| | '''OpenGL extension APPLE.client_storage |
| | |
| | This module customises the behaviour of the |
| | OpenGL.raw.GL.APPLE.client_storage to provide a more |
| | Python-friendly API |
| | |
| | Overview (from the spec) |
| | |
| | This extension provides a simple mechanism to optimize texture data handling |
| | by clients. GL implementations normally maintain a copy of texture image |
| | data supplied clients when any of the various texturing commands, such as |
| | TexImage2D, are invoked. This extension eliminates GL's internal copy of |
| | the texture image data and allows a client to maintain this data locally for |
| | textures when the UNPACK_CLIENT_STORAGE_APPLE pixel storage parameter is |
| | TRUE at the time of texture specification. Local texture data storage is |
| | especially useful in cases where clients maintain internal copies of |
| | textures used in any case. This results in what could be considered an |
| | extra copy of the texture image data. Assuming all operations are error |
| | free, the use of client storage has no affect on the result of texturing |
| | operations and will not affect rendering results. APPLE_client_storage |
| | allows clients to optimize memory requirements and copy operations it also |
| | requires adherence to specific rules in maintaining texture image data. |
| | |
| | Clients using this extension are agreeing to preserve a texture's image data |
| | for the life of the texture. The life of the texture is defined, in this |
| | case, as the time from first issuing the TexImage3D, TexImage2D or |
| | TexImage1D command, for the specific texture object with the |
| | UNPACK_CLIENT_STORAGE_APPLE pixel storage parameter set to TRUE, until the |
| | DeleteTextures command or another TexImage command for that same object. |
| | Only after DeleteTextures has completed, or new texture is specified, can |
| | the local texture memory be released, as it will no longer be utilized by |
| | OpenGL. Changing the UNPACK_CLIENT_STORAGE_APPLE pixel storage parameter |
| | will have no additional effect once the texturing command has been issued |
| | and specifically will not alleviate the client from maintaining the texture |
| | data. |
| | |
| | Client storage is implemented as a pixel storage parameter which affects |
| | texture image storage at the time the texturing command is issued. As with |
| | other pixel storage parameters this state may differ from the time the |
| | texturing command in executed if the command is placed in a display list. |
| | The PixelStore command is used to set the parameter |
| | UNPACK_CLIENT_STORAGE_APPLE. Values can either be TRUE or FALSE, with TRUE |
| | representing the use of client local storage and FALSE indicating the OpenGL |
| | engine and not the client will be responsible for maintaining texture |
| | storage for future texturing commands issued per the OpenGL specification. |
| | The default state for the UNPACK_CLIENT_STORAGE_APPLE parameter is FALSE |
| | |
| | Client storage is only available for texture objects and not the default |
| | texture (of any target type). This means that a texture object has to |
| | generated and bound to be used with client storage. Setting |
| | UNPACK_CLIENT_STORAGE_APPLE to TRUE and texturing with the default texture |
| | will result in normally texturing with GL maintaining a copy of the texture |
| | image data. |
| | |
| | Normally, client storage will be used in conjunction with normal texturing |
| | techniques. An application would use GenTextures to generate texture |
| | objects as needed. BindTexture to the texture object name of interest. |
| | Enable client storage via the PixelStore command setting the |
| | UNPACK_CLIENT_STORAGE_APPLE parameter to TRUE. Then use TexImage3D, |
| | TexImage2D or TexImage1D to specify the texture image. If no further use of |
| | client storage is desired, it is recommended to again use the PixelStore |
| | command, in this case setting the UNPACK_CLIENT_STORAGE_APPLE parameter to |
| | FALSE to disable client storage, since this pixel state is maintained unless |
| | explicitly set by the PixelStore command. |
| | |
| | If an application needs to modify the texture, using TexSubImage for |
| | example, it should be noted that the pointer passed to TexSubImage1D, |
| | TexSubImage2D or TexSubImage3D does not have to the same, or within the |
| | original texture memory. It if is not, there is the likelihood of GL |
| | copying the new data to the original texture memory owned by the client, |
| | thus actually modifying this texture image data. This does not affect |
| | requirement to maintain the original texture memory but also does not add |
| | the requirement to maintain the sub image data, due to the copy. |
| | |
| | Once a client has completed use of the texture stored in client memory, it |
| | should issue a DeleteTextures command to delete the texture object or issue |
| | a texture command, with the same target type, for the object, with either a |
| | different data pointer, or UNPACK_CLIENT_STORAGE_APPLE set to false, in any |
| | case, breaking the tie between GL and the texture buffer. An implicit Flush |
| | command is issued in these cases, ensuring all access to the texture by |
| | OpenGL is complete. Only at this point can the texture buffer be safely |
| | released. Releasing the texture buffer prior has undefined results and will |
| | very possibly display texel anomalies at run time. System level memory |
| | management and paging schemes should not affect the use of client storage. |
| | Consider in any case, that GL has an alias of the base pointer for this |
| | block of texture memory which is maintained until GL is finished rendering |
| | with the texture and it has been deleted or reassigned to another set of |
| | texture data. As long as this alias exists, applications must not |
| | de-allocate, move or purge this memory. |
| | |
| | The official definition of this extension is available here: |
| | http://www.opengl.org/registry/specs/APPLE/client_storage.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.APPLE.client_storage import * |
| | from OpenGL.raw.GL.APPLE.client_storage import _EXTENSION_NAME |
| |
|
| | def glInitClientStorageAPPLE(): |
| | '''Return boolean indicating whether this extension is available''' |
| | from OpenGL import extensions |
| | return extensions.hasGLExtension( _EXTENSION_NAME ) |
| |
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| |
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| | |
