Implement sonic blast rendering effect.

glsl/postprocess_textured_sonic.frag

@@ -0,0 +1,18 @@
+#version {VERSION}
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform sampler2D WorldTexture;
+uniform float Scale;
+
+in vec2 vTexCoord;
+out vec4 fragColor;
+
+void main()
+{
+    if (dot(vTexCoord, vTexCoord) >= 1.0)
+	    discard;
+
+	fragColor = texelFetch(WorldTexture, ivec2(gl_FragCoord.xy + Scale * vTexCoord), 0);
+}