0507 Mitrovic, Ivanovic

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New topic for Java course:Introduction to 3D graphics programming with JOGL

Dejan MitrovićProf. Dr Mirjana Ivanović

2/2910th Workshop "Software Engineering and Reverse Engineering", Ivanjica, Serbia, September 5 - 12, 2010

AGENDA

1. Motivation and goals

2. JOGL

3. Proposed subjects

4. Conclusions

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1.1. Motivation

Game development represents a large portion of the software development industry, BUT, so far very few programming courses given at our Department were focused at this area

The proposed set of subjects constitutes a small part of the recently updated Computer graphics course, which has received high grades from students


1.2. Goals

Provide students with an opportunity to practice Java programming and extend their OO programming skills in an exciting environment

Introduce the proposed set of subjects near the end of the introductory, or at the beginning of the advanced OO course, depending on the students’ progress over the semester

Give them a solid background for later, more advanced topics of the Computer graphics course

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AGENDA


2. JOGL


4. Conclusions


2.1. Why JOGL?

Based on OpenGL ‐ a professional, powerful, free, cross‐platform graphics programming library

Straightforward integration with other GUI and graphics Java APIs and libraries (e.g. Swing, Java2D)

Can serve as an example of how an OO system should notbe designed ☺

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2.2. JOGLext: A JOGL extension library

A library of helper classes built on top of JOGL

Handles common, “boring”, but necessary tasks, includes functions for vector and matrix‐based calculations, etc.

Purpose: enable students to develop simple 3D applications without any (mathematical or game programming) background

‐ Although, experience in playing FPS games can prove valuable for 3D camera handling


2.3. Core JOGLext classes

JoglFrame: a base class for all students’ applications, handles display mode changes, precise timing measurements, various maintenance tasks, etc.

Camera: a flexible, programmable, FPS‐like 3D camera for navigation through generated scenes

Mesh: a framework for loading and rendering external complex 3D models

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AGENDA


2. JOGL


4. Conclusions



1. Introduction to 3D graphics programming(1‐hour lesson)

2. 3D rendering basics(1‐hour lesson)

3. World transformations(2‐hours lesson)

4. Texturing(2‐hours lesson)

5. Complex 3D models(2‐hours lesson)

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3.1. Introduction to 3D graphics programming

What is a graphics programming library?

Introduction to OpenGL and JOGL

Elements of a 3D application: frustum definition, overview of projection and viewing transformations, viewports, etc.

Main classes of JOGLext, creating a very first 3D application by implementing methods of JoglFrame


3.1. Example: HelloWorld3D

public class HelloWorld3D extends JoglFrame{@Overrideprotected void initialize(GL gl, Color4f back,

Vector3f cameraPos, Vector3f cameraDir){

// TODO : initialize camera, set clear color}

@Overrideprotected void render(GL gl, double elapsedTime){

// TODO : perform rendering}

public static void main(String[] args){

HelloWorld3D hw = new HelloWorld3D();// Caption: Hello World 3D// Frame width: 640px// Frame height: 480px// Fullscreen mode: falsehw.start("Hello World 3D", 640, 480, false);

}}

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3.1. Results


3.2. 3D rendering basics

Coordinate system and 3D object specification using vertices

Methods glVertex3f() and glColor3f()

Different modes of rendering with glBegin() and glEnd(): triangle lists, strips, and fans, quads, and polygons

Rendering built‐in objects with GLUT

Basic 2D text rendering with TextRenderer

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3.2. Example: Hexagon

public class Hexagon{// vertices definitionprivate static final Vector3f[] vertices = new Vector3f[]{

new Vector3f( 0.0f, 0.0f, 0.0f),new Vector3f(-1.0f, 0.0f, 0.0f),new Vector3f(-0.5f, 1.0f, 0.0f),new Vector3f( 0.5f, 1.0f, 0.0f),new Vector3f( 1.0f, 0.0f, 0.0f),new Vector3f( 0.5f, -1.0f, 0.0f),new Vector3f(-0.5f, -1.0f, 0.0f)

};// each vertex will be of a different colorprivate static final Color4f[] colors = new Color4f[]{

new Color4f(1.0f, 0.0f, 0.0f),new Color4f(0.0f, 1.0f, 0.0f),new Color4f(1.0f, 1.0f, 0.0f),new Color4f(1.0f, 1.0f, 1.0f),new Color4f(0.0f, 0.0f, 1.0f),new Color4f(1.0f, 0.0f, 1.0f),new Color4f(0.0f, 1.0f, 1.0f)

};


3.2. Example: Hexagon (cont.)

// method for rendering the n-th vertexprivate void renderPoint(GL gl, int n, float z) {

// first set the n-th color, then send the coordinatesColor4f c = colors[n];gl.glColor3f(c.getRed(), c.getGreen(), c.getBlue());Vector3f v = vertices[n];gl.glVertex3f(v.getX(), v.getY(), z);

}

// using GL_TRIANGLE_FAN for hexagon renderingpublic void renderTriangleFan(GL gl, float z) {

// the first 3 vertices make up 1 triangle// every other vertex is connected to the first and the the previous onegl.glBegin(GL.GL_TRIANGLE_FAN);renderPoint(gl, 0, z);renderPoint(gl, 1, z);renderPoint(gl, 2, z);renderPoint(gl, 3, z);renderPoint(gl, 4, z);renderPoint(gl, 5, z);renderPoint(gl, 6, z);renderPoint(gl, 1, z);gl.glEnd();

