Why is my Nira scene empty?

An apparently empty scene can also occur when objects are extremely far apart: they may render smaller than a pixel. Nira displays Go to... navigation buttons for these objects. Click one to jump to it, then check why the objects are so far apart.

This can happen if you upload a single OBJ file that is extremely large in size. When exporting OBJ files from RealityCapture, it's highly recommended that you enable Save mesh by parts...

This is especially important if your model is larger than 200 million triangles. The above screenshot includes other important settings that we suggest having enabled.

Another benefit to this approach is that models can often load faster in Nira since multiple parts can be loaded simultaneously vs loading one big part sequentially.