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