TIE.md

Ties (instanced scenery)

Ties are the level's instanced static scenery: one class mesh in three levels of detail, placed many times by 0xE0-byte instance records, lit per instance in 64 light slots. The layouts start from Wrench's reader as ReRAC describes it; ReRAC corrected most of the RAC1 header, packet header and vertex records from the game's TieProc, LightTies and VU1 program 13507, and checked them on every class, packet and instance of the NTSC-U disc (1,804 classes, 42,725 packets, 1,662,131 triangles, 44,712 instances). OpenRAC's editor reads LOD 0 and the placements on PAL; PAL's func_00236A98 confirms the material table pointer, count and stride (ASSETS.md).

Games. RAC1, measured. Wrench gives the sequels a larger class header with different offsets and a 0x60-byte instance without the colours (reference). VU1 programs 13507 and 224979 were edited for RAC2 (none of their chunks is the same, VU_PROGRAMS.md). RAC3 and RAC4 are not measured.

1. Functions (NTSC-U and PAL)

Role	NTSC-U (boot)	PAL
Cull, LOD, morph factor, DMA chain	0x235BE8 (level 01: 0x2A9A90)	TieProc func_00236F00
Lighting	0x237370 (level 01: 0x2AB218)	LightTies func_00238688
GS setup conversion at load	0x203730	tie_ad_gif_convert func_00203F68
Texture paging	0x2370C0	BuildTieTextureDma func_002383D8
Level-load cap of the draw distance (720)	0x1E9B10	func_001E9EC8

2. Class blob

All offsets are relative to the blob, so a class can be moved freely. The RAC1 header is 0x80 bytes, followed by an extension up to the first packet table:

Offset	Type	Field
0x00	3 × s32	packet tables of LOD 0, 1, 2
0x0C	u32	64 light-slot normals: s16 (x, y, z, 0) in 1/32767, 0x200 bytes, just before the GS setups
0x10	3 × f32	near, mid, far distances (world units)
0x1C	f32	equal to 0x48 on disc; TieProc uses these bytes as per-frame LOD counters
0x20	3 × u8	packet counts per LOD
0x23	u8	texture count
0x24	u16	mode: TieProc skips the class when & 9; (& 6) >> 1 selects its path (0, 2, 4 on disc)
0x26, 0x28		0 on disc; instance count and list at run time
0x2C	u32	GS setup table (0x50 bytes per texture)
0x30	4 × f32	bounding sphere
0x40	f32	scale
0x44	s32	the class number
0x48	f32	a distance (5 to 20), unknown
0x50	3 × 16	per LOD: strip vertex total, triangle total, strip count, pad
0x80		bounding box min and max, then 8 corners TieProc uses for frustum tests; the first packet table is at 0x140 (0xC0 on one class)

Position in class space: s16 × scale / 1024. Packet header (16 bytes): data offset from the LOD's packet table; GS setup count; 5 × that count; 3 + strip count; control size in quadwords (unpack header and strips); vertex region offset and size (quadwords); colour-index region offset and element count; a slot step table offset and size (not used by 13507); strip count; strip vertex total.

3. Packet data

Offset	Content
0x00	four s32: GS packet positions of setups 1..3 (setup 0 is at 0)
0x10	four s32: byte offsets into the class's GS setup table (/ 0x50 = material)
0x20	unpack header, 12 bytes
0x2C	strips, 4 bytes each: vertex count, pad, GIF tag position, winding (0 in RAC1)
vertex region	"dinky" vertices (16 bytes) then "fat" vertices (24 bytes)
colour-index region	two copies of one byte per vertex: the light slot; copy B = copy A + 0x40

At most four materials per packet.

• Dinky vertex: s16 x, y, z; GS slot; s, t (/4096); q; second GS slot (or 0).
• Fat vertex: an s16 morph delta (x, y, z), GS slot, s16 position, pad, s, t, q, second GS slot. Its colour index element is four bytes (c0, c1, c2, 0xFF).
• Unpack header: dinky-single-only flag, no-fat flag, an unknown byte, strip count, the GS slots that end the four write phases (dinky single, dinky double, fat single, fat double), dinky size + 4, 3 × fat count + 6, dinky count, fat count.

