Why does my model disappear or bounce off the wall?
If you are working with a large object or trying to make an AR model you can walk around in, there is a possibility that it will not register the space properly.
This means that the object loaded might bounce off the wall, specifically for phones that do not have Lidar and occlusion capabilities. In Model Viewer, there are placement settings, where it looks for a surface to place your object. There is one for the floor and one for the wall. Without changing the settings, your Model Viewer will automatically look for both the floor and the wall.
The line of code you will need to add to keep from bouncing off the wall looks like this:
ar-placement="floor"
More about LIDAR capabilities