Dealing with Flipped Normals and therefore textures painted on the backface of model

Hi guys,

So often times I get a SketchUp model from a client to be used in our pipeline of rendering in 3DS Max.
So the main issue I always have, is that all their models have flipped normals all over the place, sometimes in the smallest of places (i.e. inside of window sills) but enough to be visible in the render.

Now I can easily flip the normals and fix the model thanks to a lot of helpful plug-ins, However the problem is then re-applying the materials after they have been flipped. I could just select each section see what was applied on the backface and then apply it to the front. But when there’s lots of flipped polys this can be very time consuming and I could easily miss some.

Since this happens with every model I get from SketchUp, I need more of an automated way of doing this as going through the model bit by bit isn’t feasible.

What I would love to be able to do

  1. Select only the bacfaces visible to the camera
  2. I can then reverse all the selected faces.
  3. Keeping the selection I can Run Plug-in - “TIG: Reverse Face Tool” - therefore applying the backface material to the front face.
  4. I can then delete the back face material on the entire model.

Thanks to anyone who can help or knows of a better way,

Have you tried selecting a front face then right clicking and selecting ‘orient faces’?

Following this you can use ‘material tools’ extension by @thomthom and select ‘remove all backface materials’.

Maybe you have tried this workflow already?

Hi Aroberts,

Thanks for the reply. Unfortunately that doesn’t work as it WILL flip the orientation of some faces but then it just flips correct faces incorrectly.

*Also a big must is retaining the selection when I’ve flipped them as I need to know what materials to fix

Ok, are you able to share a model as an example?

Unfortunately I can’t as I don’t have permission and the model in question is WIP. I may be able to share a screen grab?

This is the normal issue I have

‘Orient Faces’ works perfectly when applied to a face of a solid (in editing context) or some open structures but often “fails” at some point for this purpose: to the camera" depending on how faces are connect.
The operation loops through all faces in the geometry and can’t always decide how the new orientation (back <> front) should be, based on the other connecting faces: conflicting sides around.
A plugin that deals with what sort of face (back <> front) is exposed to the camera could make that decision per face. There’s an easier decision to make here.

Good explanation G.H.

And to be honest as I’ve stated before the main issue isn’t flipping the normals. It’s more the complication of selecting all the faces which are incorrectly faced (red is the image) and nothing else. If i could do that it would be great as I can just send the back material to the front and then just reverse the faces.

That’s my end goal anyway

How about with the selection tools plug in in that case?

Is it just for rendering?
If so, can you explode all onto same level and then use ‘selection toys’ by @thomthom

  • Select face with material requiring reversal
    *Right click and navigate to ‘select’
    *Navigate to ‘Active with selected materials’
    All required faces will then be selected based on that material.
    Then you can modify as required?
1 Like

You can use the Selection Toys plugin > Same Direction Faces

You also can ask the client to learn how to properly create 3D models in SketchUp.


I’ll give it a shot and let you know. Fingers crossed

ooooh Intriguing I’ll try that too.

Thanks guys. I’ll test these out and see where I end up

1 Like

Tig’s Fix Reversed Face Materials should sort you out.


“You also can ask the client to learn how to properly create 3D models in SketchUp.”

Haha that’s what I wish I could say haha. It’s getting close to that.

Yep have that installed. Stated it in my first comment but thanks.

It’s not the same plugin.

It isn’t the same as this?

Ok, I thought you had his other that just reverses faces. But you should be able to do it with that.

So another problem with this sketchUp model. They’ve applied two materials to a lot of this model, for no ■■■■ reason. So if I select by material it selects unwanted parts the model. The model is so messy.

@Box No problem all help is appreciated.

Alright thanks everyone. Got it sorted now with a combination of everyones helps.

The method was simpler than I thought and you were all probably a few steps ahead of me ha.

  1. ‘Selection tool’ - right click - Select Same Direction faces
  2. ‘TIG: Reverse faces tool’ - Fix Reversed Face Materials [Forced]
  3. Repeat for each axis.

You’re all great.
Thanks again

1 Like