Ray-caster: switch from draw effect to animation loop

This wastes a lot of CPU time, as explained on lines 253--258 of
`main.rs`, but it's better than the previous version, which could block
graphics updates system-wide for seconds on end.

app-proto/inversive-display/Cargo.toml

@@ -9,6 +9,7 @@ default = ["console_error_panic_hook"]
 
 [dependencies]
 js-sys = "0.3.70"
+nalgebra = "0.33.0"
 sycamore = "0.9.0-beta.2"
 
 # The `console_error_panic_hook` crate provides better debugging of panics by

app-proto/inversive-display/main.css

@@ -18,6 +18,16 @@ canvas {
   margin-top: 5px;
 }
 
-input {
-  margin-top: 5px;
+.control {
+  display: flex;
+  flex-direction: row;
+  width: 600px;
+}
+
+label {
+  width: 150px;
+}
+
+input {
+  flex-grow: 1;
 }

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

@@ -0,0 +1,12 @@
+use nalgebra::DVector;
+
+pub fn sphere(center_x: f64, center_y: f64, center_z: f64, radius: f64) -> DVector<f64> {
+    let center_norm_sq = center_x * center_x + center_y * center_y + center_z * center_z;
+    DVector::from_column_slice(&[
+        center_x / radius,
+        center_y / radius,
+        center_z / radius,
+        0.5 / radius,
+        0.5 * (center_norm_sq / radius - radius)
+    ])
+}

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

@@ -4,6 +4,32 @@ precision highp float;
 
 out vec4 outColor;
 
+// --- inversive geometry ---
+
+struct vecInv {
+    vec3 sp;
+    vec2 lt;
+};
+
+vecInv sphere(vec3 center, float radius) {
+    return vecInv(
+        center / radius,
+        vec2(
+            0.5 / radius,
+            0.5 * (dot(center, center) / radius - radius)
+        )
+    );
+}
+
+// --- uniforms ---
+
+// construction. the SPHERE_MAX array size seems to affect frame rate a lot,
+// 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];
+uniform vec3 color_list[SPHERE_MAX];
+
 // view
 uniform vec2 resolution;
 uniform float shortdim;
@@ -14,6 +40,7 @@ uniform vec2 radius;
 uniform float opacity;
 uniform float highlight;
 uniform int layer_threshold;
+uniform bool test_mode;
 
 // light and camera
 const float focal_slope = 0.3;
@@ -46,23 +73,6 @@ vec3 sRGB(vec3 color) {
     return vec3(sRGB(color.r), sRGB(color.g), sRGB(color.b));
 }
 
-// --- inversive geometry ---
-
-struct vecInv {
-    vec3 sp;
-    vec2 lt;
-};
-
-vecInv sphere(vec3 center, float radius) {
-    return vecInv(
-        center / radius,
-        vec2(
-            0.5 / radius,
-            0.5 * (dot(center, center) / radius - radius)
-        )
-    );
-}
-
 // --- shading ---
 
 struct taggedFrag {
@@ -124,40 +134,40 @@ void main() {
     vec2 scr = (2.*gl_FragCoord.xy - resolution) / shortdim;
     vec3 dir = vec3(focal_slope * scr, -1.);
     
-    // initialize two spheres
-    vecInv v [2];
-    v[0] = sphere(vec3(0.5, 0.5, -5. + ctrl.x), radius.x);
-    v[1] = sphere(vec3(-0.5, -0.5, -5. + ctrl.y), radius.y);
-    vec3 color0 = vec3(1., 0.214, 0.);
-    vec3 color1 = vec3(0., 0.214, 1.);
-    
     // cast rays through the spheres
-    vec2 u0 = sphere_cast(v[0], dir);
-    vec2 u1 = sphere_cast(v[1], dir);
+    vec2 depth_pairs [SPHERE_MAX];
+    taggedFrag frags [2*SPHERE_MAX];
+    int frag_cnt = 0;
+    for (int i = 0; i < sphere_cnt; ++i) {
+        vec2 hit_depths = sphere_cast(sphere_list[i], dir);
+        if (!isnan(hit_depths[0])) {
+            frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[0] * dir, color_list[i], i);
+            ++frag_cnt;
+        }
+        if (!isnan(hit_depths[1])) {
+            frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i);
+            ++frag_cnt;
+        }
+    }
     
