♻️ Make blur a common method

resources/shaders/common.glsl

@@ -153,6 +153,35 @@ void setOutputColor(vec4 outColor) { cogl_color_out = outColor; }
 
 #endif  // -------------------------------------------------------------------------------
 
+// A simple blur function
+vec4 getBlurredInputColor(vec2 uv, float radius, float samples) {
+  // Initialize the color accumulator to zero.
+  vec4 color = vec4(0.0);
+
+  // Define a constant for 2 * PI (tau), which represents a full circle in radians.
+  const float tau = 6.28318530718;
+
+  // Number of directions for sampling around the circle.
+  const float directions = 15.0;
+
+  // Outer loop iterates over multiple directions evenly spaced around a circle.
+  for (float d = 0.0; d < tau; d += tau / directions) {
+    // Inner loop samples along each direction, with decreasing intensity.
+    for (float s = 0.0; s < 1.0; s += 1.0 / samples) {
+      // Calculate the offset for this sample based on direction, radius, and step.
+      // The (1.0 - s) term ensures more sampling occurs closer to the center.
+      vec2 offset = vec2(cos(d), sin(d)) * radius * (1.0 - s) / uSize;
+
+      // Add the sampled color at the offset position to the accumulator.
+      color += getInputColor(uv + offset);
+    }
+  }
+
+  // Normalize the accumulated color by dividing by the total number of samples
+  // and directions to ensure the result is averaged.
+  return color / samples / directions;
+}
+
 // ----------------------------------------------------------------- compositing operators
 
 // The Shell.GLSLEffect uses straight alpha blending. This helper method allows