If the 3D scene is slow to load, there are a number of possibly explanations.
TPE 3D loads elevation data and map tiles from two separate sources and them combines them to produce the 3D scene you see in the app.
If your device is on a slow connection, it will necessarily take longer for the scene to load. The app tries to prioritize which 'blocks' are loaded first so that the area in front of the camera (i.e. where you're looking) is first to be requested.
If possible, downloading on WiFi is usually more efficient than on many cellular/mobile data connections.
You can reduce the amount of data that is required to be downloaded by reducing the Scene Complexity in settings to a lower value (this will also reduce the amount of detail you see).
Device Processor Speed
Even if your network speed is good, if you are using an older device with a slower processor or less physical memory, the scene might take longer to render.
If you suspect rendering speed is slow, consider reducing the Scene Complexity in settings to a value that works better for your device.
TPE 3D makes extensive use of caching, both in the app and in the backend services that supply elevation data the app.
The user who first visits a location within the app may experience a slower load time, due to what is called the "first pull" problem. This refers to the fact that the first person to request a piece of content (in this case, elevation data) usually has to request it from the "origin server", i.e. the computer that keeps the master copy of the data.
The second user usually receives the data faster, as by now it has been "cached", i.e. saved in a content delivery server or similar that has the data in memory, ready for quick delivery.
There are in fact four layers of caching used in TPE 3D - an application server in-memory cache, a two-tier content delivery network and local caching on your iOS device.
The very quickest performance you'll see is when the data you need is already on your device: in this case, it is loaded locally from memory or on-device storage. That's why we don't recommend clearing the cache on your device unless you absolutely need to free up storage.
The nice thing about caching is that the more users are using the app, the more data stays in cache and so performance improves for everyone - unless you're unlucky enough to be the "first pull" guy!
If you think the loading speed you're seeing is still too slow and you've tried the recommendations above, please drop us a line at firstname.lastname@example.org with details, and we'll be happy to investigate further.