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'''OpenGL extension APPLE.specular_vector |
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This module customises the behaviour of the |
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OpenGL.raw.GL.APPLE.specular_vector to provide a more |
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Python-friendly API |
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Overview (from the spec) |
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An alternative specular lighting model is enabled by passing |
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the LIGHT_MODEL_SPECULAR_VECTOR token as the <pname> parameter |
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to LightModel, and TRUE as the <param> parameter. The specular |
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vector lighting model calculates the specular intensity as the |
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dot product of the true reflection vector of the light source |
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and the vector from the vertex to the viewpoint. This yields |
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results that are visually similar to but often more realistic |
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than the existing lighting model. |
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Mathematically, the specular component s.n in the existing |
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lighting model calculation is replaced with the following |
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alternative calculation. |
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Given three vectors, n, l, and p, where n is the unit normal |
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vector at the vertex, l is the unit vector from the vertex to |
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the light position, and p is the unit vector from the vertex |
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to the viewpoint (or the vector {0,0,1} if |
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LIGHT_MODEL_LOCAL_VIEWER is false), the specular component is |
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given by |
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(2 * cross(n, cross(n, l)) + l) . p |
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All other lighting model and material parameters (shininess, |
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spotlight, attenuation, local viewer, and direction/positional |
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sources) operate normally. The specular vector lighting model |
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affects both rgba and index modes. |
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The official definition of this extension is available here: |
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http://www.opengl.org/registry/specs/APPLE/specular_vector.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.APPLE.specular_vector import * |
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from OpenGL.raw.GL.APPLE.specular_vector import _EXTENSION_NAME |
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def glInitSpecularVectorAPPLE(): |
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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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