| '''OpenGL extension ARB.framebuffer_no_attachments |
| |
| This module customises the behaviour of the |
| OpenGL.raw.GL.ARB.framebuffer_no_attachments to provide a more |
| Python-friendly API |
| |
| Overview (from the spec) |
| |
| Framebuffer objects as introduced by ARB_framebuffer_object and OpenGL 3.0 |
| provide a generalized mechanism for rendering to off-screen surfaces. |
| Each framebuffer object may have depth, stencil and zero or more color |
| attachments that can be written to by the GL. The size of the framebuffer |
| (width, height, layer count, sample count) is derived from the attachments |
| of that framebuffer. In unextended OpenGL 4.2, it is not legal to render |
| into a framebuffer object that has no attachments. Such a framebuffer |
| would be considered incomplete with the |
| FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT status. |
| |
| With OpenGL 4.2 and ARB_shader_image_load_store, fragment shaders are |
| capable of doing random access writes to buffer and texture memory via |
| image loads, stores, and atomics. This ability enables algorithms using |
| the conventional rasterizer to generate a collection of fragments, where |
| each fragment shader invocation will write its outputs to buffer or |
| texture memory using image stores or atomics. Such algorithms may have no |
| need to write color or depth values to a conventional framebuffer. |
| However, a framebuffer with no attachments will be considered incomplete |
| and no rasterization or fragment shader exectuion will occur. To avoid |
| such errors, an application may be required to create an otherwise |
| unnecessary "dummy" texture and attach it to the framebuffer (possibly |
| with color writes masked off). If the algorithm requires the rasterizer |
| to operate over a large number of pixels, this dummy texture will |
| needlessly consume a significant amount of memory. |
| |
| This extension enables the algorithms described above to work even with a |
| framebuffer with no attachments. Applications can specify default width, |
| height, layer count, and sample count parameters for a framebuffer object. |
| When a framebuffer with no attachments is bound, it will be considered |
| complete as long as the application has specified non-zero default width |
| and height parameters. For the purposes of rasterization, the framebuffer |
| will be considered to have a width, height, layer count, and sample count |
| derived from its default parameters. Framebuffers with one or more |
| attachments are not affected by these default parameters; the size of the |
| framebuffer will still be derived from the sizes of the attachments in |
| that case. |
| |
| Additionally, this extension provides queryable implementation-dependent |
| maximums for framebuffer width, height, layer count, and sample count, |
| which may differ from similar limits on textures and renderbuffers. These |
| maximums will be used to error-check the default framebuffer parameters |
| and also permit implementations to expose the ability to rasterize to an |
| attachment-less framebuffer larger than the maximum supported texture |
| size. |
| |
| The official definition of this extension is available here: |
| http://www.opengl.org/registry/specs/ARB/framebuffer_no_attachments.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.ARB.framebuffer_no_attachments import * |
| from OpenGL.raw.GL.ARB.framebuffer_no_attachments import _EXTENSION_NAME |
|
|
| def glInitFramebufferNoAttachmentsARB(): |
| '''Return boolean indicating whether this extension is available''' |
| from OpenGL import extensions |
| return extensions.hasGLExtension( _EXTENSION_NAME ) |
|
|
| |
| glGetFramebufferParameteriv=wrapper.wrapper(glGetFramebufferParameteriv).setInputArraySize( |
| 'params', None |
| ) |
| |
