Entry 131

The follow camera, from 0x80027304

2026-10-1645mengine

The port's camera eased its yaw toward the player's heading and its eye toward a point behind him. It is now 0x80027304, ported in camera.rs. The work was done by a delegated agent and merged here.

The eye. It sits on a spring. Its velocity is integrated by 0x8004fbb4 with dt 10, has drag of |v| / 32 and a top speed of 2796, and stops when the velocity reverses. It is pulled with 16 (10 when floating) toward the goal 4096 behind, which 0x8002cd7c clips. Across, the eye stays between 1024 and 4800 (7200 in level 7).

The swing. With the player facing the camera and nearer than 2049, the eye swings aside (74 / -18; 37 floating). The side is picked by a 2048 wall test and the 4096 timer. Between 2049 and 4096 it backs off along the player's axis.

The height. The goal is the look-at's y less the height. It keeps 256 off floor and ceiling (0x8002b240) and stays under ceiling hits over the eye and the player. The push is 9 (4 floating, 18 in level 15), settled within 64, with a band of 1512. The branch for "blocked at eye height, clear lower" is in too.

Probes and tests. The wall probes (0x800263c4): 37 off a wall ahead, up to 74 off walls to the sides. The view test (0x80026914): from 512 ahead of a running player, 18 off what blocks, plus 32 toward the goal.

Settling and idling. Per-axis sign bits, and the "still" bits for each axis while the player stands. When idle, the orbit (0x800284f4) at 512 runs until the eye is at the distance and past the player's back.

The look-at (0x800de454). It looks ahead by speed x 150, scaled nearer than 5192, and eases by 1/4. Its height catches up at 298 (223 floating) with a band of 512.

The reset (0x80026ddc). It uses the 8 offsets at 0x800b6e18. R1 takes the first clear one; a stuck camera takes the nearest. set_camera_yaw places the eye (0x80025e90) and resets. The end of a fixed or shaft camera resets too.

The room clamp (0x8002953c). An eye outside every room is drawn clamped.

The stick. It is turned by the camera's matrix, ratan2(-m[0][2], m[2][2]) as 0x8005be24 does. Under a fixed camera the stick now follows that camera's view.

The look-aside (L1/L2/R2), cam_hold, the shaft camera and the fixed and post cameras are kept.

Checked against the original. The oracle's recorded player path in the hub was replayed into the port's camera from an R1 reset. These windows matched frame by frame:

• 2784-2854: turning and walking, with the 4800 clamp;
• 2784-2834: walking toward the camera;
• 3004-3200: left, stop, the idle orbit back behind;
• 3204-3400 and 3404-3486.

Examples:

• the reset at 2782: eye (9301, -1589, 18229) in both;
• frame 3200: eye (8010, -1589, 16792), look-at (7267, 11, 20958) in both;
• frame 2856: (7647, -1589, 19173) against (7666, -1589, 19175).

tests/camera.rs replays two of those windows. Changing an expected value makes it fail.

Play tests. Three needed different input, with the same assertions:

• Levels 18 and 15: behind Tommy is walled off in the height field, so the reset puts the camera in front, as 0x80026ddc would. collect now steers by the camera.
• Level 6: the camera turns about 15/4096 after the first frame's push, so the test presses R1 before the climb.

The oracle logs are in /mnt/data/claude/scratch/cam/ (run1-run5 and their tables).

Resolved from earlier entries:

• 100.1: the camera's side-step tests.