OpenGL overview (đồ họa máy TÍNH SLIDE)

OpenGL and GLUT Overview• What is OpenGL & what can it do for me?... What Is OpenGL?– a cross-platform API – high-quality color images composed of geometric and image primitives • widely

OpenGL Overview

OpenGL and GLUT Overview

• What is OpenGL & what can it do for me?

What Is OpenGL?

– a cross-platform API

– high-quality color images composed of geometric and image primitives

• widely used in CAD, virtual reality, scientific visualization, information visualization and video game development

OpenGL Architecture

OpenGL as a Renderer

– points, lines and polygons

– images and bitmaps

– separate pipeline for images and geometry

• linked through texture mapping

– colors, materials, light sources, etc.

Related APIs

– glue between OpenGL and windowing systems

– part of OpenGL

– NURBS, tessellators, quadric shapes, etc.

– portable windowing API

– keyboard and mouse input

– Geometric primitives: cubes, spheres, and teapot

– not officially part of OpenGL

OpenGL and Related APIs

X, Win32, Mac O/S

software and/or hardware

application program

OpenGL Motif widget or similar

What is JOGL?

that allow OpenGL to be used in Java

Setting Up JOGL 2.0x

• Download the latest "stable" release from JogAMP

http://jogamp.org/deployment/jogamp-current/archive Select "jogamp-all-platforms.7z"

– Copy the necessary jar-file, native libraries of your operating platform, and source-files into the appropriate sub-directories

– for Win32, copy

• "jar\gluegen-rt.jar", "jar\jogl.all.jar" into "jar";

• all files in "lib\windows-i586" into "lib";

• "gluegen-java-src.zip", "jogl-java-src.zip" into "src"

• Unzip the javadocs downloaded into "javadoc".

Sample Template Program

pu blic class JO G L2Tem plate extends G LJPanel

im plem ents G LEventListener {

// Setup O penG L G raphics Renderer

private G LU glu ; // for the G L U tility

private G LU T glut ; // O penG L U tility Toolkit

/** Constructor to setup the G U I for this Com ponent */

pu blic JO G L2Tem plate() {

this.addG LEventListener( this );

}

Sample Program: init event

/**

* Called back im m ediately after the O penG L context is initialized

* Can be used to perform one - tim e initialization Run only once.

*/

pu blic void init(G LAutoD raw able draw able) {

G L2 gl = draw able.getG L().getG L2(); // get the O penG L graphics context glu = new G LU (); // get G L U tilities

gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // set background color

gl.glClearD epth(1.0f); // set clear depth value to farthest

gl.glEnable(G L_D EPTH _TEST); // enables depth testing

gl.glD epthFunc(G L_LEQ U AL); // the type of depth test to do

// best perspective correction

gl.glH int(G L_PERSPECTIVE_CO RRECTIO N _H IN T , G L_N ICEST );

// blends colors nicely, and sm oothes out lighting

gl.glShadeM odel(G L_SM O O TH );

// Your O penG L initialization code here

-}

Sample Program: reshape event

/* Call - back handler for w indow re - size event Also called w hen the

draw able is fi rst set to visible */

pu blic void reshape(G LAutoD raw able draw able,

int x, int y, int w idth, int height) {

G L2 gl = draw able.getG L().getG L2();

if (height = = 0) height = 1; // prevent divide by zero

f l oat aspect = (f l oat) w idth / height;

// Set the view port (display area) to cover the entire w indow

gl.glView port(0, 0, w idth, height);

// Setup perspective projection,

// w ith aspect ratio m atches view port

gl.glM atrixM ode(G L_PRO JECTIO N ); // choose projection m atrix

gl.glLoadIdentity(); // reset projection m atrix

glu gluPerspective(45.0, aspect, 0.1, 100.0); // fovy, aspect, zN ear, zFar // Enable the m odel-view transform

gl.glM atrixM ode(G L_M O D ELVIEW );

gl.glLoadIdentity(); // reset

}

Sample Program: display event

/* Called back by the anim ator to perform rendering */

pu blic void display(G LAutoD raw able draw able) {

// get the O penG L 2 graphics context

G L2 gl = draw able.getG L().getG L2();

