Vue d' Esprit 2 is a excellent raytracing software but it does not include caustics (like P.O.V for instance who faked it). Such effect is very important if you want to do underwater scenes. Indeed remember your holidays or your rare trips to the swimming pool, you will undoubtedly have noticed this effect on the bottom: they are the wavy and glistening luminous reflections on the immersed objects and the bottom (glug-glug °°°). It is visible only at low depth. As I already said Vue 2 cannot render it out of standard (or then I tired myself for nothing), but don't be too much disappointed, one can cheat and simulate this effect. For that Vue d'Esprit 2 has two very powerful weapons: Variable transparency Directional light

First stage:

Start Vue d' Esprit 2, and open the underwater scene of the tutorial. You can render the scene and will note that it does not have caustics. A good point, light is directional (all the rays are parallel). It is the standard solar lighting of Vue 2.

Second stage:

To add the caustics, we will exploit the transparency of water. With a right clic on the texture choose "Edit material" and click on "Transparency", push "Global transparency" up to 100% and notch "Variable transparency", the window "Transparency production" appears. Here it is necessary to modify the function and the associated filter. Many solutions are possible, but here is the one I use: Notice the filter of transparency: "Inverse absolute".

For the function (clic right on the image and " Edict function ") a simple "Noise (smooth)".

Voila the trick is played, you can backup texture thus modified to re-use it later.

A render of the scene of the tutorial with simply an addition of a lengthened white sphere, for showing the caustics.