diff --git a/app-proto/src/display.rs b/app-proto/src/display.rs
index 21c7f86..69a3659 100644
--- a/app-proto/src/display.rs
+++ b/app-proto/src/display.rs
@@ -20,15 +20,23 @@ use crate::{
     assembly::{Element, ElementColor, ElementMotion, Point, Sphere}
 };
 
-// --- scene data ---
+// --- color ---
 
 const COLOR_SIZE: usize = 3;
 type ColorWithOpacity = [f32; COLOR_SIZE + 1];
 
+fn combine_channels(color: ElementColor, opacity: f32) -> ColorWithOpacity {
+    let mut color_with_opacity = [0.0; COLOR_SIZE + 1];
+    color_with_opacity[..COLOR_SIZE].copy_from_slice(&color);
+    color_with_opacity[COLOR_SIZE] = opacity;
+    color_with_opacity
+}
+
+// --- scene data ---
+
 struct SceneSpheres {
     representations: Vec<DVector<f64>>,
-    colors: Vec<ElementColor>,
-    opacities: Vec<f32>,
+    colors_with_opacity: Vec<ColorWithOpacity>,
     highlights: Vec<f32>
 }
 
@@ -36,8 +44,7 @@ impl SceneSpheres {
     fn new() -> SceneSpheres{
         SceneSpheres {
             representations: Vec::new(),
-            colors: Vec::new(),
-            opacities: Vec::new(),
+            colors_with_opacity: Vec::new(),
             highlights: Vec::new()
         }
     }
@@ -48,8 +55,7 @@ impl SceneSpheres {
     
     fn push(&mut self, representation: DVector<f64>, color: ElementColor, opacity: f32, highlight: f32) {
         self.representations.push(representation);
-        self.colors.push(color);
-        self.opacities.push(opacity);
+        self.colors_with_opacity.push(combine_channels(color, opacity));
         self.highlights.push(highlight);
     }
 }
@@ -72,12 +78,8 @@ impl ScenePoints {
     }
     
     fn push(&mut self, representation: DVector<f64>, color: ElementColor, opacity: f32, highlight: f32, selected: bool) {
-        let mut color_with_opacity = [0.0; COLOR_SIZE + 1];
-        color_with_opacity[..COLOR_SIZE].copy_from_slice(&color);
-        color_with_opacity[COLOR_SIZE] = opacity;
-        
         self.representations.push(representation);
-        self.colors_with_opacity.push(color_with_opacity);
+        self.colors_with_opacity.push(combine_channels(color, opacity));
         self.highlights.push(highlight);
         self.selections.push(if selected { 1.0 } else { 0.0 });
     }
@@ -664,11 +666,6 @@ pub fn Display() -> View {
                 ctx.uniform1i(sphere_cnt_loc.as_ref(), sphere_cnt);
                 for n in 0..sphere_reps_world.len() {
                     let v = &sphere_reps_world[n];
-                    
-                    let sphere_color = &mut [0.0; 4];
-                    sphere_color[..3].copy_from_slice(&scene.spheres.colors[n]);
-                    sphere_color[3] = scene.spheres.opacities[n];
-                    
                     ctx.uniform3fv_with_f32_array(
                         sphere_sp_locs[n].as_ref(),
                         v.rows(0, 3).as_slice()
@@ -679,7 +676,7 @@ pub fn Display() -> View {
                     );
                     ctx.uniform4fv_with_f32_array(
                         sphere_color_locs[n].as_ref(),
-                        sphere_color
+                        &scene.spheres.colors_with_opacity[n]
                     );
                     ctx.uniform1f(
                         sphere_highlight_locs[n].as_ref(),