Enable focus for tabs and display

You can now switch tabs from the keyboard using the usual radio button
interaction.

app-proto/inversive-display/main.css

@@ -14,10 +14,15 @@ body {
 canvas {
   float: left;
   background-color: #020202;
+  border: 1px solid #555;
   border-radius: 10px;
   margin-top: 5px;
 }
 
+canvas:focus {
+  border-color: #aaa;
+}
+
 .hidden {
   display: none;
 }
@@ -29,7 +34,12 @@ canvas {
 }
 
 input[type="radio"] {
-  display: none;
+  appearance: none;
+  width: 0px;
+  height: 0px;
+  padding: 0px;
+  margin: 0px;
+  outline: none;
 }
 
 .tab-pane > label {
@@ -46,12 +56,16 @@ input[type="radio"] {
   background-color: #555;
 }
 
+.tab-pane > label:has(:focus-visible) {
+  outline: medium auto currentColor;
+}
+
 .tab-pane > label:hover:not(:has(:checked)) {
   border-color: #bbb;
   background-color: #333;
 }
 
-label {
+.control > span {
   width: 170px;
 }
 

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

@@ -1,5 +1,6 @@
 use nalgebra::DVector;
 
+// the sphere with the given center and radius, with inward-pointing normals
 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(&[
@@ -10,3 +11,17 @@ pub fn sphere(center_x: f64, center_y: f64, center_z: f64, radius: f64) -> DVect
         0.5 * (center_norm_sq / radius - radius)
     ])
 }
+
+// the sphere of curvature `curv` whose closest point to the origin has position
+// `off * dir` and normal `dir`, where `dir` is a unit vector. setting the
+// curvature to zero gives a plane
+pub fn sphere_with_offset(dir_x: f64, dir_y: f64, dir_z: f64, off: f64, curv: f64) -> DVector<f64> {
+    let norm_sp = 1.0 + off * curv;
+    DVector::from_column_slice(&[
+        norm_sp * dir_x,
+        norm_sp * dir_y,
+        norm_sp * dir_z,
+        0.5 * curv,
+        off * (1.0 + 0.5 * off * curv)
+    ])
+}

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

@@ -110,23 +110,37 @@ taggedFrag sphere_shading(vecInv v, vec3 pt, vec3 base_color, int id) {
 
 // --- ray-casting ---
 
+// if `a/b` is less than this threshold, we approximate `a*u^2 + b*u + c` by
+// the linear function `b*u + c`
+const float DEG_THRESHOLD = 1e-9;
+
+// the depths, represented as multiples of `dir`, where the line generated by
+// `dir` hits the sphere represented by `v`. if both depths are positive, the
+// smaller one is returned in the first component. if only one depth is
+// positive, it could be returned in either component
 vec2 sphere_cast(vecInv v, vec3 dir) {
     float a = -v.lt.s * dot(dir, dir);
     float b = dot(v.sp, dir);
     float c = -v.lt.t;
     
-    float scale = -b/(2.*a);
     float adjust = 4.*a*c/(b*b);
-    
     if (adjust < 1.) {
-        float offset = sqrt(1. - adjust);
-        return vec2(
-            scale * (1. - offset),
-            scale * (1. + offset)
-        );
+        // as long as `b` is non-zero, the linear approximation of
+        //
+        //   a*u^2 + b*u + c
+        //
+        // at `u = 0` will reach zero at a finite depth `u_lin`. the root of the
+        // quadratic adjacent to `u_lin` is stored in `lin_root`. if both roots
+        // have the same sign, `lin_root` will be the one closer to `u = 0`
+        float square_rect_ratio = 1. + sqrt(1. - adjust);
+        float lin_root = -(2.*c)/b / square_rect_ratio;
+        if (abs(a) > DEG_THRESHOLD * abs(b)) {
+            return vec2(lin_root, -b/(2.*a) * square_rect_ratio);
         } else {
-        // these parameters describe points behind the camera, so the
-        // corresponding fragments won't be drawn
+            return vec2(lin_root, -1.);
+        }
+    } else {
+        // the line through `dir` misses the sphere completely
         return vec2(-1., -1.);
     }
 }
@@ -179,15 +193,13 @@ void main() {
     if (debug_mode) {
         // at the bottom of the screen, show the color scale instead of the
         // layer count
-        if (gl_FragCoord.y < 10.) layer_cnt = 2 * int(8. * gl_FragCoord.x / resolution.x);
+        if (gl_FragCoord.y < 10.) layer_cnt = int(16. * gl_FragCoord.x / resolution.x);
         
