VectorPaint reversible negative space: check a shared vase-and-profile boundary

English translation of the Chinese original, translated on 2026-11-03. Original publication dates, attribution, code and version notes are retained.

One boundary can describe both a central vase and profiles at its sides. Design simplified original shapes and alternate between figure and ground without tracing an existing artwork. The aim is to support both readings, without claiming everyone must perceive the same image at the same moment or that the app can automatically judge the effect.

Sketch both intended readings first

Create an 800 by 1000 pixel canvas with a central vase and room for side figures. List vase rim, neck, body and base alongside forehead, nose, mouth and chin to find shared turns. Establish broad positions before small decoration. Neither reading needs realism. Do not draw a finished vase and add eyes to force a face; the shared silhouette should do the work, and extra features may weaken the negative-space effect. Preserve a draft and alter one important turn at a time.

Build one boundary with a few nodes

Use the Pen tool to build one edge through rim/forehead, nose, a smaller mouth change, chin/body and base. Close the central filled shape, keeping the opposite side simple initially. Give turns a hierarchy rather than equal-sized teeth along the edge. Inspect the fill without a heavy stroke. Add nodes only when needed after checking that the side supports both vase and profile readings; many small points cannot replace a clear structure.

Make the other side coherent without copying every detail

Match rim, narrowest area, widest area and base heights on the second side so the vase remains coherent. Duplication/reflection can be a starting point where supported, or draw the counterpart manually. Check both boundaries afterward. Profiles may differ, but their feature order must remain sensible. Begin with two values and judge visible areas and major turns; mathematical centring alone does not prove optical balance.

Inspect the positive and negative figures separately

Shift fills temporarily to inspect the vase alone, then the opposing profiles. These treatments guide attention rather than perform recognition. Record specific issues such as compressed nose/mouth spacing or an overly narrow body. If only one reading works, edit the shared boundary before adding unrelated decoration. Retain separate diagnostic copies and choose one intended colour treatment for the final image.

Reduce noise through spacing and edge hierarchy

Preserve readable spacing between nose and mouth and avoid fragile rim spikes. Use a controlled mixture of sharp and smooth turns. A very wide vase reduces space for faces; an overly narrow one weakens the container reading. Compare one width or curve adjustment at a time at equal size. Avoid ornamental edges that introduce unintended readings, and remove small lip details if that clarifies the shared structure.

Test stability at large and small sizes

Export large and small previews from a saved baseline and identify rim, nose and chin without reading the title first. Simplify fragile details for the smaller version. A title naming two faces is not evidence that the boundary works. Scope observations to the tested conditions and acknowledge different perceptions. Teaching prompts may guide inspection, but should not treat a person’s first perceived figure as a measure of ability; the exercise evaluates design choices.

Keep the editable boundary and final palette

Retain the shared editable contour and diagnostic copies and label final palette/size outputs. Transparent export does not turn a pale filled object into a true cut-out; inspect the intended background. Any real opening needs supported path or mask construction and renewed checks. Exclude draft markers and alternate palettes from delivery. For recolouring, hold geometry fixed first so changes in perception can be attributed to values rather than simultaneous shape edits.

Return to key turns when readings conflict

If the vase works but faces fail, check the order and spacing of forehead, nose, mouth and chin. If faces work but the vase fails, revisit rim/neck/body/base proportions. Remove surplus nodes from shaky curves. Understand the role of each original turn rather than tracing a ready-made illusion. Diagnose export edges through strokes, background and joins separately. Repeat isolated figure checks and size previews before accepting the revision.