draw fill antialiasing with indexed lines

fixes #668

Author: ansis

outline.vertex.glsl

@@ -5,10 +5,6 @@ uniform vec2 u_world;
 varying vec2 v_pos;
 
 void main() {
-    // If the x coordinate is the maximum integer, we move the z coordinates out
-    // of the view plane so that the triangle gets clipped. This makes it easier
-    // for us to create degenerate triangle strips.
-    float z = step(32767.0, a_pos.x);
-    gl_Position = u_posmatrix * vec4(a_pos, z, 1);
+    gl_Position = u_posmatrix * vec4(a_pos, 0, 1);
     v_pos = (gl_Position.xy + 1.0) / 2.0 * u_world;
 }