liquid in bottle keeps filliing to brim in render preview

[Nigle280351181r7p]

This is how it looks like before render:

After render:

Is this a bug?

[Imaginerie]

Hello!

It shouldn't be, but you might check if it isn't actually a colour spill (from the liquid) into the glass surface. To check that, change the opacity of the liquid  to - say - 50%, and/or change to colour to a lighter one. If that's the case, you should see a clear demarcation between the liquid and the void on top of it. It wouldn't appear in the non-rendered version, because not all lighting and shadows appear correctly in the 1st version. This may be far-fetched, but worth a try.

[Ares Hovhannesyan]

Usually I get correct render with filled bottles. Can you share file via cloud to test? 

Thx

[JMathews · Accepted solution]

Hello!  This is not a bug.  The real time rendering is an approximation.  It is designed to be fast, but it is not 100% accurate.  It is very important to use raytracing to preview and finalize your material settings so that it gets the look you want.

What's happening here is refraction.  The translucent bottle is refracting the liquid inside, which distorts the graphic.  Usually you can adjust the IOR of the glass and liquid to get less distortion.

First, be sure to enable the render preview:

Second, select the glass object, select the glass material and adjust the IOR.  Index of refraction is a scientific measurement of how much a translucent material distorts light as it passes through.  A lower IOR is like a air, or a pane of glass.  It has very low distortion.  A higher IOR will have a higher distortion.

[Imaginerie]

I called it colour spill, and you call it with the right term 🙂 Refraction...
It's best when the experts chime in!