surfacers

Slide Surfacers

Slide is based on the concept to sliding lines into the valleys of a surface. This surface can be based on any data. To wire it up you'll need to implement the Surfacer interface:

// A Surfacer defines what a surface needs to do to be used for sliding.
// It should define a surface in the mercator projected space (EPSG:3857).
// Better values should be positive with a maximum of 1 meter, scaled up
// to be consistent with the EPSG:3857 scaling factor for that latitude.
type Surfacer interface {
	// GradientAt and ValueAt should accept points in the EPSG:3857 (mercator) space.
	GradientAt(point *geo.Point) *geo.Point // typically derived from a smoothed surface
	ValueAt(point *geo.Point) float64       // typically the original surface value (pre smooth)

	// SuggestedOptions allows the surfacer to tell slide what the defaults should be.
	SuggestedOptions() *SuggestedOptions
}

Tile Overlay Surfacer

This surfacer is provided as a basic example. It downloads Mapbox TIGER tile layer tiles making yellow areas "deep". Vector data can now be "slided" to updated TIGER geometry. Checkout the demo.