So, you have created the perfect material simulation for a dramatic shot in the feature. It had to render over 48 hours to obtain all of the images required for a 12-second scene. As with most rendering tasks, the rendering farm, or computer, will be unattended during this process as watching a slow render is about as enjoyable as watching grass grow. It may also be the case that when you view the scene you, or the director, will feel that it would fit better into the overall production if it had different lighting or the depth was enhanced by adding more atmosphere such as air, dust, or mist.
In Chapter 6, we created an ocean scene with a rock washed by the waves. The renders required to produce the 10-second animation took 4 minutes 11.36 seconds x 250 frames on my computer, which means a 17.5-hour total render time. Although the renders look fine, in retrospect, we could have added a little atmosphere by including a little mist. This...