[Mesa-dev] [PATCH 2/2] gallium: Replaced gl_rasterization_rules with lower_left_origin and half_pixel_center.

[Marek Olšák]

This looks good to me. bottom_edge_rule should probably also be set
conditionally for Bitmap, Clear, and DrawPixels like this:

bottom_edge_rule = st_fb_orientation(ctx->DrawBuffer) == Y_0_TOP;

Marek

On Tue, Apr 23, 2013 at 6:39 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> My follow on changes can be seen at http://cgit.freedesktop.org/~jrfonseca/mesa/log/?h=gl-rasterization-rules
>
> Jose
>
> ----- Original Message -----
>> Ok. I've moved the docs to src/gallium/docs/source/cso/rasterizer.rst , and
>> renamed `lower_left_origin` to `bottom_edge_rule`.
>>
>> This is how it looks like:
>>
>>   http://people.freedesktop.org/~jrfonseca/gl_rasterization_rules/cso/rasterizer.html#other-members
>>
>> Jose
>>
>> ----- Original Message -----
>> > Yeah, I was confused when reading the comment and the diagrams. It
>> > probably shouldn't mention the screen origin at all and instead should
>> > say which one of the top and bottom edges is inclusive and which one
>> > is exclusive when determining pixel ownership.
>> >
>> > Anyway, thank you for fixing this. I would have probably never knew
>> > how to fix the triangle rasterization tests if you didn't bring this
>> > up.
>> >
>> > Marek
>> >
>> > On Sun, Apr 21, 2013 at 7:54 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
>> > > ----- Original Message -----
>> > >> Some suggestions for the name:
>> > >>
>> > >> lower_left_edge_rule
>> > >> lower_left_rasterization_edge_rule
>> > >> gl_edge_rule
>> > >> gl_rasterization_edge_rule
>> > >>
>> > >> In this case, the name is not as important as the documentation which
>> > >> defines the behavior of the state.
>> > >
>> > > On that note, I thought that James' diagrams were pretty good.  Maybe the
>> > > axis is misleading.
>> > >
>> > >
>> > > +   /**
>> > > +    * Triangle rasterization always uses a 'top,left' rule for pixel
>> > > ownership,
>> > > +    * this just alters what we consider to be the top edge for that
>> > > test.
>> > > +    *
>> > > +    * When true, screen coordinates origin is considered to be at
>> > > bottom-left
>> > > +    * (e.g., OpenGL drawables):
>> > > +    *
>> > > +    *  y ^
>> > > +    *    |
>> > > +    *    |  +=============+ <- top edge
>> > > +    *    |  |             |
>> > > +    *    |  |             |
>> > > +    *    |  |             |
>> > > +    *    |  +-------------+
>> > > +    *    |
>> > > +    *  0 +--------------------->
>> > > +    *    0                    x
>> > > +    *
>> > > +    *  When false, screen coordinates origin is considered to be at
>> > > top-left
>> > > +    *  (e.g., OpenGL FBOs, D3D):
>> > > +    *
>> > > +    *    0                    x
>> > > +    *  0 +--------------------->
>> > > +    *    |
>> > > +    *    |  +=============+ <- top edge
>> > > +    *    |  |             |
>> > > +    *    |  |             |
>> > > +    *    |  |             |
>> > > +    *    |  +-------------+
>> > > +    *    |
>> > > +    *  y V
>> > >      *
>> > > -    * Triangle rasterization always uses a 'top,left' rule for pixel
>> > > -    * ownership, this just alters which point we consider the pixel
>> > > -    * center for that test.
>> > > +    * See also:
>> > > +    * -
>> > > http://www.opengl.org/registry/specs/ARB/fragment_coord_conventions.txt
>> > > +    * -
>> > > http://msdn.microsoft.com/en-us/library/windows/desktop/cc627092.aspx
>> > > +    * -
>> > > http://msdn.microsoft.com/en-us/library/windows/desktop/bb147314.aspx
>> > >      */
>> > > -   unsigned gl_rasterization_rules:1;
>> > > +   unsigned lower_left_origin:1;
>> > >
>> > >     /**
>> > >      * When true, rasterization is disabled and no pixels are written.
>> > >
>> > > Jose
>> >
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