On most detailed ships, the icing effect comprise two things:
- indeed a mesh system in the GR2 file, for example one called _ice_hull_X (hide by default in goblin) that is a simple 3d plan where a transparent texture is applied which depict icicles. Same texture is always used and tile repeated.
- The overall textures of the boat are switched to their alternative versions ending with _ice.dds . Basically the same textures but with some ice painted on them. (some boats only have this effect and no icicles)
Can't find any controller in goblin called "Ship Render Ctrl", I supposed you meant by that nodes in the GDS_scene tree? Anyway, can't see any controller you could add/modify (like the granny caustic ctrl for example) that is controlling the switching of winter/non winter version.
Must be hardcoded somewhere I presume.