SWEyeball Saga

Eye 1 established the structure. Eye 2 asks a design question about that structure: what happens when layers are visible through each other? This stage explores SWDisk's alpha capability and deliberately clears the visual clutter from Eye 1 to prepare the canvas for the pupil layer arriving in Eye 3.

Big Picture — What This Stage Introduces

1. Alpha transparency on SWDisk — setFillAlpha()
   Both sclera disks are set to setFillAlpha(60) — 60% opaque, 40% transparent. This makes the background color visibly bleed through the white fill, proving that SWDisk respects the full HSB + alpha pipeline of SWColor. It also previews a design decision: when a pupil disk is drawn on top, can you still sense the sclera behind it? Alpha makes that possible.
2. Colored background as a testing tool
   The background switches from the default light gray to swLightBlue. This is a deliberate developer choice: a non-neutral background makes transparency visible. If the sclera were opaque white on a white background, setFillAlpha() would produce no perceptible effect. The colored background turns alpha from an invisible property into a visible one.
3. Hiding the center point — shouldShowCenter = false
   In Eye 1, both SWDisk center points were visible and labeled — useful for placement debugging. Eye 2 turns them off. This isn't about the center points being wrong; it's about readiness: the next stage will place a pupil disk at a new offset center, and having two labeled center dots would clutter the layered result. Hiding them now keeps the visual story clean.

The Layering Mental Model

An eyeball is fundamentally a stack of disks, drawn back-to-front each frame. For that model to work, the layers need to interact predictably:

• A fully opaque sclera completely hides whatever is behind it — which is fine for the final eyeball, but makes it impossible to verify layer order during development.
• A semi-transparent sclera lets you see the grid and any disk drawn beneath it, making the draw order immediately obvious.
• Eye 2 uses transparency as a development diagnostic. The final SWEyeball class uses a fully opaque sclera — but understanding how alpha interacts with layered disks is a prerequisite for building that class confidently.

What to Notice in the Sketch

• The sclera disks are visibly tinted by the light-blue background, confirming setFillAlpha() is working at the p5.js color level.
• No center-point markers appear — the disks are positionally anchored but visually clean.
• The eye positions shift slightly inward to (−2.5, 6) and (2.5, 6) compared to Eye 1, a quiet hint that spacing decisions are still being tuned.
• Clicking the canvas still toggles the grid, confirming interaction infrastructure carries forward unchanged from Eye 1.

The Road Ahead

Eye 3 adds the pupil — a second SWDisk drawn on top of the sclera, with its own independent SWPoint center. The semi-transparent sclera from Eye 2 will make it easy to verify that the pupil disk is correctly positioned over the sclera rather than behind it.