table of contents
GLTEXPARAMETER(3G) | [FIXME: manual] | GLTEXPARAMETER(3G) |
NAME¶
glTexParameter - set texture parametersC SPECIFICATION¶
void
glTexParameterf(GLenum target,
GLenum pname, GLfloat param);
void
glTexParameteri(GLenum target,
GLenum pname, GLint param);
PARAMETERS¶
targetSpecifies the target texture, which must be
either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY,
GL_TEXTURE_RECTANGLE, or GL_TEXTURE_CUBE_MAP.
pname
Specifies the symbolic name of a single-valued
texture parameter. pname can be one of the following:
GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_COMPARE_FUNC,
GL_TEXTURE_COMPARE_MODE, GL_TEXTURE_LOD_BIAS,
GL_TEXTURE_MIN_FILTER, GL_TEXTURE_MAG_FILTER,
GL_TEXTURE_MIN_LOD, GL_TEXTURE_MAX_LOD,
GL_TEXTURE_MAX_LEVEL, GL_TEXTURE_SWIZZLE_R,
GL_TEXTURE_SWIZZLE_G, GL_TEXTURE_SWIZZLE_B,
GL_TEXTURE_SWIZZLE_A, GL_TEXTURE_WRAP_S,
GL_TEXTURE_WRAP_T, or GL_TEXTURE_WRAP_R.
param
Specifies the value of pname.
C SPECIFICATION¶
void
glTexParameterfv(GLenum target,
GLenum pname,
const GLfloat * params);
void
glTexParameteriv(GLenum target,
GLenum pname,
const GLint * params);
void
glTexParameterIiv(GLenum target,
GLenum pname,
const GLint * params);
void
glTexParameterIuiv(GLenum target,
GLenum pname,
const GLuint * params);
PARAMETERS¶
targetSpecifies the target texture, which must be
either GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY,
GL_TEXTURE_RECTANGLE, or GL_TEXTURE_CUBE_MAP.
pname
Specifies the symbolic name of a texture
parameter. pname can be one of the following:
GL_TEXTURE_BASE_LEVEL, GL_TEXTURE_BORDER_COLOR,
GL_TEXTURE_COMPARE_FUNC, GL_TEXTURE_COMPARE_MODE,
GL_TEXTURE_LOD_BIAS, GL_TEXTURE_MIN_FILTER,
GL_TEXTURE_MAG_FILTER, GL_TEXTURE_MIN_LOD,
GL_TEXTURE_MAX_LOD, GL_TEXTURE_MAX_LEVEL,
GL_TEXTURE_SWIZZLE_R, GL_TEXTURE_SWIZZLE_G,
GL_TEXTURE_SWIZZLE_B, GL_TEXTURE_SWIZZLE_A,
GL_TEXTURE_SWIZZLE_RGBA, GL_TEXTURE_WRAP_S,
GL_TEXTURE_WRAP_T, or GL_TEXTURE_WRAP_R.
params
Specifies a pointer to an array where the
value or values of pname are stored.
DESCRIPTION¶
Specifies the index of the lowest defined
mipmap level. This is an integer value. The initial value is 0.
GL_TEXTURE_BORDER_COLOR
The data in params specifies four
values that define the border values that should be used for border texels. If
a texel is sampled from the border of the texture, the values of
GL_TEXTURE_BORDER_COLOR are interpreted as an RGBA color to match the
texture's internal format and substituted for the non-existent texel data. If
the texture contains depth components, the first component of
GL_TEXTURE_BORDER_COLOR is interpreted as a depth value. The initial
value is 0.0, 0.0, 0.0, 0.0.
If the values for GL_TEXTURE_BORDER_COLOR are specified with
glTexParameterIiv or glTexParameterIuiv, the values are stored
unmodified with an internal data type of integer. If specified with
glTexParameteriv, they are converted to floating point with the
following equation: f = 2 c + 1 2 b - 1. If specified with
glTexParameterfv, they are stored unmodified as floating-point
values.
GL_TEXTURE_COMPARE_FUNC
Specifies the comparison operator used when
GL_TEXTURE_COMPARE_MODE is set to GL_COMPARE_REF_TO_TEXTURE.
Permissible values are:
where r is the current interpolated texture coordinate, and D t is the depth
texture value sampled from the currently bound depth texture. result is
assigned to the the red channel.
GL_TEXTURE_COMPARE_MODE
Texture Comparison Function | Computed result |
GL_LEQUAL | <div> result = 1.0 0.0 r <= D t r > D t </div> |
GL_GEQUAL | <div> result = 1.0 0.0 r >= D t r < D t </div> |
GL_LESS | <div> result = 1.0 0.0 r < D t r >= D t </div> |
GL_GREATER | <div> result = 1.0 0.0 r > D t r <= D t </div> |
GL_EQUAL | <div> result = 1.0 0.0 r = D t r ≠ D t </div> |
GL_NOTEQUAL | <div> result = 1.0 0.0 r ≠ D t r = D t </div> |
GL_ALWAYS | <div> result = 1.0 </div> |
GL_NEVER | <div> result = 0.0 </div> |
Specifies the texture comparison mode for
currently bound depth textures. That is, a texture whose internal format is
GL_DEPTH_COMPONENT_*; see glTexImage2D()) Permissible values
are:
GL_COMPARE_REF_TO_TEXTURE
GL_TEXTURE_LOD_BIAS
Specifies that the interpolated and clamped r
texture coordinate should be compared to the value in the currently bound
depth texture. See the discussion of GL_TEXTURE_COMPARE_FUNC for
details of how the comparison is evaluated. The result of the comparison is
assigned to the red channel.
