VectorPaint cast-shadow studies: align objects, contact points and shadows

English translation of the Chinese original, translated on 2026-10-27. Original publication dates, attribution, code and version notes are retained.

A cast shadow helps ground an object when direction and contact are clear. Practise with a fictional box, bottle and sphere using manual 2D paths. These are illustrative shapes, not rendered or optically measured shadows.

Choose one light direction

Place three simple objects on one table region of a 1200 by 800 pixel canvas. Choose upper-left light and lower-right shadows with a temporary reference arrow. This is a design convention, not automatic detection. Establish compatible views and contact bases before shadows, then remove the reference from delivery.

Start shadows at contact points

Draw a restrained polygon from the box’s contact edge toward the chosen direction, behind the object and above the table. Start short and low-contrast before extending it. Establish geometry with a solid fill before adding darker contact areas. Keep each object’s shadow separately editable.

Preserve differences between object shadows

Suggest bottle-neck/body differences and use a flattened ellipse for the sphere where appropriate. Each shape should relate to its object, even as a simplification. Inspect object-shadow pairs separately before the full scene. Recompose clipped shadows deliberately rather than losing their ends accidentally. Establish identity before softness.

Compare all shadows against one direction

Check the main extension from each contact point against the same chosen direction. Avoid introducing unexplained multiple lights. Temporary parallel reference lines can help but must be removed. Investigate unusually long shadows as deliberate choices or mistakes, and compare them in one colour to isolate geometry.

Control shadow weight through contrast and area

Reduce unnecessary area before making shadows darker or lighter. Keep object opacity and occlusion intentional. Use supported gradients or restrained layered shapes for stylised softness if desired rather than assuming an unverified blur tool. Toggle effects to confirm they support contact instead of merely adding complexity.

Maintain contact when objects move

Move the bottle alone in a copy to reveal the lost contact, then update its shadow. Ordinary objects do not maintain real projection automatically. Reassess shadow shape after height changes rather than scaling the whole scene. Test sphere contact too, then organise related parts while retaining independent editability.

Inspect contact edges and dark areas after export

Save and check contact and dark separation at delivery size on relevant table/background colours. Transparent shadows composite with their destination, so inspect actual placement. Name background and revision clearly and exclude diagnostic arrows/lines. Small versions can simplify detail while retaining grounding and direction.

Fix starts before effects when shadows fail

For floating objects, inspect gaps and stacking before darkening. For inconsistent lighting, repair each direction against the reference. Check layering or object transparency if shadows cross surfaces. Simplify implausible contours rather than adding false precision. Confirm contact and direction with solid fills before restoring effects.