Toolbag baking issues - why is there no metalness output?

quasmaster

Hi!

I’m new here and I just wanted to say I really like the new Toolbag (3.01), especially the approach to baking. But there are also a few issues I have with it - or simply did not fully grasp yet. My main question is if it is possible to set up a baker so that it outputs a metalness map?

To clarify, I create a PBR texture set in Substance Painter for my highpoly mesh. After importing the high- and low-poly meshes into Toolbag I set up the material (UE4) and apply it to the high-poly mesh. I then set up the baker and check the boxes for all the necessary channels - sadly, there is no metalness to be found. So basically Toolbag converts my perfectly fine metalness maps into specular maps everytime I hit bake. Though everything I really want is to pass trough the values from the high-polys metalness map to the low-polys UVs.

Is there a particular reason why metalness is not supported as an export format? I know, there is nothing wrong with specular maps but for convenience reasons I prefer to stick with the metalness workflow that works fine in UE4 when I bring in the maps directly from Substance.

Also, albedo maps seem to get slightly darker when ran trough the baker. Is there a particular reason for those changes in value? The gloss map the baker puts out can be inverted and used as roughness - so at least that works. An option to export emmissive maps would be a great addition too!

I added a screenshot to show whats going on:

I really love the baking features in Toolbag but the lack of flexibility regarding the export options is a bit disapponting. I also gave the Scene importer plugin for Unreal a try but as the baked preview materials all lack a metalness channel the shaders get all messed up and I get warningswhile importing in UE4. It all works fine if I use the UE4 material preset with the according maps - which I do not get as the baker is not giving me the metalness map.

Any help and clarification on those issues is welcome! Thanks a lot!

EarthQuake

A metalness output is not currently support, but is something we plan to add in the future.

quasmaster

Ok, great to hear! Thanks for the answer.

A somewhat cumbersome workaround for now is to create a second set of materials for all the source meshes where only the metalness map is plugged into the albedo channel. This way I can transfer the metalness map from my high to my lowpoly anyways. 

As for the slightly darker albedo I got after the export, this was actually caused by a wrong material preset. I accidentally used the default material preset where the albedo diffuse color is set to only 74% white. Still strange that this color value has an influence even though a map is applied?

EarthQuake

quasmaster said:

Ok, great to hear! Thanks for the answer.

A somewhat cumbersome workaround for now is to create a second set of materials for all the source meshes where only the metalness map is plugged into the albedo channel. This way I can transfer the metalness map from my high to my lowpoly anyways. 

As for the slightly darker albedo I got after the export, this was actually caused by a wrong material preset. I accidentally used the default material preset where the albedo diffuse color is set to only 74% white. Still strange that this color value has an influence even though a map is applied?

Yes, loading your metalnessmap into the diffuse slot (or specular slot) is a good work around for the time being. Just make sure you go to the options (gear icon) and turn off sRGB for that texture.

Re: color value, that is working as intended. The color picker value multiplies on top of the albedo input, to allow for further adjustments directly in Toolbag. This is the case with all inputs that have both a textures lot and and a parametric color value.

quasmaster

Thanks again for the reply! 

Yeah, I made sure the sRGB checkbox is deactivated after adding the metalness maps to the albedo channel.

Just not sure how the transfer via the specular channel is supposed to work? As I described above, when I set up a UE4 material with metalness as source material, the bakers always convert the metalness values into specular values. Or is there something I have missed so far?

And is there a particular reason why the roughness values are inverted when baking? No big issue as I easily can invert them back in Unreal to how they should be - only that it's another thing to keep in mind.

EDIT: Nevermind the last question. It's a gloss map and not a roughness map that gets exported by the bakers - and those have inverted values as far as I know.

EarthQuake

quasmaster said:

Thanks again for the reply! 

Yeah, I made sure the sRGB checkbox is deactivated after adding the metalness maps to the albedo channel.

Just not sure how the transfer via the specular channel is supposed to work? As I described above, when I set up a UE4 material with metalness as source material, the bakers always convert the metalness values into specular values. Or is there something I have missed so far?

And is there a particular reason why the roughness values are inverted when baking? No big issue as I easily can invert them back in Unreal to how they should be - only that it's another thing to keep in mind.

EDIT: Nevermind the last question. It's a gloss map and not a roughness map that gets exported by the bakers - and those have inverted values as far as I know.

RE spec/metalness map - I meant this as a suggestion just for baking the map out, you could put it in the albedo, specular, even the gloss slot it's not particularly important which slot it does into. There's no real reason why it would be better to drop it in a different slot, sorry if this was confusing, it was a somewhat random thought. For importing your content into Unreal, it's best to use the standard Unreal materials, which are normal/albedo/roughness/metalness as you've discovered.

RE gloss/roughness. Yep, Toolbag uses a gloss map, which maps black = matte and white = glossy. There is an invert tick on the gloss input to support roughness maps, and if you check that it will invert it for the resulting baked content as well.