Merge pull request #10394 from Pokechu22/alpha-1-blend

Revert TEV alpha lerp change and special-case alpha=1 in blending

1 files changed, 20 insertions, 15 deletions

diff --git a/Source/Core/VideoCommon/UberShaderPixel.cpp b/Source/Core/VideoCommon/UberShaderPixel.cpp
index ebf4afa55f..fa6ad7bc75 100644
--- a/Source/Core/VideoCommon/UberShaderPixel.cpp
+++ b/Source/Core/VideoCommon/UberShaderPixel.cpp
@@ -334,8 +334,8 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
   const auto WriteTevLerp = [&out](std::string_view components) {
     out.Write(
         "// TEV's Linear Interpolate, plus bias, add/subtract and scale\n"
-        "int{0} tevLerp{0}(int{0} A, int{0} B, int{0} C, int{0} D, uint bias, bool op, bool alpha, "
-        "uint shift) {{\n"
+        "int{0} tevLerp{0}(int{0} A, int{0} B, int{0} C, int{0} D, uint bias, bool op, "
+        "uint scale) {{\n"
         " // Scale C from 0..255 to 0..256\n"
         "  C += C >> 7;\n"
         "\n"
@@ -344,12 +344,14 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
         "  else if (bias == 2u) D -= 128;\n"
         "\n"
         "  int{0} lerp = (A << 8) + (B - A)*C;\n"
-        "  if (shift != 3u) {{\n"
-        "    lerp = lerp << shift;\n"
-        "    D = D << shift;\n"
+        "  if (scale != 3u) {{\n"
+        "    lerp = lerp << scale;\n"
+        "    D = D << scale;\n"
         "  }}\n"
         "\n"
-        "  if ((shift == 3u) == alpha)\n"
+        "  // TODO: Is this rounding bias still added when the scale is divide by 2?  Currently we "
+        "do not apply it.\n"
+        "  if (scale != 3u)\n"
         "    lerp = lerp + (op ? 127 : 128);\n"
         "\n"
         "  int{0} result = lerp >> 8;\n"
@@ -360,9 +362,9 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
         "  else // Add\n"
         "    result = D + result;\n"
         "\n"
-        "  // Most of the Shift was moved inside the lerp for improved precision\n"
+        "  // Most of the Scale was moved inside the lerp for improved precision\n"
         "  // But we still do the divide by 2 here\n"
-        "  if (shift == 3u)\n"
+        "  if (scale == 3u)\n"
         "    result = result >> 1;\n"
         "  return result;\n"
         "}}\n\n",
@@ -810,13 +812,13 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
             BitfieldExtract<&TevStageCombiner::ColorCombiner::op>("ss.cc"));
   out.Write("      bool color_clamp = bool({});\n",
             BitfieldExtract<&TevStageCombiner::ColorCombiner::clamp>("ss.cc"));
-  out.Write("      uint color_shift = {};\n",
+  out.Write("      uint color_scale = {};\n",
             BitfieldExtract<&TevStageCombiner::ColorCombiner::scale>("ss.cc"));
   out.Write("      uint color_dest = {};\n",
             BitfieldExtract<&TevStageCombiner::ColorCombiner::dest>("ss.cc"));
 
   out.Write(
-      "      uint color_compare_op = color_shift << 1 | uint(color_op);\n"
+      "      uint color_compare_op = color_scale << 1 | uint(color_op);\n"
       "\n"
       "      int3 color_A = selectColorInput(s, ss, {0}colors_0, {0}colors_1, color_a) & "
       "int3(255, 255, 255);\n"
@@ -831,8 +833,8 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
   out.Write(
       "      int3 color;\n"
       "      if (color_bias != 3u) {{ // Normal mode\n"
-      "        color = tevLerp3(color_A, color_B, color_C, color_D, color_bias, color_op, false, "
-      "color_shift);\n"
+      "        color = tevLerp3(color_A, color_B, color_C, color_D, color_bias, color_op, "
+      "color_scale);\n"
       "      }} else {{ // Compare mode\n"
       "        // op 6 and 7 do a select per color channel\n"
       "        if (color_compare_op == 6u) {{\n"
@@ -880,13 +882,13 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
             BitfieldExtract<&TevStageCombiner::AlphaCombiner::op>("ss.ac"));
   out.Write("      bool alpha_clamp = bool({});\n",
             BitfieldExtract<&TevStageCombiner::AlphaCombiner::clamp>("ss.ac"));
-  out.Write("      uint alpha_shift = {};\n",
+  out.Write("      uint alpha_scale = {};\n",
             BitfieldExtract<&TevStageCombiner::AlphaCombiner::scale>("ss.ac"));
   out.Write("      uint alpha_dest = {};\n",
             BitfieldExtract<&TevStageCombiner::AlphaCombiner::dest>("ss.ac"));
 
   out.Write(
-      "      uint alpha_compare_op = alpha_shift << 1 | uint(alpha_op);\n"
+      "      uint alpha_compare_op = alpha_scale << 1 | uint(alpha_op);\n"
       "\n"
       "      int alpha_A;\n"
       "      int alpha_B;\n"
@@ -904,7 +906,7 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
             "      int alpha;\n"
             "      if (alpha_bias != 3u) {{ // Normal mode\n"
             "        alpha = tevLerp(alpha_A, alpha_B, alpha_C, alpha_D, alpha_bias, alpha_op, "
-            "true, alpha_shift);\n"
+            "alpha_scale);\n"
             "      }} else {{ // Compare mode\n"
             "        if (alpha_compare_op == 6u) {{\n"
             "          // TevCompareMode::A8, TevComparison::GT\n"
@@ -1030,6 +1032,9 @@ ShaderCode GenPixelShader(APIType api_type, const ShaderHostConfig& host_config,
             "  }}\n"
             "\n");
 
+  out.Write("  // Hardware testing indicates that an alpha of 1 can pass an alpha test,\n"
+            "  // but doesn't do anything in blending\n"
+            "  if (TevResult.a == 1) TevResult.a = 0;\n");
   // =========
   // Dithering
   // =========