Caustics in Mental Ray tutorial

Ronel K. Pabico 2011-07-05 13:19 tutorial  > Making of  > rendering

Caustics in Mental Ray tutorial by Ronel K. Pabico


Caustic (optics), the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. Caustics are light patterns that are created when light from a light source illuminates a diffuse surface via one or more specular reflections or transmissions.

1.Here is the initial scene view. MaxScene file can be downloaded here

2. Caustic Materials. In this scene sample, i use raytrace material, with white color on transparency color slot. (transparency and reflection will be discuss here as the tutorial goes) Apply Noise material on Bump

3.Activate Mental Ray as rendering engine, then go to Indirect Illumination Parameters and enable caustic under Caustic and Global Illumination (GI). Accept default as it is for the meantime.

4.Then create lights. ( in my case, i use free lights) and use Ray Traced Shadow.

5.Initial rendering - on initial render, a warning window will pop up. Hit okay for now. We will attend to it later. And so here is the initial render. As you can see, even we activate caustic on the render dialog box, still we don't have caustics.

6.Activating Objects caustic generator. I choose all the objects i want to generate caustics, right click and select Objects Properties . Go to Mental Ray Parameters and activate Caustic.

7. And now here is the initial render with generated caustics.

8.Ok let us now look to some parameters affecting the caustics effects aside for the previous settings we have done. We go first on the caustic Multiplier. Changing Multiplier will enhance the caustics brightness.

9.Changing the Photons per sample will enhance the caustic rays number.

10.Changing the Maximum Sampling Radius will take effects on the caustic size.

11.Let us now go back to the transparency and reflections of our materials. If we take on the refractive properties of the materials and take out its reflectivity, we will got this Refractive Caustics or Caustic Refraction

12.Vice versa, we take Reflection properties into account, and take out refractive properties of the material, we will got this Caustic Reflection.

13.Or we can do both. Of course we will consider the materials we are using in our scene into account.

Another Example
14.Initial view of the raw scene. Maxscene File (3D Max 2009 without the water falls object)can be downloaded here

15.Applying a caustic materials

16.Changing the settings and object properties

17.Final render completed with mini-waterfalls with some photoshop touches.

Hope it helps
Ronel k. Pabico

Here is the link for all images :
Author: Ronel K. Pabico
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ColonelSanders17:09:24  |  25-08-2011
Great quick tut on caustics, one question though. I can get shadows to cast on the fish, but how would you get the fish to cast shadows on the floor?
ronel15:49:31  |  19-09-2011
the shadow you see on the floor is the caustic generated by the water surface.
Lina Vi13:56:22  |  09-03-2012
Hi there, great work! I wanted to ask, do you know how can I animate this waterwall. I don't want to use particle flow for the waterwall, I had animate the water with caustic and maybe I can use the same way to the waterwall :?


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