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Quick Tip: Vray Caustics & Illuminative AA

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In today's quick-tip tutorial, Edgar Mihailov presents two mini-tips covering how to create caustics using Vray for Maya, and how to get your Vray lights to anti-alias correctly in the final render! We know you're going to find both tips extremely useful, so let's get started...


Part 1 - Caustics


Step 1

First of all I will show what this scene looks like. 1 and 2 are Vray lights with default settings. 3 is a simple sphere, and the Background is just an inverted cube.

Step 1 Image

Step 2

Now we have to create a material for our sphere. For this we go to the Hypershade and create a new Vraymtl. I've set the Diffuse Color under Basic Parameters to black so that we get a more green looking sphere, but you can set it to whatever you like since the diffuse color doesn't actually play a role in caustic generation. Finally in the Refraction tab, change the Refraction color to whatever color you want your caustics to be - in our case, green.

Step 2 Image

Step 3

Now we have to enable caustics. To do so go to Window > Rendering Editors > Render Settings. Once there, go to Indirect Illumination tab and find the Caustics submenu. Check On as shown to enable them.
Note: GI does not need to be on for caustics to generate.

Step 3 Image

Step 4

Now render. As you can see you now have green splotches on the ground. They are our caustics.


And I don't like them! So we will go into our sphere material settings and change the Refraction IOR under the Refraction submenu to a lower value.

Note : IOR is a number that defines how much the passing light is bent when it enters the surface. You can use google to find IOR values of materials such as water and others.

Step 4 Image

Step 5

After rendering you can see that the caustics are now a lot more laid out, but they are still very rough looking. To fix that we go into Rendering Settings, head to the Indirect illumination section and change the Max density from 1 to 0.1. Feel free to experiment with this value to see it's full effect.

Step 5 Image

Step 6

Ok, now things look much smoother. But I still don't like how it's so very green and very dense. To fix this we can reduce the amount of caustics. Return to the Rendering Settings menu and change the Multiplier from 1 to 0.5, this will reduce the amount of caustics by half.

Step 6 Image

Step 7

Now you can see that the caustics aren't as solid and actually look really nice! Those are the basic steps you need to follow to enable, and tweak, caustics within your scene. Feel free to experiment with different colors and values to see what you can come up with.

Step 7 Image

Part 2 - AA Lights


Step 1

Here I have prepared a simple scene. 3 Vray rectangle lights, a simple cube mesh to embed these lights in, and a reflective sphere.

Step 1 Image

Step 2

When you render Vray lights, whether you have the AA filter enabled or not, the lights still turn out very aliased and jaggy. Both in the scene itself and in the object reflections as seen below :

Step 2 Image

Step 3

To fix this, you have to go back into the Render Settings.

Step 3 Image

Step 4

First, make sure you have Render Using set to V-Ray. Now click on the VRay tab and open the Color mapping dropdown menu. Here tick Subpixel mapping and Clamp output.

Step 4 Image

Step 5

Now when you re-render your image, the lights in both the main scene and the reflections have nice and smooth edges!

Step 5 Image

I hope you enjoyed these quick-tips, and that you can use them in your own scenes. If you have a questions feel free to leave them in the comments below!


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