOR.
51 If pname is GL_TEXTURE_ENV_MODE, then params is (or points to) the sym‐
53 bolic name of a texture function. Four texture functions may be speci‐
54 fied: GL_MODULATE, GL_DECAL, GL_BLEND, and GL_REPLACE.
55 A texture function acts on the fragment to be textured using the tex‐
57 ture image value that applies to the fragment (see glTexParameter) and
58 produces an RGBA color for that fragment. The following table shows
59 how the RGBA color is produced for each of the three texture functions
60 that can be chosen. C is a triple of color values (RGB) and A is the
61 associated alpha value. RGBA values extracted from a texture image are
62 in the range [0,1]. The subscript f refers to the incoming fragment,
63 the subscript t to the texture image, the subscript c to the texture
64 environment color, and subscript v indicates a value produced by the
65 texture function.
66 A texture image can have up to four components per texture element (see
68 glTexImage1D, glTexImage2D, glTexImage3D, glCopyTexImage1D, and
69 glCopyTexImage2D). In a one-component image, Lt indicates that single
70 component. A two-component image uses Lt and At. A three-component
71 image has only a color value, Ct. A four-component image has both a
72 color value Ct and an alpha value At.
73 ──────────────────────────────────────────────────────────────────────
76 Base internal Texture functions
77 GL_MODULATE GL_DECAL GL_BLEND GL_REPLACE
78 ──────────────────────────────────────────────────────────────────────
79 GL_ALPHA Cv=Cf undefined Cv=Cf Cv=Cf
80 Av=AfAt Av=Af Av=At
81 ──────────────────────────────────────────────────────────────────────
82 GL_LUMINANCE Cv=LtCf undefined Cv=(1−Lt)Cf Cv=Lt
83 +LtCc
84 1 Av=Af Av=Af Av=Af
85 ──────────────────────────────────────────────────────────────────────
86 GL_LUMINANCE Cv=LtCf undefined Cv=(1−Lt)Cf Cv=Lt
87 \f3_ALPHA +LtCc
88 2 Av=AtAf Av=AtAf Av=At
89 ──────────────────────────────────────────────────────────────────────
90 GL_INTENSITY Cv=CfIt undefined Cv=(1−It)Cf Cv=It
91 +ItCc
92 c Av=AfIt Av=(1−It)Af Av=It
93 +ItAc
94 ──────────────────────────────────────────────────────────────────────
95 GL_RGB Cv=CtCf Cv=Ct Cv=(1−Ct)Cf Cv=Ct
96 +CtCc
97 3 Av=Af Av=Af Av=Af Av=Af
98 ──────────────────────────────────────────────────────────────────────
99 GL_RGBA Cv=CtCf Cv=(1−At)Cf Cv=(1−Ct)Cf Cv=Ct
100 +AtCt +CtCc
101 4 Av=AtAf Av=Af Av=AtAf Av=At
102 ──────────────────────────────────────────────────────────────────────
103 If pname is GL_TEXTURE_ENV_COLOR, params is a pointer to an array that
104 holds an RGBA color consisting of four values. Integer color compo‐
105 nents are interpreted linearly such that the most positive integer maps
106 to 1.0, and the most negative integer maps to -1.0. The values are
107 clamped to the range [0,1] when they are specified. Cc takes these
108 four values.
109 GL_TEXTURE_ENV_MODE defaults to GL_MODULATE and GL_TEXTURE_ENV_COLOR
111 defaults to (0, 0, 0, 0).
112
114 GL_REPLACE may only be used if the GL version is 1.1 or greater.
115 Internal formats other than 1, 2, 3, or 4 may only be used if the GL
117 version is 1.1 or greater.
118 When the GL_ARB_multitexture extension is supported, glTexEnv controls
120 the texture environment for the current active texture unit, selected
121 by glActiveTextureARB. GL_INVALID_ENUM is generated when target or
122 pname is not one of the accepted defined values, or when params should
123 have a defined constant value (based on the value of pname) and does
124 not.
125 GL_INVALID_OPERATION is generated if glTexEnv is executed between the
127 execution of glBegin and the corresponding execution of glEnd.
128
130 glGetTexEnv
131
133 glActiveTextureARB(3G), glCopyPixels(3G), glCopyTexImage1D(3G),
134 glCopyTexImage2D(3G), glCopyTexSubImage1D(3G), glCopyTexSubImage2D(3G),
135 glCopyTexSubImage3D(3G), glTexImage1D(3G), glTexImage2D(3G),
136 glTexImage3D(3G), glTexParameter(3G), glTexSubImage1D(3G),
137 glTexSubImage2D(3G), glTexSubImage3D(3G)
138 GLTEXENV(3G)