GLProgramming.com

home :: about :: development guides :: irc :: forums :: search :: paste :: links :: contribute :: code dump

-> Click here to learn how to get live help <-


Manpage of GLTEXPARAMETER

GLTEXPARAMETER

Index
 

NAME

glTexParameterf, glTexParameteri, glTexParameterfv, glTexParameteriv - set texture parameters

 

C SPECIFICATION

void f3glTexParameterffP( GLenum fItargetfP,
   GLenum fIpnamefP,
   GLint fIparamfP )

delim $$  

PARAMETERS

f2targetfP
Specifies the target texture, which must be either %f3GL_TEXTURE_1DfP, %f3GL_TEXTURE_2DfP, or %f3GL_TEXTURE_3DfP.
f2pnamefP
Specifies the symbolic name of a single-valued texture parameter. f2pnamefP can be one of the following: %f3GL_TEXTURE_MIN_FILTERfP, %f3GL_TEXTURE_MAG_FILTERfP, %f3GL_TEXTURE_MIN_LODfP, %f3GL_TEXTURE_MAX_LODfP, %f3GL_TEXTURE_BASE_LEVELfP, %f3GL_TEXTURE_MAX_LEVELfP, %f3GL_TEXTURE_WRAP_SfP, %f3GL_TEXTURE_WRAP_TfP, %f3GL_TEXTURE_WRAP_RfP, or %f3GL_TEXTURE_PRIORITYfP.
f2paramfP
Specifies the value of f2pnamefP.
 

C SPECIFICATION

void f3glTexParameterfvfP( GLenum fItargetfP,
   GLenum fIpnamefP,
   const GLint fI*paramsfP )

 

PARAMETERS

f2targetfP
Specifies the target texture, which must be either %f3GL_TEXTURE_1DfP, %f3GL_TEXTURE_2DfP or %f3GL_TEXTURE_3DfP.
f2pnamefP
Specifies the symbolic name of a texture parameter. f2pnamefP can be one of the following: %f3GL_TEXTURE_MIN_FILTERfP, %f3GL_TEXTURE_MAG_FILTERfP, %f3GL_TEXTURE_MIN_LODfP, %f3GL_TEXTURE_MAX_LODfP, %f3GL_TEXTURE_BASE_LEVELfP, %f3GL_TEXTURE_MAX_LEVELfP, %f3GL_TEXTURE_WRAP_SfP, %f3GL_TEXTURE_WRAP_TfP, %f3GL_TEXTURE_WRAP_RfP, %f3GL_TEXTURE_BORDER_COLORfP, or %f3GL_TEXTURE_PRIORITYfP.
f2paramsfP
Specifies a pointer to an array where the value or values of f2pnamefP are stored.
 

