| | '''OpenGL extension NV.fog_distance |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.NV.fog_distance to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | Ideally, the fog distance (used to compute the fog factor as |
| | described in Section 3.10) should be computed as the per-fragment |
| | Euclidean distance to the fragment center from the eye. In practice, |
| | implementations "may choose to approximate the eye-coordinate |
| | distance from the eye to each fragment center by abs(ze). Further, |
| | [the fog factor] f need not be computed at each fragment, but may |
| | be computed at each vertex and interpolated as other data are." |
| | |
| | This extension provides the application specific control over how |
| | OpenGL computes the distance used in computing the fog factor. |
| | |
| | The extension supports three fog distance modes: "eye plane absolute", |
| | where the fog distance is the absolute planar distance from the eye |
| | plane (i.e., OpenGL's standard implementation allowance as cited above); |
| | "eye plane", where the fog distance is the signed planar distance |
| | from the eye plane; and "eye radial", where the fog distance is |
| | computed as a Euclidean distance. In the case of the eye radial |
| | fog distance mode, the distance may be computed per-vertex and then |
| | interpolated per-fragment. |
| | |
| | The intent of this extension is to provide applications with better |
| | control over the tradeoff between performance and fog quality. |
| | The "eye planar" modes (signed or absolute) are straightforward |
| | to implement with good performance, but scenes are consistently |
| | under-fogged at the edges of the field of view. The "eye radial" |
| | mode can provide for more accurate fog at the edges of the field of |
| | view, but this assumes that either the eye radial fog distance is |
| | computed per-fragment, or if the fog distance is computed per-vertex |
| | and then interpolated per-fragment, then the scene must be |
| | sufficiently tessellated. |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/NV/fog_distance.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.NV.fog_distance import * |
| | from OpenGL.raw.GL.NV.fog_distance import _EXTENSION_NAME |
| |
|
| | def glInitFogDistanceNV(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
|
| |
|
| | |
