Geometry Handling¶

MapXZRoad¶

Expand PostGIS Way to polygon.

Obj3Type:

xv.XComponent.Obj3Type.MapXZRoad

Handler API:

xgeom.generateWayxz()

Test pages:

test/html/map3d/geopath-road.html
test/html/map3d/geopaths.html
test/html/map3d/cd-express.html

hexatile¶

Generate hexagonal prism at a location in xz plane.

Obj3Type:

xv.XComponent.Obj3Type.Hexatile

test page:

test/html/map3d/haxcylinder.html
test/html/map3d/epsg4326-points.html

Where the hexagon tile are generated with the template:

Hexatile is generated as a hexagonal cylinder. Parameters example:

paras: {
  origin: o3,
  geostyle: {
    radius: 45, height: 24,
    scale: 0.02,
    maxHeight: 40,
    groups: 2,
    onGroup: (fx, feature) => { return fx % 2; }
  }
}

paras.origin

Specifying the geographically center of xworld

paras.geostyle

Specifying how the cylinder been generated, where

– geostyle.radius: circumvent circle radius.

– geostyle.scale: geojson’s coordinates scale to xworld.

– geostyle.height: cylinder height, in xworld.

– geostyle.maxHeight: max heigth that with the highest thermal color.

The thermal colors can word only with tiledOrbs shader. If a cylinder tile’s heigth is higher than maxHeight, the higher part will be applied with the max color.

– geostyle.groups: total groups. Groups can be used by XTweener for showing different animation.

– geostyle.onGroup: optional callback for getting group index according to feature.

TexPrism & Triangulation¶

Extrude polygon to prism.

Obj3Type:

xv.XComponent.Obj3Type.texPrism

Handler API:

xgeom.texPrism3857()

Test pages:

test/html/map3d/geopath-road.html
test/html/map3d/geopaths.html
test/html/map3d/cd-express.html

The texPrism geometry in x-visual can handling polygons of day-to-day used data from OSM etc. It first generate lateral face, then use off-the-shelf npm package, npm cutear [5] to generate end face of a prism.

Broadly, there are two way’s to handle this task:

Polygon scanning like earcut or [1] or [2].
Delaunary triangulation like [4].

The boundary is blur considering how [1] finishing the task.

References:

1. Liu Yonghe, Feng Jinming, Shao Yuehong, A Simple Sweep-line Delaunay Triangulation Algorithm,

Atul Narkhede, Dinesh Manocha, Fast Polygon Triangulation based on Seidel’s Algorithm

3. Discussion: Divide a 2D polygon with N vertices into triangles draw in a 3D space, Mathatics, StackExchange.

4. Jonathan Richard Shewchuk, Triangle Open Source Project, Computer Science Division, University of California at Berkeley, Berkeley, California 94720-1776

npm earcut