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Diffstat (limited to 'src/gallium/docs/source/context.rst')
| -rw-r--r-- | src/gallium/docs/source/context.rst | 53 |
1 files changed, 49 insertions, 4 deletions
diff --git a/src/gallium/docs/source/context.rst b/src/gallium/docs/source/context.rst index d394f5b4f1..a7669575b9 100644 --- a/src/gallium/docs/source/context.rst +++ b/src/gallium/docs/source/context.rst @@ -54,7 +54,10 @@ objects. They all follow simple, one-method binding calls, e.g. * ``set_blend_color`` * ``set_clip_state`` * ``set_polygon_stipple`` -* ``set_scissor_state`` +* ``set_scissor_state`` sets the bounds for the scissor test, which culls + pixels before blending to render targets. If the :ref:`Rasterizer` does + not have the scissor test enabled, then the scissor bounds never need to + be set since they will not be used. * ``set_viewport_state`` * ``set_vertex_elements`` @@ -145,9 +148,51 @@ draws. Queries may be nested, though no state tracker currently exercises this. Queries can be created with ``create_query`` and deleted with -``destroy_query``. To enable a query, use ``begin_query``, and when finished, -use ``end_query`` to stop the query. Finally, ``get_query_result`` is used -to retrieve the results. +``destroy_query``. To start a query, use ``begin_query``, and when finished, +use ``end_query`` to end the query. + +``get_query_result`` is used to retrieve the results of a query. If +the ``wait`` parameter is TRUE, then the ``get_query_result`` call +will block until the results of the query are ready (and TRUE will be +returned). Otherwise, if the ``wait`` parameter is FALSE, the call +will not block and the return value will be TRUE if the query has +completed or FALSE otherwise. + +A common type of query is the occlusion query which counts the number of +fragments/pixels which are written to the framebuffer (and not culled by +Z/stencil/alpha testing or shader KILL instructions). + + +Conditional Rendering +^^^^^^^^^^^^^^^^^^^^^ + +A drawing command can be skipped depending on the outcome of a query +(typically an occlusion query). The ``render_condition`` function specifies +the query which should be checked prior to rendering anything. + +If ``render_condition`` is called with ``query`` = NULL, conditional +rendering is disabled and drawing takes place normally. + +If ``render_condition`` is called with a non-null ``query`` subsequent +drawing commands will be predicated on the outcome of the query. If +the query result is zero subsequent drawing commands will be skipped. + +If ``mode`` is PIPE_RENDER_COND_WAIT the driver will wait for the +query to complete before deciding whether to render. + +If ``mode`` is PIPE_RENDER_COND_NO_WAIT and the query has not yet +completed, the drawing command will be executed normally. If the query +has completed, drawing will be predicated on the outcome of the query. + +If ``mode`` is PIPE_RENDER_COND_BY_REGION_WAIT or +PIPE_RENDER_COND_BY_REGION_NO_WAIT rendering will be predicated as above +for the non-REGION modes but in the case that an occulusion query returns +a non-zero result, regions which were occluded may be ommitted by subsequent +drawing commands. This can result in better performance with some GPUs. +Normally, if the occlusion query returned a non-zero result subsequent +drawing happens normally so fragments may be generated, shaded and +processed even where they're known to be obscured. + Flushing ^^^^^^^^ |