Trim Sheets are a fantastic asset creation method to make your textures go further on Assets in Mona. Fantastic for environment development.
Trim Sheet Video Tutorial
Trim sheets are a common technique to increase your texture quality on 3D assets while at the same time reducing the number of materials/textures on them. In a Mona space, reducing materials is a very important approach to improving how a space works in a browser as this reduces drawcalls.
A drawcall is the number of things that the computer has to call on the computer to draw something. This includes things like models and materials. So trying to create assets with as few materials as possible is a great technique for optimisation.
The Trim Sheet process is basically creating a texture that allows you to apply different details (from the same texture) to a model by unwrapping the model in interesting ways. This texture can be used on multiple objects, or even just one large one, with fantastic quality results.
Most AAA games use this technique a lot on environment assets in order to have fantastic quality, save time on development, keep assets together with a set theme, and many other reasons.
As an example, lets look at a simple texture that was made in less than an hour using Blender for the base shapes, then Substance Painter for the textures, as a quick example of how to use it in interesting ways. This texture has diffuse (2048x2048), metallic/smoothness(1024x1024), and normal maps (2048x2048).
Of course how you create your Trim Sheet is up to you. Some people use ZBrush, others use the 3D Creation tool such as Blender, Maya etc. entirely. Whatever creates the assets that you want to add to your 3D asset.
Creating a base asset in Blender
Adding some texture in Substance Painter
Final Maps to use as a Trim Sheet
The main thing to consider is that if you are tiling in any direction such as vertically or horizontally, the edge will tile smoothly. This will allow you to extend your 3D asset polygons across that border without issue. Assets do not need to be in the 0-1 area (the square that most 3D applications use when unwrapping objects) of a UV map, so by positioning / rotating / scaling the UVs in interesting ways you can create fantastic assets with a lot less information. That said, a texture could tile vertically, or not at all, depending on your needs as a trim sheet.
Once you have one or more trim sheets to apply to your asset we can unwrap the asset UVs to assign the texture to the polygons on the object. By doing this we can use the one texture to create entire assets without too much hassle.
The result in Unity
If you look at the unwrapped UVs of the asset it does not look like it makes much sense, but in this approach the result is more important. And each section of the asset needs to be considered separately.
The Unwrapped result in Blender
This is of course a very different process than that used for 'hero' assets that have all of the asset within the 0-1 area of the model. This approach allows for more unique assets, but requires a lot more time in creating those assets from both the modelling, unwrapping, baking etc.
Every asset requires consideration on what is the best technique for that asset. Things like buildings and simple props in a space are fantastic use cases of using Trim Sheets. Things like characters, statues, and unique assets with custom details are usually created with their own textures as Hero assets.
For an example of professional use of trim sheets you can look at the following example by Tor Frick. This takes trim sheets to the next level using very few textures to make whole environments!
Tor Frick example of Trim Sheets