Java图形编程基础：OpenGL与Jogl实战

需积分: 10 143 浏览量更新于2024-07-16 收藏 1.32MB PDF 举报

身份认证购VIP最低享 7 折!

领优惠券(最高得80元）

"《计算机图形学基础：使用Java、OpenGL和Jogl》是David J. Eck教授在2010年春季学期编写的在线课程教材的初步部分版本。该资源主要探讨了三维计算机图形学的基本概念，使用Java编程语言，并通过Jogl库实现了对OpenGL标准图形API的访问。Jogl 1.1.1a版本被用于教学，但当时Jogl 2版正在开发中，预计与旧版不兼容，可能需要对代码进行适配。此PDF版本不包含源代码文件，但提供了指向在线版本的链接，包括内部链接和外部链接，方便阅读和学习。此外，该书遵循Creative Commons Attribution-ShareAlike 3.0 License，允许无修改分发或在相同许可下修改后分发。" 这篇资源详细介绍了计算机图形学的基础知识，尤其是如何使用Java进行图形编程。OpenGL是一种广泛应用于C语言的图形API，而Jogl则为Java程序员提供了访问OpenGL所有功能的接口。课程的目标不仅是涵盖计算机图形学的核心概念，而且是让初学者能够理解并应用这些概念，而不是被复杂的算法和公式淹没。在课程中，作者强调了选择恰当的主题对于保持学生兴趣的重要性。尽管计算机图形学是一个庞大且复杂的领域，但初学者应该首先掌握基本原理，而不是过于深入细节。因此，这些笔记重点讲述了如何使用Java和Jogl进行三维图形编程，通过实例和实践帮助学生理解基础概念。书中可能涵盖了以下关键知识点： 1. 计算机图形学的基本原理：包括坐标系统、变换（平移、旋转、缩放）、投影（正交投影和透视投影）、光照模型、颜色理论等。 2. Java编程基础：用于图形编程的Java语言特性，如面向对象编程、数据类型、控制结构等。 3. Jogl API的使用：介绍如何使用Jogl库来创建和管理OpenGL上下文，以及如何绘制基本几何形状。 4. OpenGL图形管线：解释从顶点到屏幕像素的处理过程，包括顶点处理、图元装配、光栅化和颜色混合等步骤。 5. 着色器语言（GLSL）：介绍如何使用GLSL编写自定义着色器，实现更复杂的图形效果。 6. 实践项目和案例分析：可能包含一系列的编程练习和项目，让学生将理论知识应用到实际场景中。通过这本书，学生不仅可以学习到计算机图形学的基本理论，还能掌握使用Java和OpenGL进行图形编程的技能。同时，提供的在线资源和链接为学习者提供了丰富的实践材料和进一步探索的途径。

资源详情

资源推荐

CHAPTER 1. JAVA GRAPHICS IN 2D 10

The source code ﬁles QuadraticBezierEdit.java and CubicBezierEdit.java deﬁne applications

that let you edit the curves shown in this image by dragging the control points and endpoints

of the curve. You can also ﬁnd applet versions of these applications in the web-site version of

these notes.

∗ ∗ ∗

Once you have a Path2D or a Line2D, or ind eed any object of type Shape, you can use it

with a Graphics2D. The Graphics2D class deﬁnes the methods

public void draw(Shape s)

public void fill(Shape s)

for drawing and ﬁlling S hapes. A Graphics2D has an instance variable of type Paint that tells

how shapes are to be ﬁlled. Paint is ju st an interface, but there are several standard classes

that implement that interface. One example is class Color. If the current paint in a Graphics2D

g2 is a Color, then calling g2.ﬁll(s) will ﬁll the Shape s with solid color. However, there are

other types of Paint, such as GradientPaint and TexturePaint, that represent other typ es of ﬁll.

You can set the Paint in a Graphics2D g2 by calling g2.setPaint(p). For a Color c, calling

g2.setColor(c) also sets the paint.

Calling g2.draw(s) will “stroke” the shape by moving an imaginary pen along the lines or

curves that make up the shape. You can use this m ethod, for example, to draw a line or the

boundary of a rectangle. By default, the shape will be stroked using a pen that is one unit

wide. In the usual pixel coord inates, this means one pixel wide, but in a non-standard coordinate

system, the pen will be one unit wide and one unit high, according the units of that coord inate

system. The pen is actually deﬁned by an object of type Stroke, which is another interface. To

set the stroke property of a Graphics2D g2, you can use the method g2.setStroke(stroke). The

stroke will almost certainly be of type B asicStroke, a class that implements the Stroke interface.

