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Skyline Analysis Example

This example demonstrates how to perform skyline analysis using the DMap3D SDK, extracting the skyline contour from the current viewpoint.

Preview​

Analyze the skyline from the current viewpoint in the 3D scene, marking the skyline contour of buildings or terrain with colored lines.

Complete Code​

src/components/SkylineAnalysis.tsx
import { useEffect, useRef, useState } from 'react'
import * as Cesium from 'cesium'
import DMap3D from 'dmap3d'
import './SkylineAnalysis.css'

function SkylineAnalysis() {
  const containerRef = useRef<HTMLDivElement>(null)
  const viewerRef = useRef<Cesium.Viewer | null>(null)
  const toolRef = useRef<any>(null)
  const [isActive, setIsActive] = useState(false)
  const [color, setColor] = useState('#FF0000')

  useEffect(() => {
    if (!containerRef.current) return

    Cesium.Ion.defaultAccessToken = 'your-cesium-ion-token'

    const viewer = new Cesium.Viewer(containerRef.current, {
      animation: false,
      fullscreenButton: false,
      geocoder: false,
      homeButton: false,
      sceneModePicker: false,
      selectionIndicator: false,
      timeline: false,
      navigationHelpButton: false,
      infoBox: false,
      baseLayerPicker: false,
      terrain: Cesium.Terrain.fromWorldTerrain(),
    })
    viewerRef.current = viewer

    // Load 3DTiles
    const loadTileset = async () => {
      const tileset = await Cesium.Cesium3DTileset.fromUrl(
        '/3DTiles/model/tileset.json'
      )
      viewer.scene.primitives.add(tileset)
      viewer.zoomTo(tileset)
    }
    loadTileset()

    // Create skyline analysis tool
    const tool = new DMap3D.analysis.skyline(viewer, {
      color: '#FF0000',
    })
    toolRef.current = tool

    return () => {
      tool.destroy()
      viewer.destroy()
    }
  }, [])

  const handleStart = () => {
    toolRef.current?.init()
    setIsActive(true)
  }

  const handleClear = () => {
    toolRef.current?.destroy()
    // Recreate
    const viewer = viewerRef.current
    if (viewer) {
      toolRef.current = new DMap3D.analysis.skyline(viewer, { color })
    }
    setIsActive(false)
  }

  const handleColorChange = (newColor: string) => {
    setColor(newColor)
    if (isActive) {
      toolRef.current?.destroy()
      const viewer = viewerRef.current
      if (viewer) {
        const newTool = new DMap3D.analysis.skyline(viewer, { color: newColor })
        newTool.init()
        toolRef.current = newTool
      }
    }
  }

  return (
    <div className="skyline-analysis">
      <div ref={containerRef} className="cesium-container" />

      <div className="control-panel">
        <h3>Skyline Analysis</h3>
        <p>Analyze the skyline contour from the current viewpoint</p>

        <div className="buttons">
          <button onClick={handleStart} disabled={isActive}>
            {isActive ? 'Enabled' : 'Start Analysis'}
          </button>
          <button onClick={handleClear}>Clear</button>
        </div>

        <div className="settings">
          <div className="setting-item">
            <label>Skyline Color:</label>
            <input type="color" value={color}
              onChange={(e) => handleColorChange(e.target.value)} />
          </div>
        </div>
      </div>
    </div>
  )
}

export default SkylineAnalysis

Stylesheet​

src/components/SkylineAnalysis.css
.skyline-analysis { position: relative; width: 100%; height: 100vh; }
.cesium-container { width: 100%; height: 100%; }

.control-panel {
  position: absolute; top: 20px; right: 20px;
  background: rgba(255, 255, 255, 0.95); padding: 20px;
  border-radius: 8px; box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15); min-width: 250px;
}
.control-panel h3 { margin: 0 0 10px 0; font-size: 18px; }
.control-panel p { margin: 0 0 15px 0; color: #666; font-size: 14px; }
.buttons { display: flex; gap: 10px; margin-bottom: 15px; }
.buttons button {
  flex: 1; padding: 8px 16px; border: none; border-radius: 4px;
  background: #1890ff; color: white; cursor: pointer; font-size: 14px;
}
.buttons button:hover { background: #40a9ff; }
.buttons button:disabled { background: #d9d9d9; cursor: not-allowed; }

.settings { border-top: 1px solid #e8e8e8; padding-top: 15px; }
.setting-item { display: flex; align-items: center; gap: 10px; }
.setting-item label { font-size: 13px; color: #333; }
.setting-item input[type="color"] {
  width: 50px; height: 28px; border: 1px solid #d9d9d9; border-radius: 4px; cursor: pointer;
}

Key Code Explanation​

1. Create Skyline Analysis Tool​

const tool = new DMap3D.analysis.skyline(viewer, {
  color: '#FF0000', // Skyline color
})

2. Start Analysis​

tool.init() // Start skyline analysis

3. Get 2D Skyline Data​

const result = await tool.getSkyline2D()
// result.pixelPoints: Pixel coordinates and colors
// result.groundHeights: Corresponding ground heights

4. Changing Color Requires Rebuilding​

tool.destroy()
tool = new DMap3D.analysis.skyline(viewer, { color: '#00FF00' })
tool.init()

Extended Features​

  1. Skyline Comparison - Compare skylines from different viewpoints
  2. Occlusion Analysis - Analyze building impact on the skyline
  3. Screenshot Export - Export skyline analysis screenshot
  4. Sunlight Analysis - Calculate sunlight duration combined with the skyline