Strange artefacts in a glass container

Hi everyone ! That’s my first post and my first project without following a tutorial. :slight_smile:

I’m trying to model a pyramid-shaped hourglass but I noticed strange artefacts in the glass structure when I render it. Does anyone have a clue about how I could change this?
For information, there is no texture, only materials and a lot of lights.

By the way, I’m new to this forum. Should I open a new thread for each question I’d have or a single thread about this project? :slight_smile:



Hourglass11.blend (721 KB)

It has overlapping geometry with the sand and the inside surface of the glass. Inside surface of the glass also has normals pointing in the wrong direction.

Left: overlapping surfaces. Right: face directions of the inside surface

This might be of interest also


Thanks for your answer ! I thought it would be more physically accurate to have the two surfaces perfectly match each other so I simply copy/pasted the glass to make the sand, hence the overlapping.
I have inverted the inner normals and resized the sand surface to make it be in the glass volume and it works. :slight_smile: Thank you!