When you have layers of transparent materials in your model (like a glass containing water), you get a better result when rendering with PhotoView 360 if the “liquid” body interferes by a small amount with the “glass” body.
Take a look at two renderings showing both results. Fig. 1 shows the real-life condition, where we have just “contact” between glass and water, while fig. 2 depicts the case where there is a small “interference” between the two. Which one do you like more?
As a side note, you should never leave a gap between the two transparent bodies.