3D Mesh Entity (MeshEnt)

About 2 min

3D Mesh Entity (MeshEnt)

MeshEnt represents 3D mesh entities in CAD and serves as the unified frontend representation for all 3D entity types.

Overview

MeshEnt is used to represent 3D entities imported from DWG files, including:

DWG Entity Type	sourceType	Description
AcDb3dSolid	`3DSOLID`	3D solid (box, cylinder, etc.)
AcDbRegion	`REGION`	Region
AcDbSurface and derived classes	`SURFACE`	Surface (extruded, revolved, etc.)
AcDbPolyFaceMesh	`POLYFACE`	Polyface mesh
AcDbPolygonMesh	`POLYMESH`	Polygon mesh
AcDbFace / AcDb3dFace	`3DFACE`	3D face

All 3D entities are converted to triangular meshes (vertices + triangle indices) on import and rendered in wireframe mode. Full 3D coordinate data (including Z values) is preserved to support future 3D viewing plugins.

Constructor

import { MeshEnt } from 'vjcad';

const mesh = new MeshEnt();

Typically MeshEnt does not need to be created manually; it is generated automatically when importing DWG files. To create manually:

import { MeshEnt, DbMesh } from 'vjcad';

const mesh = new MeshEnt();
mesh.fromDb({
    type: "MESH",
    sourceType: "3DSOLID",
    vertices: [0,0,0, 100,0,0, 100,100,0, 0,100,0, 50,50,80],
    indices: [0,1,4, 1,2,4, 2,3,4, 3,0,4, 0,1,2, 0,2,3],
    color: 5
} as DbMesh);
mesh.setDefaults();

Properties

Property	Type	Description
`sourceType`	string	Original DWG entity type (read-only)
`vertexCount`	number	Vertex count (read-only)
`triangleCount`	number	Triangle face count (read-only)
`vertices`	Float64Array	Vertex data, flattened `[x,y,z, x,y,z, ...]` (read-only)
`indices`	Uint32Array	Triangle face indices, flattened `[i,i,i, ...]` (read-only)

Methods

Method	Description
`fromDb(dbData)`	Load from database object
`toDb()`	Serialize to database object
`boundingBox()`	Get 2D projection bounding box
`getProjectedEdges()`	Get projected visible edges (for rendering)
`move(from, to)`	Move (supports 3D offset)
`rotate(center, angle)`	Rotate around point
`scale(center, factor)`	Scale
`mirror(start, end)`	Mirror
`stretch(from, to, box)`	Stretch
`clone()`	Clone
`getPoints()`	Get all vertices (Point2D array, with Z)

Rendering Mode

Currently MeshEnt is rendered in wireframe mode:

Contour edges (edges referenced by only one triangle) are always drawn
Internal edges (edges shared by two triangles) are drawn only when marked as visible
3D coordinates are projected onto the XY plane for display

Export Restoration

When exporting to DWG, attempts are made to restore the original entity type based on sourceType:

sourceType	Export Target	Restoration Level
`3DFACE`	OdDbFace	Exact restoration
`POLYFACE`	OdDbPolyFaceMesh	Exact restoration
`POLYMESH`	OdDbPolygonMesh (requires meshSize)	Exact/approximate
`REGION` / `SURFACE` / `3DSOLID`	Multiple OdDbFace groups	Degraded restoration

Tips

REGION, SURFACE, and 3DSOLID types are downgraded to 3D face combinations on export because the original parametric data (ACIS/SAT) is lost. This is expected behavior.

Examples

Create Cube Mesh

import { Engine, MeshEnt } from 'vjcad';

const vertices = [
    0,0,0,  100,0,0,  100,100,0,  0,100,0,
    0,0,100, 100,0,100, 100,100,100, 0,100,100
];
const indices = [
    0,1,2, 0,2,3,  // bottom
    4,6,5, 4,7,6,  // top
    0,1,5, 0,5,4,  // front
    2,3,7, 2,7,6,  // back
    0,3,7, 0,7,4,  // left
    1,2,6, 1,6,5   // right
];

const cube = new MeshEnt();
cube.fromDb({
    type: "MESH",
    sourceType: "3DSOLID",
    vertices,
    indices,
    color: 5
});
cube.setDefaults();

Engine.addEntities(cube);
Engine.zoomExtents();

Online Examples

Example	Description	Link
Create 3D Mesh	MeshEnt basic creation example (cube, pyramid, terrain)	Online Demo{target="_blank"}