}

} // class Hexagon

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3.2. Example: 3D Rendering

public class HelloWorld3D extends JoglFrame {private Hexagon hex = new Hexagon();private TextRenderer text;

@Overrideprotected void initialize(GL gl, Color4f back,

Vector3f cameraPos, Vector3f cameraDir) {// initialize TextRendererFont font = new Font("Tahoma", Font.BOLD, 12);text = new TextRenderer(font);

}

@Overrideprotected void render(GL gl, double elapsedTime) {

// render a yellow teapot using GLUTgl.glColor3f(1.0f, 1.0f, 0.0f);glut.glutSolidTeapot(1.0f);// render a colored triangle behind the teapotgl.glBegin(GL.GL_TRIANGLES);gl.glColor3f( 1.0f, 0.0f, 0.0f);gl.glVertex3f(-1.0f, -0.5f, -5.0f);gl.glColor3f( 0.0f, 1.0f, 0.0f);gl.glVertex3f( 1.0f, -0.5f, -5.0f);gl.glColor3f( 1.0f, 1.0f, 1.0f);gl.glVertex3f( 0.0f, 0.5f, -5.0f);gl.glEnd();


3.2. Example: 3D Rendering (cont.)

// render a hexagon behind the trianglehex.renderTriangleFan(gl, -10.0f);// render 2D text at the top of the windowint w = getWidth();int h = getHeight();text.beginRendering(w, h);text.setColor(1.0f, 1.0f, 0.0f, 1.0f);// first line - frame rate, below it - camera positiontext.draw("FPS: " + getFps(), 2, h - 16);text.draw("Camera: " + camera.getPosition().toString(), 2, h - 36);// end text renderingtext.endRendering();

} // render

public static void main(String[] args){

HelloWorld3D hw = new HelloWorld3D();hw.start("Hello World 3D", 640, 480, false);

}

} // class HelloWorld3D

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3.2. Results


3.3. World transformations

Motivation behind and the effects of world transformations

‐ With just a brief overview of “low level” matrix math

Methods glTranslatef(), glRotatef(), and glScalef()

Combining multiple transformations

Storing and restoring transformations with glPushMatrix() and glPopMatrix()

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3.3. Example: SolarSystem

public class Planet {private float distance; // from the sunprivate float revolution; // revolution angleprivate float scale; // size parameterprivate Color4f color; // color of the planet

public Planet(float distance, float revolution, float scale, Color4f color) {// ommitted, save parameters

}

public void render(GL gl, GLUT glut) {// set the planet colorgl.glColor3f(color.getRed(), color.getGreen(), color.getBlue());// every method that changes the world transformation // should always first save the current state and later restore itgl.glPushMatrix();// rotation around the sungl.glRotatef(revolution, 0.0f, 1.0f, 0.0f);gl.glTranslatef(distance, 0.0f, 0.0f);// scale the sphere and render itgl.glScalef(scale, scale, scale);glut.glutSolidSphere(1.0f, 25, 25);// restore the original world transformationgl.glPopMatrix();

}}


3.3. Example: SolarSystem (cont.)

public class SolarSystem extends JoglFrame {private Planet sun, venus, earth, mars; // miniature solar system

protected void initialize(GL gl, Color4f backColor, Vector3f cameraPos, Vector3f cameraDir) {

// initialize cameracameraPos.assign(1.75f, 17.0f, 38.47f);cameraDir.assign(0.0f, -0.49f, -0.87f);// initialize planetssun = new Planet(0.0f, 0.0f, 5.0f, new Color4f(1.0f, 1.0f, 0.0f));venus = new Planet(10.0f, -160.0f, 0.7f, new Color4f(0.59f, 0.3f, 0.0f));earth = new Planet(15.0f, -80.0f, 1.0f, new Color4f(0.0f, 0.0f, 1.0f));mars = new Planet(20.0f, -60.0f, 0.5f, new Color4f(1.0f, 0.0f, 0.0f));

}

protected void render(GL gl, double elapsedTime) {sun.render(gl, glut);venus.render(gl, glut);earth.render(gl, glut);mars.render(gl, glut);

}

public static void main(String[] args) {// ommitted, the usual

}}

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3.3. Results


3.4. Texturing

Textures and texture coordinates

Loading, enabling, disabling, and binding textures, assigning coordinates with glTexCoord2f()

Method glTexEnvf(), and environment modesGL_MODULATE and GL_REPLACE

Different ways of applying texture coordinates withGL_CLAMP and GL_REPEAT

2D texture rendering with TextureRenderer

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3.4. Adding textures to SolarSystem


3.5. Complex 3D models

The concept of meshes, their organization into sub‐meshes of vertices with shared properties

Using the Mesh class for loading and rendering 3D models

OBJ file format for storing meshes

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3.5. The end results


4. Conclusions

Graphics programming with JOGL represents an exciting environment for practicing Java programming and extending students’ OO programming skills (such as aggregation, inheritance and polymorphism, working with arrays, etc.)

JOGLext enables students to “dive into” the 3D application development without much previous knowledge of the subject

The proposed set of subjects is simple enough, yet it provides them with enough material for creating real 3D applications

The subjects also serve as a good foundation for senior, more advance Computer graphics course

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Thank you! ☺

Questions? Suggestions?

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0507 Mitrovic, Ivanovic