From ab60414122184851415a27ae8bcacb4aab0504b6 Mon Sep 17 00:00:00 2001
From: wwylele <wwylele@gmail.com>
Date: Fri, 16 Jun 2017 14:00:15 +0300
Subject: gl_rasterizer/lighting: fix LUT interpolation

---
 src/video_core/pica_state.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

(limited to 'src/video_core/pica_state.h')

diff --git a/src/video_core/pica_state.h b/src/video_core/pica_state.h
index f46db09fb..3b00df0b3 100644
--- a/src/video_core/pica_state.h
+++ b/src/video_core/pica_state.h
@@ -87,12 +87,18 @@ struct State {
             // LUT value, encoded as 12-bit fixed point, with 12 fraction bits
             BitField<0, 12, u32> value; // 0.0.12 fixed point
 
-            // Used by HW for efficient interpolation, Citra does not use these
-            BitField<12, 12, s32> difference; // 1.0.11 fixed point
+            // Used for efficient interpolation.
+            BitField<12, 11, u32> difference; // 0.0.11 fixed point
+            BitField<23, 1, u32> neg_difference;
 
-            float ToFloat() {
+            float ToFloat() const {
                 return static_cast<float>(value) / 4095.f;
             }
+
+            float DiffToFloat() const {
+                float diff = static_cast<float>(difference) / 2047.f;
+                return neg_difference ? -diff : diff;
+            }
         };
 
         std::array<std::array<LutEntry, 256>, 24> luts;
-- 
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