SWGhost Saga

Stage 6 adds SWGhost.stretching(sinusoid, t) — a sinusoid-driven vertical stretch that makes the ghost grow and shrink rhythmically. It is the ghost-level analogue of SWRectangle.breathe(), but operates on the composite silhouette rather than a single shape's vertices. All Stage 5 features (sinusoid hover, Perlin-noise eye wander, Follow/Track, full Control Panel) are preserved.

Big Idea 1 — How stretching() Works

Every ghost stores a rest height _baseBodyHeight (copied from the constructor argument). Each frame, stretching(sinusoid, t) computes:

bodyHeight = _baseBodyHeight + sinusoid.getValue(t)

It then calls _build() to reconstruct all child parts using the new height. The head anchor stays fixed; the body rectangle gets taller or shorter and the toe disks shift down with it. Setting sinusoid.C = 0 gives a symmetric oscillation centered on the rest height. Increasing A widens the stretch range; increasing the period slows the breathing tempo.

Big Idea 2 — Composing Three Concurrent Animations

Hover, stretch, and eye wander are fully independent and can all run simultaneously. The order in draw() matters:

1. Hover (setPosition) — repositions the head anchor and calls _build() with the current bodyHeight.
2. Stretch (stretching) — updates bodyHeight and calls _build() again with the new height and the already-updated position.
3. Eyes — lookingAround() or lookAt() updates pupil offsets; no rebuild needed.

The two _build() calls per frame (one from hover, one from stretch) are cheap — they create a handful of plain objects. Eye noise state is preserved across both rebuilds via the save/restore logic introduced in Stage 5, so the wander continues without interruption.

Big Idea 3 — Incommensurable Periods (Three Sinusoids)

The defaults — H period 5 s, V period 3 s, S period 2.5 s — share no common factor below their LCM (15 s), so the combined motion never visibly repeats within a typical viewing session. Setting all three to the same value produces a rigidly synchronized bounce-and-stretch. Setting S to exactly double the V period means the ghost is fully extended every other bob — a satisfying way to see the phase relationship directly.

Big Idea 4 — Control Panel Parameters