Read and create geometry

Extract mesh and point geometry from model data — when properties are not enough

Goal

Create or extract mesh and point geometry from Speckle model data when analysis needs vertices, areas, or lengths — not only BIM properties.

When to use this

Most AEC automation uses DataObject.properties for schedules and QA — start with Find objects by property. Read this guide when you need 3D geometry from displayValue or Speckle.Objects types.

Install separately: dotnet add package Speckle.Objects. Not a dependency of Speckle.Sdk.

Recommended approach

1. Receive model with Receive2
2. Extract meshes via Flatten().OfType<Mesh>() or TryGetDisplayValue<Mesh>()
3. For creating geometry to send, put primitives in DataObject.displayValue

Prerequisites

• Work with model objects
• Find objects by property

Complete Example

Complete example

using Speckle.Objects.Data;
using Speckle.Objects.Geometry;
using Speckle.Sdk.Common;
using Speckle.Sdk.Models;

var mesh = new Mesh
{
    vertices = new List<double> { 0, 0, 0, 1, 0, 0, 0, 1, 0 },
    faces = new List<int> { 3, 0, 1, 2 },
    units = Units.Meters,
};

var wall = new DataObject
{
    name = "Wall 01",
    properties = new Dictionary<string, object?>(),
    displayValue = new List<Base> { mesh },
};

Console.WriteLine($"Mesh has {mesh.VerticesCount} vertices");

Mesh Data Layout

Mesh.vertices and Mesh.faces are flat lists:

• vertices: flat x, y, z, x, y, z, ... triples
• faces: each face starts with vertex count (n-gon size), followed by indices — [3, 0, 1, 2, 4, 1, 2, 3, 4] is one triangle then one quad

Example

for (var i = 0; i < mesh.vertices.Count; i += 3)
{
    double x = mesh.vertices[i];
    double y = mesh.vertices[i + 1];
    double z = mesh.vertices[i + 2];
}

List<Point> points = mesh.GetPoints(); // convenient; allocates per vertex

For large meshes, iterate vertices directly instead of GetPoints().

Speckle meshes support n-gons. Triangulate before handing off to triangle-only renderers — see MeshTriangulationHelper in Speckle.Objects.Utils.

Units

Geometry types carry a units string (Units.Meters, Units.Millimeters, etc.). Objects in the same graph can use different units.

Example

var point = new Point(1.0, 2.0, 0.0, Units.Millimeters);

Extracting Geometry from Received Data

All meshes in a graph:

Example

var meshes = receivedData.Flatten().OfType<Mesh>().ToList();

Most BIM geometry is in displayValue:

Example

using Speckle.Sdk.Models.Extensions;

foreach (var obj in receivedData.Flatten())
{
    var displayMeshes = obj.TryGetDisplayValue<Mesh>();
    if (displayMeshes is null) continue;

    foreach (var mesh in displayMeshes)
    {
        Console.WriteLine($"{obj.TryGetName()}: {mesh.VerticesCount} vertices");
    }
}

Material

RenderMaterial (Speckle.Objects.Other) is typically set as a dynamic renderMaterial property on geometry. For shared materials across many objects, use RenderMaterialProxy — see Working with Proxies.

Common Pitfalls

IndexOutOfRangeException reading vertices/faces

vertices.Count must be a multiple of 3. Validate list lengths from untrusted sources.

Mesh renders with holes in a triangle-only viewer

The mesh likely contains n-gons — triangulate first.

Sent geometry doesn't appear in the viewer

Put geometry in a container’s displayValue — see Display values.

Next Steps

Objects and Traversal

displayValue and Base mechanics

Find objects by property

Extract meshes after receive

Operations API

Send and receive geometry graphs