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What is an Atlas, and how do I use them?

Hey everybody,

Quick question. I’m a Megascans user, and I saw in their library that they have Atlases. What are those? I was actually just looking for something I could use with the Grass Output tool for my landscape. Anyway, there are 3D plants and Atlases for me to choose from. Which one do I use in the grass output tool?

Thanks

An atlas has a larger image that contains several textures within it, that way you can use one texture map rather than several. In your case, it has several different grass textures within one map, so you could have different types of grass use the same texture map.

So is an atlas also an FBX file? Or is it just an image that has some opacity added to it so only the pixels with the grass on it are displayed?

Like in this example: 2. Grass Tool Actor Creation and Setup | Unreal Engine Documentation

What do they use here, Is that an atlas?

No, it’s exactly like what I said, it’s a texture that contains several textures packed together so that different objects can use the same texture map.

@junfanbl

Try and do a Content Browser search for ‘Atlas’ assets, and then open one up in UE4’s ‘Material Editor’.
I don’t do a lot with foliage… But HUD-textures for example often include several pics inside one texture…
For example the Weapon-Crosshair, the Pickup-Crosshair, a Score-Indicator / Background-Graphic etc.
Selecting an individual RGB channel out of a Texture-Sample node, lets you access each unique texture.
My read on it is they’re a shortcut vs having to manage multiple texture files when the detail level isn’t high.

It’s mostly for convenience: Texture atlas - Wikipedia

For UI in particular though, the issue is that as separate textures they need to be power of two dimensions, whereas you can drop those UI images into an atlas and they can be whatever dimensions you want because the atlas will be a power of two.

Oooh okay, well that makes sense now. Thanks for taking the time to explain that, good to learn new things!