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This movie is going to discuss some of the ways in which we can improve the look of caustic light patterns, and we have a caustic photon-emitting light set up in this scene. But as you can see, this light pattern is very blown out, and we don't have very much definition here. Let's look at some of the ways that we can improve this. I'll store this render and minimize the render view and spotLight2 is my caustic emitting light. So, the first thing I'm going to do is go to the Render Settings and under Indirect Lighting, I'm going to go to Caustics, and this is a situation in which a lower Accuracy is actually going to give us a better result, more definition to our caustic lights.
So, I'm going to set this down to about 15. The other setting I want to change is the Radius. When Radius is set to 0, you're basically telling mental ray to figure out the radius for itself. In other words, 0 radius means mental ray, you decide based on the scene, based on the way the lights are set up, and what radius works best in the scene. So in this case, by raising this to 2, I'm taking control of the radius and giving it an exact size for mental ray to use. I'm going to minimize this and create another test render and see what we get.
So now you can see we're actually getting more definition, we could see individual photons a little bit easier. It's a bit spread out and fairly blown out right here. So, another thing that I can do is actually change some of the qualities of the transparent shader that's applied to the vase. When I created the shader, all I did was apply a standard blinn, and I have Transparency set all the way up to White, so this is 100% transparent. And down here in the Raytrace Options, I have a Refractive Index of 1.2.
Refractions are activated, and this is a setting of 1.2, which essentially is a good simulation, a good value to simulate glass. But if I change this, you're going to see it has a huge impact on the way the caustics looks, and we're going to set this to 0.9 and create a test render. You can see that that's actually changed the way this looks a lot. This is spread out more of an angle this way and around the vase here. I'm going to keep this image, and then I'm going to choose this light again, and I'm turning on Wireframe on Shaded so that I can see where the vase actually is, and I'm going to choose Panels > Look Through Selected Camera.
I think if I pull this out just a little bit - I'm just zooming out and then in the Light settings, I'm going to decrease the cone angle, so that it's a little bit tighter around the vase, switch back to the Perspective view and do another render, and you can see now that I'm getting something that I like a little bit better. This is looking a little bit more realistic to me. There is a danger though, to changing the refractive index to the shader, in that it's going to change the caustic light pattern, but it's also going to change the way the glass looks.
So, if I go back here, you can see this is what a refractive index of 1.2 looks like; it looks a lot like thick glass. And by changing it down to 0.9, I'm getting something that looks a little bit different. So, when tuning this effect, it's going to be a question of balance: how much you want to change the look of the glass to get a better caustic effect.
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