Splines
A level carries thousands of splines, each a list of points in the level’s own space. There are five classes, told apart by the type of the blob section that holds them: the engine registers the section types 0, 1, 9, a and c with one spline manager that keeps five classes of up to 1,000 records of 56 bytes each, and the type is the class (0 to 4 in the order below). The disc has 33,575 splines in 231 sections. Proven · all 547 SCPs
| Class | Section type | Splines | What they are | Confidence |
|---|---|---|---|---|
| 0 | 0 | 2,334 | candidates for the grind rails | Inferred |
| 1 | 1 | 2,200 | guide ribbons and flythrough cameras; points hover about 2 above the ground | Observed |
| 2 | 9 | 25,250 | the walking network of pedestrians and AI skaters: edges between the AIJunction and NavJunction spot chunks; every point lies on the ground |
Inferred |
| 3 | a |
3,760 | records of the navigation layer (3.3 MB of sections); no known use | Unknown |
| 4 | c |
31 | short paths in three sections; no known use | Unknown |
The low 16 bits of a section’s flags are junk, not a variant: type 9 comes as 0x90000 (25,009 splines) and four other low halves, and types 0 and 1 as 0x80, 0x81 and other low halves. Reading the splines by flags, as earlier tallies did, missed the 4,015 splines of types a and c, and the earlier total of 31,105 splines does not reconcile with any recount; the 33,575 above are every record of the five section types read by a strict reader. Proven · all 547 SCPs
The registry and the manager are known from the executable: the loader of each of the five types calls the same function with the class index 0 to 4, and the unload function frees the class. Observed · static reading of the executable
All numbers are big-endian.
Record
Section titled “Record”A section holds count records of 56 bytes from its data offset. Their arrays follow in the section and the record’s pointers are offsets from the section’s start. The points are already in the level’s space; the matrix is not applied to them. Proven · all 231 sections
| Offset | Size | Type | Field | Confidence | Notes |
|---|---|---|---|---|---|
| 0x0 | 4 | u32 | id | Proven | sdbm of the spline's name |
| 0x4 | 4 | u32 | parent | Observed | the id of a group |
| 0x8 | 4 | u32 | id_again | Observed | the id again, not always |
| 0xC | 4 | u32 | unknown | Unknown | |
| 0x10 | 4 | u32 | one | Observed | 1, or 3 once |
| 0x14 | 4 | u32 | point_count | Proven | |
| 0x18 | 4 | u32 | second_count | Observed | equals point_count except in a few records, where it is one more |
| 0x1C | 4 | u32 | word7 | Unknown | 0 for every spline outside class 0; 0 to 2 for rail candidates |
| 0x20 | 4 | u32 | word8 | Unknown | 0 for every spline outside class 0; 0 or 1 for rail candidates |
| 0x24 | 4 | u32 | surface | Observed | a surfaces.id for rail candidates, 0 for all others |
| 0x28 | 4 | u32 | matrix_offset | Proven | of a 64-byte matrix |
| 0x2C | 4 | u32 | points_offset | Proven | of point_count × 3 f32 |
| 0x30 | 4 | u32 | params_offset | Proven | of point_count f32 that rise from 0 |
| 0x34 | 4 | u32 | unknown | Unknown |
Every value read is finite, every pointer is inside its section and the per-point parameters increase from 0; they are not arc length. Proven · all 33,575 splines The 64-byte matrix is a frame local to the spline. It is not applied to the points, and what it is for is not established. Observed
Rail candidates
Section titled “Rail candidates”The class-0 (type 0) splines are the best candidates for the grind rails, and the reading is not proven.
For: the surface word is a row of the database’s surfaces table (MAIN.DB). Over the 2,334 splines its values are (value: splines) 3: 683, 0: 666, 11: 381, 32: 290, 41: 141, 43: 43, 2: 34, 53: 24, 39: 23, 46: 19, 14: 13, 40: 12 and 37: 5, every nonzero one a row of the table. Proven · all 2,334 splines
The snow surfaces occur only on the snow levels. Observed
The surfaces table has PHYSICS_RAIL_* columns (rail friction and gravity), and the surfaces the candidates use are the materials of rails and ledges: concrete (3), metal (11), metal_pole (32), wood (2), plastic (14) and the snow variants snow_metal (41), snow_wood (39), snow_wood_log (43), snow_rock (40), snow_Ice (46), Snow (37) and snow_Whistler (53). Observed
The database’s grind-task volumes contain candidate points more often than other volumes: in 76% of 212 grind-task volumes against 39% of 803 other task volumes. AI paths show 35% and 26% for the same two sets, and guides 76% for both. The percentages were measured on the 2,227 candidates of the flagged sections, before the other 107 were counted. Observed
The points sit on surfaces: the median drop to the ground is 0.17 and the tenth percentile 0.01. Observed
Against: the splines of the other four classes have word7, word8 and the surface all 0, and the code that sets the grind surface (GRIND_SURFACE when the character’s physics state is the rail state, GROUND_SURFACE otherwise) takes its surface key from a collision hit record, not from a spline. No code that reads the section flags was found, and the code that chooses which class a character’s rail state follows was not found. Observed · static reading of the executable
Grinding might also be driven by collision surface types alone (the grind_types table has angle limits), or by the AI-rail scripts (SetRailData in the Lua script of each level). Unknown
A spline’s id is the sdbm of its name. Two schemes resolve names on the disc: guide splines are named NavGuide_<set><n>, with <set> one or two capital letters (A to ZZ) and <n> from 0 to 39, and the camera splines are the names in FLYTHROUGH_RAIL of a level’s <Level>_sessions table. The <set> is the NAV_SET_START of a drop spot.
1,897 splines resolve to a NavGuide_ name and 300 to a flythrough rail name (as written or in lower case); the rest are not named. Proven · all 33,575 splines
A runtime trace of a grind with the volumes of a challenge, or the code that assigns the character’s spline class, would settle it. What the classes 3 and 4 are for is open as well.