DESCRIPTION

Texture mapping is a technique that applies an image onto an object's surface as if the image were a decal or cellophane shrink-wrap. The image is created in texture space, with an ($s$, $t$) coordinate system. A texture is a one- or two-dimensional image and a set of parameters that determine how samples are derived from the image. %f3glTexParameterfP assigns the value or values in f2paramsfP to the texture parameter specified as f2pnamefP. f2targetfP defines the target texture, either %f3GL_TEXTURE_1DfP, %f3GL_TEXTURE_2DfP, or %f3GL_TEXTURE_3DfP. The following symbols are accepted in f2pnamefP:
%f3GL_TEXTURE_MIN_FILTERfP
The texture minifying function is used whenever the pixel being textured maps to an area greater than one texture element. There are six defined minifying functions. Two of them use the nearest one or nearest four 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 $2 sup n ~times~ 2 sup m$, there are $ bold max ( n, m ) + 1 $ mipmaps. The first mipmap is the original texture, with dimensions $2 sup n ~times~ 2 sup m$. Each subsequent mipmap has dimensions $2 sup { k - 1 } ~times~ 2 sup { l - 1 }$, where $2 sup k ~times~ 2 sup l$ are the dimensions of the previous mipmap, until either $k ~=~ 0$ or $l~=~0$. At that point, subsequent mipmaps have dimension $ 1 ~times~ 2 sup { l - 1 } $ or $ 2 sup { k - 1} ~times~ 1 $ until the final mipmap, which has dimension $1 ~times~ 1$. To define the mipmaps, call %f3glTexImage1DfP, %f3glTexImage2DfP, %f3glTexImage3DfP, %f3glCopyTexImage1DfP, or %f3glCopyTexImage2DfP with the f2levelfP argument indicating the order of the mipmaps. Level 0 is the original texture; level $ bold max ( n, m ) $ is the final $1 ~times~ 1$ mipmap.
f2paramsfP supplies a function for minifying the texture as one of the following:
%f3GL_NEARESTfP
Returns the value of the texture element that is nearest (in Manhattan distance) to the center of the pixel being textured.
%f3GL_LINEARfP
Returns the weighted average of the four texture elements that are closest to the center of the pixel being textured. These can include border texture elements, depending on the values of %f3GL_TEXTURE_WRAP_SfP and %f3GL_TEXTURE_WRAP_TfP, and on the exact mapping.
%f3GL_NEAREST_MIPMAP_NEARESTfP
Chooses the mipmap that most closely matches the size of the pixel being textured and uses the %f3GL_NEARESTfP criterion (the texture element nearest to the center of the pixel) to produce a texture value.
%f3GL_LINEAR_MIPMAP_NEARESTfP
Chooses the mipmap that most closely matches the size of the pixel being textured and uses the %f3GL_LINEARfP criterion (a weighted average of the four texture elements that are closest to the center of the pixel) to produce a texture value.
%f3GL_NEAREST_MIPMAP_LINEARfP
Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the %f3GL_NEARESTfP criterion (the texture element nearest to the center of the pixel) to produce a texture value from each mipmap. The final texture value is a weighted average of those two values.
%f3GL_LINEAR_MIPMAP_LINEARfP
Chooses the two mipmaps that most closely match the size of the pixel being textured and uses the %f3GL_LINEARfP criterion (a weighted average of the four texture elements that are closest to the center of the pixel) 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 %f3GL_NEARESTfP and %f3GL_LINEARfP minification functions can be faster than the other four, they sample only one or four texture elements to determine the texture value of the pixel being rendered and can produce moire patterns or ragged transitions. The initial value of %f3GL_TEXTURE_MIN_FILTERfP is %f3GL_NEAREST_MIPMAP_LINEARfP.
%f3GL_TEXTURE_MAG_FILTERfP
The texture magnification function is used when the pixel being textured maps to an area less than or equal to one texture element. It sets the texture magnification function to either %f3GL_NEARESTfP or %f3GL_LINEARfP (see below). %f3GL_NEARESTfP is generally faster than %f3GL_LINEARfP, but it can produce textured images with sharper edges because the transition between texture elements is not as smooth. The initial value of %f3GL_TEXTURE_MAG_FILTERfP is %f3GL_LINEARfP.
%f3GL_NEARESTfP
Returns the value of the texture element that is nearest (in Manhattan distance) to the center of the pixel being textured.
%f3GL_LINEARfP
Returns the weighted average of the four texture elements that are closest to the center of the pixel being textured. These can include border texture elements, depending on the values of %f3GL_TEXTURE_WRAP_SfP and %f3GL_TEXTURE_WRAP_TfP, and on the exact mapping.
%f3GL_TEXTURE_MIN_LODfP
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.
%f3GL_TEXTURE_MAX_LODfP
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.
%f3GL_TEXTURE_BASE_LEVELfP
Specifies the index of the lowest defined mipmap level. This is an integer value. The initial value is 0.
%f3GL_TEXTURE_MAX_LEVELfP
Sets the index of the highest defined mipmap level. This is an integer value. The initial value is 1000.
%f3GL_TEXTURE_WRAP_SfP
Sets the wrap parameter for texture coordinate $s$ to either %f3GL_CLAMPfP, %f3GL_CLAMP_TO_EDGEfP, or %f3GL_REPEATfP. %f3GL_CLAMPfP causes $s$ coordinates to be clamped to the range [0,1] and is useful for preventing wrapping artifacts when mapping a single image onto an object. %f3GL_CLAMP_TO_EDGEfP causes $s$ coordinates to be clamped to the range $left [ {1 over 2N}, 1 - {1 over 2N} right ]$, where $N$ is the size of the texture in the direction of clamping. %f3GL_REPEATfP causes the integer part of the $s$ coordinate to be ignored; the GL uses only the fractional part, thereby creating a repeating pattern. Border texture elements are accessed only if wrapping is set to %f3GL_CLAMPfP. Initially, %f3GL_TEXTURE_WRAP_SfP is set to %f3GL_REPEATfP.
%f3GL_TEXTURE_WRAP_TfP
Sets the wrap parameter for texture coordinate $t$ to either %f3GL_CLAMPfP, %f3GL_CLAMP_TO_EDGEfP, or %f3GL_REPEATfP. See the discussion under %f3GL_TEXTURE_WRAP_SfP. Initially, %f3GL_TEXTURE_WRAP_TfP is set to %f3GL_REPEATfP.
%f3GL_TEXTURE_WRAP_RfP
Sets the wrap parameter for texture coordinate $r$ to either %f3GL_CLAMPfP, %f3GL_CLAMP_TO_EDGEfP, or %f3GL_REPEATfP. See the discussion under %f3GL_TEXTURE_WRAP_SfP. Initially, %f3GL_TEXTURE_WRAP_RfP is set to %f3GL_REPEATfP.
%f3GL_TEXTURE_BORDER_COLORfP
Sets a border color. f2paramsfP contains four values that comprise the RGBA color of the texture border. Integer color components are interpreted linearly such that the most positive integer maps to 1.0, and the most negative integer maps to -1.0. The values are clamped to the range [0,1] when they are specified. Initially, the border color is (0, 0, 0, 0).
%f3GL_TEXTURE_PRIORITYfP
Specifies the texture residence priority of the currently bound texture. Permissible values are in the range [0, 1]. See %f3glPrioritizeTexturesfP and %f3glBindTexturefP for more information.
 

