Covarr brought to my attention a shading issue in del3 (Costa del Sol with the beach), where Cloud's head is shaded differently to PSX. I think this is unrelated to the shading issue we have been discussing.
Field Model graphic filter - UNKNOWN9
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Field Model graphic filter - UNKNOWN9
is being set on the characters in this field, which makes them shine and shimmer as they walk. It looks pretty poor to be honest in PC version, since it's the KAWAI function, which is broken. The effect is hardly even noticeable on the PSX version.
Speaking of KAWAI, the field opcode function is only a basic set up. It sends values that are used in the main function (called all the time to draw and sort all 3d objects) at 6392BB. For example, the main operation to be carried out is found at points like 63959E