app-proto/inversive-display/src/inversive.frag

@@ -23,8 +23,10 @@ vecInv sphere(vec3 center, float radius) {
 
 // --- uniforms ---
 
-// construction
+// construction. the SPHERE_MAX array size seems to affect frame rate a lot,
-const int SPHERE_MAX = 256;
+// even though we should only be using the first few elements of each array
+const int SPHERE_MAX = 12;
+uniform int sphere_cnt;
 uniform vecInv sphere_list[SPHERE_MAX];
 
 // view
@@ -128,13 +130,11 @@ vec2 sphere_cast(vecInv v, vec3 dir) {
 }
 
 void main() {
-    const int sphere_cnt = 3;
-    
     vec2 scr = (2.*gl_FragCoord.xy - resolution) / shortdim;
     vec3 dir = vec3(focal_slope * scr, -1.);
     
     // initialize two spheres
-    vecInv sphere_list_internal [sphere_cnt];
+    vecInv sphere_list_internal [SPHERE_MAX];
     if (use_test_construction) {
         /* DEBUG */
         // spheres 0 and 1 are identical in the test construction hard-coded
@@ -149,14 +149,14 @@ void main() {
             sphere_list_internal[i] = sphere_list[i];
         }
     }
-    vec3 color_list [sphere_cnt];
+    vec3 color_list [SPHERE_MAX];
     color_list[0] = vec3(1., 0.25, 0.);
     color_list[1] = vec3(0., 0.25, 1.);
     color_list[2] = vec3(0.25, 0., 1.0);
     
     // cast rays through the spheres
-    vec2 depth_pairs [sphere_cnt];
+    vec2 depth_pairs [SPHERE_MAX];
-    taggedFrag frags [2*sphere_cnt];
+    taggedFrag frags [2*SPHERE_MAX];
     int frag_cnt = 0;
     for (int i = 0; i < sphere_cnt; ++i) {
         vec2 hit_depths = sphere_cast(sphere_list_internal[i], dir);

app-proto/inversive-display/src/main.rs

@@ -101,7 +101,7 @@ fn main() {
         
         on_mount(move || {
             // list construction elements
-            const SPHERE_MAX: usize = 256;
+            const SPHERE_MAX: usize = 12;
             let mut sphere_vec = Vec::<DVector<f64>>::new();
             
             // get the display canvas
@@ -142,14 +142,32 @@ fn main() {
             console::log_1(&JsValue::from(link_msg));
             ctx.use_program(Some(&program));
             
+            /* DEBUG */
+            // print the maximum number of vectors that can be passed as
+            // uniforms to a fragment shader. the OpenGL ES 3.0 standard
+            // requires this maximum to be at least 224, as discussed in the
+            // documentation of the GL_MAX_FRAGMENT_UNIFORM_VECTORS parameter
+            // here:
+            //
+            //   https://registry.khronos.org/OpenGL-Refpages/es3.0/html/glGet.xhtml
+            //
+            // there are also other size limits. for example, on Aaron's
+            // machine, the the length of a float or genType array seems to be
+            // capped at 1024 elements
+            console::log_2(
+                &ctx.get_parameter(WebGl2RenderingContext::MAX_FRAGMENT_UNIFORM_VECTORS).unwrap(),
+                &JsValue::from("uniform vectors available")
+            );
+            
             // find indices of vertex attributes and uniforms
+            let position_index = ctx.get_attrib_location(&program, "position") as u32;
+            let sphere_cnt_loc = ctx.get_uniform_location(&program, "sphere_cnt");
             let sphere_sp_locs = get_uniform_array_locations::<SPHERE_MAX>(
                 &ctx, &program, "sphere_list", "sp"
             );
             let sphere_lt_locs = get_uniform_array_locations::<SPHERE_MAX>(
                 &ctx, &program, "sphere_list", "lt"
             );
-            let position_index = ctx.get_attrib_location(&program, "position") as u32;
             let resolution_loc = ctx.get_uniform_location(&program, "resolution");
             let shortdim_loc = ctx.get_uniform_location(&program, "shortdim");
             let ctrl_loc = ctx.get_uniform_location(&program, "ctrl"); /* DEBUG */
@@ -192,6 +210,7 @@ fn main() {
                 ctx.uniform1f(shortdim_loc.as_ref(), width.min(height));
                 
                 // pass the construction
+                ctx.uniform1i(sphere_cnt_loc.as_ref(), sphere_vec.len() as i32);
                 for n in 0..sphere_vec.len() {
                     let v = &sphere_vec[n];
                     ctx.uniform3f(