An additional, more advanced, AGOL feature involves placing custom 3D models within a 3D scene. Incorporating such models alongside an OS mesh offers a lot of scope for creativity and interest. This could be particularly effective, should you wish to demonstrate how a new building or structure might fit in, visually, with existing surroundings.
Many tools are available that allow you to create whatever 3D model you need. Blender, for example, is a popular open-source choice that can work well for this. Alternatively, repositories of pre-made models are available online, should a stock model be sufficient for your requirements.
Unfortunately, it’s not currently possible to add a 3D model directly into the AGOL Content area. Instead, an ESRI-specific ‘3D Object’ feature type needs to be prepared, within ArcGIS Pro, as a preliminary step. This ESRI tutorial - Import and incorporate 3D models in a scene | Documentation - covers this well. Once the model has been prepared and exists as an ArcGIS Pro layer, it can then be ‘shared to web’ (left-click the layer and select ‘Share As Web Layer’…), thus copying it directly into your AGOL Content store.
We’ve found that, after a 3D model is shared into AGOL, error messages may appear if you try to use that model immediately (even though everything appears to be complete). If this happens, wait for a few minutes and try again! This seems to resolve the issue.
When creating a 3D asset, it’s usually good practice to locate each object’s origin towards the bottom of the model. If using Blender, it’s also advisable to apply any rotation and scaling, along with any active modifiers, before export. Also, if you’ve used any advanced procedural shading tools, you’ll need to bake those into a texture.
Finally, upon export, the suggested 3D file format is .glTF/.glb. This is a good option, as it’s able to pack textures within the file, making it straightforward to manage.