Track element building
This article aims to present what is currently know on how Stunts stores the data which is used to assemble track elements such as roads, bridges, loops and scenery. The ultimate goal is to be able to effectively modify the existing elements and create new ones. There is still much to learn before that becomes possible, though - which also means there will be large gaps on this article for the time being.
General observations
Track elements have two different models. The graphical model consists of a 3D shape stored in either of GAME1.P3S or GAME2.P3S . Like any regular 3D shape, it can be modified using stressed. The graphical model, however, only controls the looks of the element. Actual physical behaviour is determined by a physical model. The physical model data appears to be spread over a number of files, and only parts of such data were located thus far. Briefly, track elements are made of potentially several plane surfaces, whose description is stored at the plan resource of GAME.PRE . Such plane surfaces, which are in principle boundless, are then weld together by a set of rules stored elsewhere. Another important piece of data which is not in plan is the type of surface associated with each plane (asphalt, grass, etc.). It is important to notice that plane surfaces in plan are not unique - for instance, the same planes are used for creating hill slopes and bridge ramps, and thus alterations to the plane surfaces will be reflected in both elements. The difference between the two elements is merely one of assembly - that is, where the planes are cut within the track tile in order to result in the track element shape. A similar situation is observed for the cork l/r and the pipe round surface. GAME.PRE also contains the wall resource, which stores data for non-drivable surfaces (such as bridge and building walls) in a poorly understood format.
GAME.PRE data
The plan resource
plan is composed of 536 structures of 34 bytes each, each associated with a plane which in turn forms part of a drivable surface. The structures consist of:
struct PLANE {
WORD angleYZ;
WORD angleXY;
VECTOR origin;
VECTOR normal;
VECTOR[3] rotationMatrix;
};
In the above, WORD = 2-byte signed integer and:
struct VECTOR {
WORD x;
WORD y;
WORD z;
};
origin sets a point in space belonging to the plane (coordinate system is the same track tile system of the 3D shapes in GAME1/2), and normal sets a normal vector to the plane "normalized" to a length of 8192. These two vectors are enough to define a (boundless) plane. angleYZ and angleXY appear to contain the inclination of the planes (given in units of 360/1024 degree, with values ranging form 0 to 1023). Since such data is made redundant by origin and normal and the values have no obvious effect on the surface behaviour their actual function is unknown. Finally, rotationMatrix appears to be a rotation matrix (of column vectors "normalized" to 16384) which changes the orientation of the car normal vector when it changes surfaces. It must be correctly set so that the surface displays reasonable physical behaviour.
The 536 structures in plan are arranged in 134 sets of 4 plane surfaces. Each plane in these quartets corresponds to the same part of the associated track element(s), the only difference being orientation relative to the track grid. The order on each quartet is predictable: the first one is in S->N orientation (pointing to +z) and the others correspond to counter-clockwise rotations (for pieces of bridge corners and banked roads, the first plane of the quartet is from the corner going S->W, the second one E->S and so on.).
List of planes
