From 39490f3c3a79e9c2e1acad37609108b4c14bd459 Mon Sep 17 00:00:00 2001
From: Triang3l <triang3l@yandex.ru>
Date: Thu, 9 Jul 2020 12:22:45 +0300
Subject: [PATCH] [GPU] Centroid interpolation usage comment

---
 src/xenia/gpu/xenos.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/xenia/gpu/xenos.h b/src/xenia/gpu/xenos.h
index 7b8105556..7bd8c3cf7 100644
--- a/src/xenia/gpu/xenos.h
+++ b/src/xenia/gpu/xenos.h
@@ -558,6 +558,12 @@ enum class SampleControl : uint32_t {
 // - sample_control is SQ_CONTEXT_MISC::sc_sample_cntl.
 // - interpolator_control_sampling_pattern is
 //   SQ_INTERPOLATOR_CNTL::sampling_pattern.
+// Centroid interpolation can be tested in Red Dead Redemption. If the GPU host
+// backend implements guest MSAA properly, using host MSAA, with everything
+// interpolated at centers, the Diez Coronas start screen background may have
+// a few distinctly bright pixels on the mesas/buttes, where extrapolation
+// happens. Interpolating certain values (ones that aren't used for gradient
+// calculation, not texture coordinates) at centroids fixes this issue.
 inline uint32_t GetInterpolatorSamplingPattern(
     MsaaSamples msaa_samples, SampleControl sample_control,
     uint32_t interpolator_control_sampling_pattern) {