📄 build2dmipmaps.html
字号:
<HTML><BODY><PRE> <STRONG>NAME</STRONG> <STRONG>gluBuild2DMipmaps</STRONG> - builds a 2-D mipmap <STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG> GLint <STRONG>gluBuild2DMipmaps</STRONG>( GLenum <EM>target</EM>, GLint <EM>internalFormat</EM>, GLsizei <EM>width</EM>, GLsizei <EM>height</EM>, GLenum <EM>format</EM>, GLenum <EM>type</EM>, const void *<EM>data</EM> ) <STRONG>PARAMETERS</STRONG> <EM>target</EM> Specifies the target texture. Must be <STRONG>GL_TEXTURE_2D</STRONG>. <EM>internalFormat</EM> Requests the internal storage format of the texture image. Must be 1, 2, 3, or 4 or one of the following symbolic constants: <STRONG>GL_ALPHA</STRONG>, <STRONG>GL_ALPHA4</STRONG>, <STRONG>GL_ALPHA8</STRONG>, <STRONG>GL_ALPHA12</STRONG>, <STRONG>GL_ALPHA16</STRONG>, <STRONG>GL_LUMINANCE</STRONG>, <STRONG>GL_LUMINANCE4</STRONG>, <STRONG>GL_LUMINANCE8</STRONG>, <STRONG>GL_LUMINANCE12</STRONG>, <STRONG>GL_LUMINANCE16</STRONG>, <STRONG>GL_LUMINANCE_ALPHA</STRONG>, <STRONG>GL_LUMINANCE4_ALPHA4</STRONG>, <STRONG>GL_LUMINANCE6_ALPHA2</STRONG>, <STRONG>GL_LUMINANCE8_ALPHA8</STRONG>, <STRONG>GL_LUMINANCE12_ALPHA4</STRONG>, <STRONG>GL_LUMINANCE12_ALPHA12</STRONG>, <STRONG>GL_LUMINANCE16_ALPHA16</STRONG>, <STRONG>GL_INTENSITY</STRONG>, <STRONG>GL_INTENSITY4</STRONG>, <STRONG>GL_INTENSITY8</STRONG>, <STRONG>GL_INTENSITY12</STRONG>, <STRONG>GL_INTENSITY16</STRONG>, <STRONG>GL_RGB</STRONG>, <STRONG>GL_R3_G3_B2</STRONG>, <STRONG>GL_RGB4</STRONG>, <STRONG>GL_RGB5</STRONG>, <STRONG>GL_RGB8</STRONG>, <STRONG>GL_RGB10</STRONG>, <STRONG>GL_RGB12</STRONG>, <STRONG>GL_RGB16</STRONG>, <STRONG>GL_RGBA</STRONG>, <STRONG>GL_RGBA2</STRONG>, <STRONG>GL_RGBA4</STRONG>, <STRONG>GL_RGB5_A1</STRONG>, <STRONG>GL_RGBA8</STRONG>, <STRONG>GL_RGB10_A2</STRONG>, <STRONG>GL_RGBA12</STRONG> or <STRONG>GL_RGBA16</STRONG>. <EM>width</EM>, <EM>height</EM> Specifies the width and height, respectively, in pixels of the texture image. <EM>format</EM> Specifies the format of the pixel data. Must be one of: <STRONG>GL_COLOR_INDEX</STRONG>, <STRONG>GL_RED</STRONG>, <STRONG>GL_GREEN</STRONG>, <STRONG>GL_BLUE</STRONG>, <STRONG>GL_ALPHA</STRONG>, <STRONG>GL_RGB</STRONG>, <STRONG>GL_RGBA</STRONG>, <STRONG>GL_LUMINANCE</STRONG>, and <STRONG>GL_LUMINANCE_ALPHA</STRONG>. <EM>type</EM> Specifies the data type for <EM>data</EM>. Must be one of: <STRONG>GL_UNSIGNED_BYTE</STRONG>, <STRONG>GL_BYTE</STRONG>, <STRONG>GL_BITMAP</STRONG>, <STRONG>GL_UNSIGNED_SHORT</STRONG>, <STRONG>GL_SHORT</STRONG>, <STRONG>GL_UNSIGNED_INT</STRONG>, <STRONG>GL_INT</STRONG>, or <STRONG>GL_FLOAT</STRONG>. <EM>data</EM> Specifies a pointer to the image data in memory. <STRONG>DESCRIPTION</STRONG> <STRONG>gluBuild2DMipmaps</STRONG> builds a series of prefiltered 2-D texture maps of decreasing resolutions called a mipmap. This is used for the antialiasing of texture mapped primitives. A return value of 0 indicates success, otherwise a GLU error code is returned (see <STRONG>gluErrorString</STRONG>). Initially, the <EM>width</EM> and <EM>height</EM> of <EM>data</EM> are checked to see if they are a power of two. If not, a copy of <EM>data</EM> (not <EM>data</EM>), is scaled up or down to the nearest power of two. This copy will be used for subsequent mipmapping operations described below. (If <EM>width</EM> or <EM>height</EM> is exactly between powers of 2, then the copy of <EM>data</EM> will scale upwards.) For example, if <EM>width</EM> is 57 and <EM>height</EM> is 23 then a copy of <EM>data</EM> will scale up to 64 and down to 16, respectively, before mipmapping takes place. Then, proxy textures (see <STRONG>glTexImage2D</STRONG>) are used to determine if the implementation can fit the requested texture. If not, both dimensions are continually halved until it fits. (If the OpenGL version is <= 1.0, both maximum texture dimensions are clamped to the value returned by <STRONG>glGetIntegerv</STRONG> with the argument <STRONG>GL_MAX_TEXTURE_SIZE</STRONG>.) Next, a series of mipmap levels is built by decimating a copy of <EM>data</EM> in half along both dimensions until size 1x1 is reached. At each level, each texel in the halved mipmap level is an average of the corresponding four texels in the larger mipmap level. (In the case of rectangular images, the decimation will ultimately reach an N x 1 or 1 x N configuration. Here, two texels are averaged instead.) <STRONG>glTexImage2D</STRONG> is called to load each of these mipmap levels. Level 0 is a copy of <EM>data</EM>. The highest level is log2(max(width,height)). For example, if width is 64 and height is 16 and the implementation can store a texture of this size, the following mipmap levels are built: 64x16, 32x8, 16x4, 8x2, 4x1, 2x1 and 1x1. These correspond to levels 0 through 6, respectively. See the <STRONG>glTexImage1D</STRONG> reference page for a description of the acceptable values for <EM>format</EM>. See the <STRONG>glDrawPixels</STRONG> reference page for a description of the acceptable values for <EM>type</EM>. <STRONG>NOTES</STRONG> Note that there is no direct way of querying the maximum level. This can be derived indirectly via <STRONG>glGetTexLevelParameter</STRONG>. First, query for the width & height actually used at level 0. (The width & height may not be equal to <EM>width</EM> & <EM>height</EM> respectively since proxy textures might have scaled them to fit the implementation.) Then the maximum level can be derived from the formula log2(max(width,height)). <STRONG>ERRORS</STRONG> <STRONG>GLU_INVALID_VALUE</STRONG> is returned if <EM>width</EM> or <EM>height</EM> are < 1. <STRONG>GLU_INVALID_ENUM</STRONG> is returned if <EM>internalFormat</EM>, <EM>format</EM> or <EM>type</EM> are not legal. <STRONG>SEE</STRONG> <STRONG>ALSO</STRONG> <STRONG>glDrawPixels</STRONG>, <STRONG>glTexImage1D</STRONG>, <STRONG>glTexImage2D</STRONG>, <STRONG>gluBuild1DMipmaps</STRONG>, <STRONG>gluErrorString</STRONG>, <STRONG>gluScaleImage</STRONG></PRE></BODY></HTML>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -