Reorganise shaders

shader/twoD/arc.frag

@@ -0,0 +1,34 @@
+#version 430 core
+in vec4 gColor;
+in vec2 cenPosT;
+in float gRadIn;
+in float gRadOut;
+in vec2 angles;
+out vec4 fColor;
+out float gl_FragDepth;
+
+uniform float rotation;
+
+void main()
+{
+  vec2 pos = gl_FragCoord.xy;
+  float d = distance(pos,cenPosT);
+  float dTest = max ( step(gRadOut/2,d)
+                    , 1 - step(gRadIn/2,d)
+                    );
+
+  vec2 posDiff = pos - cenPosT;
+  float sa = angles.x - rotation;
+  vec2 sv = vec2 (-sin(sa), cos(sa));
+  float saTest = dot(sv,posDiff) >= 0 ? 0 : 1;
+  float ea = angles.y - rotation;
+  vec2 ev = vec2 (-sin(ea), cos(ea));
+  float eaTest = dot(ev,posDiff) <= 0 ? 0 : 1;
+  float aTest = ea - sa < radians(180) ? max (saTest,eaTest) 
+                                       : min (saTest,eaTest);
+
+  float onArcTest = max(dTest,aTest); 
+
+  gl_FragDepth = max(gl_FragCoord.z , onArcTest);
+  fColor = gColor;
+}