GL_NONE
Specifies that the red channel should be
assigned the appropriate value from the currently bound depth texture.
The texture minifying function is used
whenever the level-of-detail function used when sampling from the texture
determines that the texture should be minified. There are six defined
minifying functions. Two of them use either the nearest texture elements or a
weighted average of multiple texture elements to compute the texture value.
The other four use mipmaps.
A mipmap is an ordered set of arrays representing the same image at
progressively lower resolutions. If the texture has dimensions 2 n × 2 m,
there are max n m + 1 mipmaps. The first mipmap is the original
texture, with dimensions 2 n × 2 m. Each subsequent mipmap has dimensions
2 k - 1 × 2 l - 1, where 2 k × 2 l are the dimensions of the
previous mipmap, until either k = 0 or l = 0. At that point, subsequent
mipmaps have dimension 1 × 2 l - 1 or 2 k - 1 × 1 until the final
mipmap, which has dimension 1 × 1. To define the mipmaps, call
glTexImage1D(), glTexImage2D(), glTexImage3D(),
glCopyTexImage1D(), or glCopyTexImage2D() with the level
argument indicating the order of the mipmaps. Level 0 is the original texture;
level max n m is the final 1 × 1 mipmap.
params supplies a function for minifying the texture as one of the
following:
GL_NEAREST
As more texture elements are sampled in the minification process, fewer aliasing
artifacts will be apparent. While the GL_NEAREST and GL_LINEAR
minification functions can be faster than the other four, they sample only one
or multiple texture elements to determine the texture value of the pixel being
rendered and can produce moire patterns or ragged transitions. The initial
value of GL_TEXTURE_MIN_FILTER is
GL_NEAREST_MIPMAP_LINEAR.
GL_TEXTURE_MAG_FILTER
Returns the value of the texture element that
is nearest (in Manhattan distance) to the specified texture coordinates.
GL_LINEAR
Returns the weighted average of the four
texture elements that are closest to the specified texture coordinates. These
can include items wrapped or repeated from other parts of a texture, depending
on the values of GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, and on
the exact mapping.
GL_NEAREST_MIPMAP_NEAREST
Chooses the mipmap that most closely matches
the size of the pixel being textured and uses the GL_NEAREST criterion
(the texture element closest to the specified texture coordinates) to produce
a texture value.
GL_LINEAR_MIPMAP_NEAREST
Chooses the mipmap that most closely matches
the size of the pixel being textured and uses the GL_LINEAR criterion
(a weighted average of the four texture elements that are closest to the
specified texture coordinates) to produce a texture value.
GL_NEAREST_MIPMAP_LINEAR
Chooses the two mipmaps that most closely
match the size of the pixel being textured and uses the GL_NEAREST
criterion (the texture element closest to the specified texture coordinates )
to produce a texture value from each mipmap. The final texture value is a
weighted average of those two values.
GL_LINEAR_MIPMAP_LINEAR
Chooses the two mipmaps that most closely
match the size of the pixel being textured and uses the GL_LINEAR
criterion (a weighted average of the texture elements that are closest to the
specified texture coordinates) to produce a texture value from each mipmap.
The final texture value is a weighted average of those two values.
The texture magnification function is used
whenever the level-of-detail function used when sampling from the texture
determines that the texture should be magified. It sets the texture
magnification function to either GL_NEAREST or GL_LINEAR (see
below). GL_NEAREST is generally faster than GL_LINEAR, but it
can produce textured images with sharper edges because the transition between
texture elements is not as smooth. The initial value of
GL_TEXTURE_MAG_FILTER is GL_LINEAR.
GL_NEAREST
GL_TEXTURE_MIN_LOD
Returns the value of the texture element that
is nearest (in Manhattan distance) to the specified texture coordinates.
GL_LINEAR
Returns the weighted average of the texture
elements that are closest to the specified texture coordinates. These can
include items wrapped or repeated from other parts of a texture, depending on
the values of GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T, and on
the exact mapping.
Sets the minimum level-of-detail parameter.
This floating-point value limits the selection of highest resolution mipmap
(lowest mipmap level). The initial value is -1000.
GL_TEXTURE_MAX_LOD
Sets the maximum level-of-detail parameter.
This floating-point value limits the selection of the lowest resolution mipmap
(highest mipmap level). The initial value is 1000.