         // convert number to color
-        vec3 color;
-        if (layer_cnt % 2 == 0) {
-            ivec3 bits = layer_cnt / ivec3(2, 4, 8);
-            color = mod(vec3(bits), 2.);
-        } else {
-            color = vec3(0.5);
+        ivec3 bits = layer_cnt / ivec3(1, 2, 4);
+        vec3 color = mod(vec3(bits), 2.);
+        if (layer_cnt % 16 >= 8) {
+            color = mix(color, vec3(0.5), 0.5);
         }
         outColor = vec4(color, 1.);
         return;

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

@@ -10,7 +10,6 @@
 extern crate js_sys;
 use core::array;
 use nalgebra::{DMatrix, DVector};
-use std::f64::consts::FRAC_1_SQRT_2;
 use sycamore::{prelude::*, motion::create_raf, rt::{JsCast, JsValue}};
 use web_sys::{console, window, WebGl2RenderingContext, WebGlProgram, WebGlShader, WebGlUniformLocation};
 
@@ -86,30 +85,61 @@ fn bind_vertex_attrib(
 
 fn push_gen_construction(
     sphere_vec: &mut Vec<DVector<f64>>,
+    color_vec: &mut Vec<[f32; 3]>,
     construction_to_world: &DMatrix<f64>,
     ctrl_x: f64,
     ctrl_y: f64,
     radius_x: f64,
     radius_y: f64
 ) {
+    // push spheres
     sphere_vec.push(construction_to_world * engine::sphere(0.5, 0.5, ctrl_x, radius_x));
     sphere_vec.push(construction_to_world * engine::sphere(-0.5, -0.5, ctrl_y, radius_y));
     sphere_vec.push(construction_to_world * engine::sphere(-0.5, 0.5, 0.0, 0.75));
     sphere_vec.push(construction_to_world * engine::sphere(0.5, -0.5, 0.0, 0.5));
     sphere_vec.push(construction_to_world * engine::sphere(0.0, 0.15, 1.0, 0.25));
     sphere_vec.push(construction_to_world * engine::sphere(0.0, -0.15, -1.0, 0.25));
+    
+    // push colors
+    color_vec.push([1.00_f32, 0.25_f32, 0.00_f32]);
+    color_vec.push([0.00_f32, 0.25_f32, 1.00_f32]);
+    color_vec.push([0.25_f32, 0.00_f32, 1.00_f32]);
+    color_vec.push([0.25_f32, 1.00_f32, 0.00_f32]);
+    color_vec.push([0.75_f32, 0.75_f32, 0.00_f32]);
+    color_vec.push([0.00_f32, 0.75_f32, 0.50_f32]);
 }
 
