To setup a test scene, start with the scene from this tutorial.

I’ve cleaned it up by removing the side glass examples, and leaving just the center one. Also, a V-Ray Sphere is a nice touch:

The caustics are with default settings. As you can see, there are way too many reflections simulated by the refractions. Those settings are:

Multiplier: 1.0
Search dist: 5″
Max photons: 60
Max density: 0″

Lets adjust each to see how they affect the default glass characteristics. First, we drop the multiplier to 0.5:

All this did was darken the light (increase the shadow?). This didn’t help at all with the frequency of the imperfections, or their intensity (which is right now making the refractions look unrealistic). Put the multiplier back to 1.0, and change the Search dist from 5″ to 0.5″. As our glass is 1″ thick, this produces a lot more imperfections (increased frequency) in the refractions:

Increasing this past the thickness of the glass has no effect. You can safely return it to the default 5″. Next to adjust is Max photons (default = 60). As we want less imperfaction in the glass, double this to 120, allowing more light imperfections to mix into the straight light:

Much better. Now we turn up Search dist. to 1′ and Max photons to 120:

Still, this is a poor way to see the effect, as we haven’t got the right environmental lighting.

-Check Environment and Reflection/refraction in V-Ray::Environment
-Load up a separate HDRI image for each (V-Ray HDRI)
-The environemnt HDRI can be left at a 1.0 multiplier
-The reflection/refraction multiplier can be set to 0.5
-Indirect illuniaiton is on, but only select Reflective
-(same roll-up) Primary bounces at 0.5 and Irradiance map
-Secondary bounces at 0.7 using Quasi-Monte Carlo
-V-Ray Caustics: Multiplier: 0.92, Search dist: 4′, Max photons: 240, and Max density remains at 0
-Everything else stock…
-Oh, and I rounded the edges of the glass “box” to highlight the caustics better

You should end up with:

Not that hard, really! Keep playing with things and you’ll get what you’re looking for!

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