Allow for interpolating colors from center to edge of ellipses

shader/ellipseInterpolate.frag

@@ -0,0 +1,15 @@
+#version 430 core
+in vec4 gColorC;
+in vec4 gColorE;
+in vec2 gBoundingBox;
+
+out vec4 fColor;
+//out float gl_FragDepth;
+
+void main()
+{
+  float d = dot(gBoundingBox,gBoundingBox);
+  if ( d > 1) { discard; }
+  fColor = mix (gColorE , gColorC, d);
+}
+//note it is the fragdepth that stops this from being square

shader/ellipseInterpolate.geom

@@ -0,0 +1,36 @@
+#version 430 core
+layout (triangles) in;
+layout (triangle_strip, max_vertices = 4) out;
+in vec4 vCol[];
+out vec4 gColorC;
+out vec4 gColorE;
+out vec2 gBoundingBox;
+
+uniform vec2 winSize;
+uniform float zoom;
+
+void main()
+{
+  vec3 pa = gl_in[0].gl_Position.xyz;
+  vec3 pb = gl_in[1].gl_Position.xyz;
+  vec3 pc = gl_in[2].gl_Position.xyz;
+  gColorC = vCol[0];
+  gColorE = vCol[1];
+
+  gBoundingBox = vec2 (-1,1);
+  gl_Position = vec4 (pb, 1);
+  //gl_Position = vec4 (0.5,0,0, 1);
+  EmitVertex();
+  gBoundingBox = vec2 (1,1);
+  gl_Position = vec4 (pa, 1);
+  EmitVertex();
+  gBoundingBox = vec2 (-1,-1);
+  gl_Position = vec4 (pc, 1);
+//  gl_Position = vec4 (0.5,0.5,0, 1);
+  EmitVertex();
+  gBoundingBox = vec2 (1,-1);
+  gl_Position = vec4 (pa + pc - pb, 1);
+  EmitVertex();
+
+  EndPrimitive();
+}

shader/ellipseInterpolate.vert

@@ -0,0 +1,16 @@
+#version 430 core
+layout (location = 0) in vec3 position;
+layout (location = 1) in vec4 col;
+out vec4 vCol;
+
+uniform vec2 winSize;
+uniform float zoom;
+uniform vec2 translation;
+uniform float rotation;
+uniform mat4 worldMat;
+
+void main()
+{
+  gl_Position = worldMat * vec4(position,1);
+  vCol = col;
+}