Open GL Super Bible:Texture Mapping















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Open GL Super Bible


(Publisher: Macmillan Computer Publishing)

Author(s): Waite group Press

ISBN: 1571690735

Publication Date: 08/01/96

 




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glTexImage1D

Purpose
Defines a one-dimensional texture image.
Include File
<GL/gl.h>
Syntax
void glTexImage1D(GLenum target, GLint level, Glint components, GLsizei width, GLint border GLenum format, GLenum type, const GLvoid *pixels);
Description
This function defines a one-dimensional texture
image. The image data is subject to modes defined with glPixelMap,
glPixelStore, and glPixelTransfer.


Parameters

target

GLenum: Must be GL_TEXTURE_1D.
level

GLint: The level of detail. Usually 0 unless mipmapping is used.
components

GLint: The number of color components, from 1 to 4.
width

GLsizei: The width of the texture image. This must be a power of 2 or follow the formula 2n + 2*border.
border

GLint: The width of the border. Must be 0, 1, or 2.
format

GLenum: The format of the pixel data. Valid
formats are as follows:





GL_COLOR_INDEX
Pixel values are color indices.

GL_RED
Pixel values are red intensities.

GL_GREEN
Pixel values are green intensities.

GL_BLUE
Pixel values are blue intensities.

GL_ALPHA
Pixel values are alpha intensities.

GL_RGB
Pixel values are RGB colors.

GL_RGBA
Pixel values are RGBA colors.

GL_LUMINANCE
Pixel values are grayscale colors.

GL_ALPHA_LUMINANCE
Pixel values are alpha and grayscale
colors.



type

GLenum: The data type of each pixel value (see glDrawPixels).
pixels

GLvoid *: The pixel data.
Returns
None.
Known Bugs
The GL_PACK_ALIGNMENT and GL_UNPACK_ALIGNMENT parameters for glPixelStore are presently ignored.
Example
See the example in CH12\TEX1D.C on the source code CD-ROM.
See Also
glPixelMap, glPixelStore, glPixelTransfer,
glTexImage2D


glTexImage2D

Purpose
Defines a two-dimensional texture image.
Include File
<GL/gl.h>
Syntax
void glTexImage2D(GLenum target, GLint level, Glint components, GLsizei width, GLsizei height, GLint border GLenum format, GLenum type, const GLvoid *pixels);
Description
This function defines a two-dimensional texture
image. The image data is subject to modes defined with glPixelMap,
glPixelStore, and glPixelTransfer.


Parameters

target

GLenum: Must be GL_TEXTURE_2D.
level

GLint: The level of detail. Usually 0 unless mipmapping is used.
components

GLint: The number of color components, from 1 to 4.
width

GLsizei: The width of the texture image. This must be a power of 2 or follow the formula 2n + 2*border.
height

GLsizei: The height of the texture image. This must be a power of two or follow the formula 2m+2*border.
border

GLint: The width of the border. Must be 0, 1, or 2.
format

GLenum: The format of the pixel data. Valid
formats are as follows:





GL_COLOR_INDEX
Pixel values are color indices.

GL_RED
Pixel values are red intensities.

GL_GREEN
Pixel values are green intensities.

GL_BLUE
Pixel values are blue intensities.

GL_ALPHA
Pixel values are alpha intensities.

GL_RGB
Pixel values are RGB colors.

GL_RGBA
Pixel values are RGBA colors.

GL_LUMINANCE
Pixel values are grayscale colors.

GL_ALPHA_LUMINANCE
Pixel values are alpha and grayscale
colors.



type

GLenum: The data type of each pixel value (see glDrawPixels).
pixels

GLvoid *: The pixel data.
Returns
None.
Known Bugs
The GL_PACK_ALIGNMENT and GL_UNPACK_ALIGNMENT parameters for glPixelStore are presently ignored.
Example
See the example in CH12\TEX2D.C on the source code CD-ROM.
See Also
glPixelMap, glPixelStore, glPixelTransfer,
glTexImage1D


glTexParameter

Purpose
Sets texture image parameters.
Include File
<GL/gl.h>
Syntax
void glTexParameterf(GLenum target, GLenum pname, GLfloat param);

void glTexParameterfv(GLenum target, GLenum pname, GLfloat *param);

void glTexParameteri(GLenum target, GLenum pname, GLint param);

void glTexParameteriv(GLenum target, GLenum pname, GLint *param);
Description
This function sets filter and repetition
parameters for texture images.


Parameters

target

GLenum: Must be one of GL_TEXTURE_1D or GL_TEXTURE_2D.
pname

GLenum: The texturing parameter to set. Valid
names are:





Parameter
Description

GL_TEXTURE_MIN_FILTER
Specifies the texture image minification (reduction) method or filter.

GL_TEXTURE_MAX_FILTER
Specifies the texture image magnification (enlargement) method or filter.

GL_TEXTURE_WRAP_S
Specifies handling of texture S coordinates outside the range of 0.0 to 1.0.

GL_TEXTURE_WRAP_T
Specifies handling of texture T coordinates outside the range of 0.0 to 1.0.

GL_BORDER_COLOR
Specifies a border color for textures
without borders.



param

For GL_TEXTURE_MIN_FILTER, param is one of the following:
For GL_TEXTURE_MAX_FILTER, param is either GL_NEAREST or GL_LINEAR.GL_TEXTURE_WRAP_S and GL_TEXTURE_WRAP_T can be set to GL_REPEAT or GL_CLAMP. GL_REPEAT causes the texture image to be repeated over the polygon. GL_CLAMP uses the specified border pixels or a constant border color (see below) on areas that fall outside of the 0.0
1.0 texture coordinate range.
For GL_BORDER_COLOR, param is an RGBA color array that is used as a constant border color when a texture image has no border pixels defined.
Returns
None.
Example
See the example in CH12\TEXSCENE.C on the source code CD-ROM.
See Also
glTexCoord, glTexEnv, glTexGen, glTexImage1D,
glTexImage2D






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