SketchWave Tri-Disk Demo

This demo explores how three overlapping SWDisk circles produce the illusion of a light source and a shadow. A center disk sits in front; a light disk peeks out on one side (white by default), and a shadow disk peeks out on the other (black by default).

The Geometry

• All three disk centers lie on a single line controlled by Axis Angle.
• The two side disks are offset from the center by Center Offset user-units, one in each direction along the axis.
• Their radius = k × center radius, where k ∈ [0, 1].
• At offset = 0, all three share the same center (fully hidden).
• At offset = center radius, side disk centers lie on the circumference of the center disk (maximum peek).

Controls

• Center Radius — size of the main (green) disk, in grid units.
• Side Disk Size Factor k — side disk radius as a fraction of center radius.
• Center Offset — how far each side disk center is displaced along the axis.
• Axis Angle — direction of the displacement line (0° = horizontal; CCW positive).
• Stroke Thickness — outline weight for all three disks.
• Disk Colors — pick fill and stroke color (linked) for each of the three disks.
• Opacity — per-disk alpha (0 = transparent, 100 = opaque).
• Spin — rotates the axis angle continuously. Negative speed = clockwise.
• Drag the center disk center point to move the entire group.
• Click the canvas (not on center) to toggle the grid.

Drawing Order

The disks are drawn back-to-front: right first, then left, then center on top. This ensures the center always occludes the side disks, giving the shadow/light illusion regardless of color.

Keyboard Shortcuts

• s — toggle spin
• r — factory reset
• q — stop spin (keep geometry)