[Substance Painter-UE4] Metallic and Specular export process?

Croftyness

Hey,

I'm really enjoying substance painter right now. However I'm confused as to how I can export Specular maps for UE4. IN SP the only shader option I have is Metal-Rough, from my UE4 understanding metalness is not what I want as I've been painting specular maps. In the export options there IS a gloss-specular option which is what I want, however doesn't export the maps I want.

What would that standard file set-up and export process be for albedo, spec, rough and NM from substance painter to UE4?

Much appreciated.

WarrenM

UE4 wants albedo, metal, roughness and normal maps. It doesn't use specular really - it's legacy.

Croftyness

But I though specular provided a range of reflectance while metallic only had two states, metal or not.

WarrenM

Metal should be used to denote metal or not-metal. Basically black and white 99% of the time.

Variances in reflections should be done through the roughness map.

Croftyness

But for clothing I would use a specular map and roughness map. Is this incorrect? I would only consider using a metalness map if I was making something like a gun.

almighty_gir

specular in UE4 is a multiplier on the internal value of 0.04 for non metals, that's all.

WarrenM

Well, cloth would be black in the metal map and then whatever interplay you get between the albedo, roughness and normal map.

Croftyness

So in substance painter, what would a typical export look like for something like clothing? Perhaps with blood on it.

almighty_gir

uh... an albedo map with the cloth and blood colour, a black metallic map, and whatever roughness values in your roughness map?

Bek

Substance painter on export has the option to export packed maps for various engines, including ue4. I assume that's what you meant by 'metal-rough shader' in your OP.

Croftyness

Cool cheers. Out of interest does anyone know if you can use the UE4 HDRI_Epic_Courtyard in substance painter?

Croftyness

Bek wrote: »

Substance painter on export has the option to export packed maps for various engines, including ue4. I assume that's what you meant by 'metal-rough shader' in your OP.

Ye, cheers. : )

ActionDawg

You will likely run into trouble because cloth breaks the assumptions of the shading model. Clothing has a very different distribution to its specular reflection than most materials due to being composed of tiny translucent fibers. Ideally you'd want to use a custom cloth shader that fully models these, but aside from that you could look into hacking asperity scattering into the shader by modulating the roughness. I'd take a look at The Order's SIGGRAPH talk if you're interested: http://blog.selfshadow.com/publications/s2013-shading-course/rad/s2013_pbs_rad_notes.pdf
Their cloth talk starts at the bottom of page 5. There's also supplementary content here http://blog.selfshadow.com/publications/s2013-shading-course/

Another thing to note is that the specular input (which really shouldn't be touched unless you have a good reason) has a default value of 0.5. This gives you the 0.04 (4% specular reflection) almighty_gir mentioned, so naturally bringing it up to a value of 1 will bring that to 0.08. You might find it necessary to boost that based on view angle if you try to approximate some kind of cloth shading.

In the end though it may not make a visually significant difference to do all that work