How do I fix this weird material/ texture of the glass?

Question

I was adding a condensation normal Map to the cup near the rim. I was doing this in material preview which made nothing look wrong. Then when I did a test render it didn't look correct. Like the bottom half of the liquid was cut off and that for some reason the condensation texture was there.

It's like the bottom portion of the liquid material I had inside somehow got removed during the UV editing. I've looked at the UV tab, shading tab, and all through my materials tab and I can't find what caused the problem. Nothing looks wrong in the material preview mode which is even more confusing. I haven't been able to find anyone with similar problems.

Here is the .blend file for anyone who wants to go hands on.

I am relatively new to Blender so don't be surprised if it is something fairly obvious.

Answer 1

The lower faces of the liquid are interfering with the lower faces of the inside of the cup. You can fix this by scaling the liquid in the Z axis so that these lower faces are a little above the lower inner faces of the cup. To do this:

1. Select the Liquid object and in Edit mode with Face select mode active, select the face in the middle of the top face of the Liquid.

2. With the keyboard shortcut Shft + S choose the Cursor to Selected option.

3. In the Header change the Pivot Point to 3D Cursor (see screenshot below).

4. Still in Edit mode select All of the Liquid object.
5. Now scale a little along the Z axis so that the bottom of the liquid is not touching the bottom of the cup.

Tab out of edit mode and try a render :