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3ds max and 3ds max Design both ship with two ways to render images: scanline and mental ray® rendering engines. This book will focus on mental ray techniques in settings that will not only teach you which buttons to push but also the reasoning behind the rendering process. An understanding of how things work will help you make decisions during your production rendering to obtain a balance of efficiency and rendering quality.
With each new release of mental ray, there have been significant improvements in the default settings that allow you to obtain a usable rendered image "out-of-the-box." But because each scene is different, you must constantly tweak and refine a myriad of adjustments until you get the quality the project demands.
Any time you randomly adjust mental ray settings without a basic understanding of why you're making the adjustment, you are simply heading into a potential abyss of confusion that will be difficult to recover from. This book will provide you with a framework of information that will help you become more productive with less experimentation. We don't want to discourage you from experimenting, but that effort should be saved for after the production deadline has been satisfied.
We hope to provide you with a "top-down" learning experience with the most relevant information presented first so that you can absorb the information and use it as a platform on which to build more detailed knowledge. mental ray is complex, and many of the details, while very important, are just confusing when presented too soon. Work your way through the descriptions and exercises and make sure that you understand the concepts being presented before moving on. Simply performing the sequential steps of the exercises themselves will not be enough for you to learn mental ray because those exact steps probably will not be relevant to your particular scenes.
The general topics included in this book will include
mental ray in 3ds max and 3ds max Design
Basic mental ray concepts
Rendering with mental ray
mental ray and lights
mental ray and materials
mental ray and shaders
Rendering efficiently in mental ray requires you to balance the effects of the render engine, the 3D model, the lighting in the scene, the materials assigned to objects in the scene, and the use of shaders within those materials.
Please start from the beginning of the book and work your way through the chapters and lessons in order so that you don't miss critical steps that can lead to confusion in later lessons. The exercises are designed to work well on moderately powerful computers, so the final renderings will not be the elusive "photorealistic" images that many mental ray users strive for. The term photorealistic is subjective at best and is most often not a cost-effective goal in day-to-day production. In any case, you need to have the foundation provided in this book before you can logically progress into super-quality renderings.
Good luck and have fun.
1.2 Getting started
This book is intended for users of both 3ds max and 3ds max Design. The two software programs are the same except for two relatively minor points that are not relevant to the lessons presented here. 3ds max contains the software developer's kit (SDK) that is required for complex programming used by third-party developers. 3ds max Design contains an advanced lighting analysis tool that is used primarily by lighting engineers rendering with mental ray.
However, there are also differences in the interface and the presets that you will learn to adjust so that users of both programs can follow the exercises. The changes will in no way affect the functionality of the software, and you will learn to easily switch back and forth between interface and default presets.
It is also extremely important that your scenes are modeled in the real-world units. Because all the mental ray rendering calculations are based on real physical lighting, the distance from the lights to surfaces will affect the outcome of your renderings greatly. For example, rooms that are 100' × 100' × 100' will be affected by a 75 W light bulb much differently than a room that is 1' × 1' × 1'. You will learn to set the system and display units properly before performing any of the exercises.
1.2.1 Setting 3ds max and 3ds max Design interface and defaults
Consistent interface and default presets are easy to set up in both versions of 3ds max and are necessary for the exercises in this book. The exercises have been written to use 3ds max with mental ray. You may be using 3ds max Design, which has features like real-world mapping coordinates enabled and ProMaterials as the default settings, for example. These features can be viewed as a subset of the fundamental 3ds max functions, and the learning experience will be richer if you learn the basics of how features function.
You can switch back and forth between any of the default interfaces and presets without affecting any current or previously created files.
184.108.40.206 Exercise: Switching defaults and user interface
1. Open 3ds max or 3ds max Design.
2. Choose Customize from the pull-down menu and then choose Custom UI and Defaults Switcher (see Figure 1.1).
3. In the left pane of the initial settings dialog, highlight Max.mentalray, and in the right pane, make sure DefaultUI is highlighted (see Figure 1.2). You can read through the overview of the setting changes and then click the Set button at the bottom of the dialog.
4. A warning will appear that you must restart the 3ds max for the changes. Click OK and then close 3ds max and restart it.
You will now be using the same defaults and user interface for consistency throughout the book's exercises. When you return to production work, you can easily switch back to the 3ds max or 3ds max Design user interface that you use in production. Just remember to switch to the Max.mentalray Custom UI and Defaults setting any time you are working with this book.
1.2.2 Units in 3ds max
3ds max and 3ds max Design are used in most countries throughout the world. Different countries use different measurement and units systems based on local requirements. Again, for consistency's sake throughout the exer- cises in this book, you'll set System and Display units to minimize mismatched units warnings when opening the exercise files.
