From ba1d87812f0049c0e3e88fe5de88977da579394e Mon Sep 17 00:00:00 2001
From: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Date: Sun, 18 May 2025 13:35:01 -0700
Subject: [PATCH] Allow each sphere to have its own opacity

To confirm that we haven't accidentally changed the rendering behavior,
we still give every sphere the same default opacity.
---
 app-proto/src/display.rs   | 11 +++++++----
 app-proto/src/spheres.frag | 13 +++++++------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/app-proto/src/display.rs b/app-proto/src/display.rs
index a2fe4b6..b663030 100644
--- a/app-proto/src/display.rs
+++ b/app-proto/src/display.rs
@@ -469,7 +469,6 @@ pub fn Display() -> View {
         );
         let resolution_loc = ctx.get_uniform_location(&sphere_program, "resolution");
         let shortdim_loc = ctx.get_uniform_location(&sphere_program, "shortdim");
-        let opacity_loc = ctx.get_uniform_location(&sphere_program, "opacity");
         let layer_threshold_loc = ctx.get_uniform_location(&sphere_program, "layer_threshold");
         let debug_mode_loc = ctx.get_uniform_location(&sphere_program, "debug_mode");
         
@@ -646,6 +645,11 @@ 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] = OPACITY;
+                    
                     ctx.uniform3fv_with_f32_array(
                         sphere_sp_locs[n].as_ref(),
                         v.rows(0, 3).as_slice()
@@ -654,9 +658,9 @@ pub fn Display() -> View {
                         sphere_lt_locs[n].as_ref(),
                         v.rows(3, 2).as_slice()
                     );
-                    ctx.uniform3fv_with_f32_array(
+                    ctx.uniform4fv_with_f32_array(
                         sphere_color_locs[n].as_ref(),
-                        &scene.spheres.colors[n]
+                        sphere_color
                     );
                     ctx.uniform1f(
                         sphere_highlight_locs[n].as_ref(),
@@ -665,7 +669,6 @@ pub fn Display() -> View {
                 }
                 
                 // pass the display parameters
-                ctx.uniform1f(opacity_loc.as_ref(), OPACITY);
                 ctx.uniform1i(layer_threshold_loc.as_ref(), LAYER_THRESHOLD);
                 ctx.uniform1i(debug_mode_loc.as_ref(), DEBUG_MODE);
                 
diff --git a/app-proto/src/spheres.frag b/app-proto/src/spheres.frag
index d50cb1e..fa317a8 100644
--- a/app-proto/src/spheres.frag
+++ b/app-proto/src/spheres.frag
@@ -17,7 +17,7 @@ struct vecInv {
 const int SPHERE_MAX = 200;
 uniform int sphere_cnt;
 uniform vecInv sphere_list[SPHERE_MAX];
-uniform vec3 color_list[SPHERE_MAX];
+uniform vec4 color_list[SPHERE_MAX];
 uniform float highlight_list[SPHERE_MAX];
 
 // view
@@ -25,7 +25,6 @@ uniform vec2 resolution;
 uniform float shortdim;
 
 // controls
-uniform float opacity;
 uniform int layer_threshold;
 uniform bool debug_mode;
 
@@ -69,7 +68,7 @@ struct Fragment {
     vec4 color;
 };
 
-Fragment sphere_shading(vecInv v, vec3 pt, vec3 base_color) {
+Fragment sphere_shading(vecInv v, vec3 pt, vec4 base_color) {
     // the expression for normal needs to be checked. it's supposed to give the
     // negative gradient of the lorentz product between the impact point vector
     // and the sphere vector with respect to the coordinates of the impact
@@ -79,7 +78,7 @@ Fragment sphere_shading(vecInv v, vec3 pt, vec3 base_color) {
     
     float incidence = dot(normal, light_dir);
     float illum = mix(0.4, 1.0, max(incidence, 0.0));
-    return Fragment(pt, normal, vec4(illum * base_color, opacity));
+    return Fragment(pt, normal, vec4(illum * base_color.rgb, base_color.a));
 }
 
 float intersection_dist(Fragment a, Fragment b) {
@@ -192,10 +191,11 @@ void main() {
     vec3 color = vec3(0.);
     int layer = layer_cnt - 1;
     TaggedDepth hit = top_hits[layer];
+    vec4 sphere_color = color_list[hit.id];
     Fragment frag_next = sphere_shading(
         sphere_list[hit.id],
         hit.depth * dir,
-        hit.dimming * color_list[hit.id]
+        vec4(hit.dimming * sphere_color.rgb, sphere_color.a)
     );
     float highlight_next = highlight_list[hit.id];
     --layer;
@@ -206,10 +206,11 @@ void main() {
         
         // shade the next fragment
         hit = top_hits[layer];
+        sphere_color = color_list[hit.id];
         frag_next = sphere_shading(
             sphere_list[hit.id],
             hit.depth * dir,
-            hit.dimming * color_list[hit.id]
+            vec4(hit.dimming * sphere_color.rgb, sphere_color.a)
         );
         highlight_next = highlight_list[hit.id];