Entry 170

The ground probes as the original runs them

2026-10-1655mplay

The ground move's probes against the height field are now the original's, in its integers (actors::ground), proved against the original called on the live player (examples/ground_check: 2,700 of 2,700 spots, levels 1 and 18, the return, floor delta, wall normal, tangent and slant all the same):

• Three probes ahead of the body (0x80064a34): the middle at the body's depth (the larger of its box's z extents) past the step, and one to each side at its half width (the larger x extent). The offsets are the way's own frame: ratan2 of the way, its heading matrix (0x80020d10, then MatrixNormal) and ApplyMatrixLV - not a float rotation: the slant and tangent were off by 1 to 3 before.
• The floor under each (0x80067448), asked from the body's top: no record is no floor (0xffff0000); above the tile's ceiling, the floor on top of it. The wall on the way (0x80064178): up across at half the rise or just over the higher floor, down from 1024 ahead to 1024 behind. Its kind (0x80064444): level, a rise, a step to climb, a small drop, a step down, a drop past the limit, or held (a normal too steep, a step past the limit, no floor).
• The decision on the three kinds: had, slid along the held probe's wall, or stopped (a stop leaves no floor to climb to). The slide's tangent (0x800763d0) is ((n.a) n - a) of the way turned back, made a unit, the slant the arc cosine of the dot (the libgte acos table); the slide (0x80065120) sets the way along it and probes again, kept when clear or met again at 512 to 1024.
• The run's handler takes a slant under 384 (220 for Spike) as head-on: the climb test from the held probe's floor delta, measured from the floor the probes used (a thing stood on: level 6's last box climbed onto the -6144 block from its top, not from the floor under it), climbable within the body's reach, too tall from 1024 to 3071 (message 16), the bump otherwise.
• The step limit is the character's (0x800c430c by size class 0x80062eac): 750 for Spike and Reptar (characters 6 and 21), else 256; Spike's body box is 1400 deep (0x800450ac).

libgte's VectorNormal (its rsqrt table), acos and asin (their table), ratan2, MatrixNormal and ApplyMatrixLV are in gte::Trig, exact.

The objects' side has begun the same way (world::boxhit, proved by examples/boxhit_check on 100,000 random cases each, in a fresh oracle):

• The slab test (0x80068e68): a segment against a box from 0 to its size in the box's frame, by the start's outcode: inside (the start), one axis out (that face), two out (the face the segment reaches first by a cross product's sign), all three out (the z face, then x, then y; a flat box's far face reads as its near one). Each plane crossing (0x8006876c, 0x80068914, 0x80068ac8) works in 20-bit differences with truncating division, kept within 0..4096 of the segment and the box's other extents. A miss on one or two axes out still writes the face's normal, which a later box's start-inside hit then carries.
• An object's boxes (0x80069c40): the segment less the object's position, turned by its angles' matrix (0x80020ee0, MatrixNormal), less each model box's low corner; the first box met, its point and normal turned back. A character's body (0x8006a008) is the same with its hierarchy's one box.

Both are not yet wired into the ground move: the player still meets things through the float boxes of before.