PARAMETERS¶
target
Specifies 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_DEPTH_STENCIL_TEXTURE_MODE, 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¶
glTexParameter assigns the value or values in params
to the texture parameter specified as pname. target defines
the target texture, either GL_TEXTURE_1D, GL_TEXTURE_2D,
GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY,
GL_TEXTURE_RECTANGLE, or GL_TEXTURE_3D. The following symbols
are accepted in pname:
GL_DEPTH_STENCIL_TEXTURE_MODE
Specifies the mode used to read from depth-stencil format
textures. params must be one of GL_DEPTH_COMPONENT or
GL_STENCIL_COMPONENT. If the depth stencil mode is
GL_DEPTH_COMPONENT, then reads from depth-stencil format textures will
return the depth component of the texel in Rt and the stencil component will
be discarded. If the depth stencil mode is GL_STENCIL_COMPONENT then
the stencil component is returned in Rt and the depth component is discarded.
The initial value is GL_DEPTH_COMPONENT.
GL_TEXTURE_BASE_LEVEL
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:
| 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> |
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
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
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.
GL_TEXTURE_LOD_BIAS
params specifies a fixed bias value that is to be
added to the level-of-detail parameter for the texture before texture
sampling. The specified value is added to the shader-supplied bias value (if
any) and subsequently clamped into the implementation-defined range - bias max
bias max, where bias max is the value of the implementation defined constant
GL_MAX_TEXTURE_LOD_BIAS. The initial value is 0.0.
GL_TEXTURE_MIN_FILTER
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
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.
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
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
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.
GL_TEXTURE_MIN_LOD
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.