From the course: SketchUp: Rendering with V-Ray Next

Generating a caustic effect

From the course: SketchUp: Rendering with V-Ray Next

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Generating a caustic effect

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- [Instructor] Caustics are a lighting effect that can be seen all around us in one form or another on a day-to-day basis. Indeed, they are often times such a familiar and expected sight that we don't always notice they're there. Of course, there's naturally occurring lighting effect that doesn't generally show up by default inside a CG lighting setup where, typically speaking, we have to deliberately enable caustics and then work with a unique set of controls in order to tweak and tune the effect. Which is exactly what we're going to be doing here. Well what we have in our scene are the essential building blocks from which to create a caustic lighting effect. So we have a strong directional light source in the form of a V-Ray Spot Light, we have suitable geometry in the form of our shader ball meshes, and we very importantly have a reflective, refractive material applied to those meshes which in this instance is a standard glass shader. As things sit then, we would probably expect to see caustics generated in a render once we enable those in the scene, which we can go ahead and do by jumping into the Settings tab on the asset editor and then from the advanced global illumination UI, enable the photon mapped caustics option. If I go ahead and hit the Render button now though, we may be surprised to note that enabling caustics in the scene and then actually getting them to show up in our renders can sometimes be two very different things. Now, don't be fooled into thinking that caustics just aren't working here because if I save the render that we have just taken to the history list, crank the global multiplier for the caustics found in the caustics rollout up to a value of 10 and then render again, you can see as I compare the images that we definitely have caustics being generated. The problem is that all we are currently getting from our material setup are reflective caustics rather than the perhaps more familiar and expected refracted variety. The problem that we need to tackle then is in fact a material one. And so let's jump into the materials tab in the asset editor. And from the active list, select the glass material in order to access its properties. Down in the refraction section, we have this effect shadows option which is currently causing the refractive properties of the material to generate the transparent shadow effect that we are seeing. If I turn that off though, and then re-render, we can very clearly see that we do indeed have refractive caustics now showing up. If we wanted to darken or brighten the caustics being created without affecting the intensity of the light being used to create them that is, then we could, which you have already seen, tweak the global multiplier option which in this instance, I will dial back down to the default value of one. What if we also wanted to sharpen our caustics though given that the effect we are seeing here does look a little soft? Well to do that, we can jump into the lights tab, increase the caustics of the value on our spotlight to about 6000 and then take another render. With what we see now giving a much sharper, cleaner look to our caustic effect. Of course, we have added quite a bit to our render times and if we were in a scene where even more caustic effects were going on, then things could slow down by quite a bit if we don't increase our subdiv counts with care that is. Seeing as we have been able to create a very nice reflective refractive caustic setup in V-Ray with very little effort though, I would say generally speaking that the increased render times would probably be well worth the wait.

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