Block Line Address Description 1 1 37E Flat ground 2 5 406 Boulevard divider 3 9 48E Bridges (Viaducts may not work if set too low) 4 13 516 Ramps and hill slopes 5 17 59E Angled hill slopes (outer) 6 21 626 Angled hill slopes (inner) 7 25 6AE Straight banked road 8 29 736 Banked corner 9 33 7BE Banked corner 10 37 846 Banked corner 11 41 8CE Banked corner 12 45 956 Banked corner 13 49 9DE Banked corner 14 53 A66 Banked corner 15 57 AEE Banked corner 16 61 B76 Banked corner 17 65 BFE Banked corner 18 69 C86 Banked corner 19 73 D0E Banked corner 20 77 D96 Banked corner 21 81 E1E Banked corner 22 85 EA6 Banked corner 23 89 F2E Banked corner 24 93 FB6 Banked corner 25 97 103E Banked corner 26 101 10C6 Banked road entrance (1st orientation is inner=left) 27 105 114E Banked road entrance 28 109 11D6 Banked road entrance 29 113 125E Banked road entrance 30 117 12E6 Banked road entrance 31 121 136E Banked road entrance 32 125 13F6 Banked road entrance 33 129 147E Banked road entrance 34 133 1506 Banked road entrance 35 137 158E Banked road entrance 36 141 1616 (unknown) 37 145 169E (unknown) 38 149 1726 (unknown) 39 153 17AE (unknown) 40 157 1836 (unknown) 41 161 18BE (unknown) 42 165 1946 (unknown) 43 169 19CE (unknown) 44 173 1A56 (unknown) 45 177 1ADE (unknown) 46 181 1B66 Loop surface 47 185 1BEE Loop surface 48 189 1C76 Loop surface 49 193 1CFE Loop surface 50 197 1D86 Loop surface 51 201 1E0E Loop surface 52 205 1E96 Loop surface 53 209 1F1E Loop surface 54 213 1FA6 Loop surface 55 217 202E Loop surface 56 221 20B6 Loop surface 57 225 213E Loop surface 58 229 21C6 Pipe surface (grounded) 59 233 224E Pipe, cork l/r surface 60 237 22D6 Pipe, cork l/r surface 61 241 235E Pipe, cork l/r surface 62 245 23E6 Pipe, cork l/r surface 63 249 246E Pipe, cork l/r surface 64 253 24F6 Pipe, cork l/r surface 65 257 257E Pipe, cork l/r surface 66 261 2606 Pipe, cork l/r surface 67 265 268E Pipe, cork l/r surface 68 269 2716 Pipe, cork l/r surface 69 273 279E Pipe, cork l/r surface 70 277 2826 Pipe obstacle 71 281 28AE Pipe entrance (grounded) 72 285 2936 Pipe entrance 73 289 29BE Pipe entrance 74 293 2A46 Pipe entrance 75 297 2ACE Pipe entrance 76 301 2B56 Pipe entrance 77 305 2BDE Pipe entrance 78 309 2C66 Pipe entrance 79 313 2CEE Pipe entrance 80 317 2D76 LH cork u/d entrance 81 321 2DFE Left-handed cork u/d 82 325 2E86 Left-handed cork u/d 83 329 2F0E Left-handed cork u/d 84 333 2F96 Left-handed cork u/d 85 337 301E Left-handed cork u/d 86 341 30A6 Left-handed cork u/d 87 345 312E Left-handed cork u/d 88 349 31B6 Left-handed cork u/d 89 353 323E Left-handed cork u/d 90 357 32C6 Left-handed cork u/d 91 361 334E Left-handed cork u/d 92 365 33D6 Left-handed cork u/d 93 369 345E Left-handed cork u/d 94 373 34E6 Left-handed cork u/d 95 377 356E Left-handed cork u/d 96 381 35F6 Left-handed cork u/d 97 385 367E Left-handed cork u/d 98 389 3706 Left-handed cork u/d 99 393 378E Left-handed cork u/d 100 397 3816 Left-handed cork u/d 101 401 389E Left-handed cork u/d 102 405 3926 Left-handed cork u/d 103 409 39AE Left-handed cork u/d 104 413 3A36 Left-handed cork u/d 105 417 3ABE LH cork u/d bridge 106 421 3B46 RH cork u/d entrance 107 425 3BCE Right-handed cork u/d 108 429 3C56 Right-handed cork u/d 109 433 3CDE Right-handed cork u/d 110 437 3D66 Right-handed cork u/d 111 441 3DEE Right-handed cork u/d 112 445 3E76 Right-handed cork u/d 113 449 3EFE Right-handed cork u/d 114 453 3F86 Right-handed cork u/d 115 457 400E Right-handed cork u/d 116 461 4096 Right-handed cork u/d 117 465 411E Right-handed cork u/d 118 469 41A6 Right-handed cork u/d 119 473 422E Right-handed cork u/d 120 477 42B6 Right-handed cork u/d 121 481 433E Right-handed cork u/d 122 485 43C6 Right-handed cork u/d 123 489 444E Right-handed cork u/d 124 493 44D6 Right-handed cork u/d 125 497 455E Right-handed cork u/d 126 501 45E6 Right-handed cork u/d 127 505 466E Right-handed cork u/d 128 509 46F6 Right-handed cork u/d 129 513 477E Right-handed cork u/d 130 517 4806 Right-handed cork u/d 131 521 488E RH corh u/d bridge 132 525 4916 133 529 499E 134 533 4A26 Tunnel roof
The wall resource
wall is composed of the following structures:
struct WALL {
WORD angleXZ;
WORD x;
WORD z;
};
The data in these structures appear to be ground-plane projections of wall segments, with x and z making endpoints and angleXZ defining segment angles. Verification of that, and identification of wall pieces, is best performed by plotting the x and z values. There must be additional pieces of data involved in wall assembly through, as there is no info on wall heights, nor any obvious link to data in plan; also, simple alterations to wall pieces associated with elements such as block houses or slalom blocks do not work as intended.
