| | '''OpenGL extension NV.packed_depth_stencil |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.NV.packed_depth_stencil to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | Many OpenGL implementations have chosen to interleave the depth and |
| | stencil buffers into one buffer, often with 24 bits of depth |
| | precision and 8 bits of stencil data. 32 bits is more than is needed |
| | for the depth buffer much of the time; a 24-bit depth buffer, on the |
| | other hand, requires that reads and writes of depth data be unaligned |
| | with respect to power-of-two boundaries. On the other hand, 8 bits |
| | of stencil data is more than sufficient for most applications, so it |
| | is only natural to pack the two buffers into a single buffer with |
| | both depth and stencil data. OpenGL never provides direct access to |
| | the buffers, so the OpenGL implementation can provide an interface to |
| | applications where it appears the one merged buffer is composed of |
| | two logical buffers. |
| | |
| | One disadvantage of this scheme is that OpenGL lacks any means by |
| | which this packed data can be handled efficiently. For example, when |
| | an application reads from the 24-bit depth buffer, using the type |
| | GL_UNSIGNED_SHORT will lose 8 bits of data, while GL_UNSIGNED_INT has |
| | 8 too many. Both require expensive format conversion operations. A |
| | 24-bit format would be no more suitable, because it would also suffer |
| | from the unaligned memory accesses that made the standalone 24-bit |
| | depth buffer an unattractive proposition in the first place. |
| | |
| | Many applications, such as parallel rendering applications, may also |
| | wish to draw to or read back from both the depth and stencil buffers |
| | at the same time. Currently this requires two separate operations, |
| | reducing performance. Since the buffers are interleaved, drawing to |
| | or reading from both should be no more expensive than using just one; |
| | in some cases, it may even be cheaper. |
| | |
| | This extension provides a new data format, GL_DEPTH_STENCIL_NV, that |
| | can be used with the glDrawPixels, glReadPixels, and glCopyPixels |
| | commands, as well as a packed data type, GL_UNSIGNED_INT_24_8_NV, |
| | that is meant to be used with GL_DEPTH_STENCIL_NV. No other formats |
| | are supported with GL_DEPTH_STENCIL_NV. If SGIX_depth_texture is |
| | supported, GL_DEPTH_STENCIL_NV/GL_UNSIGNED_INT_24_8_NV data can also |
| | be used for textures; this provides a more efficient way to supply |
| | data for a 24-bit depth texture. |
| | |
| | GL_DEPTH_STENCIL_NV data, when passed through the pixel path, |
| | undergoes both depth and stencil operations. The depth data is |
| | scaled and biased by the current GL_DEPTH_SCALE and GL_DEPTH_BIAS, |
| | while the stencil data is shifted and offset by the current |
| | GL_INDEX_SHIFT and GL_INDEX_OFFSET. The stencil data is also put |
| | through the stencil-to-stencil pixel map. |
| | |
| | glDrawPixels of GL_DEPTH_STENCIL_NV data operates similarly to that |
| | of GL_STENCIL_INDEX data, bypassing the OpenGL fragment pipeline |
| | entirely, unlike the treatment of GL_DEPTH_COMPONENT data. The |
| | stencil and depth masks are applied, as are the pixel ownership and |
| | scissor tests, but all other operations are skipped. |
| | |
| | glReadPixels of GL_DEPTH_STENCIL_NV data reads back a rectangle from |
| | both the depth and stencil buffers. |
| | |
| | glCopyPixels of GL_DEPTH_STENCIL_NV data copies a rectangle from |
| | both the depth and stencil buffers. Like glDrawPixels, it applies |
| | both the stencil and depth masks but skips the remainder of the |
| | OpenGL fragment pipeline. |
| | |
| | glTex[Sub]Image[1,2,3]D of GL_DEPTH_STENCIL_NV data loads depth data |
| | into a depth texture. glGetTexImage of GL_DEPTH_STENCIL_NV data can |
| | be used to retrieve depth data from a depth texture. |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/NV/packed_depth_stencil.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.packed_depth_stencil import * |
| | from OpenGL.raw.GL.NV.packed_depth_stencil import _EXTENSION_NAME |
| |
|
| | def glInitPackedDepthStencilNV(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
|
| |
|
| | |
| | |
| | from OpenGL import images |
| | from OpenGL.raw.GL.VERSION.GL_1_1 import GL_UNSIGNED_INT |
| | images.TYPE_TO_ARRAYTYPE[ GL_UNSIGNED_INT_24_8_NV ] = GL_UNSIGNED_INT |
| | images.TIGHT_PACK_FORMATS[ GL_UNSIGNED_INT_24_8_NV ] = 4 |
| | images.COMPONENT_COUNTS[ GL_DEPTH_STENCIL_NV ] = 4 |
| |
|