-    // shade and depth-sort the impact points
-    taggedFrag front_hits[2] = sort(
-        sphere_shading(v[0], u0[0] * dir, color0, 0),
-        sphere_shading(v[1], u1[0] * dir, color1, 1)
-    );
-    taggedFrag back_hits[2] = sort(
-        sphere_shading(v[0], u0[1] * dir, color0, 0),
-        sphere_shading(v[1], u1[1] * dir, color1, 1)
-    );
-    taggedFrag middle_frags[2] = sort(front_hits[1], back_hits[0]);
-    
-    // finish depth sorting
-    taggedFrag frags_by_depth[4];
-    frags_by_depth[0] = front_hits[0];
-    frags_by_depth[1] = middle_frags[0];
-    frags_by_depth[2] = middle_frags[1];
-    frags_by_depth[3] = back_hits[1];
+    // sort the fragments by depth, using an insertion sort
+    for (int take = 1; take < frag_cnt; ++take) {
+        taggedFrag pulled = frags[take];
+        for (int put = take; put >= 0; --put) {
+            if (put < 1 || frags[put-1].pt.z >= pulled.pt.z) {
+                frags[put] = pulled;
+                break;
+            } else {
+                frags[put] = frags[put-1];
+            }
+        }
+    }
     
     // highlight intersections and cusps
-    for (int i = 3; i >= 1; --i) {
+    for (int i = frag_cnt-1; i >= 1; --i) {
         // intersections
-        taggedFrag frag0 = frags_by_depth[i];
-        taggedFrag frag1 = frags_by_depth[i-1];
+        taggedFrag frag0 = frags[i];
+        taggedFrag frag1 = frags[i-1];
         float ixn_sin = length(cross(frag0.normal, frag1.normal));
         vec3 disp = frag0.pt - frag1.pt;
         float ixn_dist = max(
@@ -165,21 +175,21 @@ void main() {
             abs(dot(frag0.normal, disp))
         ) / ixn_sin;
         float ixn_highlight = 0.5 * highlight * (1. - smoothstep(2./3.*ixn_threshold, 1.5*ixn_threshold, ixn_dist));
-        frags_by_depth[i].color = mix(frags_by_depth[i].color, vec4(1.), ixn_highlight);
-        frags_by_depth[i-1].color = mix(frags_by_depth[i-1].color, vec4(1.), ixn_highlight);
+        frags[i].color = mix(frags[i].color, vec4(1.), ixn_highlight);
+        frags[i-1].color = mix(frags[i-1].color, vec4(1.), ixn_highlight);
         
         // cusps
         float cusp_cos = abs(dot(dir, frag0.normal));
-        float cusp_threshold = 2.*sqrt(ixn_threshold * v[frag0.id].lt.s);
+        float cusp_threshold = 2.*sqrt(ixn_threshold * sphere_list[frag0.id].lt.s);
         float cusp_highlight = highlight * (1. - smoothstep(2./3.*cusp_threshold, 1.5*cusp_threshold, cusp_cos));
-        frags_by_depth[i].color = mix(frags_by_depth[i].color, vec4(1.), cusp_highlight);
+        frags[i].color = mix(frags[i].color, vec4(1.), cusp_highlight);
     }
     
     // composite the sphere fragments
     vec3 color = vec3(0.);
-    for (int i = 3; i >= layer_threshold; --i) {
-        if (frags_by_depth[i].pt.z < 0.) {
-            vec4 frag_color = frags_by_depth[i].color;
+    for (int i = frag_cnt-1; i >= layer_threshold; --i) {
+        if (frags[i].pt.z < 0.) {
+            vec4 frag_color = frags[i].color;
             color = mix(color, frag_color.rgb, frag_color.a);
         }
     }

