I work in the Blender and the Unity.

In Blender the roughness and metal textures are created separately, and in Unity you need them to be in one picture. How can they be combined in a Blender?

Unity R for metal and A for roughness


This is something that is more easily done in an image editing application, from two different bakes, but it is possible to use Blender to do it, using compositing.

Start by setting your render resolution equal to the size of your texture images in properties/output/format, then, in properties/render/color management, set the Display Device to "none" to prevent any post-compositing color transform.

Next open up a compositing viewport, enable "use nodes", and create two image texture nodes. The easiest way to get these started is to just drag and drop image files into the compositor:

enter image description here

Set these images to non-color data. Again, we don't want to be doing any color transforms to the underlying data.

A simple Combine RGBA node lets us plug the output of these two grayscale images into whatever color channels we want.

Now we can f12 to render and save the render as a new image, with one image baked into the red channel and the other baked into the alpha channel.

If we weren't using the alpha channel, we could do this from a single bake, no compositing, by emitting the two channels to, for example, Red and Green emission, but unfortunately Blender doesn't support the alpha channel for baking. For this case, we need individually baked images.


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