Dynamic Simplification
This example shows a map of the United States that continuously simplifies its boundaries, alternating between depicting all counties and reducing them to a coarse outline. The animation cycles through progressive shapes while preserving topology. The code uses `topojson.presimplify` to precompute point importance, a custom `d3.geo.transform` geometry stream to filter points based on a dynamic area threshold, and `d3.geo.path` to render the result onto a Canvas via its 2D context, driven by `transition.tween` and `d3.interpolate`.
AI-generated descriptionThis example demonstrates dynamic topology-preserving shape simplification using topojson.presimplify, a new feature in TopoJSON 1.3. The presimplify method computes the importance of each point using a configurable importance function; the default implementation uses Cartesian triangular area for Visvalingam simplification. Then, a custom geometry stream (d3.geo.transform) uses the previously-computed point importance to filter the geometry during rendering.