# VectorPaint paired line gratings: inspect moiré and export differences in static overlays

Language: en
Canonical: [VectorPaint paired line gratings: inspect moiré and export differences in static overlays](<https://allluckly.cn/en/guides/vectorpaint-moire-line-overlays/>)
中文：[中文 HTML](<https://allluckly.cn/guides/vectorpaint-moire-line-overlays/>)
English: [English HTML](<https://allluckly.cn/en/guides/vectorpaint-moire-line-overlays/>)
Published: 2026-11-05T00:00:00+08:00
Modified: 2026-11-05T09:38:59+08:00
Author: Bison

Build an equally spaced line source, rotate only one layer and distinguish overlay relationships from changes introduced by scaled display.

English translation of the [Chinese original](<https://allluckly.cn/guides/vectorpaint-moire-line-overlays/>), translated on 2026-11-05. Original publication dates, attribution, code and version notes are retained.

Two simple line sets can produce larger light/dark patterns when overlaid. Build two static gratings and change only their relative angle, without calling the result an animation or automatically generated app effect. Retain individual lines and layer sources. Check the actual output rather than guaranteeing identical patterns on every display and at every zoom level.

## Create one equally spaced parallel-line source

On a 1000 by 1000 pixel canvas, reserve a 700-pixel square working area. Draw one vertical narrow black rectangle or line and duplicate it into sixteen equally long, equally weighted and equally spaced lines. Maintain equal centre intervals rather than moving the last line inward to fit. Test a small repeat before extending and record the count. Save a single-layer baseline; both sets must share its source so an angle comparison does not secretly change spacing too. These are screen-sample parameters, not print-screen or optical-device specifications.

## Keep the two layers genuinely see-through between lines

Name the first set lower grating and its copy upper grating, initially coincident. Each contains black lines only; a white backing behind the upper set would conceal the lower. If clipping to a square window, verify both sets’ scope and remember masking does not delete lines. Opaque black lines with open gaps are sufficient; lowering whole-group opacity is not initially necessary. Hide each set in turn to count sixteen complete lines independently. Save this coincident state as the baseline for relative rotation and display comparisons.

## Rotate only the upper grating and record the change

Keep the lower set fixed and rotate only the upper slightly in a copy using a verified method, recording a numerical value or manual approximation. Check that selection excludes the lower set and window. Use the shared working-area centre as reference; if controls rotate about a bounding-box centre, establish whether it matches. Observe larger light/dark bands and record their actual direction and spacing without inventing a universal uncalculated period formula. If no clear pattern appears, retain that observation and investigate line weight, spacing and display conditions separately.

## Explain the overlay separately from either line set

The [Exploratorium moiré exhibit](<https://annex.exploratorium.edu/xref/exhibits/moire_patterns_table.html>) describes observing overlaid repetitive patterns; it establishes no dedicated app generator. Hide one layer and inspect whether larger patterns disappear or change with the two-set relationship, then restore both. Do not trace visible bands as a third set of objects, which would alter this exercise’s sources. Study static coverage without flashing or rapid switching. If viewing is uncomfortable, stop and retain the file for ordinary-size inspection; prolonged staring is not a completion requirement.

## Keep file and angle fixed when comparing display scales

Without editing geometry, inspect two recorded display scales and note differences in fine lines, bands and edges. Display changes do not automatically mean paths were rewritten and cannot guarantee identical exported appearance. Return to the first scale and verify that different-angle files were not confused. A line-weight test belongs in another copy with angle fixed. Record visible and uncertain results simply, without presenting eye observations as display-precision measurements. The comparison informs output choices rather than unverified physical parameters.

## Prepare an explanatory version rather than an unexplained effect

Create an explanatory triptych of lower set, upper set and overlay at equal displayed size, stating angle or manual approximation. Place text outside dense lines so sources are understood before the result. Keep one window range; differing crops can mislead. Title it a static line-overlay sample without automatic movement or a guaranteed effect. State any size restriction instead of treating one successful screenshot as universal evidence. Save decorative and explanatory versions separately while retaining independently selectable source groups.

## Check fine lines and open gaps in the real output

Export at the intended size and reopen it, inspecting sixteen source lines, window edges and overlay. Small raster output may lose detail; adjust size or spacing for its purpose in a new version and compare again. SVG extensions do not guarantee identical viewers. Check transparent gaps on another background, ensuring no upper white backing. Include count, relative state and dimensions in filenames without overwriting the final with tests. Printing needs an actual proof; screen bands do not validate a physical print screen.

## Inspect layers separately for absent bands or solid black

For solid black, check whether line width consumes the gaps or a large fill entered the upper layer. For no change, verify that only the upper set rotated. Missing edge lines call for inspecting rotation extent and masks, not arbitrary extra lines breaking spacing. Patterns at only one zoom need a fixed-file view comparison before editing every path. Repeat single-set, coincident, relative-rotation and real-export checks. A useful sample explains its repeated sources and which differences belong only to current viewing conditions.

## Related tutorials and sources

[VectorPaint two-colour overlaps: compare opacity and stacking order](<https://allluckly.cn/en/guides/vectorpaint-transparent-overlap/>), [Choose VectorPaint export formats: SVG, PDF, PNG and editable originals](<https://allluckly.cn/en/guides/vectorpaint-export-formats/>).

Sources checked on November 5, 2026: VectorPaint 1.0.8, requiring iOS / iPadOS 17 or later. Capability scope follows the [official App Store description](<https://apps.apple.com/cn/app/id1587272880>) and [Apple public version lookup](<https://itunes.apple.com/lookup?id=1587272880&country=cn>). These are exercises and checks you can perform, without a claim of step-by-step physical-device testing or verification in every target environment. Example content is instructional; follow the controls in your installed version.