Fix free vs boundary halfedges

Author: minitoine

package.json

@@ -8,7 +8,7 @@
     "csg",
     "halfedge"
   ],
-  "version": "1.0.1",
+  "version": "1.0.2",
   "author": {
     "name": "Axel Antoine",
     "email": "ax.antoine@gmail.com",

src/core/Halfedge.ts

@@ -47,12 +47,20 @@ export class Halfedge {
   }
 
   /**
-   * Indicates whether the halfedge is a boundary (i.e. it has no twin)
+   * Indicates whether the halfedge is free (i.e. no connected face)
    *
    * @type       {boolean}
    */
-  get isBoundary() {
-    return this.face !== null;
+  isFree() {
+    return this.face === null;
+  }
+
+  /**
+   * Indicated wetcher the halfedge is a boundary (i.e. no connected face but
+   * twin has a face)
+   */
+  isBoundary() {
+    return this.face === null && this.twin.face !== null;
   }
 
   /**

src/core/Vertex.test.ts

@@ -117,14 +117,14 @@ test('Vertex loop CCW', () => {
 
 test('Boundary in halfedges loop', () => {
 
-  let array = generatorToArray(v1.boundaryHalfedgesInLoop());
+  let array = generatorToArray(v1.freeHalfedgesInLoop());
   expect(array).toHaveLength(0);
 
   const v1v2 = addEdge(struct, v1, v2);
   const v1v3 = addEdge(struct, v1, v3);
   const v1v4 = addEdge(struct, v1, v4);
 
-  array = generatorToArray(v1.boundaryHalfedgesInLoop());
+  array = generatorToArray(v1.freeHalfedgesInLoop());
   expect(array).toHaveLength(3);
   expect(array).toContain(v1v2.twin);
   expect(array).toContain(v1v3.twin);
@@ -133,7 +133,7 @@ test('Boundary in halfedges loop', () => {
   // Close 1-2-3 triangles
   const v2v3 = addEdge(struct, v2, v3);
   addFace(struct, [v1v2, v2v3, v1v3.twin]);
-  array = generatorToArray(v1.boundaryHalfedgesInLoop());
+  array = generatorToArray(v1.freeHalfedgesInLoop());
   expect(array).toHaveLength(2);
   expect(array).toContain(v1v2.twin);
   expect(array).toContain(v1v4.twin);
@@ -145,20 +145,20 @@ test('Boundary in halfedges loop', () => {
   const v4v2 = addEdge(struct, v4, v2);
   addFace(struct, [v4v2, v1v2.twin, v1v4]);
 
-  array = generatorToArray(v1.boundaryHalfedgesInLoop());
+  array = generatorToArray(v1.freeHalfedgesInLoop());
   expect(array).toHaveLength(0);
 });
 
 test('Boundary out halfedges loop', () => {
 
-  let array = generatorToArray(v1.boundaryHalfedgesOutLoop());
+  let array = generatorToArray(v1.freeHalfedgesOutLoop());
   expect(array).toHaveLength(0);
 
   const v1v2 = addEdge(struct, v1, v2);
   const v1v3 = addEdge(struct, v1, v3);
   const v1v4 = addEdge(struct, v1, v4);
 
-  array = generatorToArray(v1.boundaryHalfedgesOutLoop());
+  array = generatorToArray(v1.freeHalfedgesOutLoop());
   expect(array).toHaveLength(3);
   expect(array).toContain(v1v2);
   expect(array).toContain(v1v3);
@@ -167,7 +167,7 @@ test('Boundary out halfedges loop', () => {
   // Close 1-2-3 triangles
   const v2v3 = addEdge(struct, v2, v3);
   addFace(struct, [v1v2, v2v3, v1v3.twin]);
-  array = generatorToArray(v1.boundaryHalfedgesOutLoop());
+  array = generatorToArray(v1.freeHalfedgesOutLoop());
   expect(array).toHaveLength(2);
   expect(array).toContain(v1v3);
   expect(array).toContain(v1v4);
@@ -179,7 +179,7 @@ test('Boundary out halfedges loop', () => {
   const v4v2 = addEdge(struct, v4, v2);
   addFace(struct, [v4v2, v1v2.twin, v1v4]);
 
