Polygon Example & Support

[traik06]

Hello,

Is there an example of create a .dxf of multiple polygons? I cant seem to find it in the documentation on how to implement it.

Please bear with me here I am new to creations of .dxf files

Here is an example of the code I am trying to use as a tester

These would be lat and lng coordinates

const coordinates = [
   // polygon number 1
   [
   [0, 0, 0], // Vertex 1: x, y, z
   [0, 10, 0], // Vertex 2: x, y, z
   [10, 10, 0],// Vertex 3: x, y, z
   [10, 0, 0], // Vertex 4: x, y, z
   [0, 0, 0], // Closing vertex to complete the polygon
   ],
   // polygon number 2
   [
   [5, 0, 0], // Vertex 1: x, y, z
   [55, 10, 0], // Vertex 2: x, y, z
   [67, 10, 6],// Vertex 3: x, y, z
   [87, 0, 8], // Vertex 4: x, y, z
   [5, 0, 0] // Closing vertex to complete the polygon
   ],
];

Thanks very much

[tarikjabiri]

Hi

You can use the Polyline 3D

import {
  DxfWriter,
  PolylineFlags,
  type PolylineVertex,
} from "@tarikjabiri/dxf";
import { writeFileSync } from "node:fs";

const coordinates = [
  // polygon number 1
  [
    [0, 0, 0], // Vertex 1: x, y, z
    [0, 10, 0], // Vertex 2: x, y, z
    [10, 10, 0], // Vertex 3: x, y, z
    [10, 0, 0], // Vertex 4: x, y, z
  ],
  // polygon number 2
  [
    [5, 0, 0], // Vertex 1: x, y, z
    [55, 10, 0], // Vertex 2: x, y, z
    [67, 10, 6], // Vertex 3: x, y, z
    [87, 0, 8], // Vertex 4: x, y, z
  ],
];

// No need to duplicate the first vertex to close the polygon

const dxf = new DxfWriter();
const pvs = coordinates.map((vertices) => {
  return vertices.map((v) => {
    const pv: PolylineVertex = {
      point: {
        x: v[0],
        y: v[1],
        z: v[2],
      },
    };
    return pv;
  });
});
for (const pv of pvs) {
  dxf.addPolyline3D(pv, {
    flags: PolylineFlags.Closed,
  });
}

writeFileSync("polygons.dxf", dxf.stringify(), {
  encoding: "utf-8",
});

[tarikjabiri]

These would be lat and lng coordinates

Important

There is no support for geographic coordinates, you need to use projected coordinates using some transformation.
DXF support only cartesien coordinates

[traik06]

@tarikjabiri

Do you have any recommendations on a good approach?

So what I would need to do is convert these coordinates against something like an EPSG code?

then once they are transformed I should just be able to import it into CAD and view it in the region that I have set for the projection?

[tarikjabiri]

proj4js can do transformations, you can use https://epsg.io/ to get the the code for proj4js, you can search for you projection there and select proj4js