CAP 202 - Computer Animation II

Lesson 20 - Mental Ray

Objectives:

This lesson lets you practice using the Mental Ray renderer. Objectives important to this lesson:

  1. Mental Ray versus the default scanline renderer
  2. Option changes with Mental Ray
  3. Arch & Design materials
  4. Enabling Final Gather
  5. Daylight system
Concepts:

This lesson begins by continuing the discussion of ambient light. The discussion takes a different turn, explaining that light reflected off a surface will typically be colored by that surface. This makes sense, even if you have never thought about it. Light we use to see things is mostly white, which means it contains all visible colors. (Yes, visible. I can't see x-ray colors, can you?) The reason you see a red apple as red is that the white light reflected from its surface becomes mostly red. (Think of the red surface as absorbing the other colors and reflecting the red light.)

The text also explains that no surface is truly smooth. There are always bumps and irregularities, no matter how small. The bumps will cause light to be reflected in multiple directions, which means that light reflected from almost any object will spread in more directions than simple optic reflection would predict. This effect creates ambient light in more places than might be expected, and colors that ambient light in colors that did not appear int the initial source.

Why do we care? We care because this effect can be handled by more powerful render engines than the default engine in 3DS Max, which the text refers to as the scanline renderer. The lesson uses the Mental Ray renderer, which we are shown can produce superior results when rendering reflective and refractive surfaces. Both renderers can produce raytracing results, which means they can follow rays of light through the scene, determining where the light will reflect, and where it will go next.

The text turns to instructions for changing to the Mental Ray renderer. Be aware of some facts about this conversion:

  • You change render engines by opening the Render Setup dialog: on the Common tab, open the Assign Renderer rollout, and click the Production button.
  • Changing the renderer changes several available options. They are summarized under the Customize menu, Custom UI and Defaults switcher. (This is noted in exercise 1.)
  • One of the obvious things that changes is the selection of default materials in the Material Editor. It also provides access to the Arch (Architecture) & Design material templates.

More terminology is offered. The Mental Ray renderer provide better, more complex rendering of light effects. The next effect discussed is Ambient Occlusion. The text explains that this term refers to shadows cast by ambient light. We are told that this effect is available under the Special Effects rollout of the Material Editor, but also requires a change in the Render dialog that the text does not explain at this point, enabling Final Gather. More later.

Exercise Notes and Questions

Work through the exercises and turn in your answers to all questions below as part of the homework for this assignment.

Exercise 1: This time, before you open a file, you change the configuration of the program.
Follow the directions on page 558 to change the renderer for 3DS Max.
In step 5, open the the indicated file.
In step 6, note that the image in the text does not match the camera viewport. The viewport shows the view of camera 3 when the file is opened. You will need to change the viewport to look through camera 4 to continue.
Question 1: How do you change the viewport to the correct view?
Go through the steps to change the material on the statue. You will see the improvement on the next render. Note that the text tells you to select material sample slots, change them, and name them. In my version of the file, the slots already have names and materials in them. The exercise still changes them.

The lesson turns to the subject of lighting. The text recommends that we use the Daylight system for external lighting, which takes several parameters to simulate reality: location, date, and time of day. In includes elements for sunlight and for skylight, which is th illumination from light that is scattered by the sky itself.

The text returns to the Final Gather option. We are told that it is an option on the Render dialog, Indirect Illumination tab.

Exercise 2: This is an area in which the 2009 version of the program differs greatly from the version the text is about. If you are doing this on your own workstation, you will not be able to follow the directions. Please carry out the labs for this lesson in the classrooom in order to follow the instructions and get the desired results.