For example to draw lines with g2 that are 2.5 times as wide as usual, you would say

g2.setStroke( new BasicStroke(2.5F) );

Note that the parameter in the constructor is of type ﬂoat. BasicStroke has several alternative

constructors that can be used to specify various characteristics of the pen, such as how an

endpoint should be drawn and how one piece of a curve should be joined to the next. Most

interesting, perhaps, is the ability to draw dotted and dashed lines. Unfortunately, the details

CHAPTER 1. JAVA GRAPHICS IN 2D 11

are somewhat complicated, but as an example, here is how you can create a pen that draws a

pattern of dots and dashes:

float[] pattern = new float[] { 1, 3, 5, 3 }; // pattern of lines and spaces

BasicStroke pen = new BasicStroke( 1, BasicStroke.CAP

BUTT,

BasicStroke.JOIN

ROUND, 0, pattern, 0 );

This pen would draw a one-unit-long dot, followed by a 3-unit-wide space, followed by a 5-

unit-long dash, followed by a 3-unit-wide space, with the pattern repeating after that. You can

adjust the pattern to get diﬀerent types of dotted and dashed lines.

Note that in addition to the current Stroke, the eﬀect of g2.draw(s) also depends on the

current Paint in g2. The area covered by the pen is ﬁlled with the curr ent paint.

∗ ∗ ∗

Before leaving the topic of drawing with Graphi cs2D, I sh ould mention antialiasing. Aliasing

is a problem for raster-type graphics in general, caused by the fact that raster images are made

up of small, solid-colored pixels. It is not possible to draw geometrically perfect pictures by

coloring pixels. A diagonal geometric line, for example, will cover some pixels only partially,

and it is not possible to make a pixel half black and half white. When you try to draw a

line with black and w hite pixels only, the r esult is a jagged staircase eﬀect. This eﬀect is an

example of aliasing. Aliasing can also be s een in the outlines of characters drawn on the screen

and in diagonal or cur ved boun daries between any two regions of diﬀerent color. (The term

aliasing likely comes f rom the fact that most pictures are n aturally described in real-number

co ordinates. When you try to represent the image using pixels, many real-number co ordinates

will map to the same integer pixel coordinates; they can all be considered as diﬀerent names or

“aliases” for th e same pixel.)

Antialiasing is a term for techniques that are designed to mitigate the eﬀects of aliasing.

The idea is that when a pixel is only partially covered by a shape, the color of the pixel should

be a mixture of the color of the shape and the color of the background. When drawing a

black line on a w hite background, the color of a partially covered pixel would be gray, with the

shade of gray depending on the fraction of the pixel that is covered by the line. (In practice,

calculating this area exactly for each pixel would be too diﬃcult, so some approximate method

is used.) Here, for example, are two lines, greatly magniﬁed so that you can see the individual

pixels. The one on the right is drawn using antialiasing, while the one on the left is n ot:

CHAPTER 1. JAVA GRAPHICS IN 2D 12

Note that antialiasing does not give a perf ect image, but it can reduce the “jaggies” that are

caused by aliasing.

You can turn on antialiasing in a Graphics2D, and d oing so is generally a good idea. To do

so, simply call

g2.setRenderingHint(RenderingHints.KEY ANTIALIASING, RenderingHints.VALUE ANTIALIAS ON);

before using the Graphics2D g2 for drawing. Antialiasing can be applied to lines, to text, and

to the curved shapes such as ellipses. Note that turning on antialiasing is considered to be a

“hint,” which means that its exact eﬀect is not guaranteed, and it might even have no eﬀect

at all. In general, though, it does give an imp roved image. Turning antialiasing on does slow

down the drawing process, and the slow-down might be noticeable when drawing a very complex

image.

1.3 Transformations and Modeling

We now turn to another aspect of two-dimensional graphics in Java: geometric trans- (online)

formations. The material in this section will carry over nicely to three dimensions an d OpenGL.

It is an important foundation for th e rest of the course.

1.3.1 Geometric Transforms

Being able to draw geometric shapes is important, b ut it is only part of the story. Just as

important are geometric transforms that allow you to modify the shapes that you draw,

such as by moving them, changing their size, or rotating them. Some of this, you can do by

hand, by doing your own calculations. For example, if you want to move a shape three units to

the right, you can simply add 3 to each of th e horizontal coordinates that are used to draw the

shape. This would quickly become tedious, however, so its nice that we can get th e computer

to do it for us simply by specifying an appropriate geometric trans form. Fur th ermore, there

are things that you simply can’t do in Java without transforms. For example, when you draw

a string of text without a transform, th e baseline of the text can only be horizontal. There is

no way to draw the string tilted to a 30-degree angle. Similarly, the only way to draw a tilted

image is by applying a transform. Here is an example of a string and an image drawn by Java

in their normal orientation and w ith a counterclockwise 30-degree rotation:

CHAPTER 1. JAVA GRAPHICS IN 2D 13

Every Graphics2D graphics context has a current transform that is applied to all drawing

that is done in that context. You can change the transform, and the new value will apply to

all subsequent drawing operations; it will not aﬀect things that have already been drawn in

the graphics context. Generally, in a newly created Graphics2D, the current transform is the

identity transform, which has no eﬀect at all on drawing. (There are some exceptions to

this. For example, when drawing to a printer, the pixels are very small. If the same coordinates

are used when drawing to the pr inter as are us ed on the screen, the resulting picture would

be tiny. So, when drawing to a printer, Java provides a default transform that magniﬁes the

picture to make it look about the same size as it does on the screen.)

