Update/merge examples back into main repo (#192)

Examples/resources/shaders/glsl120/fisheye.fs

@@ -0,0 +1,41 @@
+#version 120
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+// NOTE: Add here your custom variables
+
+const float PI = 3.1415926535;
+
+void main()
+{
+    float aperture = 178.0;
+    float apertureHalf = 0.5 * aperture * (PI / 180.0);
+    float maxFactor = sin(apertureHalf);
+
+    vec2 uv = vec2(0.0);
+    vec2 xy = 2.0 * fragTexCoord.xy - 1.0;
+    float d = length(xy);
+
+    if (d < (2.0 - maxFactor))
+    {
+        d = length(xy * maxFactor);
+        float z = sqrt(1.0 - d * d);
+        float r = atan(d, z) / PI;
+        float phi = atan(xy.y, xy.x);
+
+        uv.x = r * cos(phi) + 0.5;
+        uv.y = r * sin(phi) + 0.5;
+    }
+    else
+    {
+        uv = fragTexCoord.xy;
+    }
+
+    gl_FragColor = texture2D(texture0, uv);
+}