Add barrel distortion shader

shader/texture/barrel.frag

@@ -0,0 +1,18 @@
+#version 430 core
+in vec2 cenPos;
+in vec2 texPos;
+in vec2 texDist;
+in float factor;
+out vec4 fColor;
+layout (binding = 1) uniform sampler2D screenTexture;
+float f ( float x) {
+ return max (1, 1 / (2 * x + 0.5)) ;
+// return min (1, x) ;
+}
+void main()
+{
+    vec4 tColor = vec4(texture(screenTexture , texPos) );
+    float t = distance(cenPos,texDist);
+    fColor = vec4(tColor.xy,t,tColor.w);
+      //, cenPos + f(distance(cenPos,texDist)) * (texPos - cenPos))) ;
+}