From e7a851e6cf6b828c51af6664c2df4b83c0f1e403 Mon Sep 17 00:00:00 2001
From: Aleksi Sapon <aleksi.sapon@autodesk.com>
Date: Tue, 8 Oct 2024 10:58:54 -0400
Subject: [PATCH] softpipe: Fix anisotropic sampling aliasing bug

"Backport" of the llvmpip fix.

Nearest sampling was being done using coordinates
on texel boundaries, which caused aliasing bugs.
Shift coordinates by half a texel to correct this.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31562>
---
 src/gallium/drivers/softpipe/sp_tex_sample.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/softpipe/sp_tex_sample.c b/src/gallium/drivers/softpipe/sp_tex_sample.c
index 149dd9597aa..57e3720123f 100644
--- a/src/gallium/drivers/softpipe/sp_tex_sample.c
+++ b/src/gallium/drivers/softpipe/sp_tex_sample.c
@@ -2444,8 +2444,8 @@ img_filter_2d_ewa(const struct sp_sampler_view *sp_sview,
                const float weight = weightLut[qClamped];
 
                weight_buffer[buffer_next] = weight;
-               s_buffer[buffer_next] = u / ((float) width);
-               t_buffer[buffer_next] = v / ((float) height);
+               s_buffer[buffer_next] = (u + 0.5f) / width;
+               t_buffer[buffer_next] = (v + 0.5f) / height;
             
                buffer_next++;
                if (buffer_next == TGSI_QUAD_SIZE) {