Update wireframe display

Author: gwaldron

src/osgEarthImGui/RenderingGUI

@@ -83,11 +83,9 @@ void oeui_render_winding_fs(inout vec4 color) {
 #define VP_STAGE_FRAGMENT
 void oeui_render_outlines(inout vec4 color) {
     float b = min(gl_BaryCoordNV.x, min(gl_BaryCoordNV.y, gl_BaryCoordNV.z))*32.0;
-    vec3 line_color = color.rgb;
-    if (color.r < 0.5) line_color.r += 0.5; else line_color.r -= 0.5;
-    if (color.b < 0.5) line_color.b += 0.5; else line_color.b -= 0.5;
-    if (color.g < 0.5) line_color.b += 0.5; else line_color.g -= 0.5;
-    color = vec4(mix(line_color, color.rgb, clamp(b,0,1)), color.a);
+    float mono = dot(color.rgb, vec3(0.299, 0.587, 0.114));
+    mono = mod(mono + 0.25, 1.0); 
+    color = vec4(mix(vec3(mono), color.rgb, clamp(b,0,1)), color.a);
 }
 )";