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

@@ -8,8 +8,12 @@
 //
 
 extern crate js_sys;
-use sycamore::{prelude::*, rt::{JsCast, JsValue}};
-use web_sys::{console, WebGl2RenderingContext, WebGlShader};
+use core::array;
+use nalgebra::DVector;
+use sycamore::{prelude::*, motion::create_raf, rt::{JsCast, JsValue}};
+use web_sys::{console, WebGl2RenderingContext, WebGlProgram, WebGlShader, WebGlUniformLocation};
+
+mod engine;
 
 fn compile_shader(
     context: &WebGl2RenderingContext,
@@ -22,6 +26,21 @@ fn compile_shader(
     shader
 }
 
+fn get_uniform_array_locations<const N: usize>(
+    context: &WebGl2RenderingContext,
+    program: &WebGlProgram,
+    var_name: &str,
+    member_name_opt: Option<&str>
+) -> [Option<WebGlUniformLocation>; N] {
+    array::from_fn(|n| {
+        let name = match member_name_opt {
+            Some(member_name) => format!("{var_name}[{n}].{member_name}"),
+            None => format!("{var_name}[{n}]")
+        };
+        context.get_uniform_location(&program, name.as_str())
+    })
+}
+
 // load the given data into the vertex input of the given name
 fn bind_vertex_attrib(
     context: &WebGl2RenderingContext,
@@ -70,6 +89,7 @@ fn main() {
     console_error_panic_hook::set_once();
     
     sycamore::render(|| {
+        // controls
         let ctrl_x = create_signal(0.0);
         let ctrl_y = create_signal(0.0);
         let radius_x = create_signal(1.0);
@@ -77,9 +97,21 @@ fn main() {
         let opacity = create_signal(0.5);
         let highlight = create_signal(0.2);
         let layer_threshold = create_signal(0.0);
+        let debug_mode = create_signal(false);
+        
+        // display
         let display = create_node_ref();
         
         on_mount(move || {
+            // list construction elements
+            const SPHERE_MAX: usize = 12;
+            let mut sphere_vec = Vec::<DVector<f64>>::new();
+            let color_vec = vec![
+                [1.00_f32, 0.25_f32, 0.00_f32],
+                [0.00_f32, 0.25_f32, 1.00_f32],
+                [0.25_f32, 0.00_f32, 1.00_f32]
+            ];
+            
             // get the display canvas
             let canvas = display
                 .get::<DomNode>()
@@ -118,15 +150,43 @@ 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", Some("sp")
+            );
+            let sphere_lt_locs = get_uniform_array_locations::<SPHERE_MAX>(
+                &ctx, &program, "sphere_list", Some("lt")
+            );
+            let color_locs = get_uniform_array_locations::<SPHERE_MAX>(
+                &ctx, &program, "color_list", None
+            );
             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");
-            let radius_loc = ctx.get_uniform_location(&program, "radius");
+            let ctrl_loc = ctx.get_uniform_location(&program, "ctrl"); /* DEBUG */
+            let radius_loc = ctx.get_uniform_location(&program, "radius"); /* DEBUG */
             let opacity_loc = ctx.get_uniform_location(&program, "opacity");
             let highlight_loc = ctx.get_uniform_location(&program, "highlight");
             let layer_threshold_loc = ctx.get_uniform_location(&program, "layer_threshold");
+            let debug_mode_loc = ctx.get_uniform_location(&program, "debug_mode");
             
             // create a vertex array and bind it to the graphics context
             let vertex_array = ctx.create_vertex_array().unwrap();
@@ -147,75 +207,144 @@ fn main() {
             bind_vertex_attrib(&ctx, position_index, 3, &positions);
             
