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