 fn push_low_curv_construction(
     sphere_vec: &mut Vec<DVector<f64>>,
+    color_vec: &mut Vec<[f32; 3]>,
     construction_to_world: &DMatrix<f64>,
-    curv_x: f64,
-    curv_y: f64
+    off1: f64,
+    off2: f64,
+    off3: f64,
+    curv1: f64,
+    curv2: f64,
+    curv3: f64,
 ) {
-    sphere_vec.push(construction_to_world * DVector::from_column_slice(&[0.0, -1.0, 0.0, 0.5*curv_x, 0.0]));
-    sphere_vec.push(construction_to_world * DVector::from_column_slice(&[-FRAC_1_SQRT_2, 0.0, -FRAC_1_SQRT_2, 0.5*curv_y, 0.0]));
-    sphere_vec.push(construction_to_world * engine::sphere(0.5, 0.0, 0.5, FRAC_1_SQRT_2));
-    sphere_vec.push(construction_to_world * engine::sphere(-0.5, 0.0, -0.5, FRAC_1_SQRT_2));
+    // push spheres
+    let a = 0.75_f64.sqrt();
+    sphere_vec.push(construction_to_world * engine::sphere(0.0, 0.0, 0.0, 1.0));
+    sphere_vec.push(construction_to_world * engine::sphere_with_offset(0.0, 0.0, 1.0, 0.0, 0.0));
+    sphere_vec.push(construction_to_world * engine::sphere_with_offset(1.0, 0.0, 0.0, off1, curv1));
+    sphere_vec.push(construction_to_world * engine::sphere_with_offset(-0.5, a, 0.0, off2, curv2));
+    sphere_vec.push(construction_to_world * engine::sphere_with_offset(-0.5, -a, 0.0, off3, curv3));
+    sphere_vec.push(construction_to_world * engine::sphere(-4.0/3.0, 0.0, 0.0, 1.0/3.0));
+    sphere_vec.push(construction_to_world * engine::sphere(2.0/3.0, -4.0/3.0 * a, 0.0, 1.0/3.0));
+    sphere_vec.push(construction_to_world * engine::sphere(2.0/3.0, 4.0/3.0 * a, 0.0, 1.0/3.0));
+    
+    // push colors
+    color_vec.push([0.75_f32, 0.75_f32, 0.75_f32]);
+    color_vec.push([0.75_f32, 0.75_f32, 0.75_f32]);
+    color_vec.push([1.00_f32, 0.00_f32, 0.25_f32]);
+    color_vec.push([0.25_f32, 1.00_f32, 0.00_f32]);
+    color_vec.push([0.00_f32, 0.25_f32, 1.00_f32]);
+    color_vec.push([0.75_f32, 0.75_f32, 0.75_f32]);
+    color_vec.push([0.75_f32, 0.75_f32, 0.75_f32]);
+    color_vec.push([0.75_f32, 0.75_f32, 0.75_f32]);
 }
 
 #[derive(Clone, Copy, PartialEq)]
@@ -136,8 +166,12 @@ fn main() {
         
         // controls for low-curvature example
         let low_curv_controls = create_node_ref();
-        let curv_x = create_signal(0.0);
-        let curv_y = create_signal(0.0);
+        let curv1 = create_signal(0.0);
+        let curv2 = create_signal(0.0);
+        let curv3 = create_signal(0.0);
+        let off1 = create_signal(1.0);
+        let off2 = create_signal(1.0);
+        let off3 = create_signal(1.0);
         
         // shared controls
         let opacity = create_signal(0.5);
@@ -168,8 +202,12 @@ fn main() {
             radius_y.track();
             
             // track controls for low-curvature example
-            curv_x.track();
-            curv_y.track();
+            curv1.track();
+            curv2.track();
+            curv3.track();
+            off1.track();
+            off2.track();
+            off3.track();
             
             // track shared controls
             opacity.track();
@@ -199,17 +237,10 @@ fn main() {
                 }
             });
             
-            // list construction elements
+            // create list of construction elements
             const SPHERE_MAX: usize = 200;
             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],
-                [0.25_f32, 1.00_f32, 0.00_f32],
-                [0.75_f32, 0.75_f32, 0.00_f32],
-                [0.00_f32, 0.75_f32, 0.50_f32],
-            ];
+            let mut color_vec = Vec::<[f32; 3]>::new();
             
             // timing
             let mut last_time = 0.0;
@@ -365,17 +396,21 @@ fn main() {
                     
                     // update the construction
                     sphere_vec.clear();
+                    color_vec.clear();
                     match tab_selection.get() {
                         Tab::GenTab => push_gen_construction(
                             &mut sphere_vec,
+                            &mut color_vec,
                             &construction_to_world,
                             ctrl_x.get(), ctrl_y.get(),
                             radius_x.get(), radius_y.get()
                         ),
                         Tab::LowCurvTab => push_low_curv_construction(
                             &mut sphere_vec,
+                            &mut color_vec,
                             &construction_to_world,
-                            curv_x.get(), curv_y.get()
+                            off1.get(), off2.get(), off3.get(),
+                            curv1.get(), curv2.get(), curv3.get(),
                         )
                     };
                     
