Reviewed shaders and added comments

examples/resources/shaders/glsl100/swirl.fs

@@ -0,0 +1,45 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 fragTintColor;
+
+// NOTE: Add here your custom variables
+
+const float renderWidth = 800.0;      // HARDCODED for example!
+const float renderHeight = 480.0;     // Use uniforms instead...
+
+float radius = 250.0;
+float angle = 0.8;
+
+uniform vec2 center = vec2(200.0, 200.0);
+
+void main (void)
+{
+    vec2 texSize = vec2(renderWidth, renderHeight);
+    vec2 tc = fragTexCoord*texSize;
+    tc -= center;
+    
+    float dist = length(tc);
+
+    if (dist < radius) 
+    {
+        float percent = (radius - dist)/radius;
+        float theta = percent*percent*angle*8.0;
+        float s = sin(theta);
+        float c = cos(theta);
+        
+        tc = vec2(dot(tc, vec2(c, -s)), dot(tc, vec2(s, c)));
+    }
+
+    tc += center;
+    vec3 color = texture2D(texture0, tc/texSize).rgb;
+
+    gl_FragColor = vec4(color, 1.0);;
+}