City-Lifeline-Cockpit/dynamic-component-service-master/openspec/changes/add-bus-line-network-component/design.md

Design

The component loads GeoJSON client-side and converts each LineString or MultiLineString route into a Line2 object from three-stdlib.

The rendering pipeline is intentionally simple:

• Fetch the configured GeoJSON URL with an abortable request; the default URL points to the local public/data/bj-bus.json copy.
• Normalize route coordinate arrays from GeoJSON features.
• Project [lng, lat] pairs with Web Mercator and subtract a local center.
• Apply a configurable mapScale so the whole Beijing network fits the preview camera by default.
• Assign each route to a height and color bucket, matching the Mars3D sample's layered green palette by default.
• Use LineMaterial with worldUnits for stable width in the Three scene.

This avoids generating heavy tube meshes for roughly 64,000 source points and keeps the logic readable.

Configuration

The component exposes:

• Data: dataUrl, dataUrlDraft, maxRoutes, pointSampleStep.
• Projection: autoCenter, centerLng, centerLat, mapScale.
• Shape: lineWidth, baseHeight, heightStep, heightGroups.
• Style: colorTheme, opacity, pulseSpeed, pulseIntensity.

Defaults use the local Mars3D dataset copy, automatic bounds centering, full route count, and a light point sample step for preview performance. Hosts can edit dataUrlDraft and click the confirm action to apply a different URL; they can set pointSampleStep to 1 for full coordinate fidelity.

Constraints

• The generic preview views remain unchanged.
• The component must dispose line geometries/materials when data or props change.
• Fetch errors must not break the scene; the component should clear its own lines and log a scoped warning.