Maya艺术与3D图形入门

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"《Maya艺术》——3D图形入门" 《Maya艺术》是一本介绍3D图形技术的书籍，特别关注Autodesk Maya这一强大的3D建模和动画软件的基础知识。Maya是由Autodesk公司开发的，广泛应用于电影、电视、游戏以及视觉特效行业，因其强大的功能和灵活性而备受赞誉。本书旨在为初学者提供一个了解3D图形世界的窗口，通过学习Maya的基本操作，读者可以掌握如何创建三维模型、进行纹理贴图、设置动画以及渲染最终的视觉效果。Maya的基本概念包括工作界面、视图控制、建模工具（如多边形建模、曲线建模和NURBS建模）、材质与纹理、灯光和摄像机的使用，以及复杂的动画系统。书中可能涵盖了以下关键知识点： 1. **Maya界面与基础操作**：熟悉Maya的工作界面，理解时间线、通道盒、层次编辑器等核心组件的作用，学会基本的导航和选择工具。 2. **3D建模**：学习多边形建模，如创建基本几何体、融合、切削、平滑等操作；了解NURBS建模用于创建平滑曲面；探索曲线和曲线网格建模，用于制作有机形状。 3. **纹理与材质**：理解UV纹理坐标，学习如何应用和修改纹理，以及使用材质节点来创建复杂效果，如金属、玻璃、布料等不同表面特性。 4. **灯光与摄像机**：学习创建和控制各种类型的灯光，理解光影在3D场景中的重要性；掌握摄像机的设置，实现动态视角和镜头效果。 5. **动画原理**：学习关键帧动画、路径动画和骨骼IK/FK系统，理解运动捕捉数据的应用，以及如何创建流畅的角色动作。 6. **渲染与后期**：了解Maya内置的渲染器，如Arnold，设置渲染参数，导出图像或视频；学习基本的合成和后期处理技巧，提升最终作品的质量。值得注意的是，Autodesk公司在法律声明中指出，他们对这些材料不做任何明示或暗示的保证，包括但不限于对商品性和特定用途适用性的保证。同时，对于因获取或使用这些材料所造成的任何特殊、附带、间接或后果性损害，Autodesk公司不承担责任。购买者只能在"按原样"的基础上使用这些材料，且Autodesk保留在认为合适时修订和改进产品的权利。尽管如此，这本书对于想要进入3D图形领域，特别是想精通Maya的人来说，仍是一份宝贵的资源。随着时间的推移，尽管产品可能会有所更新，但基本的概念和技术原理通常保持一致，因此本书中的内容依然具有很高的学习价值。

Time and Space

With 3D computer animation, artists work in a digital world where space,

color, texture, time, shape and form are tools for creating images and

sequences of images.

All of these physical realities must be translated into a computer

language based on numbers. In fact, Maya scenes and images are really

just databases of numbers that are interpreted by Maya software and

presented on the computer screen in a more visual and artist-friendly manner.

While artists do not have to know how the numbers are interpreted by

the computer, they do need to understand some of the ways in which space,

color and time are quantified and recorded. Learning how the computer

interprets digital information—such as 3D coordinates, frames per second

or the RGB information stored in a bitmap image—can help artists under-

stand how this information relates to their own perception of time and space.

time and space

3D Space

Two Dimensions

When you measure the width and height of an

object, you are analyzing two of its dimensions.

The X and Y axes can be used to find points on

an object, such as the center of the wheel or

the position of the headlight in this two-

dimensional space.

Three Dimensions

When you measure the length, width and height of

an object, you must consider a third dimension as

defined by the Z-axis when defining points in space.

Transformations

When an object is moved, rotated or scaled, the X,

Y and Z axes are used for reference. An object is

moved along, rotated around, or scaled along the

chosen axis line. Values for these transformations

are stored for each of the three axes.

Y-up and Z-up Worlds

By default, Maya is Y-up where the Y-axis

represents the height. Some 3D packages,

especially CAD applications, might use Z as

the height. If you import a model from one of

these packages, you have to either re-orient

the model or set up Maya as a Z-up world.

Origin

Points in a 3D coordinate system are measured against

an origin point. This point is assigned a value of 0, 0, 0.

Axis indicator

To help you visualize the three axes,

each is given a corresponding RGB color.

X – red

Y – green

Z – blue

The Ground Grid

To create a ground surface to reference your work in

XYZ, Maya includes a grid that maps out an area 24

x 24 units. The X and Z axes are on the ground and

form the lines of the grid. The Y-axis is the height.

The axes indicators point

in the positive direction

for X, Y and Z.

very day, you come into contact with three-dimensional objects

and spaces. You have learned how to recognize and work with

three dimensions in your daily routine and have an intuitive feel

for how it works. If you have ever drawn a sketch, built a model or

sculpted a model, you also have a creative feel for how shape and

form can be described in 3D.

Three-dimensional objects can be measured and quantified. If

you have ever measured the length, width and height of an object,

you have analyzed its three dimensions. You can also determine an

object’s position by measuring it in relation to another object or to a

point in space. In Maya, you can explore three-dimensional objects

and recreate them on screen as rendered images complete with lights

and shadows.

XYZ Coordinate Space

In Maya, 3D space is measured using three axes that are defined as

the X-axis, the Y-axis and the Z-axis. If you imagine looking into a

movie screen, the width would be the X-axis, the height would be

the Y-axis and the depth would be the Z-axis. In Maya, these axes are

presented with X and Z on the ground and Y as the height.

You can find any point in this 3D world by defining a coordinate

for each of the axes. To help you visualize these coordinates, a grid

with axis indicators shows you their orientation.

