# Glass of water and meniscus

I have noticed that a number of people have modelled glasses with liquids in them, but to me even with hdri the render looks totally unconvincing. I think the model has not accounted for the interaction of the liquid with the surface. Liquids wet surfaces. A liquid drop on a surface will have a definite contact angle with a surface. For some surfaces and liquids the contact angle is small so that liquid spread out over the surface. In the case of liquids in a container interaction between the container’s surface and the liquid leads to the formation of a meniscus.

The first picture below, for water in a glass, illustrates that there are subtle reflections around the edge of the liquid due to the meniscus. The next shows that the meniscus has quite a width, its the band below the red band in the center of the glass. Finally, reflections on the surface of the water are quite hard to obtain, and it appears that only the most intense light sources (a light bulb) are reflected. The ring clearly visible near the inner wall of the glass is probably due to the curvature of the liquid surface and shows that the effect the meniscus has on specularity extends quite a distant from the inner surface of the glass, ie there is still a detectable curvature, albeit small, in the surface some cm away from the inner wall.

If anyone would like to model a glass of water with a meniscus, please post your results here. I’m going to give it ago, but I’m a noob :-? .

i give it a try now. ive already created a meniscus using a uv sphere

Here is my first try. I modelled the water first with a simple cylinder and then added 2 rings of points around the cylinder with the knife tool ctrl-R. I then grabbed and scaled the top two rings so one was close and below the wall of the cylinder and one further out and slightly below the first. These two concentric rings formed the meniscus. I then selected the surface of the water that was in contact with the glass, and duplicated shift-D and made it a separate mesh P. I then made the glass by extruding normals to this surface alt-S. I fixed up the top surface of the glass so that it was flat. The glass and water require crtl-N to redo the normals and also set smooth and autosmoothed.

I think this looks realistic. The water looks like it is in a glass. The meniscus is clearly visible from the effect it has on the angular map, there is a ring of specularity reflecting off the curvature of the meniscus. I made the size of the meniscus larger than in my photos of a real glass for emphasis; all this means is that the glass modelled here is smaller, a shot glass.

One problem remains I haven’t been able to generate caustics. I have a photon light and a spot light on the glass, but even without the angular map no caustics. I have set the number of caustics bounces for the photon light and also in the Yafray GI to 5. Can someone please help here and also explain why there is a global setting in the Yafray GI and also a local photon setting for the number of caustic bounces.