Non-Planar Quads

Hi all,

I’m new to Blender.
I’d like to use Blender for creating game assets for Unity, and I know Unity does not render non-planar quads well.

I have two questions:

  1. Is there a technique for minimizing the number of non-planar quads during modeling, without having to check each new quad? (I know about mesh analysis, but using it to adjust new quads interrupts the workflow)

  2. What is Unity’s threshold for non-planar quads? What I mean is will Unity render quads that are almost planar (say, deformed by 2 or 3 degrees) as badly as very non-planar quads? Or is there a deformation angle below which the rendering of a non-planar quad is the same as the rendering of a planar quad?

Thanks in advance.

Unless you’re modelling something made of only perfectly flat surfaces , you’re always going to run into non planar faces, even more if you’re modelling low poly characters for games that own animations can distort faces that were perfectly planar at first.

Usually when i had a game asset that had one or more non planar face that were deformed enough to not being displayed by a specific engine, i simply triangulated such quad, because triangles are always planar and so will fix a “non planar quad with too much distorted angle” problem easily.

To make it fast, first simply complete your model the best way you can without worrying too much about deformed quads.

Once done, enable the Mesh : 3D Print Toolbox addon that comes with Blender (File -> User Preferences -> Addon panel and in the Mesh category).
Select your model and go to Edit Mode, on the toolshelf click on the now present “Print3D” tab (blender 2.70) and click on the “Distorted” button

By default the angle it will check for non planarity is 45° but you can lower or increase it according to your need.
It will display then display the number of faces that it found to be non planar according to that angle

Just click on that button and it will automatically select those faces on your model.

From there a simple CTRL+F -> Triangulate will fix your problem.
And if triangulated face break the shading by having the new edge not in the correct orientation, just select the edge and press CTRL+E -> Rotate Edge

Thanks, Sanctuary.

I activated the addon, played around with it and and found it very useful.

What is unclear to me is how thorough I have to be. Is a distortion of 5 degrees acceptable, or do I have to triangulate also 5-degree-distorted quads?

Is there a general rule of thumb for each game engine, or is it case-by-case even within a game engine?


i think 5, 10 , 20 or even 30 and probably more degrees should be perfectly acceptable, i doubt any modern game engine would have trouble with them unless an animation distort them to some extreme.

Now for finding -the- value that may give trouble it’s more difficult because there’s no standard with game engines as they’re each coded differently, so it’s indeed a case-by-case.
But a value of 45 should be some good test as with animation those non planar faces may distort more.
But to be sure, maybe get it to +/- 20/30 so you have some margin to breath around.

And that without even mentionning graphic cards drivers that may manage those non planar quads differently from a card to another.