-  array = generatorToArray(v1.boundaryHalfedgesOutLoop());
+  array = generatorToArray(v1.freeHalfedgesOutLoop());
   expect(array).toHaveLength(0);
 });
 

src/core/Vertex.ts

@@ -41,27 +41,51 @@ export class Vertex {
   }
 
   /**
-   * Returns a generator of free halfedges (i.e. without face) starting from this 
-   * vertex.
+   * Returns a generator of free halfedges starting from this vertex.
    * @param start The halfedge to start, default is vertex halfedge
    */
-  *boundaryHalfedgesOutLoop(start = this.halfedge) {
+  *freeHalfedgesOutLoop(start = this.halfedge) {
     for (const halfedge of this.loopCW(start)) {
-      if (halfedge.face === null) {
+      if (halfedge.isFree()) {
         yield halfedge;
       }
     }
     return null;
   }
 
   /**
-   * Returns a generator of free halfedges (i.e. without face) arriving to this 
-   * vertex.
+   * Returns a generator of free halfedges arriving to this vertex.
+   * @param start The halfedge to start, default is vertex halfedge
+  */
+  *freeHalfedgesInLoop(start = this.halfedge) {
+    for (const halfedge of this.loopCW(start)) {
+      if (halfedge.twin.isFree()) {
+        yield halfedge.twin;
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Returns a generator of boundary halfedges starting from this vertex.
+   * @param start The halfedge to start, default is vertex halfedge
+   */
+  *boundaryHalfedgesOutLoop(start = this.halfedge) {
+    for (const halfedge of this.loopCW(start)) {
+      if (halfedge.isBoundary()) {
+        yield halfedge;
+      }
+    }
+    return null;
+  }
+  
+  /**
+   * Returns a generator of boundary halfedges arriving to this vertex.
    * @param start The halfedge to start, default is vertex halfedge
   */
   *boundaryHalfedgesInLoop(start = this.halfedge) {
     for (const halfedge of this.loopCW(start)) {
-      if (halfedge.twin.face === null) {
+      if (halfedge.twin.isBoundary()) {
         yield halfedge.twin;
       }
     }
@@ -81,7 +105,7 @@ export class Vertex {
       return true;
     }
     for (const halfEdge of this.loopCW()) {
-      if (halfEdge.face === null) {
+      if (halfEdge.isFree()) {
         return true;
       }
     }

src/operations/addEdge.ts

@@ -74,7 +74,7 @@ export function addEdge(
 
 
   // Update refs around v1 if not isolated
-  const in1 = v1.boundaryHalfedgesInLoop().next().value;
+  const in1 = v1.freeHalfedgesInLoop().next().value;
   if (in1) {
     const out1 = in1.next;
     h1.prev = in1;
@@ -87,7 +87,7 @@ export function addEdge(
   }
 
   // Update refs around v2 if not isolated
-  const in2 = v2.boundaryHalfedgesInLoop().next().value;
+  const in2 = v2.freeHalfedgesInLoop().next().value;
   if (in2) {
 
     const out2 = in2.next;

src/operations/addFace.ts

@@ -82,7 +82,7 @@ function makeHalfedgesAdjacent(
 
   // Find a boundary halfedge different from out.twin and in 
   let g: Halfedge | null = null; 
-  const loop = halfOut.vertex.boundaryHalfedgesInLoop(halfOut);
+  const loop = halfOut.vertex.freeHalfedgesInLoop(halfOut);
   let he = loop.next();
   while (!g && !he.done) {
     if (he.value !== halfIn) {

src/operations/cutFace.ts

@@ -101,7 +101,7 @@ export function cutFace(
   h2.prev = h1;
 
   // If v1 is not part of face, get any outgoing halfedge
-  out1 = out1 ?? v1.boundaryHalfedgesOutLoop().next().value;
+  out1 = out1 ?? v1.freeHalfedgesOutLoop().next().value;
 
   // Update refs around v1 if not isolated
   if (out1) {
@@ -116,7 +116,7 @@ export function cutFace(
   }
 
   // If v2 is not part of face, get any outgoing halfedge
-  out2 = out2 ?? v2.boundaryHalfedgesOutLoop().next().value;
+  out2 = out2 ?? v2.freeHalfedgesOutLoop().next().value;
 
   // Update refs around v2 if not isolated
   if (out2) {