Merge pull request #2792 from wwylele/lutlutlut

gl_rasterizer: fix lighting LUT interpolation

1 files changed, 9 insertions, 3 deletions

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;