Entry 171

The camera's rows and the objects in the probe

2026-10-161h 8mplay

The follow camera's rows are now the original's integers, and the ground probe meets objects as the original does: every part proved against the original called on the live player.

The camera. The stick reads its heading off the camera matrix (+0x224), and the port built that matrix in floats: a unit off now and then, so the heading the stick set drifted (level 18's slide was off by 5 by frame 12). The original's (0x8001e838 for the follow camera): the look-at from the eye as drawn toward the look-at point (0x800211e8: z the way there by VectorNormal, x (z.z, 0, -z.x), y (-(zx zy), zx^2 + zz^2, -(zy zz)) in 12-bit steps, then MatrixNormal), then the look aside, the swing about y if there is one, else the tilt about x, never both (0x80020c30, 0x80020ca0, MulMatrix0). Its rows are not unit (4093 to 4119 long: libgte's VectorNormal). Logged against the original frame by frame it is the same matrix to the unit. The row scaling for the screen (0x8001e0f4: x by 512/320) is the drawn copy's, not the one the stick reads. The ground step's length now uses the exact VectorNormal too (along, 0x80076944): along a wall the port stepped 169 where the original steps 170.

Objects in the probe (actors::ground::Ground, world::boxhit):

• The dispatch (0x8006a714): the bound's cube about the object (half side the largest of +0x78's extents, 0x800698fc), then a model's boxes (0x80069c40, first met wins), a character's one hierarchy box (0x8006a008), or a hierarchy of posed parts (0x8006a318: each part's matrix from +0x158, the nearest hit of all parts kept, by part).
• The object probe (0x80063d3c): each object near (the nearby list, +0x100) but those of type flag 8, a model's every box but the one stood on, a segment from the body at the box's middle height (within the body's span) to the probe; met past its start (0x80067284), and no height-field wall as near (0x80063c3c: sums of squares, unsigned), it is +0xf4 and +0xfc.
• The normal is a buffer, not a result: each box's slab test writes its face's normal there, hit or not (one or two axes out), in the box's own frame; a hit turns it back. A segment starting inside a box turns back whatever the buffer held. The port carries it as the original does, across boxes, objects and probes.
• The floor on an object met (0x80067448): across at the box's middle (turned by the object's angles, 0x80075ee8 = 0x80020d10's matrix) toward the point, the point nudged 16 on along the body's own z (0x80067374), then down through 2 * +0x86 above and below the body's origin; met again on the same box that is the floor (none if met at its start), else the box's bottom face unturned.
• The thing stood on (+0xf8, +0xfd): a floor probe down through it takes its top when as high; going down a step, the wall test meets it on the drop's way back; the object probe passes its box by.
• The wall test (0x80064178): going up, an object met keeps its face.
• The record left on the player is the one decided on, copied back; where none is (both sides held, the middle clear) the stop is on the last probe's, the right's.
• The run's probe of its own step (0x800645d8, mode 2): its kind sets the thing stood on; a rise or small drop is followed (position and floor by the delta); a step up or down with an upright face starts the eased step (flag 0x80, +0x150 to +0x14c, 0x80066f28); a drop past the limit falls (state 4).
• On a slippery floor (the floor's flag 2, player flag 0x100000 set each frame by 0x8005bd9c) a wall turns the way back off it, a reflection (0x8007627c), not along it.

Proved: boxhit_check (slab, object, dispatch: 100,000 random cases each, 0 different); object_check (the object probe, 2,500 spots by objects in five levels); ground_check (the whole probe with the objects near: 4,400 spots in ten levels, 0 different, 400 meeting a thing); below_check (standing on a thing, both modes: 946 spots in seven levels, 0 different).

The original's frame time is not always 10: D_800c3f1c is 5 a vertical blank, 15 when a frame takes three (level 2 at its start). The checks read it; the port steps at a fixed 10.

Placed objects' angles (Trig::placed_angles): the placement's quaternion inverted (0x8001f684), its matrix (0x8001f9fc: 2^24 over the squared length, 12-bit products, MatrixNormal), the angles read off it (0x8002114c: b = -asin m21, a = ratan2(-m02, m22), c = ratan2(-m10, m11)). Exact for all 747 placed objects of levels 1, 3 and 18 (solids_dump). An object's size (+0x86) and bound are its model's radius, its boxes the model's, for nine in ten; characters have size 8192.

With the camera exact, level 18's slide matches the original exactly for its first 17 frames (from frame 5 before).