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This tutorial explains how to model a glass of water in Arion.

The correct way to do this is often subject to discussion among our users, so the goal of this tutorial is to provide a definitive guide to correct liquid-in-glass modeling, from the point of view of the engine.

The first step is to model the shape of your glass.

 

The glass profile
The glass profile.

 

Now, select the inner part of the shape you'd like the liquid to be in contact with, and detach it to a separate object. That will be the liquid body.

This is the only way Arion will resolve the media interface correctly.

 

Detaching the water part from the glass profile
Detaching the liquid part from the glass profile

 

Now add the line that will enclose the liquid body after the shapes are revolved.

For better realism, you can model a little pinch near the contact point to simulate the typical capillarity effect that happens in real life.

 

Closing the water volume, with a little capillarity.
Closing the water volume, with a little capillarity.

 

The part (1) is glass (for example). We will load the glass material preset from the Arion's materials library. ND (the Index of Refraction) value ranges from 1.5 to 1.6 for most glasses.

The part (2) is the liquid body. It can be whatever liquid you want, but for this tutorial we will use the water material preset in the library. The ND value is 1.33 in this case.

 

Distribution of materials on the different volumes.
Distribution of materials on the different volumes.

 

When a light path hits the glass, it enters the glass medium and is refracted by the right ND (1.51 in this case). The light path will travel inside the glass body until:

  • it exits (that is, it hits the same glass material again).
  • it hits another medium, like water in this case.

 

The engine keeps a stack that lets each path know what media have been crossed so far. Thanks to this stack, the engine knows where to use a simple ND when a new hit happens, or a combined ND that mixes the ND of the medium the ray was in and the ND of the medium the ray will be in after the hit.

As an explicit reminder, the three modeling solutions below produce *WRONG* results:

 


Example #1 of a wrong setup.



Example #2 of a wrong setup.



Example #3 of a wrong setup.

 

Below is a render made with the technique described in this tutorial, using the glass and water materials provided in the default Materials Library. The light setup is a basic studio?like environment.

 

The final render.
The final render.