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Consistent Bone Roll of your bones will ensure that your deformation angles are correct. Blender has some tools for this to aling your bone roll to either local or world axis which you can choose. Some manual alignement still be necessary

It is beneficial to rig animated parts, even if they are non organic. It is much easier to parent your models parts to specific bones and transfrom them than it is to fiddle with the objects itself. It also makes those bones available in Units for furthe manipulation. It also seperates an objects hirarchy from the rig hirarchy, which enables us to deal with a much less complex hirarchy of bones rather than a lot more complex hirarchy of objects and sub objects

If not using a normalmap that will overwrite the normals of the objects on a per pixel basis thru a texture, make sure you have set up your hard and soft edges orderly, so that you have no "dirty" shading going on on the model and the faces look clean.

Triangulation is also important for baking, because it determines the vertex order. See Baking for further Info

This map is different from the last gen color map called "Diffuse". It is called Albedo or Base Color couse it optimally should not contain baked in lighting. In modern shaders, when using PBR like in Unitys standard shader, there is an extra pass for the Ambient Occlusion to dynamically take place depending on the indirect lighting in the scene. That means instead of taking the drawback of having shadows on an object even if it is lit, we instead use the ambient occlusion input to get subtle self shadowing on objects, but not bake or paint that into the AO. (Rule of thumb here is: "let the lighting do its work") Emphasizing edges and cravises in you Base Color texture is ok and can enhance the objects readability, but putting greyscale AO simply on top of your Albedo map should be avoided. Instead, you should only use it as a mask and introduce some Hue shift as well to keep a clean Base Color map.

This one simple at first glance and will stay simple for objects that are supposed to look new and are made of plane, unaltered or painted metal. It is a greyscale map representing float values. White means the surface is metallic. Black means the surface is a non metal surface. Painted metal is also a non metal surface and should not contain any metallic values. With weathered and used objects , with some wear and tear, scratches and crevices will reveal some of the metal underneath, which would mean that the metallic map should be grey orr white, wherever some of that metal reveals. NOTE that when using the metallic workflow, as opposed to specualr/glossiness workflow, all non non metallic surfaces have a hard coded specular value of 0.04 in them, as this is appropriate for most non metallic surfaces in the real world. This makes them metallic workflow much simpler to stay in the bounds of creating physiically accurate results, but is also a bit limiting artistically, as it prohibits setting a surfaces specualr value directly. There are certain surfaces, especially cloithing like silk, where metallic values can be used to mimic the specualr effect. With silk, a value of about 0.5 metalness would be fine for example.

Roughness is a greyscale map which consists of greyscale float values. Each float value determines how much reflection of the environment contributes to the final render result. A total reflecting surface ´like mirror or water, would have about 0 roughness. The more roughness, the more diffues the objects highlight gets and reflection get less appearent. Glossiness, the map unity uses, is simply the invert of roughness. It should be noted that roughness is a crucial map to get right for realism. Because every object in reality has some sort of reflection, every object has some king of glossiness(or lack of rouighness) to it. And even very new objects wont look ral if there is no breakup in the surface glossiness, even if it is very subtle. Subtlty is king when authoring roughness/glossmaps. Best PRactice is to not have a glossiness feast. A good rule of thumb is that most surfaces outside of metal or water or mirror, have a roughness value of about.0.75-1 , or a gloss value of 0-0.35 . By closely observing the surfaces of the real world, and looking at reference, you can get a better graps of how to author roughness/glossines maps. But utilising roughness artistically should also not be forgotten, It is always advisable to break your surfaces roughness up and make those breakups not looking too procedural or obviously tiling. Roughness/Glossmaps take a good amount of time to author depending on the quality you are going for, cause it is such a crucial factor.

The Normalmap consisst of vectors coded as RGB values and interpreted by the shader on a per pixel or per texel basis. Therefore it is possible to capture high poly surface detail and projekt(bake) it onto the low polys texture, making the low poly look closely to the high poly. This is a common techniwue for performance to reduce vertex count. It is also most curcial for the final detailed look of your model. Baking errors in normalmaps can destroy quality and should be avoided. Most texture authoring softwares nowadays offer the option to paint out your normal map errors. However, this provides very difficult, because the human eye does not really know how to interpret rgb vectors into the surface normal they represent. So a clean bake should be alsways the starting point. Even when it means to do a lot of rebakes, adjusting your low poly geo better to the hp or adjust your baking cage. It will be always worth it on the long run.

The Height map is a greyscale represantation of the highs and lows of your High poly. It is also called a displacement map. It is mostly used in tessalation. However, because tessalation creates additional geometry on the shader side, it is not very performance friendly. Therefore, there is also an option which fakes this kind of depht without the cost of extra geometry. It is calles parallax mapping and is what unity has implemented when You use unitys height map slot.

Even with a sophisticated shading model like PBR, there is still no way to capture the small cracks and crevices which sallow light which is very important to mimic how complexity of real lighting works. Lighting systems, also in Unity, can only take the bare geometry of the model into account when dropping shadows. It wont cover the small crevices in a model which are simulated via a normal map. Thats where AMbient Occlusion or short AO comes inhandy. It bakes the cracks and crevices, the small areas where light gets occluded and can be applied to make your model look muc hbetter and more realistic. It is a hack, but a pretty important one. Getting good AO will enhance your model quite a bit. But too dark and unrealistic looking ao on the other hand, can make it look dirty and low quality. Rule of thumb for PBR: Have your AO mostly in the corners and crevices, avoid large scale or gradient AO

Maps that describe convexity and concavity of a model. Can be used as masks in your texturing authoting software, but are not included oin the final product.

Rigging is the process of weighting or parenting geometry or whole objects to bones.

Triangulation prevents you from being able to : reuse parts of the model properly, re- uv map parts of a model properly and also makes all the edge loops of the model uneditable