In this very short tutorial, we’ll see how to fix a Normal Map that, when imported into Unreal Engine, makes surface details appear incorrectly lit.
Video Transcript
Hello everyone! In this very short tutorial, we’ll see how to fix a Normal Map that, when imported into Unreal Engine, makes surface details appear incorrectly lit.
One possible cause of this type of issue is that the map uses the OpenGL convention, while Unreal Engine expects the DirectX convention. This can happen, for example, when the Normal Map has been exported using the OpenGL convention from Substance Painter or other software.
If this is what’s causing the issue, all you need to do to fix it is invert the green channel of the Normal Map by enabling the Flip Green Channel option in the Unreal Engine editor. Let’s see how to do it.
The 3D model I’m using for this example contains a metal platform whose surface details are not modeled into the geometry, which is flat, but are simulated using a Normal Map. I’m adjusting the camera and directional light to make the light and shadow on these details more noticeable, so we can identify the problem more easily.
To get a better look at the surface, I switch to the Detail Lighting view mode, which applies a neutral material while preserving the Normal Maps of the original materials. This allows us to examine the light and shadow on the surface details without being distracted by the texture colors.
I double-click the Normal Map in the Content Browser to open it in the Texture Editor. In the search field of the Details panel, I type Flip to find the Flip Green Channel option. The tooltip for this checkbox tells us that this option is specifically useful for some Normal Maps.
When we enable Flip Green Channel, we can see the difference both in the image Texture Editor and in the 3D view. Before closing the Texture Editor, remember to click Save This Asset.
I switch back to the Lit view mode to show you the difference with and without Flip Green Channel on the fully textured and lit object.
And that’s it for this very short tutorial! As with my other videos, the text version of this tutorial and additional resources are available on my website, including in other languages, at the link in the description. If you found this tutorial helpful, you can thank me by leaving a Like and subscribing to the channel! See you soon!