NOTES

%f3GL_TEXTURE_3DfP, %f3GL_TEXTURE_MIN_LODfP, %f3GL_TEXTURE_MAX_LODfP, %f3GL_TEXTURE_BASE_LEVELfP, and %f3GL_TEXTURE_MAX_LEVELfP are only available if the GL version is 1.2 or greater. Suppose that a program has enabled texturing (by calling %f3glEnablefP with argument %f3GL_TEXTURE_1DfP, %f3GL_TEXTURE_2DfP, or %f3GL_TEXTURE_3DfP) and has set %f3GL_TEXTURE_MIN_FILTERfP to one of the functions that requires a mipmap. If either the dimensions of the texture images currently defined (with previous calls to %f3glTexImage1DfP, %f3glTexImage2DfP, %f3glTexImage3DfP, %f3glCopyTexImage1DfP, or %f3glCopyTexImage2DfP) 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 it is as if texture mapping were disabled. Linear filtering accesses the four nearest texture elements only in 2D textures. In 1D textures, linear filtering accesses the two nearest texture elements. When the %f3GL_ARB_multitexturefP extension is supported, %f3glTexParameterfP specifies the texture parameters for the active texture unit, specified by calling %f3glActiveTextureARBfP.  

ERRORS

%f3GL_INVALID_ENUMfP is generated if f2targetfP or f2pnamefP is not one of the accepted defined values. %f3GL_INVALID_ENUMfP is generated if f2paramsfP should have a defined constant value (based on the value of f2pnamefP) and does not. %f3GL_INVALID_OPERATIONfP is generated if %f3glTexParameterfP is executed between the execution of %f3glBeginfP and the corresponding execution of %f3glEndfP.  

ASSOCIATED GETS

%f3glGetTexParameterfP
%f3glGetTexLevelParameterfP  

SEE ALSO

%f3glActiveTextureARB(3G)fP, %f3glBindTexture(3G)fP, %f3glCopyPixels(3G)fP, %f3glCopyTexImage1D(3G)fP, %f3glCopyTexImage2D(3G)fP, %f3glCopyTexSubImage1D(3G)fP, %f3glCopyTexSubImage2D(3G)fP, %f3glCopyTexSubImage3D(3G)fP, %f3glDrawPixels(3G)fP, %f3glPixelStore(3G)fP, %f3glPixelTransfer(3G)fP, %f3glPrioritizeTextures(3G)fP, %f3glTexEnv(3G)fP, %f3glTexGen(3G)fP, %f3glTexImage1D(3G)fP, %f3glTexImage2D(3G)fP, %f3glTexImage3D(3G)fP, %f3glTexSubImage1D(3G)fP, %f3glTexSubImage2D(3G)fP, %f3glTexSubImage3D(3G)fP


 

Index

NAME
C SPECIFICATION
PARAMETERS
C SPECIFICATION
PARAMETERS
DESCRIPTION
NOTES
ERRORS
ASSOCIATED GETS
SEE ALSO