3D Space

THE ART OF MAYA

Perspective Space

When you visualize objects in the real world, you do

not usually think about axis lines and 3D coordinates.

Instead, you see the world in perspective where lines

vanish to the horizon and objects get smaller as they

get further away. A Perspective view allows you to

visualize a 3D space in a way similar to how you

view the world through either your eyes or the lens

of a camera.

Most artists have learned to sketch a 3D scene

in perspective or use drafting techniques to create

more accurate perspective drawings. With Maya,

the 3D Perspective view is automatically calculated

for you, based on a camera position and a view

angle that you set.

Orthographic Projections

While a Perspective view can help you compose a

shot, it is not always the ideal method for modeling

and animating objects. Therefore, an Orthographic

view lets you analyze your scene using parallel

projections of only two axes at a time. Using these

views, you can more accurately determine how an

object is positioned.

Most 3D animators find themselves using

perspective views to compose a shot while Orthographic

views offer a place to view the scene in a more

analytical manner. Both views are crucial to working

properly in 3D.

World Space and Local Space

When you build objects in 3D, it is possible

to parent one object to another. This creates a

hierarchy where the parent object determines the

position of the group in world space. The child

objects inherit this positioning and combine this

with their own local space position. This parent-child

relationship is used during the animation of an

object where keyframes can be set on both the

child and the parent.

UV Coordinate Space

One of the object types you will build in Maya is surfaces. While

surfaces are positioned in 3D space using X, Y, Z coordinates, they also

have their own coordinate system that is specific to the topology of

the surface. Instead of using X, Y, Z axes, this system uses U, V and N,

where U and V represent the two axes that lie on the surface and N is

the “surface normal” axis that points out from the front of the surface.

When you create a curve, it has a U direction that lets you measure

points along the curve. When a surface is created, it has a U and a V

direction that define the surface parameterization. You can draw and

manipulate curves in this 2D surface space. The placement of textures

can also take place in UV space.

The Complete Picture

The different points of view afforded

by Orthographic and Perspective views

let you build and evaluate your models.

The Camera

Perspective views are generated by

cameras that simulate real-world

camera attributes. It is possible to

Local Space

The handle bar and the front

wheel use an angled axis line

to set up the local rotations.

World Space

When the whole object moves in world

space, child objects such as the handle

bar and the wheels move with it.

UV Coordinates

The origin of the UV system lies at one of

the surface corners. U runs along one axis

and V along the other.

Curve-on-Surface

Curves can be drawn in UV

space. Later edits will be in 2D

along U and V axes.

Moving Curves

When you select and move a curve in UV space,

you can only move along the two axes of the

surface grid. Curve control points can also be

edited in UV space.

Normal

The surface Normal always points out from the

front of the surface. You can see the Normal lines

pointing out from each intersection on the UV grid.

Top view

Front view Side view

Perspective view

Perspective Camera

Local Space

The wheel rotates around its cen-

ter using a local rotation axis.

time and space

Frames per Second

Frames can be played back at different speeds that

are measured in frames per second (fps). This is

known as the frame rate and it is used to set the

timing of an animation. The frame rate is required

output animation to film or video and to synchronize

that animation with sound and live-action footage.

In Maya, you can set your frame rate by

selecting Window > Settings/Preferences >

Preferences and selecting the Settings category.

By default, the Maya software

frame rate is 24 fps. If you have

a background in animation,

confirm your time units to

ensure you set keys properly.

Because seconds are the

base unit of time, it is possible

to set keys at 24 fps, then

change your frame rate to 30

fps. This will scale the timing

of your animation to match the

timing as measured in seconds.

n the world of 3D animation, time is the fourth

dimension. An object will appear animated if it either

moves, rotates or changes shape from one point in

time to another. Therefore, learning how time works

is crucial to the animation process.

Both live-action and animation use either film

or video to capture motion. Both media formats use

a series of still images that appear animated when

played back as a sequence.

Film and video images are often referred to as

frames and most animation is measured using frames

as the main unit of time. The relationship between

these frames and real time differs depending on

whether you are working with video, film or other

digital media.

Time Code

Time code is a frame numbering system that assigns

a number to each frame of video that indicates

hours, minutes, seconds and frames. This is what

gets burned onto video tape. This gives you an

accurate representation of time for synchronization.

You can set up time code display in Maya from the

Preferences window.

Fields

The concept of Fields is important if you output your

animation to video. To make video play back smoothly,

Fields are used in place of frames. Each Field uses

alternating rows of pixels—called scanlines—that are

interlaced during playback. Fields are timed at 60 fps

for NTSC, with each Field containing only half the

number of scanlines as a typical frame.

In Maya, you can render directly to Fields that

have the 60 fps (50 fps PAL) timing or you can

output a 30 fps (25 fps PAL) sequence and use a

compositing system to convert it to Fields. For fast-

moving objects,rendering directly to Fields offers

smoother playback since each Field displays half-frame

intervals.

Playback

When you preview your animations, you will often

use interactive playback. You can set the Playback

Speed by selecting Window > Settings/Preferences

> Preferences and selecting the Timeline category.

The default Playback Speed is Play Every Frame.

At this speed, Maya will play every frame in your

scene one after another. The actual playback speed

will depend on your workstation’s ability to process

the animated elements in your scene. Setting your

Playback Speed to Real-time asks Maya to maintain

your chosen frame rate as accurately as possible.

This means that Maya may skip frames in order to

maintain the frame rate. Note that if you are synchro-

nizing to sound, your Playback Speed should be

set to Real-time, but if you are previewing dynamic

simulations, it should be set to Play Every Frame.

Frame 1

Frame 2

Field 2 Odd Field 2 Even

Field 1 Odd

Field 1 Even

Time

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