The transform in a Graphics2D can be any aﬃne transform. An aﬃne transform has the

property that when it is applied to any s et of parallel lines, the result is also a set of parallel

lines (or, possibly, a single line or even a single point). An aﬃne transform in two dimensions

can be speciﬁed by six numbers a, b, c, d, e, and f, which have the property that when the

transform is applied to a point (x,y), the resulting point (x1,y1) is given by th e formulas:

x1 = a*x + b*y + e

y1 = c*x + d*y + f

Aﬃne transform s have th e important property that if you apply one aﬃne transform and then

follow it with a second aﬃne transform, the result is another aﬃne transform. For example,

moving each point three u nits to the right is an aﬃne transform, and so is rotating each point by

30 degrees about the origin (0,0). Therefore the combined transform that ﬁrst moves a point to

the right and then r otates it is also an aﬃne transform. Combining two aﬃne transformations

in this way is called multiplying them (although it is not multiplication in the usual s en s e).

Mathematicians often use the term composing rather than multiplying.

It’s possible to build up any two-dimensional aﬃne transformation from a few basic kinds

of simple transforms: translation, rotation, and scaling . I t’s good to have an intuitive

understanding of these basic transforms and how they can be used, so we will go through them

in some detail. The eﬀect of a transform depends on what coordinate system you are using for

drawing. For this discussion, we assume that the origin, (0,0), is at the center of the picture,

with the positive direction of the x-axis pointing to the right and the positive direction of the y-

axis pointing up. Note that this orientation for the y-axis is the opposite of the usual orientation

CHAPTER 1. JAVA GRAPHICS IN 2D 14

in Java; it is, however, the more common orientation in mathematics and in OpenGL.

∗ ∗ ∗

A translation simply moves each point by a certain amount horizontally and a certain

amount vertically. The formula for a translation is

x1 = x + e

y1 = y + f

where the point (x,y) is moved e units horizontally and f units vertically. (Thus for a translation,

a = d = 1, and b = c = 0.) I f you wanted to apply this translation to a Graphics2D g, you

could simply say g.translate(e,f ). This would mean that for all subsequent d rawing operations,

e would be added to the x-coordinate and f would be added to the y-coordinate. Let’s look

at an example. Suppose that you are going to draw an “F” centered at (0,0). If you say

g.translate(4,2) before drawing the “F”, then every point of the “F” will be moved over 4

units and up 2 un its, and the “F” that appears on the screen will actually be centered at (4,2).

Here is a picture:

The light gray “F” in this picture shows what would be drawn without the translation; the

dark red “F” sh ows the same “F” drawn after applying a translation by (4,2). The arrow shows

that the upper left corner of the “F” has been moved over 4 units and up 2 units. Every point

in the “F” is subjected to the same displacement.

Remember that when you say g.translate(e,f ), the tr anslation applies to all the drawing that

you do after that, not just to the next shape that you draw. If you apply another transformation

to the same g, the second transform will not replace the translation. It will be multiplied by

the translation, so th at subsequent drawing will be aﬀected by the combined transformation.

This is an important point, and there w ill be a lot more to say about it later.

∗ ∗ ∗

A rotation rotates each point about the origin, (0,0). Every p oint is rotated through the

same angle, called the angle of rotation. For this pur pose, angles in Java are measured in

radians, not degrees. For example, the measure of a right angle is π/2, not 90. Positive angles

move the positive x-axis in the direction of the positive y-axis. (This is counterclockwise in the

co ordinate system that we are using here, but it is clockwise in the usual pixel coordinates,

where the y -axis points down rather than u p.) Although it is not obvious, when rotation

through an angle of r radians about the origin is applied to the point (x,y), then the resulting

point (x1,y1) is given by

x1 = cos(r) * x - sin(r) * y

y1 = sin(r) * x + cos(r) * y

剩余136页未读，继续阅读

S6162

粉丝: 0
资源: 5

Java图形编程基础：OpenGL与Jogl实战

计算机图形学《fundamentals of computer graphics》

Computer graphics with opengl 4th edition(计算机图形学第四版原版)

Fundamentals of Computer Graphics (3rd Edition)

fundamentals of computer graphics第三版和第四版差别

fundamentals of computer graphics pdf 4th

fundamentals of computer graphics第五版pdf

fundamentals of computer graph

【数字逻辑fundamentals of digital logic with verilog design | 3rd editio

Fundamentals of Physics. Extended

数字逻辑fundamentals of digital logic with verilog design | 3rd edition solu

text: fundamentals of digital logic with verilog design, third edition,

fundamentals of power electronics 高清 pdf

fundamentals of physics 第10版 课件

计算机领域包括计算机科学基础、软件工程、硬件工程、网络工程、人工智能、计算机图形学、人机交互那他们又包括什么呢？请一一列举出来

fundamentals of electric circuits 6th edition

core java, volume i: fundamentals, 12e

fundamentals of power electronic

fundamentals of massive mimo

fundamentals of logic design

fundamentals of photonics 答案

最新资源

fundamentals of physics 第10版课件