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Lighting, and why not Phong

Where the lights are​

Not in the .rm2. Each level is two files, and the one this mod had never opened is the other one:

hubd.rm2scripts, objects, instances, triggers, characters, collision
hubd.sm2the scenery: its models, materials, textures, LOD models, the skydome - and the lights

The lights live in a single SceneryData item per scenery file, in four lists: ambient, directional, point and negative. Each light carries a colour (RGB plus a fourth channel), a radius, a position and two direction vectors.

twinsdump Levels/Earth/Hub/huba.sm2 lights -v
scenery 0 levels\earth\hub\huba: ambient 1, directional 2, point 4, negative 0
    ambient     rgb (0.33, 0.33, 0.33)  radius 4.5     at (136.6, -1.5, -50.9)
    directional rgb (0.56, 0.44, 0)     radius 5.37    at (136.4, -1.5, -50.6)
    directional rgb (0.24, 0.26, 0.5)   radius 5.05    at (136.4, -1.5, -50.6)
    point       rgb (0.41, 0.39, 0.2)   radius 146.53  at (-3.3, 8.6, -24.7)
    point       rgb (0.41, 0.39, 0.2)   radius 146.53  at (-42.2, 8.6, 37.4)
    point       rgb (0.41, 0.39, 0.2)   radius 146.53  at (-55.3, 8.6, 97.3)
    point       rgb (0.41, 0.39, 0.2)   radius 146.53  at (-57.4, 10.9, 136.2)

That is a proper little lighting rig: a grey ambient, a warm key and a cool fill, and four wide point lights walking up the hub to keep the ground from going flat. It is not baked - these are evaluated at runtime.

What the game uses, across all 134 scenery files​

TotalNotes
Ambient140Essentially one per file
Directional432The workhorse - up to 10 in one file
Point103Wide radii, used to shape hubs and arenas
Negative11Supported, and almost never used

The most common rig by far is one ambient and two directional (42 files), then one and five (27), one and four (21). Eleven files have no directional or point light at all - labint, altlabin, airship, the Psychetron corridors - and those interiors lean on ambient plus a handful of negative lights instead, which subtract light to carve out shadowed pockets.

Why Phong is not on the table​

Short version: the PlayStation 2's Graphics Synthesizer has no programmable per-pixel stage at all. Gouraud is not a setting the game picked over Phong; it is one bit in the GS primitive register (IIP), and the only other value is flat. Every one of the game's 10,464 material shaders already asks for gouraud, so there is nothing to turn up.

Lighting happens per vertex, on VU1, before the triangle ever reaches the rasteriser. The lights above are transformed and accumulated into a colour per vertex, and the GS then interpolates those colours across the triangle. That interpolation is Gouraud shading, and it is the only shading the hardware does.

Getting per-pixel lighting on a PS2 means faking it with multiple passes - lookup-table normal maps, projected light textures, that family of tricks. In practice that would mean rewriting the VU1 microprogram, adding two or three passes over every surface, and paying for it in fill rate on hardware that this mod has just finished getting to a steady 60 fps. It is not a patch; it is a different renderer.

What is actually available

The lighting data is completely open, and this mod has never touched a single .sm2 file. Colours, radii, positions, the number of lights and the unused negative lights are all editable, and none of it costs anything at runtime. If the goal is "the game looks better lit", that is the lever - not a shading model the hardware cannot run.

The shadow pass is separate​

Character shadows are not part of this lighting at all - they are a screen-space mask pass, described in Graphics. The receiver set is settled: after the crate fix, everything still excluded is a character or a boss, which cast the shadow volumes themselves and would shadow themselves if included. A test build that made all 3,218 remaining opaque materials receivers was indistinguishable from the shipped 580 at every spot checked.