Add barrel distortion shader

shader/texture/barrel.geom

@@ -0,0 +1,48 @@
+#version 430 core
+layout (points) in;
+layout (triangle_strip, max_vertices = 4) out;
+in vec2 vRad1[];
+in vec2 vRad2[];
+in float vFactor[];
+out vec2 cenPos;
+out vec2 texPos;
+out vec2 texDist;
+out float factor;
+//const float root = 1 / sqrt(2);
+const float root = 1;
+vec2 cpos = gl_in[0].gl_Position.xy;
+vec2 rad1 = vRad1[0];
+vec2 rad2 = vRad2[0];
+vec2 g(float x,float y)
+    { return vec2 
+        //(x,y);
+        (dot(rad1-cpos,vec2(x,y)-cpos)
+        ,dot(rad2-cpos,vec2(x,y)-cpos)
+        ); 
+    }
+void main() {
+  float factor = vFactor[0];
+  cenPos = cpos;
+  texPos = vec2(1,1);
+  //texDist = g(root,root);
+  texDist = vec2(root,root);
+  gl_Position = vec4 (1,1,0,1);
+  //gl_Position = vec4 (cenPos,0,1);
+  EmitVertex();
+  texPos = vec2(1,0);
+  //texDist = g(root,-root);
+  texDist = vec2(root,-root);
+  gl_Position = vec4 (1,-1,0,1);
+  EmitVertex();
+  texPos = vec2(0,1);
+  //texDist = g(-root,root);
+  texDist = vec2(-root,root);
+  gl_Position = vec4 (-1,1,0,1);
+  EmitVertex();
+  texPos = vec2(0,0);
+  //texDist = g(-root,-root);
+  texDist = vec2(-root,-root);
+  gl_Position = vec4 (-1,-1,0,1);
+  EmitVertex();
+  EndPrimitive();
+}