Lots of great questions, Fantam_Mayfly, I’ll do my best:
- Diffuse, Albedo, Color - you’ll hear these terms and they can mean the same thing. It’s become a bit messy with terminology as techniques and technology advanced. Diffuse refers to a color map which has the AO and localized lighting (edge and cavity) incorporated into it - it is an older term for the legacy model of material systems (blinn, phong, etc.). Albedo or Color is more common now that PBR is the common application of material models. Albedo or Color would be the pure color of the material, it explains just color and no lighting (so AO and such is not integrated into it). They get used interchangeably, and tend to mean the same thing, but historically there is a recognized difference.
As we get into more interchangeable terms, remember that there is a certain point where it’s an experimental artform, using texture maps have a a standard expected use, but there are plenty of games out there that do it different than convention - something to keep in mind.
- Cavity and Roughness are not really interchangeable, in concept at least. Though can work well in a pinch. The material parameter “roughness” uses greyscale information to define shiny and rough interactions of light. A cavity map and roughness map are both grayscale, so the information can be accepted by the parameter. Black means smooth, White means rough, so whatever greyscale map is plugged in, will drive the roughness parameter.
This gets complicated with the addition of Specular, which is typically left as a scalar (not texture driven).
Yes. Height and Displacement, so long as both are greyscale (there are vector displacement maps which cannot be used the same) are essentially the same, but there are reasons for why they are termed differently. Height is describes elevation where black is the lowest and white is highest - they can be used as a blending mask like you say, also for parallax mapping or bump offset, and some other special uses, which comes down to something I’ll explain below. Displacement maps are meant for displacement shaders, that would be tessellating a target model to then offset the vertices which can be understood as what the landscape does (it can also be seen as height).
This is a common use for height information, yes. Blending textures in landscape tends to use height maps, but it can be used for more reasons.
When it comes to blending, and if we take a step back, to placement control of texture information, we think in masks. Roughness, cavity, height, displacement, AO, metallic - they are all black and white and they specify where information should occur and should not occur. So… metallic may look nice plugged into roughness; they are both just greyscale masks. Studios would prefer to use the map that is named “metallic” in the metallic slot and that’s it, don’t want to be confused.
The sky’s the limit when it comes to this area though. Some other greyscale maps, used for specific cases, involves masking for emissive control, patterns or multiple material control, thickness, sharpness, projections and light functions, voxel generation, opacity, layering, and stepped visibility control.