From 93ab4451fc155bc1e841d3daafc4c85099dfb292 Mon Sep 17 00:00:00 2001
From: Ariel Antonitis <arant@mit.edu>
Date: Mon, 19 Apr 2021 23:50:50 -0400
Subject: [PATCH] Testing combined averaging function.

---
 include/palette.h |  1 +
 src/overworld.c   | 25 ++++-----------
 src/palette.c     | 77 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 19 deletions(-)

diff --git a/include/palette.h b/include/palette.h
index 071af1c12c..346091c64a 100644
--- a/include/palette.h
+++ b/include/palette.h
@@ -80,6 +80,7 @@ void AveragePalettes(u16 *palette0, u16* palette1, u16* dest, u16 weight);
 void TimeBlendPalette(u16 palOffset, u32 coeff, u32 blendColor);
 void TintPalette_RGB_Copy(u16 palOffset, u32 blendColor);
 void TimeBlendPalettes(u32 palettes, u32 coeff, u32 blendColor);
+void TimeMixPalettes(u32 palettes, u32 coeff0, u32 color0, u32 coeff1, u32 color1, u16 weight);
 void TintPalette_GrayScale(u16 *palette, u16 count);
 void TintPalette_GrayScale2(u16 *palette, u16 count);
 void TintPalette_SepiaTone(u16 *palette, u16 count);
diff --git a/src/overworld.c b/src/overworld.c
index aa66280fc2..8ccdf412bb 100644
--- a/src/overworld.c
+++ b/src/overworld.c
@@ -1535,25 +1535,12 @@ void UpdatePalettesWithTime(u32 palettes) {
     palettes &= ~0xE000; // Don't blend tile palettes [13,15]
     if (!palettes)
       return;
-    for (i = 0; palettes; i+=16) {
-      if (palettes & 1) {
-        if (sTimeOfDayBlendVars[currentTimeBlend.time0].isTint)
-          TintPalette_RGB_Copy(i, sTimeOfDayBlendVars[currentTimeBlend.time0].blendColor);
-        else
-          TimeBlendPalette(i, sTimeOfDayBlendVars[currentTimeBlend.time0].coeff, sTimeOfDayBlendVars[currentTimeBlend.time0].blendColor);
-        if (currentTimeBlend.weight == 256) {
-          palettes >>= 1;
-          continue;
-        }
-        CpuFastCopy(&gPlttBufferFaded[i], tempPaletteBuffer, 32);
-        if (sTimeOfDayBlendVars[currentTimeBlend.time1].isTint)
-          TintPalette_RGB_Copy(i, sTimeOfDayBlendVars[currentTimeBlend.time1].blendColor);
-        else
-          TimeBlendPalette(i, sTimeOfDayBlendVars[currentTimeBlend.time1].coeff, sTimeOfDayBlendVars[currentTimeBlend.time1].blendColor);
-        AveragePalettes(tempPaletteBuffer, &gPlttBufferFaded[i], &gPlttBufferFaded[i], currentTimeBlend.weight);
-      }
-      palettes >>= 1;
-    }
+    TimeMixPalettes(palettes,
+      sTimeOfDayBlendVars[currentTimeBlend.time0].coeff,
+      sTimeOfDayBlendVars[currentTimeBlend.time0].blendColor,
+      sTimeOfDayBlendVars[currentTimeBlend.time1].coeff,
+      sTimeOfDayBlendVars[currentTimeBlend.time1].blendColor,
+      currentTimeBlend.weight);
   }
 }
 
diff --git a/src/palette.c b/src/palette.c
index 36dfdfffa3..c2029adf01 100644
--- a/src/palette.c
+++ b/src/palette.c
@@ -1131,6 +1131,83 @@ void TimeBlendPalettes(u32 palettes, u32 coeff, u32 blendColor) {
   } while (palettes);
 }
 
