| '''OpenGL extension MESAX.texture_stack |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GL.MESAX.texture_stack to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| There are a number of circumstances where an application may wish to |
| blend two textures out of a larger set of textures. Moreover, in some |
| cases the selected textures may vary on a per-fragment basis within |
| a polygon. Several examples include: |
| |
| 1. High dynamic range textures. The application stores several |
| different "exposures" of an image as different textures. On a |
| per-fragment basis, the application selects which exposures are |
| used. |
| |
| 2. A terrain engine where the altitude of a point determines the |
| texture applied to it. If the transition is from beach sand to |
| grass to rocks to snow, the application will store each texture |
| in a different texture map, and dynamically select which two |
| textures to blend at run-time. |
| |
| 3. Storing short video clips in textures. Each depth slice is a |
| single frame of video. |
| |
| Several solutions to this problem have been proposed, but they either |
| involve using a separate texture unit for each texture map or using 3D |
| textures without mipmaps. Both of these options have major drawbacks. |
| |
| This extension provides a third alternative that eliminates the major |
| drawbacks of both previous methods. A new texture target, |
| TEXTURE_2D_STACK, is added that functions identically to TEXTURE_3D in |
| all aspects except the sizes of the non-base level images. In |
| traditional 3D texturing, the size of the N+1 LOD is half the size |
| of the N LOD in all three dimensions. For the TEXTURE_2D_STACK target, |
| the height and width of the N+1 LOD is halved, but the depth is the |
| same for all levels of detail. The texture then becomes a "stack" of |
| 2D textures. The per-fragment texel is selected by the R texture |
| coordinate. |
| |
| References: |
| |
| http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=011557 |
| http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=000516 |
| http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=011903 |
| http://www.delphi3d.net/articles/viewarticle.php?article=terraintex.htm |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/MESAX/texture_stack.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.MESAX.texture_stack import * |
| from OpenGL.raw.GL.MESAX.texture_stack import _EXTENSION_NAME |
|
|
| def glInitTextureStackMESAX(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
|
|
| |