4. From packet to triangles

TieProc uploads per packet: the setup positions (VU 0), the GS setups (VU 1 + 5k), MSCAL 4, the unpack header and strips (V4-8), the vertices (V4-16, VU 0x32), MSCAL 6 (place setups and strip tags, convert vertices), the two colour-index copies (VU 0xCC and 0xF8). Then per instance: six quadwords of transform and LOD data at VU 0xC6, the instance's 64 lit colours (16 quadwords at 0x346 or 0x386), MSCAL 0.

Program 13507 writes setup k to its GS slot, each strip's GIF tag with NLOOP = the strip's stored vertex count (EOP on the last), and each vertex's ST, RGBAQ, XYZ to its slot, in stored order. Vertices in a "double" phase are written to their second slot as well; this is how one stored vertex serves two strips. A reader can rebuild the packet the same way: fill a slot map (the last writer wins; 93 retail slots are written twice with the same data), then walk from slot 0: a setup advances 6 quadwords, a strip reads its vertices from slots cursor + 1 + 3i and advances 1 + 3 × count. Strips are GS triangle strips. Wrench's reconstruction (sort by slot, drop duplicates, walk) gives the same result on every retail packet.

5. LOD and morph

Cull (per instance, world units): skipped when the distance is 0, when the sphere is beyond min(draw distance, 720), behind the near plane, outside a side plane, or when its occlusion bit is clear (OCCLUSION.md). An instance not wholly inside the guard band is drawn by the clipping program 224979 at the same LOD.

LOD from the depth of the sphere centre (no radius, no instance scale):

Condition, in order	LOD	Morph factor k
depth ≤ near	0	0
depth > far	2	0
depth ≤ mid	0	(depth − near) / (mid − near)
otherwise	1	(depth − mid) / (far − mid)

VU1 draws a fat vertex at position + k × delta and its colour as c0 × (1 − k) + ((c1 + c2) / 2) × k, truncated; dinky vertices take palette[c0]. ReRAC checked on Novalis that at k = 1 every LOD-0 fat vertex lies on the LOD-1 surface and every LOD-1 fat vertex on the LOD-2 surface, so the switches at mid and far are seamless. LOD 2 has no fat vertices. Typical distance sets are 10/20/30 and 10/20/1024.

Fog for a tie is one value per instance, from the centre depth: clamp(cf24 + depth × cf20, If, In) with the view context's fog constants (CAMERA_FOG.md).

6. Textures

Five A+D registers per setup, in the order TEX0, TEX1, MIPTBP1, CLAMP, MIPTBP2 (not the terrain's order). The load-time conversion and the paging follow terrain's rules: TEX0 from the class's texture slot, MXL = type − 1, MMIN and K from TEX1, CLAMP from the disc fields, mip 1 after the base level (TFRAG.md).

7. Instances and lighting

Instance record (0xE0, gameplay section 0x34): class number, draw distance (an s32 the loader converts to float; 720 on every Novalis tie), pad, occlusion index, column-major matrix (W of the last column: 0.01 on 39,954 retail instances, 0.0 on 4,758), 64 RGBA5551 ambient colours, one per light slot, directional light selector (0–8, 15, once 0xFF00), uid, two pads.

The loader builds a 0x20-byte run-time record per instance (world sphere, pointer to a 0x1C0-byte record, draw distance, occlusion index, class index, relight flag, light selector, point-light nibbles) and a 0x1C0-byte record (the matrix with each column's w = 1 / its length and the class scale, 64 lit colours, the 64 ambient colours). LightTies computes 64 colours per instance from the slot normals, the ambient colours and up to three lights; see LIGHTING.md. Colours clamp at 243, not 255.

Open

• RAC1: the unpack header's byte 2; the slot step table's consumer; the meaning of the 0.01 in the matrix; the reflection pass; the vertex path of 224979.
• RAC2–RAC4: not measured in OpenRAC.

Sources: ReRAC (https://github.com/re-rac/rerac, ISC, Copyright (c) 2026 ReRAC contributors), docs/formats/tie_rac1.md, docs/plan/tie_lighting.md; PAL names from games/rac1/config/overlays/us_map.tsv and RENDERER.md.