| '''OpenGL extension SGIS.pixel_texture |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GL.SGIS.pixel_texture to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| The geometry rasterization and pixel pipeline "convert to fragment" |
| stages each produce fragments. The fragments are processed by |
| a unified per fragment pipeline that begins with the application |
| of the texture to the fragment color. Because the pixel pipeline |
| shares the per fragment processing with the geometry pipeline, the |
| fragments produced by the pixel pipeline must have the same fields |
| as the ones produced by the geometry pipeline. When |
| pixel groups are being converted to fragments, the parts |
| of the fragment that aren't derived from the pixel groups |
| are taken from the associated values in the current raster position. |
| |
| A fragment consists of x and y window coordinates and their |
| associated color value, depth value, and texture coordinates. |
| In the 1.1 OpenGL specification, when the pixel group is RGBA |
| the fragment color is always derived from the pixel group, |
| and the depth value and texture coordinates always come |
| from the raster position. |
| |
| This extension provides a way to specify how the texture coordinates |
| of the fragments can be derived from RGBA pixel groups. When |
| this option is enabled, the source of the fragment color value |
| when the pixel group is RGBA can be specified to come from either |
| the raster position or the pixel group. |
| |
| Deriving the fragment texture coordinates from the pixel group |
| effectively converts a color image into a texture coordinate image. |
| The multidimensional texture mapping lookup logic also makes this |
| extension useful for implementing multidimensional color lookups. |
| Multidimensional color lookups can be used to implement very |
| accurate color space conversions. |
| |
| Deriving texture coordinates from the pixel groups in the pixel |
| pipeline introduces a problem with the lambda parameter in the |
| texture mapping equations. When texture coordinates are |
| being taken from the current raster position texture coordinates, |
| the texture coordinate values don't change from pixel to pixel, |
| and the equation for calculating lambda always produces zero. |
| Enabling pixel_texture introduces changes in the texture |
| coordinates from pixel to pixel which are not necessarily |
| meaningful for texture lookups. This problem is addressed |
| by specifying that lambda is always set to zero when pixel_texture |
| is enabled. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/SGIS/pixel_texture.txt |
| ''' |
| from OpenGL import platform, constant, arrays |
| from OpenGL import extensions, wrapper |
| import ctypes |
| from OpenGL.raw.GL import _types, _glgets |
| from OpenGL.raw.GL.SGIS.pixel_texture import * |
| from OpenGL.raw.GL.SGIS.pixel_texture import _EXTENSION_NAME |
|
|
| def glInitPixelTextureSGIS(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
| |
| glPixelTexGenParameterivSGIS=wrapper.wrapper(glPixelTexGenParameterivSGIS).setInputArraySize( |
| 'params', None |
| ) |
| |
| glPixelTexGenParameterfvSGIS=wrapper.wrapper(glPixelTexGenParameterfvSGIS).setInputArraySize( |
| 'params', None |
| ) |
| glGetPixelTexGenParameterivSGIS=wrapper.wrapper(glGetPixelTexGenParameterivSGIS).setOutput( |
| 'params',size=_glgets._glget_size_mapping,pnameArg='pname',orPassIn=True |
| ) |
| glGetPixelTexGenParameterfvSGIS=wrapper.wrapper(glGetPixelTexGenParameterfvSGIS).setOutput( |
| 'params',size=_glgets._glget_size_mapping,pnameArg='pname',orPassIn=True |
| ) |
| |