+// Blends a weighted average of two blend parameters
+void TimeMixPalettes(u32 palettes, u32 coeff0, u32 color0, u32 coeff1, u32 color1, u16 weight) {
+  s32 r0, g0, b0, r1, g1, b1, defR, defG, defB, altR, altG, altB;
+  u16 * palDataSrc;
+  u16 * palDataDst;
+  u32 defaultColor = DEFAULT_LIGHT_COLOR;
+
+  if (!palettes)
+    return;
+
+  // TODO: Check coeff for tint
+  coeff0 *= 2;
+  coeff1 *= 2;
+  r0 = (color0 << 27) >> 27;
+  g0 = (color0 << 22) >> 27;
+  b0 = (color0 << 17) >> 27;
+  r1 = (color1 << 27) >> 27;
+  g1 = (color1 << 22) >> 27;
+  b1 = (color1 << 17) >> 27;
+  defR = (defaultColor << 27) >> 27;
+  defG = (defaultColor << 22) >> 27;
+  defB = (defaultColor << 17) >> 27;
+  palDataSrc = gPlttBufferUnfaded;
+  palDataDst = gPlttBufferFaded;
+
+  do {
+    if (palettes & 1) {
+      u16 *palDataSrcEnd = palDataSrc + 16;
+      u16 altBlendIndices = *palDataDst++ = *palDataSrc++; // color 0 is copied through
+      u32 altBlendColor;
+      if (altBlendIndices >> 15) { // High bit set; bitmask of which colors to alt-blend
+        // Note that bit 0 of altBlendIndices specifies color 1
+        altBlendColor = palDataSrc[14]; // color 15
+        if (altBlendColor >> 15) { // Set alternate blend color
+          altR = (altBlendColor << 27) >> 27;
+          altG = (altBlendColor << 22) >> 27;
+          altB = (altBlendColor << 17) >> 27;
+        } else {
+          altBlendColor = 0;
+        }
+      } else {
+        altBlendIndices = 0;
+      }
+      while (palDataSrc != palDataSrcEnd) {
+        u32 palDataSrcColor = *palDataSrc;
+        s32 r = (palDataSrcColor << 27) >> 27;
+        s32 g = (palDataSrcColor << 22) >> 27;
+        s32 b = (palDataSrcColor << 17) >> 27;
+
+        if (altBlendIndices & 1) { // No need to average; colors will be the same
+          if (altBlendColor) { // Use alternate blend color
+            *palDataDst = ((r + (((altR - r) * coeff0) >> 5)) << 0)
+                        | ((g + (((altG - g) * coeff0) >> 5)) << 5)
+                        | ((b + (((altB - b) * coeff0) >> 5)) << 10);
+          } else { // Use default blend color
+            *palDataDst = ((r + (((defR - r) * coeff0) >> 5)) << 0)
+                        | ((g + (((defG - g) * coeff0) >> 5)) << 5)
+                        | ((b + (((defB - b) * coeff0) >> 5)) << 10);
+          }
+        } else { // Use provided blend colors
+          r = (weight*(r + (((r0 - r) * coeff0) >> 5)) + (256-weight)*(r + (((r1 - r) * coeff1) >> 5))) >> 8;
+          g = (weight*(g + (((g0 - g) * coeff0) >> 5)) + (256-weight)*(g + (((g1 - g) * coeff1) >> 5))) >> 8;
+          b = (weight*(b + (((b0 - b) * coeff0) >> 5)) + (256-weight)*(b + (((b1 - b) * coeff1) >> 5))) >> 8;
+          *palDataDst = RGB2(r, g, b);
+        }
+        palDataSrc++;
+        palDataDst++;
+        altBlendIndices >>= 1;
+      }
+    } else {
+      palDataSrc += 16;
+      palDataDst += 16;
+    }
+    palettes >>= 1;
+  } while (palettes);
+}
+
 void BlendPalettesUnfaded(u32 selectedPalettes, u8 coeff, u16 color)
 {
     void *src = gPlttBufferUnfaded;