Texture Tags

Sonic the Hedgehog (2006) uses a number of suffix "tags" in the filenames of its textures. Each of these have a very specific meaning that affects how the object is rendered.

Four Character Tags

Some textures contain a four character tag composed of two halves.

Tag	Description
`_ntxx`	Tangent-Space Normal
`_nwxx`	World-Space Normal
`_dfxx`	Diffuse
`_dsxx`
`_enxx`	Environment
`_ofxx`
`_ptxx`
`_luxx`

Tag	Description
`_xxnt`	Tangent-Space Normal (Again?)
`_xxsp`	Specular
`_xxpt`	Punchthrough
`_xxlu`	Luminance

Other Tags


Tag	Description
`_nt`	Tangent-Space Normal
`_nw`	World-Space Normal
`_df`	Diffuse
`_dif`	Diffuse?
`_dis`
`_sp`	Specular
`_lm`	Shadowmap
`_zlm`	Lightmap
`_lu`	Luminance
`_rf`	Reflectance
`_rfa`	Reflectance + Alpha?
`_envmap`	Environment Map
`_dm`
`_pm`

Unknowns

It is unclear what the difference between _nt, _ntxx, _xxnt, or even potentially _ntnt is, although that last one never appears in the files. The same applies for all other tags which can appear as both part of the four character code, or as standalone tags.

Textures can appear with a final single letter suffix. The only letter that does not appear as a suffix is _w. It is unknown as to whether these serve purely as an organisational tool, or actually affect rendering.