| '''OpenGL extension NV.geometry_program4 |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GL.NV.geometry_program4 to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| NV_geometry_program4 defines a new type of program available to be run on |
| the GPU, called a geometry program. Geometry programs are run on full |
| primitives after vertices are transformed, but prior to flat shading and |
| clipping. |
| |
| A geometry program begins with a single primitive - a point, line, or |
| triangle. Quads and polygons are allowed, but are decomposed into |
| individual triangles prior to geometry program execution. It can read the |
| attributes of any of the vertex in the primitive and use them to generate |
| new primitives. A geometry program has a fixed output primitive type, |
| either a point, a line strip, or a triangle strip. It emits vertices |
| (using the EMIT opcode) to define the output primitive. The attributes of |
| emitted vertices are specified by writing to the same set of result |
| bindings (e.g., "result.position") provided for vertex programs. |
| Additionally, a geometry program can emit multiple disconnected primitives |
| by using the ENDPRIM opcode, which is roughly equivalent to calling End |
| and then Begin again. The primitives emitted by the geometry program are |
| then clipped and then processed like an equivalent OpenGL primitive |
| specified by the application. |
| |
| This extension provides four additional primitive types: lines with |
| adjacency, line strips with adjacency, separate triangles with adjacency, |
| and triangle strips with adjacency. Some of the vertices specified in |
| these new primitive types are not part of the ordinary primitives. |
| Instead, they represent neighboring vertices that are adjacent to the two |
| line segment end points (lines/strips) or the three triangle edges |
| (triangles/tstrips). These "adjacency" vertices can be accessed by |
| geometry programs and used to match up the outputs of the geometry program |
| with those of neighboring primitives. |
| |
| Additionally, geometry programs allow for layered rendering, where entire |
| three-dimensional, cube map, or array textures (EXT_texture_array) can be |
| bound to the current framebuffer. Geometry programs can use the |
| "result.layer" binding to select a layer or cube map face to render to. |
| Each primitive emitted by such a geometry program is rendered to the layer |
| taken from its provoking vertex. |
| |
| Since geometry programs expect a specific input primitive type, an error |
| will occur if the application presents primtives of a different type. For |
| example, if an enabled geometry program expects points, an error will |
| occur at Begin() time, if a primitive mode of TRIANGLES is specified. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/NV/geometry_program4.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.geometry_program4 import * |
| from OpenGL.raw.GL.NV.geometry_program4 import _EXTENSION_NAME |
|
|
| def glInitGeometryProgram4NV(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
|
|
| |
