Add natural shadows using parametric blend (#125)

README.md

@@ -28,6 +28,7 @@ This effect started as a fork of [shapecorners](https://sourceforge.net/projects
 - Disable effect when window gets maximized - by [matinlotfali](https://github.com/matinlotfali)
 - Cleanups for the plugin logic, remove unneeded dependencies from CMakeLists.txt file - by [alex1701c](https://github.com/alex1701c)
 - Separate outline color for active and inactive windows - by [OrkenWhite](https://github.com/OrkenWhite)
+- Add natural shadows using parametric blend - by [paletteOvO](https://github.com/paletteOvO)
 
 # How to build from source code:
 

src/shaders_110/shapecorners.frag

@@ -24,6 +24,11 @@ varying vec2 texcoord0;          // The XY location of the rendering pixel. Star
 bool isDrawingShadows() { return  windowSize != windowExpandedSize && shadowColor.a > 0.0; }
 bool isDrawingOutline() { return  outlineColor.a > 0.0 && outlineThickness > 0.0; }
 
+float parametricBlend(float t) {
+    float sqt = t * t;
+    return sqt / (2.0 * (sqt - t) + 1.0);
+}
+
 /*
  *  \brief This function generates the shadow color based on the distance_from_center
  *  \param distance_from_center: Distance of the rendering point and the reference point that is being used for rounding corners.
@@ -33,6 +38,8 @@ vec4 getShadowColor(float distance_from_center) {
     if(!isDrawingShadows())
         return vec4(0.0, 0.0, 0.0, 0.0);
     float percent = -distance_from_center/shadowSize + 1.0;
+    percent = clamp(percent, 0.0, 1.0);
+    percent = parametricBlend(percent);
     if (percent < 0.0)
         return vec4(0.0, 0.0, 0.0, 0.0);
     else

src/shaders_140/shapecorners.frag

@@ -23,6 +23,11 @@ out vec4 fragColor;              // The RGBA color that can be rendered
 bool isDrawingShadows() { return  windowSize != windowExpandedSize && shadowColor.a > 0.0; }
 bool isDrawingOutline() { return  outlineColor.a > 0.0 && outlineThickness > 0.0; }
 
+float parametricBlend(float t) {
+    float sqt = t * t;
+    return sqt / (2.0 * (sqt - t) + 1.0);
+}
+
 /*
  *  \brief This function generates the shadow color based on the distance_from_center
  *  \param distance_from_center: Distance of the rendering point and the reference point that is being used for rounding corners.
@@ -32,6 +37,8 @@ vec4 getShadowColor(float distance_from_center) {
     if(!isDrawingShadows())
         return vec4(0,0,0,0);
     float percent = -distance_from_center/shadowSize + 1;
+    percent = clamp(percent, 0, 1);
+    percent = parametricBlend(percent);
     if(percent < 0)
         return vec4(0,0,0,0);
     else