Read each map as surface data
The maps describe one aligned surface. Color management and channel conventions matter because some textures represent visible color while others store numeric material data.
Albedo or base color
Albedo stores the visible surface color without directional lighting, cast shadows, or shiny highlights. It usually uses sRGB color handling because it represents color rather than numeric shader data.
If strong highlights or shadows are baked into albedo, they can conflict with the lighting in the 3D scene and make the material repeat obvious.
Normal and height
A normal map changes how light reacts across a surface without changing the silhouette. A height map is grayscale data that can drive bump, parallax, or geometric displacement depending on the renderer.
Normal maps can use OpenGL or DirectX orientation. The difference is the green channel. Flip that channel when bumps appear to point inward instead of outward.
Roughness and smoothness
Roughness controls the spread of reflections. Darker values are commonly smoother and more reflective, while lighter values produce broader, softer reflections.
Some applications use smoothness instead. Smoothness is the inverse of roughness, so invert the grayscale map when moving between those conventions.
Metallic and packed maps
Metallic identifies areas that behave as metal. Most clean materials use values close to zero or one, with intermediate values mainly appearing around transitions, contamination, or blended layers.
Real-time engines often pack several grayscale maps into the red, green, blue, and alpha channels of one texture. twirl currently downloads separate maps, so create the required packed texture in your engine pipeline or image tool.