# Inconsistent face visibility even though normals are facing the same direction **URL:** \ **Category:** Questions\ **Created:** [April 15, 2020, 7:51am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008 "2020-04-15T07:51:44Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 15, 2020, 7:51am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/1 "2020-04-15T07:51:44Z")
Hello Babylonians! So i am working on this triangulated mesh, triangulated with an [delaunay algorithm implementation](https://www.npmjs.com/package/delaunay): ![wireframe](https://us1.discourse-cdn.com/flex024/uploads/babylonjs/original/2X/1/1468f3c361eddf7a09b02635bf057a131cd9f7f1.jpeg) My issue is now that the faces ‘face’ in different directions. Here a view w/o wireframe from the top: ![top](https://us1.discourse-cdn.com/flex024/uploads/babylonjs/original/2X/5/55cde31312555c9a613d65fc7c17c2ab2ab957f5.jpeg) Here a view from the bottom: ![bottom](https://us1.discourse-cdn.com/flex024/uploads/babylonjs/original/2X/3/33a6198b08c7c3b00faaba61ba3272f25af8dcd4.jpeg) The thing is: I am not creating normals with [VertexData.ComputeNormals](https://doc.babylonjs.com/api/classes/babylon.vertexdata#computenormals) but by creating a buffer with 0.0, 1.0, 0.0 x the amount of vertices i have. So i guess my normals are fine. I am wondering if it might have to do with the cw or ccw definition of the triangles in the indices buffer (this is the next thing i am gonna check). Even though i am wondering if cw/ccw triangles and normals may interfere somehow? And i know i could use backfaceculling = true but that wouldn’t work when texturing i guess. And it is a hacky solution in my opinion. Btw. Long time no see! I am very happy to work with Babylon.js again. Hope you all are doing well… Greetings from Thuringia, Germany. ---
**Author:** ![JohnK](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/johnk/32/26764_2.png) [@JohnK](https://forum.babylonjs.com/u/JohnK)\ **Post date:** [April 15, 2020, 9:01am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/2 "2020-04-15T09:01:43Z")
Welcome back. CW and CCW difference is the problem, in the following PG facet 0, 1, 2 is CCW and 3, 4, 5 CW, both have normals in same direction. [https://www.babylonjs-playground.com/#VKBJN#508](https://www.babylonjs-playground.com/#VKBJN#508) ---
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 15, 2020, 9:10am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/3 "2020-04-15T09:10:55Z")
Before i (try to) implement a solution. Is there some function to recompute index order based on normals? ---
**Author:** ![JohnK](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/johnk/32/26764_2.png) [@JohnK](https://forum.babylonjs.com/u/JohnK)\ **Post date:** [April 15, 2020, 9:15am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/4 "2020-04-15T09:15:46Z")
Not that I know of, you would need to create your own. Did you know about [Use PolygonMeshBuilder - Babylon.js Documentation](https://doc.babylonjs.com/how_to/polygonmeshbuilder) or even [Create Parametric Shapes - Babylon.js Documentation](https://doc.babylonjs.com/how_to/parametric_shapes#non-regular-polygon) ---
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 15, 2020, 10:26am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/5 "2020-04-15T10:26:26Z")
Yes i know about those. I used those in an earlier version of the project. ---
**Author:** ![JohnK](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/johnk/32/26764_2.png) [@JohnK](https://forum.babylonjs.com/u/JohnK)\ **Post date:** [April 15, 2020, 1:20pm UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/6 "2020-04-15T13:20:10Z")
Are you happy to create a function that would recompute index order based on normals? ---
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 15, 2020, 1:48pm UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/7 "2020-04-15T13:48:24Z")
I guess that might be a rabbit hole. Changing from ccw to cw is easy. You just need to swap a pair of indices. But how do i find out that an index order ist ccw?! I will try out earcut instead of the other triangulation algorithm to see if its results have no need for recomputing index order. ---
**Author:** ![JohnK](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/johnk/32/26764_2.png) [@JohnK](https://forum.babylonjs.com/u/JohnK)\ **Post date:** [April 15, 2020, 3:23pm UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/8 "2020-04-15T15:23:30Z")
[https://www.babylonjs-playground.com/#VKBJN#509](https://www.babylonjs-playground.com/#VKBJN#509) Above PG will recalculate index order if needed. It is based on all vertices of all triangles having the same normal (0, 0, -1), some tweaking needed if the normals are in a different direction ---
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 16, 2020, 6:38am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/9 "2020-04-16T06:38:24Z")
Thanks John! In my implementation i used normal.equalsWithEpsilon(Vector3.Down()) ([see API](https://doc.babylonjs.com/api/classes/babylon.vector3#equalswithepsilon)). To see which indices are the ones being ordered ccw. But i may could also use if(normal.equalsWithEpsilon(Vector3.Up()) == false). One new thing ocurred that i don’t understand: some of my normals are (0,0,0). How could that happen? I made a [playground](https://playground.babylonjs.com/#92YIVJ#14) Version #14 is the “default” scene without any index reordering. Update on [playground version 32](https://playground.babylonjs.com/#92YIVJ#32) I added the code to compute the normals and there are no 0,0,0 normals (check the console, i console.log() the values). Weird. Update: This issue is resolved!! 🤪 Update on [playground 52](https://playground.babylonjs.com/#92YIVJ#52): Determine wether facet is cw or ccw based on the normal. I realize that the facets that i am looking at from above are the facets that are ccw. After the reordering you don’t see anything because all facets are facing to negative y. Update on [playground 53](https://playground.babylonjs.com/#92YIVJ#53): So if i am reordering facets that are similar to Vector3.Up() then i see my mesh from above. That is a little confusing because in my mind it should be exactly the opposite. I must have some knot in my head. ---
**Author:** ![JohnK](https://sea2.discourse-cdn.com/flex024/user_avatar/forum.babylonjs.com/johnk/32/26764_2.png) [@JohnK](https://forum.babylonjs.com/u/JohnK)\ **Post date:** [April 16, 2020, 8:46am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/10 "2020-04-16T08:46:25Z")
> [@mamu](#): > > That is a little confusing because in my mind it should be exactly the opposite. Swap the cross product over [https://playground.babylonjs.com/#92YIVJ#56](https://playground.babylonjs.com/#92YIVJ#56). Since the cross product is non commutative order of vectors matter. Note I changed to an ArcRotateCamera because I like to see all around the mesh easily during construction. Also note from my PG [https://www.babylonjs-playground.com/#VKBJN#509](https://www.babylonjs-playground.com/#VKBJN#509) that I declared my vectors prior to using them in a loop and then calculated their values using `set`, `subtractToRef` and `CrossToRef`. By reusing the same variables I cut down on how often Garbage Collection is called. Could not see where you got (0, 0, 0) for any normals so cannot comment on this. ---
**Author:** ![mamu](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@mamu](https://forum.babylonjs.com/u/mamu)\ **Post date:** [April 16, 2020, 8:56am UTC](https://forum.babylonjs.com/t/inconsistent-face-visibility-even-though-normals-are-facing-the-same-direction/10008/11 "2020-04-16T08:56:32Z")
Ah okay. I used the equation from [https://gamedev.stackexchange.com/a/152993](https://gamedev.stackexchange.com/a/152993). Does he assume some other coordiante system? Will keep in mind the ArcRotateCamera for future PGs of that manner 😉 Ah thanks for noting that. I was wondering why you wrote your code like this. Now it makes totally sense. I will apply that to my implementation. Surely there are some other places i can apply this to. Anyways, i mark your last answer as a solution to my post, since all issues are resolved. Thanks a lot John!