             // set up a repainting routine
-            create_effect(move || {
+            let (_, start_updating_display, _) = create_raf(move || {
+                // update the construction
+                sphere_vec.clear();
+                sphere_vec.push(engine::sphere(0.5, 0.5, -5.0 + ctrl_x.get(), radius_x.get()));
+                sphere_vec.push(engine::sphere(-0.5, -0.5, -5.0 + ctrl_y.get(), radius_y.get()));
+                sphere_vec.push(engine::sphere(-0.5, 0.5, -5.0, 0.75));
+                
                 // set the resolution
                 let width = canvas.width() as f32;
                 let height = canvas.height() as f32;
                 ctx.uniform2f(resolution_loc.as_ref(), width, height);
                 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(
+                        sphere_sp_locs[n].as_ref(),
+                        v[0] as f32, v[1] as f32, v[2] as f32
+                    );
+                    ctx.uniform2f(
+                        sphere_lt_locs[n].as_ref(),
+                        v[3] as f32, v[4] as f32
+                    );
+                    ctx.uniform3fv_with_f32_array(
+                        color_locs[n].as_ref(),
+                        &color_vec[n]
+                    );
+                }
+                
                 // pass the control parameters
-                ctx.uniform2f(ctrl_loc.as_ref(), ctrl_x.get() as f32, ctrl_y.get() as f32);
-                ctx.uniform2f(radius_loc.as_ref(), radius_x.get() as f32, radius_y.get() as f32);
+                ctx.uniform2f(ctrl_loc.as_ref(), ctrl_x.get() as f32, ctrl_y.get() as f32); /* DEBUG */
+                ctx.uniform2f(radius_loc.as_ref(), radius_x.get() as f32, radius_y.get() as f32); /* DEBUG */
                 ctx.uniform1f(opacity_loc.as_ref(), opacity.get() as f32);
                 ctx.uniform1f(highlight_loc.as_ref(), highlight.get() as f32);
                 ctx.uniform1i(layer_threshold_loc.as_ref(), layer_threshold.get() as i32);
+                ctx.uniform1i(debug_mode_loc.as_ref(), debug_mode.get() as i32);
                 
                 // draw the scene
                 ctx.draw_arrays(WebGl2RenderingContext::TRIANGLES, 0, VERTEX_CNT as i32);
             });
+            
+            /*
+            this wastes CPU time by running an animation loop, which updates the
+            display even when nothing has changed. there should be a way to make
+            Sycamore do single-frame updates in response to changes, but i
+            haven't found it yet
+            */
+            start_updating_display();
         });
         
         view! {
             div(id="app") {
                 canvas(ref=display, width="600", height="600")
+                div(class="control") {
+                    label(for="ctrl-x") { "Sphere 0 depth" }
                     input(
                         type="range",
+                        id="ctrl-x",
                         min=-1.0,
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=ctrl_x
                     )
+                }
+                div(class="control") {
+                    label(for="ctrl-y") { "Sphere 1 depth" }
                     input(
                         type="range",
+                        id="ctrl-y",
                         min=-1.0,
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=ctrl_y
                     )
+                }
+                div(class="control") {
+                    label(for="radius-x") { "Sphere 0 radius" }
                     input(
                         type="range",
+                        id="radius-x",
                         min=0.5,
                         max=1.5,
                         step=0.001,
                         bind:valueAsNumber=radius_x
                     )
+                }
+                div(class="control") {
+                    label(for="radius-y") { "Sphere 1 radius" }
                     input(
                         type="range",
+                        id="radius-y",
                         min=0.5,
                         max=1.5,
                         step=0.001,
                         bind:valueAsNumber=radius_y
                     )
+                }
+                div(class="control") {
+                    label(for="opacity") { "Opacity" }
                     input(
                         type="range",
+                        id="opacity",
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=opacity
                     )
+                }
+                div(class="control") {
+                    label(for="highlight") { "Highlight" }
                     input(
                         type="range",
+                        id="highlight",
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=highlight
                     )
+                }
+                div(class="control") {
+                    label(for="layer-threshold") { "Layer threshold" }
                     input(
                         type="range",
-                    max=3.0,
+                        id="layer-threshold",
+                        max=5.0,
                         step=1.0,
                         bind:valueAsNumber=layer_threshold
                     )
                 }
+                div(class="control") {
+                    label(for="debug-mode") { "Debug mode" }
+                    input(
+                        type="checkbox",
+                        id="debug-mode",
+                        bind:checked=debug_mode
+                    )
+                }
+            }
         }
     });
 }