| | '''OpenGL extension SUN.global_alpha |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.SUN.global_alpha to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | Transparency is done in OpenGL using alpha blending. An alpha value |
| | of 0.0 is used for fully transparent objects, while an alpha value |
| | of 1.0 is used for fully opaque objects. A value of 0.25 is 75% |
| | transparent, and so on. |
| | |
| | OpenGL defines alpha as a component of the vertex color state. |
| | Whenever a color is set, the alpha component is set along with the |
| | red, green, and blue components. This means that transparency |
| | can't be changed for primitives with per-vertex colors without |
| | modifying the color of each vertex, replacing the old alpha |
| | component with the new alpha component. This can be very expensive |
| | for objects that are drawn using vertex arrays; it all but |
| | precludes the use of display lists. |
| | |
| | This extension defines a new global alpha attribute that can be |
| | used to specify an alpha factor that is independent from the alpha |
| | component of the color value. The global alpha factor is |
| | multiplied by the fragment's alpha value after primitive |
| | rasterization and prior to texture mapping, replacing the |
| | fragment's alpha value. The global alpha extension is only |
| | specified in RGBA mode and must be applied prior to any texture |
| | mapping operation. It is enabled by a new GLOBAL_ALPHA flag. |
| | |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/SUN/global_alpha.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.SUN.global_alpha import * |
| | from OpenGL.raw.GL.SUN.global_alpha import _EXTENSION_NAME |
| |
|
| | def glInitGlobalAlphaSUN(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
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| |
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| | |
