VJMAP

# Professional Algorithms

# Requirements

"Can we take several sets of 3D coordinates (or 3D polylines drawn in CAD), give a cross-section shape, and directly generate 3D pipes?"

For example, the original CAD drawing is as follows:

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The required 3D pipe effect generated automatically by obtaining 3D line coordinate data with threejs is as follows:

image-20240822194923933

# Behind the Scenes

If you directly use THREE.TubeGeometry in threejs to draw each line, gaps will appear at intersections, as shown below:

image-20240822195608479

How to solve the gap problem at intersections became a challenge.

Searching online, I found similar issues in the energy industry—"3D automatic modeling of mine roadways" is a hot topic, with many master's and doctoral students researching it.

So I spent a few yuan on Taobao for a 90-day literature download account and began the process of downloading papers, studying them, and researching algorithms...

image-20240822200613545

After many days of research, few papers explained the entire algorithm flow thoroughly—they only gave a general principle, with details left for you to figure out...

Until I accidentally found a professional book 3D Mine Roadway Network Modeling and Spatial Network Analysis

image-20240822201446618

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After reading it, I was inspired. Using the "half-roadway model" to handle intersections and optimizing some details, I finally achieved satisfactory results.

image-20240822201805360

Online demo: https://vjmap.com/map3d/demo/#/demo/map/builtin/objects/03builtinobjtubepathauto (opens new window)

# 3D Personnel Positioning System (Example Open Source)

After solving the above challenge, many applications can be developed based on 3D roadways, such as a "3D personnel positioning system."

Implemented features:

  • Parse 3D polyline objects in CAD drawings to obtain 3D line coordinates (CAD source: https://vjmap.com/app/cloud/#/map/sys_tube?version=v1&mapopenway=GeomRender&vector=false (opens new window))

  • Automatically build topology from 3D line coordinates. (Because drawing is done as a single line, it needs to be processed into node-based relationship analysis for intersections)

  • Automatically generate 3D roadways and handle intersections from data

  • Simulate personnel movement data and display personnel positions in real time on the 3D map

  • Click on personnel to view details

  • View personnel history tracks

  • Automatically find the nearest exit from a given coordinate

Implementation effect:

image-20240822202414719

image-20240822202514515

image-20240822202548702

This example code is open source. Visit https://vjmap.com/effect/person/ (opens new window) to view it online.

More examples: https://vjmap.com/map3d/example.html (opens new window)

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