From cc7f77a5a944cac4dd54f78eb76c7a0885cbb0f0 Mon Sep 17 00:00:00 2001
From: Mike Lynch <m.lynch@sydney.edu.au>
Date: Sat, 8 Nov 2025 17:47:47 +1100
Subject: [PATCH] Added a shape with a single link to make testing easier

---
 gui.js         |  2 +-
 polytopes.js   | 27 +++++++++++++++++++---
 taperedLink.js | 61 +++++++++++++++++++++++++++++---------------------
 3 files changed, 60 insertions(+), 30 deletions(-)

diff --git a/gui.js b/gui.js
index 06d83c9..5c0d57e 100644
--- a/gui.js
+++ b/gui.js
@@ -7,7 +7,7 @@ const DEFAULTS = {
 	linksize: 1.0,
 	linkopacity: 0.75,
 	link2opacity: 0.75,
-	shape: '16-cell',
+	shape: 'linky',
 	option: 'none',
 	visibility: 5,
 	inscribed: false,
diff --git a/polytopes.js b/polytopes.js
index 91816c2..fe69529 100644
--- a/polytopes.js
+++ b/polytopes.js
@@ -55,8 +55,28 @@ export function auto_detect_edges(nodes, neighbours, debug=false) {
 	return links;
 }
 
+
+export const linkTest = () => {
+    return {
+        name: 'linky',
+        nodes: [
+            { id:1, label: 1, x: -1, y: -1, z:-1, w: 0 },
+            { id:2, label: 2, x: 1, y: 1, z: 1, w: 0 },
+        ],
+        links: [
+            { id: 1, source: 1, target: 2 }
+        ],
+  		options: [ { name: '--' }],
+		description: `link`,
+	  }
+};
+
+
+
 // too small and simple to calculate
 
+
+
 export const cell5 = () => {
 	const c1 = Math.sqrt(5) / 4;
 	return {
@@ -844,7 +864,8 @@ export const icosahedron = () => {
 
 export const build_all = () => {
 	return [
-		tetrahedron(),
+	        linkTest(),
+/*		tetrahedron(),
 		octahedron(),
 		cube(),
 		icosahedron(),
@@ -858,9 +879,9 @@ export const build_all = () => {
 		cell600_layered(),
 	 	cell120_inscribed(),
 	 	cell120_layered()
-	 	];
+	*/ 	];
 }
 
 export const radii = (shape) => {
 	return shape.nodes.map(n => Math.sqrt(n.x * n.x + n.y * n.y + n.z * n.z + n.w * n.w))
-}
\ No newline at end of file
+}
diff --git a/taperedLink.js b/taperedLink.js
index 2473430..41d270b 100644
--- a/taperedLink.js
+++ b/taperedLink.js
@@ -9,46 +9,55 @@ class TaperedLink extends THREE.Group {
     const geometry = new THREE.ConeGeometry( 0.75, 1, 32, true );
     const cplane = new THREE.Plane(new THREE.Vector3(0, -1, 0), 0.5);
     const material = baseMaterial.clone();
-//    material.clippingPlanes = [ cplane ];
-    this.object = new THREE.Mesh( geometry, material );
-    this.add( this.object );
+    material.clippingPlanes = [ cplane ];
+    this.cone = new THREE.Mesh( geometry, material );
+    this.add( this.cone );
     this.update(n1, n2, r1, r2);
   }  
 
   update(n1, n2, r1, r2) {
     const kraw = r1 - r2;
-    const k = ( kraw == 0 ) ? 0.001 : kraw;
-    let nbase = n1;
-    let napex = n2;
+    let k = ( kraw == 0 ) ? 0.001 : kraw;
+    let nbase = n1.v3;
+    let napex = n2.v3;
     let rbase = r1;
     let rapex = r2;
     if( k < 0 ) {
-      nbase = n2;
-      napex = n1;
+      nbase = n2.v3;
+      napex = n1.v3;
       rbase = r2;
       rapex = r1;
+      k = -k;
     }
-    const l = nbase.v3.distanceTo(napex.v3);
 
+    // FIXME - the problem is that when the h_offset > 1, the centroid
+    // of the cone is on the other side of napex, so it looks the wrong way
+
+    const l = nbase.distanceTo(napex);
     const h = l * rbase / k;
-    //const pos = new THREE.Vector3(0, h/2 - l/2, 0);
-    //pos.add(nbase.v3);
-    this.object.scale.copy(new THREE.Vector3(rbase, h, rbase));
-    this.object.position.copy(nbase.v3);
-    this.object.lookAt(napex.v3);
-    this.object.rotation.x = Math.PI / 2.0;
+    const h_offset = 0.5 * h / l;
+    const pos = new THREE.Vector3();
+    if( l > 0 ) {
+      pos.lerpVectors(nbase, napex, h_offset);
+    }
+    if( h_offset < 1 ) { 
+      this.cone.scale.copy(new THREE.Vector3(rbase, h, rbase));
+    } else {
+      // you're on the other side of napex so flip the cone
+      this.cone.scale.copy(new THREE.Vector3(rbase, -h, rbase));      
+    }
+    this.lookAt(napex);
+    this.position.copy(pos);
+    this.cone.rotation.x = Math.PI / 2.0;
+    const clipnorm = new THREE.Vector3();
+    clipnorm.copy(napex);
+    clipnorm.sub(nbase);
+    clipnorm.negate();
+    clipnorm.normalize();
+    this.cone.material.clippingPlanes[0].setFromNormalAndCoplanarPoint(
+      clipnorm, napex
+      );
   }
-      // this.object.material.clippingPlanes[0].normal.y = -1;
-      // this.object.material.clippingPlanes[0].constant = l / 2;
-      //this.object.position.copy(new THREE.Vector3(0, h/2 - l/2, 0));
-  //   } else {
-  //     const h = l * r2 / k;
-  //     this.object.scale.copy(new THREE.Vector3(r2, h, r2));
-  //     // this.object.material.clippingPlanes[0].normal.y = 1;
-  //     // this.object.material.clippingPlanes[0].constant = l / 2;
-  //     //this.object.position.copy(new THREE.Vector3(0, h / 2 + l / 2, 0));
-  //   }
-  // }
 
 }