[Mesa-dev] [PATCH 0/40] Implement GL_ARB_viewport_array

[Ian Romanick]

On 01/10/2014 05:44 PM, Ian Romanick wrote:
> (Sent after the fact... sorry.)
> 
> This represents a medling of GL_ARB_viewport_array code written by
> Courtney Goeltzenleuchter (LunarG) and myself over the last couple
> months.  It implements all of the core Mesa code for the extension and
> enables it in the i965 driver.
> 
> Like layered rendering, this extension depends on geometry shaders, so
> it is currently only enabled in core profiles.  There is one bit of core
> Mesa code that behaves differently when the extension is enabled (see
> "mesa: Add new viewport and depth-range entry points for
> GL_ARB_viewport_array"), so the enable flag is only set by the i965
> driver in core profile.
> 
> When multiple viewports, depth ranges, or scissor rectangles are updated
> in one API call, the driver is only notified once, at the end.  There is
> also no per-viewport "dirty" tracking.  The i965 driver has to send all
> of the data when anything changes, so it didn't need that feature.  If
> some other hardware could use per-viewport dirty tracking as an
> optimization, it would be trivial to add that tracking to the
> gl_context.  Then the driver state update (or
> dd_function_table::Viewport) function could consult the appropriate
> dirty bits before doing the update.

I should also note that this is available in the viewport-array-blended
(blending meaning that it's code from two sources blended together)
branch of my fd.o Mesa tree.

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