While we are setting the units in 3ds max for compatibility with the exercises, it's also worth repeating that all scenes to be rendered with mental ray must be modeled to real-world sizes so that the real-world intensity of mental ray lights is properly calculated. All exercises have been designed with this issue in mind.
3ds max allows units to be set in two areas:
System units are the units used in internal mathematical calculations, and display units determine the format in which numeric values are entered in the user interface. You'll set both the system and display units for the exercises in this book.
220.127.116.11 Exercise: Setting display and system units in 3ds max
1. Open 3ds max and click Customize in the main toolbar (see Figure 1.3).
2. In the Units Setup dialog, click the System Units Setup button. In the Units System Scale area, enter 1.0 in the left field and choose Inches from the drop-down list of the right-field (see Figure 1.4). Click OK. This sets internal system units at one unit = 1 inch and returns you to the System Units dialog.
3. In the Display Units Scale area of the Units Setup dialog, choose the US Standard radio button. In the left drop-down list, choose Feet w/Fractional Inches and, in the right drop-down list, set the display rounding to 1/8 inch (see Figure 1.5). Click OK to exit Units Setup.
4. Exit 3ds max. The unit settings are stored in the 3ds max.ini file and will be remembered until you change them again.
You'll now be able to work through the exercises in the book more easily. Remember to change the units back to your production settings when finished with the book exercises.
The concepts behind the design and functionality of mental ray must be understood before the process of rendering a scene will make sense. It's not enough for you to know which buttons to push or click to get mental ray to render a scene, but you need to understand why certain steps are necessary and what some of your options are for cost-effective rendering. The most perfect realistic rendering isn't worth anything if it isn't cost effective.
This section of the book will explain some of the concepts of setting up and adjusting a mental ray rendering, and the following chapters will apply these concepts in exercises that teach you where the buttons are as well as optimization techniques for efficient rendering.
Read the descriptions presented here before moving on to the exercises so that you will approach mental ray rendering understanding the "big picture" that will provide the framework for the myriad of tweaks and adjustments required in a typical mental ray workflow. Without an understanding of these concepts, you'll simply be experimenting and hoping the end result is something useful.
Some of the concepts and descriptions you will read in this section are
Working with mental ray requires you to learn a complete new vocabulary in which the words themselves often make no sense at face value. Do not be intimidated by these new terms; the following information will help define the terms and clarify the concepts behind them.
1.3.1 Global illumination
Global illumination is the result of all sources of lights and shaders that affect the rendered output of a scene (see Figure 1.6).
This concept can't get much simpler. Global illumination (also referred to as GI) is a term that is often heard when any type of rendering is discussed, but it is usually not well defined and is often repeated with almost religious reverence.
Some of the global illumination components that will be discussed throughout this book are
Materials and shaders
It's not necessary to include all these components in a rendered mental ray scene, but you do need to understand how each can affect the global illumination results to take full advantage of mental ray for your purposes. Next, you'll learn the basics of what each component offers in the global illumination solution.
18.104.22.168 Direct light
Calculating direct light from a light source to a surface is very quick and efficient (see Figure 1.7). However, surfaces in the scene that are not perpendicular to the light source become darker as the angle-of-incidence to the surface becomes more steeply angled. Surfaces parallel to the light source are rendered pure black. If the light source is casting shadows, the shadows are also rendered pure black in this scene, which looks very unconvincing.
Before mental ray appeared in 3ds max, direct light was the most commonly used component of a rendered scene.
The light bounced from surfaces (also known as diffuse light) is used by mental ray to calculate the transfer of energy and color to other nearby surfaces in a scene (see Figure 1.8). The number of times the light energy is allowed to bounce is controlled by the mental ray user and is a powerful tool to balance accuracy and efficiency. You can't have both.
Adding a bounced light component results in light and color transfer into the shadow and shaded areas of the scene, thereby lightening those areas and reducing the overall contrast of the scene for a more convincing and natural look. In the real world, light bounces repeatedly until it is absorbed or loses its energy through attenuation, and while theoretically possible in mental ray, it would be very inefficient. Three or four bounces in mental ray are often enough to provide very good result without overtaxing computer resources.
22.214.171.124 Environment light
Environment light is generally an outdoor occurrence of light being scattered by water vapor and dust particles in the atmosphere. If you go outdoors in the morning before the sun comes over the horizon, your surroundings are lit entirely by environment light, for example. However, it's an important component because it greatly affects the brightness and color of shadows and shaded areas of your scene. In mental ray, environment light or skylight is a component of the Daylight system used in outdoor scenes (see Figure 1.9).
Excerpted from Rendering with mental ray and 3ds Max by Joep van der Steen Ted Boardman Copyright © 2010 by ELSEVIER Inc.. Excerpted by permission of Focal Press. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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