// clear color and depth buff ers

gl.glClear(G L_CO LO R_BU FFER_BIT | G L_D EPTH _BU FFER_BIT );

gl.glLoadIdentity(); // reset the m odel-view m atrix

// Your O penG L rendering code here

// (Render a w hite triangle for testing)

gl.glTranslatef(0.0f, 0.0f, -6.0f); // translate into the screen

gl.glBegin(G L_TRIAN G LES ); // draw using triangles

Sample Program: dispose event

**

* Called back before the O penG L context is destroyed

* Release resource such as buff ers.

*/

p ublic void dispose(G LAutoD raw able draw able) {

}

pu blic static void m ain(String[] args) {

Sw ingU tilities.invokeLater( new Runnable() {

pu blic void run() {

// Create the O penG L rendering canvas

G LJPanel panel = new JO G L2Tem plate();

panel.setPreferredSize( new D im ension(640 , 480 ));

// Create a anim ator

FPSAnim ator anim ator = new FPSAnim ator(panel, 60 , true );

JFram e fram e = new JFram e();

fram e.getContentPane().add(panel);

fram e.addW indow Listener( new W indow Adapter() {

p u blic void w indow Closing(W indow Event e) {

// stop the anim ator stops before program exits.

new Thread() {

pu blic void run() {

if (anim ator.isStarted()) anim ator.stop();

fram e.setTitle( "JO G L2 Tem plate");

fram e.pack(); fram e.setVisible( true );

anim ator.start(); // start the anim ation loop

}

});

Elementary Rendering

Elementary Rendering

OpenGL Geometric Primitives

• All geometric primitives are specified by vertices

GL_QUAD_STRIP GL_POLYGON

GL_TRIANGLE_STRIP GL_TRIANGLE_FAN

GL_POINTS

GL_LINES

GL_LINE_LOOP GL_LINE_STRIP

GL_TRIANGLES

GL_QUADS

OpenGL Command Formats

Enumerated Types

Specifying Geometric Primitives

glBegin(primType);

glEnd();

– primType determines how vertices are combined

void drawRhombus(GL2 gl, float[] color) { gl.glColor3fv(color);

OpenGL Color Models

color index mode

Display 1

24 25 26

ww

ww

RGBA mode

Shapes Tutorial

Controlling Rendering Appearance

OpenGL’s State Machine

– rendering styles

– shading

– lighting

– texture mapping

Manipulating OpenGL State

update OpenGL state

Controlling current state

– cap is a feature like:

• GL_LIGHTING, GL_TEXTURE_2D, GL_CULL_FACE, GL_BLEND,

OpenGL State Variables

• You can query the State Machine to determine the state of any variable

• Any feature you enable or disable with glEnable / glDisable as well as numeric settings set with glSet can be queried with the many variations of glGet

Animation and Depth Buffering

Depth Buffering and Animation

Animation using Double Buffering

1

2 4 8 16

1

2 4 8 16

Front Buffer

Back Buffer

Display

Animation and Double Buffering

– Default for JOGL

Depth Buffering

and Hidden Surface Removal

1

2 4 8 16

1

2 4 8 16

Color Buffer

Depth Buffer

Display

Hidden Surface Removal

Depth Buffering Using OpenGL

An Updated Program Template

public void display(G LAutoD raw able draw able) {

G L2 gl = draw able.getG L().getG L2();

gl.glClear(G L_CO LO R_BU FFER_BIT | G L_D EPTH _BU FFER_BIT );

gl.glLoadIdentity();

gl.glTranslatef(0.0f, 0.0f, -5.0f);

}

An Updated Program Template (cont)