Using tiny texture for UV mapping(Overlapped UV, Lightmap)

passerby_z
Wed, 28 Jul 2021 15:31:47 +0000
Asset Creation

I am an individual developer, so as you can guess, I need to save efforts to create assets as much as possible. I could save some effort using low poly, but UV painting has been a headache for years.

Then recently I found quite interesting technique from this youtube.

Easy Low Poly Character Modeling in Blender 2.9x

The Youtuber just uses a 8x8 pixels image to paint meshes. This is possible because he shrinks faces into small pixels in UV mapping. For example, the UV mapping becomes like this. Please note that the entire UV maps are actually on a 8x8 pixel image, and some pixels has very tiny shrunken faces.

It works okay in Blender as below.

If I import the FBX into Unreal engine, it looks okay in the beginning as below.

But when I build the project, It shows the following error,

‘Object has overlapping UVs’

‘Lightmap UV are overlapping by 85.3%. Please adjust content - Enable Error Coloring to visualize’

and becomes like below

It seems that Unreal engine applies a special rendering technology during light building, and makes some part of roof black. I guess maybe I can disable “the special rendering technology” and leave the roof color as it was in Blender, but I am not sure how to do it.

I know this is not a correct way of using the engine, but this technique is really helpful for an individual developer like me. Is there any way I can use UV mapping this way?

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