What the idea would constitute of: A simulated light source cicle glow that you can scale and move around the canvas. Special layers act as different parts of the PBR/game development workflow which give previews of what they would look like in a game environment with shaders working.

This could potentially be expanded with a 3D view port window where you have a cube that you can spin around so you can preview the effects even better while having two or more light sources.


The point of this would be that you could easily create game ready textures in Krita using it's powerful seamless preview wrapping mode (W) while having a chance to preview them before exporting reducing a lot of time.

A export to export each selected map type and it's layers would also be required.


Special Layers that represent different PBR and game design maps:


Metalness layer (reacts to light simulating texture to be more metallic or less making it a varying degrees of shininess

metal= white pixels
non metall= black pixels
Darker and lighter greys don't really act as a middle ground. (If this post is true: "https://polycount.com/discussion/171689/pbr-the-problem-with-greyscale-metalness" ) So there could be an option to force a brush to paint full black or white on this layer depending if the selected colour is closer to white or black in darkness.

G"rey values can also be used for materials that partially metallic; however, these are generally quite rare. Usually, when a metal object has any sort of coating, it acts as an insulator." (So generally for a coating it will be painted as a non metallic on a metalness map


"Colour of reflection is defined by base colour" (base colour is the the normal layers you make. For pbr it should not have painted shadows detailed in. It should be flat sort of like scanning a flat image in a scanner. The normal maps, roughness and metallic based on what you are making will create the final illusion of detail. Base colour is commonly refereed to as an Albedo map "when metallic input is one. For non-metals, you have no control over reflection colour."

https://www.chaosgroup.com/blog/understanding-metalness

roughness

Makes a texture less or more rough

"The input is a grayscale value from 0 (smooth) to 1(rough)"


Other maps that are essential or work well with a PBR implementation to KRITA:

Normal Map
Fakes height detailed based depending on the directional values used. Was used way before PBR was added as a workflow to games.

Documentation from Unity: https://docs.unity3d.com/Manual/StandardShaderMaterialParameterNormalMap.html

Height Map
More detail than a normal map but more intensive. So generally not used for game textures. It's commonly used for generating a landscape Either way it would be a good feature to go along with the light simulation if it can interact with it by faking shadows or 3d viewport

Alpha Map/transparency
Black or White pixels determine what areas will be invisible on the canvas when this map is show. This would work in a game engine as well to make pieces of a texture invisible or transparent.

Emission Map
Black is the background then any other colour can create a glow such as green. You should have a slider to preview intensity in real time as you see all the other layers.

Misc Maps:

Cavity Map
Black is the background then any other colour can create a glow such as green. You should have a slider to preview intensity in real time as you see all the other layers.

https://www.cg3dankfun.com/improve-organic-textures-cavity-map_by-paul-h-paulino/

Curvature Map

http://wiki.polycount.com/wiki/Curvature_map


Benefits of PBR:
"A well-crafted PBR material will "look right" even in changing lighting situations
Energy conservation - An object cannot reflect more light than it receives
>With rare exception, materials are either entirely metal or entirely non-metal - painted metal is not metal, it is paint, except for where the raw metal is exposed - you don't have a material that is 30% metallic"
https://forum.allegorithmic.com/index.php?topic=16670.0

Old game texture workflows that are used instead of metal, roughness from PBR. This would also be useful to add since a game's art style can dictate whether or not to use PBR or other texture types such as below:

specular

gloss

https://www.youtube.com/watch?v=mrNMpqdNchY


Documentation:

https://docs.google.com/document/d/1Fb9_KgCo0noxROKN4iT8ntTbx913e-t4Wc2nMRWPzNk/edit

Hi,
This is a good idea; but probably a too massive feature request that would take years and change some fundamentals stone of Krita; In short, it would require Krita to be rewritten as a 3D software, in my opinion.

That being said, the good news is a FLOSS tool already exist to do real time PBR painting with a real 3D viewport where you can add as many lamps as possible and can see your final texture in a what-you-see-is-what you get environment and paint real time on it. This is the future Blender 2.8 (in beta right now) with the Eevee viewport, you can find already tutorials about it (eg. https://youtu.be/svzKoq3vew0 ). If you do a template file in Blender with just a squary plane (a canvas) mapped to all PBR channels, you'll be able to paint material glossyness, reflection, roughness etc... in a PBR fashion (and you can put around your canvas "duplicate linked" canvas with Alt+D ; so you'll get a similar effect than the wrap-around mode).