diff --git a/web/app/brep/geom/impl/nurbs.js b/web/app/brep/geom/impl/nurbs.js
index cc1c58ce..d6582529 100644
--- a/web/app/brep/geom/impl/nurbs.js
+++ b/web/app/brep/geom/impl/nurbs.js
@@ -85,8 +85,11 @@ export class NurbsSurface {
     this.verb = verbSurface;
   }
 
-  coplanarUnsigned(other, tolerance) {
-    const tess = this.verb.tessellate({maxDepth: 3});
+  toNurbs() {
+    return this;
+  }
+
+  coplanarUnsignedForSameClass(other, tolerance) {
+    throw 'not implemented'
   }
-  
 }
\ No newline at end of file
diff --git a/web/app/brep/geom/impl/plane.js b/web/app/brep/geom/impl/plane.js
index 422c44a1..8a93fb18 100644
--- a/web/app/brep/geom/impl/plane.js
+++ b/web/app/brep/geom/impl/plane.js
@@ -52,16 +52,14 @@ export class Plane extends Surface {
     return this.__3dTr;
   }
 
-  coplanarUnsigned(other, tol) {
-    return other instanceof Plane && 
-      math.areVectorsEqual(this.normal.multiply(this.w), other.normal.multiply(other.w), tol);
+  coplanarUnsignedForSameClass(other, tol) {
+    return math.areVectorsEqual(this.normal.multiply(this.w), other.normal.multiply(other.w), tol);
     //TODO: store this.normal.multiply(this.w) in a field since it's constant value
   }
 
-  equals(other, tol) {
-    return other instanceof Plane &&
-      math.areVectorsEqual(this.normal, other.normal, tol) &&
-      math.areEqual(this.w, other.w, tol);
+  equalsForSameClass(other, tol) {
+    return math.areVectorsEqual(this.normal, other.normal, tol) &&
+           math.areEqual(this.w, other.w, tol);
   }
 
   toParametricForm() {
diff --git a/web/app/brep/geom/surface.js b/web/app/brep/geom/surface.js
index 3d655a20..1f81b7ab 100644
--- a/web/app/brep/geom/surface.js
+++ b/web/app/brep/geom/surface.js
@@ -13,8 +13,30 @@ export class Surface {
     throw 'not implemented';
   }
 
+  coplanarUnsignedForSameClass(other, tol) {
+    throw 'not implemented';
+  }
+
+  equalsUnsignedForSameClass(other, tol) {
+    throw 'not implemented';
+  }
+
   isSameClass(other) {
     return this.constructor.name == other.constructor.name;
   }
+  
+  coplanarUnsigned(other, tol) {
+    if (this.isSameClass(other)) {
+      return this.coplanarUnsignedForSameClass(other, tol)
+    }
+    return this.toNurbs().coplanarUnsignedForSameClass(other.toNurbs());
+  }
+
+  equals(other, tol) {
+    if (this.isSameClass(other)) {
+      return this.equalsForSameClass(other, tol)
+    }
+    return this.toNurbs().equalsForSameClass(other.toNurbs());
+  }
 }
 Surface.prototype.isPlane = false;