Entry 165

The screen shake: cameraShake, cameraShockAbsorber and cameraSet's offset

2026-09-26render

Filescrates/piney-world/src/camera.rscrates/piney-world/src/combat/stage.rscrates/piney-world/src/field_world.rscrates/piney-game/src/fx.rscrates/piney-game/src/area.rscrates/piney-world/examples/shake_probe.rstools/test_camera_shake_rs.py

Hits and spells did not shake the screen. The effects already raised Event::CameraShake for the criticals, the spells' blasts and the shockwaves, but nothing took the events. The enemies' note 0x8002 asked checkCameraShakeRange, which answered no. docs/engine/field-game.md, "The screen shake", has the rules.

camera::Shake holds camera.cpp's eight camShockForce slots and the vibrate statics:

• cameraShake (main 0x00162cd0) keeps or drops a new shock against the held ones, and a turning shake (dirc 2) takes its heading from rand().
• cameraShockAbsorber (0x001629b0) runs at the end of every cameraMain. The strongest shock sets the force (10, 20 or 30), the cycle and a Ry(dirc) matrix, which a turning one turns 0x1000 a frame. The oscillator gives the offset's z, each crossing of 0 keeps a fifth of the force, and the slots count down.
• cameraSet, for camera 1, moves the eye by o = 0.5 (Rz(a) vibrateMatrix) vibrateOffset, with a the heading (a double atan2). The target moves by o and then again by o times min(dist / 280, 1).

The first comparison caught that last one: the port had moved the target only by the scaled part.

Two statics matter at the start. vibrateRotate starts at 0, not -1, so slot 0's heading turns every frame until a shake without rot comes. vibrateCycle starts at 0, so the game's first absorber divides by zero. The force is 0 then, so the oscillator is reset right after, and the port skips the division.

The shakes now reach the camera three ways:

• the enemies' note, through Stage::shake_range (ccCheckCameraDeg 67.5 degrees, and within 2000 of the eye), then Call::CameraShake at the note;
• the effects' events, which FieldFx::take_shakes hands over after the frame;
• FieldWorld::camera_shake, which draws rand() from the battle's generator.

tools/test_camera_shake_rs.py (new) runs the game's cameraShake, cameraShockAbsorber and cameraSet in eemu. It does 12 runs of 400 frames with random shakes, and rand() hooked to the port's generator from one seed. SetMatrix_PosTarget is hooked to take the eye and target. The shake_probe example answers with the port's state. All 801 shakes, 4,406 shaking frames and 4,800 eyes and targets were equal. test_world_rs (18) and test_field_rt (5) still pass, as do 605 workspace tests.