[Mesa-dev] [PATCH 1/6] anv: Set viewport extents correctly when height is negative

[Lionel Landwerlin]

On 24/01/17 17:40, Jason Ekstrand wrote:
> On Tue, Jan 24, 2017 at 12:49 AM, Iago Toral <itoral at igalia.com 
> <mailto:itoral at igalia.com>> wrote:
>
>     On Mon, 2017-01-23 at 14:12 -0800, Jason Ekstrand wrote:
>     > As per VK_KHR_maintenance1, setting a negative height in the
>     viewport
>     > can be used to get flipped coordinates.  This is, aparently, very
>     > useful
>     > when porting D3D apps to Vulkan.  All we need to do to support this
>     > is
>     > to make sure we actually set the min and max correctly.
>     > ---
>     >  src/intel/vulkan/gen8_cmd_buffer.c | 4 ++--
>     >  1 file changed, 2 insertions(+), 2 deletions(-)
>     >
>     > diff --git a/src/intel/vulkan/gen8_cmd_buffer.c
>     > b/src/intel/vulkan/gen8_cmd_buffer.c
>     > index f22037b..ab68872 100644
>     > --- a/src/intel/vulkan/gen8_cmd_buffer.c
>     > +++ b/src/intel/vulkan/gen8_cmd_buffer.c
>     > @@ -59,8 +59,8 @@ gen8_cmd_buffer_emit_viewport(struct
>     anv_cmd_buffer
>     > *cmd_buffer)
>     >           .YMaxClipGuardband = 1.0f,
>     >           .XMinViewPort = vp->x,
>     >           .XMaxViewPort = vp->x + vp->width - 1,
>     > -         .YMinViewPort = vp->y,
>     > -         .YMaxViewPort = vp->y + vp->height - 1,
>     > +         .YMinViewPort = MIN2(vp->y, vp->y + vp->height),
>     > +         .YMaxViewPort = MAX2(vp->y, vp->y + vp->height) - 1,
>     >        };
>
>     If we have y = 0 and height = -100, shouldn't we use YMinVP = -99 and
>     YMaxVP = 0 instead of (-100, -1)?
>
>
> No, I think we still want -100, -1.  In the case mentioned, the Y 
> region, in floating-point, is [-100, 0]. However, it appears that, 
> even though it's float, we're expected to provide max-1 in the max fields.

Thanks for the explanation!

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

>     >        GENX(SF_CLIP_VIEWPORT_pack)(NULL, sf_clip_state.map + i * 64,
>
>
>
>
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