This article is referring to vectorized mesh normals, not point cloud normals. It is recommended to upload point clouds with normals. The "Use Normals" option does not apply and will not change anything when uploading point clouds.

Triangle mesh normals:

When uploading 3D mesh models to Nira, you'll be asked whether you'd like to use vertex normals.  This means that Nira will retain the normals of the 3D mesh model being uploaded or will generate normals if none exist.  By default, normals are disabled for assets specified as Photogrammetry, Sculpt, or Volumetric Video.  Whereas, PBR will have normals enabled.  When uploading to an existing Photogrammetry asset, you have an option to "Use Normals" for the models you'll be uploading to the existing asset.  The "Use Normals" options is useful if you'd like to combine CAD models (see below) with photogrammetry models.

The remainder of this article will provide more details. If you need further clarification, feel free to leave a comment.

Photogrammetry models:

Vertex normals, also known simply as normals, can enhance 3D surfaces by interacting with the virtual lighting to simulate a smooth surface.  However, if you're uploading photogrammetry models, which already have real-world lighting information "baked" into their textures, combining these textures with vertex normals and virtual lighting will often degrade the model's appearance and realism.  Another drawback with using normals is that loading and rendering performance will suffer because of the extra data required to store and render models with normals.  For these reasons, we highly recommend not enabling normals for photogrammetry models.

For photogrammetry models, enabling lighting (View Options > Environment > Lighting [✔]) will make the model look less realistic.

CAD and Animation models:

It's best to use normals for lower resolution 3D models created with CAD or animation tools tools like Blender, Rhino, Solidworks, Inventor, 3ds max, Maya, SketchUp, or Revit. For applications that generate a substantial number of triangles, such as sculpting tools like ZBrush, we suggest not using normals. When you have sufficient geometric detail to achieve smoothness, simulating a smooth surface with normals is unnecessary and inefficient.

Normals enhance the detail of lower-resolution, curved, reflective surfaces.