Partially working ellipse shader

shader/ellipse.frag

@@ -0,0 +1,26 @@
+#version 430 core
+in vec4 gColor;
+in vec2 gFocusA;
+in vec2 gFocusB;
+in float gRad;
+
+out vec4 fColor;
+//out float gl_FragDepth;
+
+void main()
+{
+  vec2 pos = gl_FragCoord.xy;
+ // fColor = vec4( gColor.xyz , 0 );
+ // fColor = vec4( gColor.xyz , 1 - step(distance(pos,cenPos.xy),gRad) );
+ // fColor = vec4( gColor.xyz , distance(pos,cenPos.xy)/gRad );
+//  fColor = vec4( gColor.rgb, gColor.a * (1-step(gRad/2,distance(pos,cenPosT))) );
+  gl_FragDepth = max( gl_FragCoord.z 
+                    , step(gRad/2
+                          , distance(pos,gFocusA) + distance(gFocusA,gFocusB)
+                            //+ distance(pos,gFocusB)
+                          )
+                    );
+  fColor = gColor;
+//  fColor = vec4 (1,1,1,1);
+}
+//note it is the fragdepth that stops this from being square