_glTexImage1D: specify a one-dimensional texture image
SUB _glTexImage1D (BYVAL target AS _UNSIGNED LONG, BYVAL level AS LONG, BYVAL internalformat AS LONG, BYVAL width AS LONG, BYVAL border AS LONG, BYVAL format AS _UNSIGNED LONG, BYVAL type AS _UNSIGNED LONG, pixels AS _OFFSET) void _glTexImage1D(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLint border, GLenum format, GLenum type, const GLvoid * data);
- Specifies the target texture. Must be _GL_TEXTURE_1D or _GL_PROXY_TEXTURE_1D.
- Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
- Specifies the number of color components in the texture. Must be one of base internal formats given in Table 1, one of the sized internal formats given in Table 2, or one of the compressed internal formats given in Table 3, below.
- Specifies the width of the texture image. All implementations support texture images that are at least 1024 texels wide. The height of the 1D texture image is 1.
- This value must be 0.
Texturing maps a portion of a specified texture image onto each graphical primitive for which texturing is enabled. To enable and disable one-dimensional texturing, call _glEnable and _glDisable with argument _GL_TEXTURE_1D.
Texture images are defined with _glTexImage1D. The arguments describe the parameters of the texture image, such as width, width of the border, level-of-detail number (see _glTexParameter), and the internal resolution and format used to store the image. The last three arguments describe how the image is represented in memory.
If target is _GL_PROXY_TEXTURE_1D, no data is read from data, but all of the texture image state is recalculated, checked for consistency, and checked against the implementation's capabilities. If the implementation cannot handle a texture of the requested texture size, it sets all of the image state to 0, but does not generate an error (see _glGetError). To query for an entire mipmap array, use an image array level greater than or equal to 1.
If target is _GL_TEXTURE_1D, data is read from data as a sequence of signed or unsigned bytes, shorts, or longs, or single-precision floating-point values, depending on type. These values are grouped into sets of one, two, three, or four values, depending on format, to form elements. Each data byte is treated as eight 1-bit elements, with bit ordering determined by _GL_UNPACK_LSB_FIRST (see _glPixelStore).
If a non-zero named buffer object is bound to the _GL_PIXEL_UNPACK_BUFFER target (see _glBindBuffer) while a texture image is specified, data is treated as a byte offset into the buffer object's data store.
The first element corresponds to the left end of the texture array. Subsequent elements progress left-to-right through the remaining texels in the texture array. The final element corresponds to the right end of the texture array.
format determines the composition of each element in data. It can assume one of these symbolic values:
- Each element is a single red component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for green and blue, and 1 for alpha. Each component is then multiplied by the signed scale factor _GL_c_SCALE, added to the signed bias _GL_c_BIAS, and clamped to the range [0,1].
- Each element is a red/green pair. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for blue, and 1 for alpha. Each component is then multiplied by the signed scale factor _GL_c_SCALE, added to the signed bias _GL_c_BIAS, and clamped to the range [0,1].
- _GL_RGB or _GL_BGR
- Each element is an RGB triple. The GL converts it to floating point and assembles it into an RGBA element by attaching 1 for alpha. Each component is then multiplied by the signed scale factor _GL_c_SCALE, added to the signed bias _GL_c_BIAS, and clamped to the range [0,1].
- _GL_RGBA or _GL_BGRA
- Each element contains all four components. Each component is multiplied by the signed scale factor _GL_c_SCALE, added to the signed bias _GL_c_BIAS, and clamped to the range [0,1].
- Each element is a single depth value. The GL converts it to floating point, multiplies by the signed scale factor _GL_DEPTH_SCALE, adds the signed bias _GL_DEPTH_BIAS, and clamps to the range [0,1].
If an application wants to store the texture at a certain resolution or in a certain format, it can request the resolution and format with internalFormat. The GL will choose an internal representation that closely approximates that requested by internalFormat, but it may not match exactly. (The representations specified by _GL_RED, _GL_RG, _GL_RGB and _GL_RGBA must match exactly.)
internalFormat may be one of the base internal formats shown in Table 1, below
internalFormat may also be one of the sized internal formats shown in Table 2, below
Finally, internalFormat may also be one of the generic or compressed compressed texture formats shown in Table 3 below
If the internalFormat parameter is one of the generic compressed formats, _GL_COMPRESSED_RED, _GL_COMPRESSED_RG, _GL_COMPRESSED_RGB, or _GL_COMPRESSED_RGBA, the GL will replace the internal format with the symbolic constant for a specific internal format and compress the texture before storage. If no corresponding internal format is available, or the GL can not compress that image for any reason, the internal format is instead replaced with a corresponding base internal format.
If the internalFormat parameter is _GL_SRGB, _GL_SRGB8, _GL_SRGB_ALPHAor _GL_SRGB8_ALPHA8, the texture is treated as if the red, green, or blue components are encoded in the sRGB color space. Any alpha component is left unchanged. The conversion from the sRGB encoded component c<sub>s</sub> to a linear component c<sub>l</sub> is:
Assume c<sub>s</sub> is the sRGB component in the range [0,1].
Use the _GL_PROXY_TEXTURE_1D target to try out a resolution and format. The implementation will update and recompute its best match for the requested storage resolution and format. To then query this state, call _glGetTexLevelParameter. If the texture cannot be accommodated, texture state is set to 0.
A one-component texture image uses only the red component of the RGBA color from data. A two-component image uses the R and A values. A three-component image uses the R, G, and B values. A four-component image uses all of the RGBA components.
Image-based shadowing can be enabled by comparing texture r coordinates to depth texture values to generate a boolean result. See _glTexParameter for details on texture comparison.
_glPixelStore modes affect texture images.
data may be a null pointer. In this case texture memory is allocated to accommodate a texture of width width. You can then download subtextures to initialize the texture memory. The image is undefined if the program tries to apply an uninitialized portion of the texture image to a primitive.
_glTexImage1D specifies the one-dimensional texture for the current texture unit, specified with _glActiveTexture.
_GL_INVALID_ENUM is generated if type is not a type constant.
_GL_INVALID_VALUE is generated if level is less than 0.
_GL_INVALID_VALUE is generated if internalFormat is not one of the accepted resolution and format symbolic constants.
_GL_INVALID_VALUE is generated if border is not 0.
_GL_INVALID_OPERATION is generated if type is one of _GL_UNSIGNED_SHORT_4_4_4_4, _GL_UNSIGNED_SHORT_4_4_4_4_REV, _GL_UNSIGNED_SHORT_5_5_5_1, _GL_UNSIGNED_SHORT_1_5_5_5_REV, _GL_UNSIGNED_INT_8_8_8_8, _GL_UNSIGNED_INT_8_8_8_8_REV, _GL_UNSIGNED_INT_10_10_10_2, or _GL_UNSIGNED_INT_2_10_10_10_REV and format is neither _GL_RGBA nor _GL_BGRA.
_GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the _GL_PIXEL_UNPACK_BUFFER target and the data would be unpacked from the buffer object such that the memory reads required would exceed the data store size.
_GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the _GL_PIXEL_UNPACK_BUFFER target and data is not evenly divisible into the number of bytes needed to store in memory a datum indicated by type.
Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2011 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.