GL_TEXTURE_MAX_LEVEL
Sets the index of the highest defined mipmap
level. This is an integer value. The initial value is 1000.
GL_TEXTURE_SWIZZLE_R
Sets the swizzle that will be applied to the r
component of a texel before it is returned to the shader. Valid values for
param are GL_RED, GL_GREEN, GL_BLUE,
GL_ALPHA, GL_ZERO and GL_ONE. If
GL_TEXTURE_SWIZZLE_R is GL_RED, the value for r will be taken
from the first channel of the fetched texel. If GL_TEXTURE_SWIZZLE_R is
GL_GREEN, the value for r will be taken from the second channel of the
fetched texel. If GL_TEXTURE_SWIZZLE_R is GL_BLUE, the value for
r will be taken from the third channel of the fetched texel. If
GL_TEXTURE_SWIZZLE_R is GL_ALPHA, the value for r will be taken
from the fourth channel of the fetched texel. If GL_TEXTURE_SWIZZLE_R
is GL_ZERO, the value for r will be subtituted with 0.0. If
GL_TEXTURE_SWIZZLE_R is GL_ONE, the value for r will be
subtituted with 1.0. The initial value is GL_RED.
GL_TEXTURE_SWIZZLE_G
Sets the swizzle that will be applied to the g
component of a texel before it is returned to the shader. Valid values for
param and their effects are similar to those of
GL_TEXTURE_SWIZZLE_R. The initial value is GL_GREEN.
GL_TEXTURE_SWIZZLE_B
Sets the swizzle that will be applied to the b
component of a texel before it is returned to the shader. Valid values for
param and their effects are similar to those of
GL_TEXTURE_SWIZZLE_R. The initial value is GL_BLUE.
GL_TEXTURE_SWIZZLE_A
Sets the swizzle that will be applied to the a
component of a texel before it is returned to the shader. Valid values for
param and their effects are similar to those of
GL_TEXTURE_SWIZZLE_R. The initial value is GL_ALPHA.
GL_TEXTURE_SWIZZLE_RGBA
Sets the swizzles that will be applied to the
r, g, b, and a components of a texel before they are returned to the shader.
Valid values for params and their effects are similar to those of
GL_TEXTURE_SWIZZLE_R, except that all channels are specified
simultaneously. Setting the value of GL_TEXTURE_SWIZZLE_RGBA is
equivalent (assuming no errors are generated) to setting the parameters of
each of GL_TEXTURE_SWIZZLE_R, GL_TEXTURE_SWIZZLE_G,
GL_TEXTURE_SWIZZLE_B, and GL_TEXTURE_SWIZZLE_A
successively.
GL_TEXTURE_WRAP_S
Sets the wrap parameter for texture coordinate
s to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. GL_CLAMP_TO_EDGE causes
s coordinates to be clamped to the range 1 2N 1 - 1 2N, where N is the size of
the texture in the direction of clamping. GL_CLAMP_TO_BORDER evaluates
s coordinates in a similar manner to GL_CLAMP_TO_EDGE. However, in
cases where clamping would have occurred in GL_CLAMP_TO_EDGE mode, the
fetched texel data is substituted with the values specified by
GL_TEXTURE_BORDER_COLOR. GL_REPEAT causes the integer part of
the s coordinate to be ignored; the GL uses only the fractional part, thereby
creating a repeating pattern. GL_MIRRORED_REPEAT causes the s
coordinate to be set to the fractional part of the texture coordinate if the
integer part of s is even; if the integer part of s is odd, then the s texture
coordinate is set to 1 - frac s, where frac s represents the
fractional part of s. Initially, GL_TEXTURE_WRAP_S is set to
GL_REPEAT.
GL_TEXTURE_WRAP_T
Sets the wrap parameter for texture coordinate
t to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. See the discussion under
GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_T is set to
GL_REPEAT.
GL_TEXTURE_WRAP_R
Sets the wrap parameter for texture coordinate
r to either GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER,
GL_MIRRORED_REPEAT, or GL_REPEAT. See the discussion under
GL_TEXTURE_WRAP_S. Initially, GL_TEXTURE_WRAP_R is set to
GL_REPEAT.
NOTES¶
Suppose that a program attempts to sample from a texture and has set GL_TEXTURE_MIN_FILTER to one of the functions that requires a mipmap. If either the dimensions of the texture images currently defined (with previous calls to glTexImage1D(), glTexImage2D(), glTexImage3D(), glCopyTexImage1D(), or glCopyTexImage2D()) do not follow the proper sequence for mipmaps (described above), or there are fewer texture images defined than are needed, or the set of texture images have differing numbers of texture components, then the texture is considered incomplete. Linear filtering accesses the four nearest texture elements only in 2D textures. In 1D textures, linear filtering accesses the two nearest texture elements. In 3D textures, linear filtering accesses the eight nearest texture elements.ERRORS¶
ASSOCIATED GETS¶
SEE ALSO¶
COPYRIGHT¶
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.05/30/2012 | [FIXME: source] |