From: Marek Olšák <marek.ol...@amd.com>
Copied from the i965 driver, including the big comment.
Cc: 9.2 10.0 <mesa-sta...@lists.freedesktop.org>
---
src/mesa/state_tracker/st_cb_blit.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/src/mesa/state_tracker/st_cb_blit.c
b/src/mesa/state_tracker/st_cb_blit.c
index a236a08..82c2e38 100644
--- a/src/mesa/state_tracker/st_cb_blit.c
+++ b/src/mesa/state_tracker/st_cb_blit.c
@@ -44,6 +44,34 @@
static void
+st_adjust_blit_for_msaa_resolve(struct pipe_blit_info *blit)
+{
+ /* Even though we do multisample resolves at the time of the blit, OpenGL
+ * specification defines them as if they happen at the time of rendering,
+ * which means that the type of averaging we do during the resolve should
+ * only depend on the source format; the destination format should be
+ * ignored. But, specification doesn't seem to be strict about it.
+ *
+ * It has been observed that mulitisample resolves produce slightly better
+ * looking images when averaging is done using destination format. NVIDIA's
+ * proprietary OpenGL driver also follows this approach.
+ *
+ * When multisampling, if the source and destination formats are equal
+ * (aside from the color space), we choose to blit in sRGB space to get
+ * this higher quality image.
+ */
+ if (blit->src.resource->nr_samples > 1 &&
+ blit->dst.resource->nr_samples <= 1) {
+ blit->dst.format = blit->dst.resource->format;
+
+ if (util_format_is_srgb(blit->dst.resource->format))
+ blit->src.format = util_format_srgb(blit->src.resource->format);
+ else
+ blit->src.format = util_format_linear(blit->src.resource->format);
+ }
+}
+
+static void
st_BlitFramebuffer(struct gl_context *ctx,
GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
@@ -192,6 +220,8 @@ st_BlitFramebuffer(struct gl_context *ctx,
blit.src.box.z = srcAtt->Zoffset + srcAtt->CubeMapFace;
blit.src.format = util_format_linear(srcObj->pt->format);
+ st_adjust_blit_for_msaa_resolve(&blit);
+
st->pipe->blit(st->pipe, &blit);
}
}
@@ -227,6 +257,8 @@ st_BlitFramebuffer(struct gl_context *ctx,
blit.src.box.z = srcSurf->u.tex.first_layer;
blit.src.format = util_format_linear(srcSurf->format);
+ st_adjust_blit_for_msaa_resolve(&blit);
+
st->pipe->blit(st->pipe, &blit);
}
}
--
1.8.3.2
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