8. Filling a glass with water
To fill a glass with water, you should model
the water. This isn’t as easy as it sounds.
First of all, the surface of the water will
bend up where it touches the glass because
of adhesion forces. We call this curved top
surface the meniscus. This effect has to be
modeled or your water will not look very
realistic.
Then there’s the problem of coincident
faces. If you model the liquid exactly as
large as the inner surface of the glass, the
rendering will look weird because of these
coincident faces (right glass). The best way
is to model the water a bit larger than the
inner glass surface (middle glass). If you
model it slightly smaller, it’s not realistic
either (left glass).
Click on the image to see examples of all
three. I modeled the glass in rhino, it’s a
revolved curve. I show you these curves
also to see how the glass vs water is mod-
eled.