Global Illumination in MentalRay for Maya (revision 2 for Maya 8) INTRODUCTION Today, nearly all respectable 3D programs have some sort of GI (global illumination) algorythm integrated, and basically every new renderer that apears on market has been engineered from the start to support GI as better as it can. Unfortunately for Maya users, the default integrated renderer doesnt support any kind of GI, and I suppose there are no artist today who doesn't need a touch of GI. So, from the Maya 5, Alias decided to integrate one of the best renderer on the market today, the MentalRay. If someone of you have used XSI before, you know how powerfull MRay is. One of the most interesting features in MRay for Maya is capability to compute additional light distribution in the scene which is usually known as global illumination. This tutorial is targeted at the begginer/intermediate users and I will try to describe as best as I can how do I use MRay to add global illumination to my scenes. There are a lot of pictures in this tutorial, so be patient if you don't have fast connection. Or if you like you can download complete tutorial in one zip file and read it offline. Well, let's start with a little introduction to MentalRays globall illumination algorythms. The renderer has two solutions for computing additional light distribution in the scene. One is Globall Illumination, and other is Final Gather. In some situations, you can get satisfiying results with use of only one of this solutions, but the most powerfull use is to combine these two together. Globall Illumination algorythm shoots photons from light and tracks their path through the scene, and everytime the photon hit some object in the scene it leaves the part of his energy on it. It is fast solution, and produces nice additional lighting of the scene, but it just isn't as accurate as you will want in most situations. But, thats why you would use second method which combined with GI would produce some stunning results. This second method is called Final Gather. The goal of final gather is same as global illumination, but aproach is very different. Final gather is computed from point of view, and not from the light source like global illumination. After primary ray hits the intersection point on objects under the pixel, final gather is activated and shoots additional rays in the scene collecting color informations around the point for which we are computing color. In real world, the light is bouncing around unlimited times distributing ligh energy all over the scene. In computer computer situation this is impossible, and because of that many optimisations were needed. Because of that, no mather how high you set the parameters that controls quality of GI, you will never get the perfect solution, and your rendering times will bump up drastically. So our goal in next tutorials will be to balance between quality and speed. Through this tutorial, we will use two types of scenes for which we will create Globall Illumination and Final Gather solutions. First two scenes represent indoor type of scene and the second are outdoor. For the first Indoor scene, we will go throughout proces step by step, and for other scenes i'll just point out what are satisfying values used to produce globall illumination and final gather. For the outdoor scenes, we will show how FinalGather can be used along with HDRI to light up the scene. Because the mentalray comes with fresh instalation of Maya, check if it is started, so run Maya and go to Window > Setting/Prefferences >Plug-in Manager to check if Mayatomr is loaded. If it isn't, click on the box near option loaded. If you want to use MRay everyday you can also check the auto load box. Just to check if it is loaded, go to the Windows > Rendering Editors > Render View and in Options > Render Using check MentalRay.
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Toni Bratincevic - toni@vizije.hr - http://www.interstation3d.com |