@@ -447,46 +482,42 @@ fn main() {
                     }
                 }
                 div { "Mean frame interval: " (mean_frame_interval.get()) " ms" }
-                canvas(ref=display, width="600", height="600")
+                canvas(ref=display, width=600, height=600, tabindex=0)
                 div(ref=gen_controls) {
-                    div(class="control") {
-                        label(for="ctrl-x") { "Sphere 0 depth" }
+                    label(class="control") {
+                        span { "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" }
+                    label(class="control") {
+                        span { "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" }
+                    label(class="control") {
+                        span { "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" }
+                    label(class="control") {
+                        span { "Sphere 1 radius" }
                         input(
                             type="range",
-                            id="radius-y",
                             min=0.5,
                             max=1.5,
                             step=0.001,
@@ -495,72 +526,105 @@ fn main() {
                     }
                 }
                 div(ref=low_curv_controls) {
-                    div(class="control") {
-                        label(for="curv-x") { "Sphere 0 curvature" }
+                    label(class="control") {
+                        span { "Sphere 1 offset" }
+                        input(
+                            type="range",
+                            min=-1.0,
+                            max=1.0,
+                            step=0.001,
+                            bind:valueAsNumber=off1
+                        )
+                    }
+                    label(class="control") {
+                        span { "Sphere 2 offset" }
+                        input(
+                            type="range",
+                            min=-1.0,
+                            max=1.0,
+                            step=0.001,
+                            bind:valueAsNumber=off2
+                        )
+                    }
+                    label(class="control") {
+                        span { "Sphere 3 offset" }
+                        input(
+                            type="range",
+                            min=-1.0,
+                            max=1.0,
+                            step=0.001,
+                            bind:valueAsNumber=off3
+                        )
+                    }
+                    label(class="control") {
+                        span { "Sphere 1 curvature" }
                         input(
                             type="range",
-                            id="curv-x",
                             min=0.0,
                             max=2.0,
                             step=0.001,
-                            bind:valueAsNumber=curv_x
+                            bind:valueAsNumber=curv1
                         )
                     }
-                    div(class="control") {
-                        label(for="curv-y") { "Sphere 1 curvature" }
+                    label(class="control") {
+                        span { "Sphere 2 curvature" }
                         input(
                             type="range",
-                            id="curv-y",
                             min=0.0,
                             max=2.0,
                             step=0.001,
-                            bind:valueAsNumber=curv_y
+                            bind:valueAsNumber=curv2
+                        )
+                    }
+                    label(class="control") {
+                        span { "Sphere 3 curvature" }
+                        input(
+                            type="range",
+                            min=0.0,
+                            max=2.0,
+                            step=0.001,
+                            bind:valueAsNumber=curv3
                         )
                     }
                 }
-                div(class="control") {
-                    label(for="opacity") { "Opacity" }
+                label(class="control") {
+                    span { "Opacity" }
                     input(
                         type="range",
-                        id="opacity",
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=opacity
                     )
                 }
-                div(class="control") {
-                    label(for="highlight") { "Highlight" }
+                label(class="control") {
+                    span { "Highlight" }
                     input(
                         type="range",
-                        id="highlight",
                         max=1.0,
                         step=0.001,
                         bind:valueAsNumber=highlight
                     )
                 }
-                div(class="control") {
-                    label(for="turntable") { "Turntable" }
+                label(class="control") {
+                    span { "Turntable" }
                     input(
                         type="checkbox",
-                        id="turntable",
                         bind:checked=turntable
                     )
                 }
-                div(class="control") {
-                    label(for="layer-threshold") { "Layer threshold" }
+                label(class="control") {
+                    span { "Layer threshold" }
                     input(
                         type="range",
-                        id="layer-threshold",
                         max=5.0,
                         step=1.0,
                         bind:valueAsNumber=layer_threshold
                     )
                 }
-                div(class="control") {
-                    label(for="debug-mode") { "Debug mode" }
+                label(class="control") {
+                    span { "Debug mode" }
                     input(
                         type="checkbox",
-                        id="debug-mode",
                         bind:checked=debug_mode
                     )
                 }