Switch to cos interpolation of shadow alpha

bug:16852257

Updates default shadow opacities to compensate.

Also, update variable/constant naming related to vertex alpha.

Change-Id: I9055b4ac3c9ac305ca9d515f21b52d6aa6dc9c5c

1 files changed, 19 insertions, 25 deletions

diff --git a/libs/hwui/ProgramCache.cpp b/libs/hwui/ProgramCache.cpp
index 2dd89b857107..c802b183d41c 100644
--- a/libs/hwui/ProgramCache.cpp
+++ b/libs/hwui/ProgramCache.cpp
@@ -46,7 +46,7 @@ const char* gVS_Header_Attributes_TexCoords =
         "attribute vec2 texCoords;\n";
 const char* gVS_Header_Attributes_Colors =
         "attribute vec4 colors;\n";
-const char* gVS_Header_Attributes_AAVertexShapeParameters =
+const char* gVS_Header_Attributes_VertexAlphaParameters =
         "attribute float vtxAlpha;\n";
 const char* gVS_Header_Uniforms_TextureTransform =
         "uniform mat4 mainTextureTransform;\n";
@@ -64,7 +64,7 @@ const char* gVS_Header_Varyings_HasTexture =
         "varying vec2 outTexCoords;\n";
 const char* gVS_Header_Varyings_HasColors =
         "varying vec4 outColors;\n";
-const char* gVS_Header_Varyings_IsAAVertexShape =
+const char* gVS_Header_Varyings_HasVertexAlpha =
         "varying float alpha;\n";
 const char* gVS_Header_Varyings_HasBitmap =
         "varying highp vec2 outBitmapTexCoords;\n";
@@ -122,9 +122,7 @@ const char* gVS_Main_Position =
         "    vec4 transformedPosition = projection * transform * position;\n"
         "    gl_Position = transformedPosition;\n";
 
-const char* gVS_Main_ShadowAAVertexShape =
-        "    alpha = pow(vtxAlpha, 0.667);\n";
-const char* gVS_Main_AAVertexShape =
+const char* gVS_Main_VertexAlpha =
         "    alpha = vtxAlpha;\n";
 
 const char* gVS_Main_HasRoundRectClip =
@@ -239,10 +237,10 @@ const char* gFS_Main_FetchColor =
         "    fragColor = color;\n";
 const char* gFS_Main_ModulateColor =
         "    fragColor *= color.a;\n";
-const char* gFS_Main_AccountForAAVertexShape =
+const char* gFS_Main_ApplyVertexAlphaLinearInterp =
         "    fragColor *= alpha;\n";
-const char* gFS_Main_AccountForShadowAAVertexShape =
-        "    fragColor *= pow(alpha, 1.5);\n";
+const char* gFS_Main_ApplyVertexAlphaShadowInterp =
+        "    fragColor *= (1.0 - cos(alpha)) / 2.0;\n";
 
 const char* gFS_Main_FetchTexture[2] = {
         // Don't modulate
@@ -473,8 +471,8 @@ String8 ProgramCache::generateVertexShader(const ProgramDescription& description
     if (description.hasTexture || description.hasExternalTexture) {
         shader.append(gVS_Header_Attributes_TexCoords);
     }
-    if (description.isAA) {
-        shader.append(gVS_Header_Attributes_AAVertexShapeParameters);
+    if (description.hasVertexAlpha) {
+        shader.append(gVS_Header_Attributes_VertexAlphaParameters);
     }
     if (description.hasColors) {
         shader.append(gVS_Header_Attributes_Colors);
@@ -497,8 +495,8 @@ String8 ProgramCache::generateVertexShader(const ProgramDescription& description
     if (description.hasTexture || description.hasExternalTexture) {
         shader.append(gVS_Header_Varyings_HasTexture);
     }
-    if (description.isAA) {
-        shader.append(gVS_Header_Varyings_IsAAVertexShape);
+    if (description.hasVertexAlpha) {
+        shader.append(gVS_Header_Varyings_HasVertexAlpha);
     }
     if (description.hasColors) {
         shader.append(gVS_Header_Varyings_HasColors);
@@ -520,12 +518,8 @@ String8 ProgramCache::generateVertexShader(const ProgramDescription& description
         } else if (description.hasTexture || description.hasExternalTexture) {
             shader.append(gVS_Main_OutTexCoords);
         }
-        if (description.isAA) {
-            if (description.isShadowAA) {
-                shader.append(gVS_Main_ShadowAAVertexShape);
-            } else {
-                shader.append(gVS_Main_AAVertexShape);
-            }
+        if (description.hasVertexAlpha) {
+            shader.append(gVS_Main_VertexAlpha);
         }
         if (description.hasColors) {
             shader.append(gVS_Main_OutColors);
@@ -575,8 +569,8 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
     if (description.hasTexture || description.hasExternalTexture) {
         shader.append(gVS_Header_Varyings_HasTexture);
     }
-    if (description.isAA) {
-        shader.append(gVS_Header_Varyings_IsAAVertexShape);
+    if (description.hasVertexAlpha) {
+        shader.append(gVS_Header_Varyings_HasVertexAlpha);
     }
     if (description.hasColors) {
         shader.append(gVS_Header_Varyings_HasColors);
@@ -617,7 +611,7 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
     }
 
     // Optimization for common cases
-    if (!description.isAA
+    if (!description.hasVertexAlpha
             && !blendFramebuffer
             && !description.hasColors
             && description.colorOp == ProgramDescription::kColorNone
@@ -759,11 +753,11 @@ String8 ProgramCache::generateFragmentShader(const ProgramDescription& descripti
         // Apply the color op if needed
         shader.append(gFS_Main_ApplyColorOp[description.colorOp]);
 
-        if (description.isAA) {
-            if (description.isShadowAA) {
-                shader.append(gFS_Main_AccountForShadowAAVertexShape);
+        if (description.hasVertexAlpha) {
+            if (description.useShadowAlphaInterp) {
+                shader.append(gFS_Main_ApplyVertexAlphaShadowInterp);
             } else {
-                shader.append(gFS_Main_AccountForAAVertexShape);
+                shader.append(gFS_Main_ApplyVertexAlphaLinearInterp);
             }
         }