Area Viewshed Analysis Example

This example demonstrates how to perform area viewshed analysis using the DMap3D SDK, showing visible and non-visible areas within the frustum range of an observation point.

Preview

The user clicks in the scene to set an observation point and analyzes the visibility of the area through a frustum, with support for dynamically adjusting horizontal/vertical field of view angles.

Complete Code

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

function ViewshedAreaAnalysis() {
  const containerRef = useRef<HTMLDivElement>(null)
  const viewerRef = useRef<Cesium.Viewer | null>(null)
  const toolRef = useRef<any>(null)
  const [isActive, setIsActive] = useState(false)
  const [fovx, setFovx] = useState(90)
  const [fovy, setFovy] = useState(60)

  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 area viewshed analysis tool
    const tool = new DMap3D.analysis.viewshedArea(viewer, {
      fovx: 90,
      fovy: 60,
      visibleColor: '#00ff00',
      invisibleColor: '#ff0000',
      visibleColorAlpha: 0.5,
      invisibleColorAlpha: 0.5,
      heightOffset: 1.8,
      showFrustumRefLines: true,
    })
    toolRef.current = tool

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

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

  const handleClear = () => {
    const tool = toolRef.current
    if (tool) {
      tool.destroy()
      // Recreate
      const viewer = viewerRef.current
      if (viewer) {
        const newTool = new DMap3D.analysis.viewshedArea(viewer, {
          fovx, fovy,
          visibleColor: '#00ff00',
          invisibleColor: '#ff0000',
          visibleColorAlpha: 0.5,
          invisibleColorAlpha: 0.5,
          heightOffset: 1.8,
          showFrustumRefLines: true,
        })
        toolRef.current = newTool
      }
    }
    setIsActive(false)
  }

  const handleFovxChange = (value: number) => {
    setFovx(value)
    if (toolRef.current) {
      toolRef.current.fovx = value
    }
  }

  const handleFovyChange = (value: number) => {
    setFovy(value)
    if (toolRef.current) {
      toolRef.current.fovy = value
    }
  }

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

      <div className="control-panel">
        <h3>Area Viewshed Analysis</h3>
        <p>Click to set observation point, drag to adjust direction</p>

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

        <div className="settings">
          <h4>Parameter Settings</h4>
          <div className="setting-item">
            <label>Horizontal FOV: {fovx} deg</label>
            <input type="range" min="1" max="130" value={fovx}
              onChange={(e) => handleFovxChange(Number(e.target.value))} />
          </div>
          <div className="setting-item">
            <label>Vertical FOV: {fovy} deg</label>
            <input type="range" min="1" max="179" value={fovy}
              onChange={(e) => handleFovyChange(Number(e.target.value))} />
          </div>
        </div>

        <div className="legend">
          <div className="legend-item">
            <span className="color-box" style={{background: '#00ff00'}}></span>
            <span>Visible Area</span>
          </div>
          <div className="legend-item">
            <span className="color-box" style={{background: '#ff0000'}}></span>
            <span>Non-visible Area</span>
          </div>
        </div>
      </div>
    </div>
  )
}

export default ViewshedAreaAnalysis

Stylesheet

src/components/ViewshedAreaAnalysis.css
.viewshed-area-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: 260px;
}
.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; margin-bottom: 15px; }
.settings h4 { margin: 0 0 12px 0; font-size: 14px; color: #666; }
.setting-item { margin-bottom: 12px; }
.setting-item label { display: block; font-size: 13px; color: #333; margin-bottom: 4px; }
.setting-item input[type="range"] { width: 100%; }

.legend-item { display: flex; align-items: center; gap: 8px; margin: 4px 0; font-size: 14px; }
.color-box { width: 20px; height: 12px; border-radius: 2px; }

Key Code Explanation

1. Create Area Viewshed Tool

const tool = new DMap3D.analysis.viewshedArea(viewer, {
  fovx: 90,                  // Horizontal field of view (1-130 deg)
  fovy: 60,                  // Vertical field of view (1-179 deg)
  visibleColor: '#00ff00',   // Visible area color
  invisibleColor: '#ff0000', // Non-visible area color
  heightOffset: 1.8,         // Observation point height offset (meters)
  showFrustumRefLines: true, // Show frustum reference lines
})

2. Dynamically Adjust Parameters

// Modify properties for immediate effect
tool.fovx = 120
tool.fovy = 90
tool.visibleColor = '#00ff00'
tool.invisibleColor = '#ff0000'
tool.heightOffset = 2.0

3. Difference from Single-Point Viewshed

Feature	viewshed	viewshedArea
Analysis Range	Ray detection	Frustum area
Parameter Adjustment	Fixed	Dynamic adjustment supported
Field of View	None	fovx + fovy
Use Case	Quick check	Precise analysis

Extended Features

Multiple Observation Points - Analyze multiple observation points simultaneously
Optimal Position - Calculate the best observation position
Viewshed Coverage - Calculate regional visibility coverage rate
Dynamic Analysis - Update analysis in real-time as the camera moves

Preview​

Complete Code​

Stylesheet​

Key Code Explanation​

1. Create Area Viewshed Tool​

2. Dynamically Adjust Parameters​

3. Difference from Single-Point Viewshed​

Extended Features​

Related API​