Add shaders that will just return positional information

shader/posTwoD/arc.frag

@@ -0,0 +1,14 @@
+#version 430 core
+in vec4 vColor;
+in vec3 vparams;
+
+out vec4 fColor;
+
+void main()
+{
+  float d = (dot(vec2(vparams.xy),vec2(vparams.xy)));
+  if ( d > 1 || d < vparams.z ) {discard;}
+  //if ( d > 1 ) {discard;}
+  fColor = vColor;
+  //fColor = (10,0,0,10);
+}