| '''OpenGL extension EXT.geometry_shader |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GLES2.EXT.geometry_shader to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| EXT_geometry_shader defines a new shader type available to be run on the |
| GPU, called a geometry shader. Geometry shaders are run after vertices are |
| transformed, but prior to color clamping, flatshading and clipping. |
| |
| A geometry shader begins with a single primitive (point, line, |
| triangle). It can read the attributes of any of the vertices in the |
| primitive and use them to generate new primitives. A geometry shader has a |
| fixed output primitive type (point, line strip, or triangle strip) and |
| emits vertices to define a new primitive. A geometry shader can emit |
| multiple disconnected primitives. The primitives emitted by the geometry |
| shader are clipped and then processed like an equivalent primitive |
| specified by the application. |
| |
| Furthermore, EXT_geometry_shader 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 vertices can be accessed by |
| geometry shaders and used to match up the vertices emitted by the geometry |
| shader with those of neighboring primitives. |
| |
| Since geometry shaders expect a specific input primitive type, an error |
| will occur if the application presents primitives of a different type. |
| For example, if a geometry shader expects points, an error will occur at |
| drawing time if a primitive mode of TRIANGLES is specified. |
| |
| This extension also adds the notion of layered framebuffer attachments |
| and framebuffers that can be used in conjunction with geometry shaders |
| to allow programs to direct primitives to a face of a cube map or layer |
| of a three-dimensional texture or two-dimensional array texture. The |
| layer used for rendering can be selected by the geometry shader at run |
| time. The framebuffer layer count present in GL 4.x and removed from |
| ES 3.1 is restored. |
| |
| Not all geometry shader implementations have the ability to write the |
| point size from a geometry shader. Thus a second extension string and |
| shading language enable are provided for implementations which do |
| support geometry shader point size. |
| |
| This extension relies on the EXT_shader_io_blocks extension to provide |
| the required functionality for declaring input and output blocks and |
| interfacing between shaders. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/EXT/geometry_shader.txt |
| ''' |
| from OpenGL import platform, constant, arrays |
| from OpenGL import extensions, wrapper |
| import ctypes |
| from OpenGL.raw.GLES2 import _types, _glgets |
| from OpenGL.raw.GLES2.EXT.geometry_shader import * |
| from OpenGL.raw.GLES2.EXT.geometry_shader import _EXTENSION_NAME |
|
|
| def glInitGeometryShaderEXT(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
|
|
| |
