keep sketches of consumed shells

web/app/brep/io/brepIO.js

@@ -21,7 +21,12 @@ export function readBrep(data) {
       format: 'verbose',
       data: normalizeTesselationData(faceData.tess, inverted, faceData.surface.normal)
     };
-      
+    if (faceData.ref !== undefined) {
+      bb._face.data.externals = {
+        ref: faceData.ref
+      }  
+    }  
+    
     for (let loop of faceData.loops) {
       bb.loop();
       for (let edgeData of loop) {

web/app/cad/model/mshell.js

@@ -27,7 +27,7 @@ export class MBrepShell extends MShell {
     let vertexCounter = 0;
 
     for (let brepFace of this.brepShell.faces) {
-      const mFace = new MBrepFace(this.id + '/F:' + faceCounter++, this, brepFace);
+      const mFace = new MBrepFace(brepFace.data.id || (this.id + '/F:' + faceCounter++), this, brepFace);
       this.faces.push(mFace);
     }
 

web/app/cad/scene/wrappers/entityIO.js

@@ -1,6 +1,36 @@
 import {readBrep} from '../../../brep/io/brepIO';
 import {MBrepShell} from '../../model/mshell';
 
-export function readShellEntityFromJson(data) {
-  return new MBrepShell(readBrep(data));  
-}
+export function readShellEntityFromJson(data, consumed) {
+  
+  let refIndex = indexFacesByRef(consumed);
+
+  let shell = readBrep(data);
+  for (let face of shell.faces) {
+    let ref = getRef(face);
+    if (ref !== undefined) {
+      let consumedFace = refIndex.get(ref);
+      if (consumedFace) {
+        face.data.id = consumedFace.id; 
+      }
+    }
+  }
+  return new MBrepShell(shell);  
+}
+
+function indexFacesByRef(shells) {
+  let index = new Map();
+  if (shells) {
+    for (let shell of shells) {
+      for (let face of shell.faces) {
+        let ref = getRef(face.brepFace);
+        if (ref !== undefined) {
+          index.set(ref, face);
+        }
+      }
+    }
+  }
+  return index;
+}
+
+const getRef = brepFace => brepFace && brepFace.data.externals && brepFace.data.externals.ref;