Disable feathering to prevent artifacts in visualizer (#26)

Fixes artifacts in the visualizations of some of the IPA polygons by
disabling feathering in the tesselation which seemed to be the root
cause. Previously you would see long lines shooting out from some of the
triangles in the triangulations, particularly very thin obtuse ones,
those artifacts are gone with this change.

visualizer/src/app.rs

@@ -56,6 +56,15 @@ impl eframe::App for TemplateApp {
                 }
             });
 
+        // This was needed to workaround some artifacts in the plot for
+        // highly obtuse triangles in triangulations. It's possible it
+        // causes other problems down the road, so can try setting to
+        // true if other things look strange.
+        // https://github.com/adamconkey/computational_geometry/issues/17
+        ctx.tessellation_options_mut(|to| {
+            to.feathering = false;
+        });
+
         egui::CentralPanel::default().show(ctx, |ui| {
             self.visualizer.ui(ui, &self.selected_polygon);
         });