CG[LWJGL0005] || Menggambar Segi Empat

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Pada postingan kali ini kita akan membahas tentang cara menggambar segi empat OpenGL menggunakan library LWJGL. tutorial kali ini berhubungan dengan materi yang telah dibahas sebelumnya tentang cara menggambar segi tiga openGL. berikut ini source code untuk menggambar segi empat OpenGL menggunakan library LWJGL:

import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;

import org.lwjgl.opengl.GL11;
import org.lwjgl.util.glu.GLU;


public class TutorialLWJGL0005 {

String windowTitle = "CG[LWJGL0005] || Menggambar Segi Empat";
public boolean closeRequested = false;

public void run() {
createWindow();
initializeGL();

// main loop
while (!closeRequested) {
pollInput();
updateLogic();
renderGL();
Display.update();
}

cleanup();
}

private void initializeGL() {
int width = Display.getDisplayMode().getWidth();
int height = Display.getDisplayMode().getHeight();

GL11.glViewport(0, 0, width, height); // Reset The Current Viewport
GL11.glMatrixMode(GL11.GL_PROJECTION); // Select The Projection Matrix
GL11.glLoadIdentity(); // Reset The Projection Matrix
GLU.gluPerspective(45.0f, ((float) width / (float) height), 0.1f, 100.0f); // Calculate The Aspect Ratio Of The Window
GL11.glMatrixMode(GL11.GL_MODELVIEW); // Select The Modelview Matrix
GL11.glLoadIdentity(); // Reset The Modelview Matrix

GL11.glShadeModel(GL11.GL_SMOOTH); // Enables Smooth Shading
//GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // Black Background
GL11.glClearColor(0.20392156862f, 0.59607843137f, 0.85882352941f, 0.0f);
GL11.glClearDepth(1.0f); // Depth Buffer Setup
GL11.glEnable(GL11.GL_DEPTH_TEST); // Enables Depth Testing
GL11.glDepthFunc(GL11.GL_LEQUAL); // The Type Of Depth Test To Do
GL11.glHint(GL11.GL_PERSPECTIVE_CORRECTION_HINT, GL11.GL_NICEST); // Really Nice Perspective Calculations
}

private void updateLogic() {
//
}

private void renderGL() {
GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
GL11.glLoadIdentity(); // Reset The View
GL11.glTranslatef(-1.5f, 0.0f, -6.0f);

GL11.glTranslatef(3.0f, 0.0f, 0.0f); // Move Right 3 Units
GL11.glBegin(GL11.GL_QUADS); // Draw A Quad
GL11.glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
GL11.glVertex3f(1.0f, 1.0f, 0.0f); // Top Right
GL11.glVertex3f(1.0f, -1.0f, 0.0f); // Bottom Right
GL11.glVertex3f(-1.0f, -1.0f, 0.0f); // Bottom Left
GL11.glEnd(); // Done Drawing The Quad
}

public void pollInput() {

// scroll through key events
while (Keyboard.next()) {
if (Keyboard.getEventKeyState()) {
if (Keyboard.getEventKey() == Keyboard.KEY_ESCAPE)
closeRequested = true;
}
}

if (Display.isCloseRequested()) {
closeRequested = true;
}
}

private void createWindow() {
try {
Display.setDisplayMode(new DisplayMode(640, 480));
Display.setVSyncEnabled(true);
Display.setTitle(windowTitle);
Display.create();
} catch (LWJGLException e) {
Sys.alert("Error", "Initialization failed!\n\n" + e.getMessage());
System.exit(0);
}
}

private void cleanup() {
Display.destroy();
}

public static void main(String[] args) {
TutorialLWJGL0005 tutorial = new TutorialLWJGL0005();
tutorial.run();
}

}

jika pada materi sebelumnya kita menggunakan perintah 

GL11.glBegin(GL11.GL_TRIANGLES);

untuk menggambar segitiga kemudian menentukan posisi titik-titik sudutnya, maka untuk menggambar segi empat digunakan perintah berikut:

GL11.glBegin(GL11.GL_QUADS); 

ternyata cukup sederhana bukan...
berikut ini preview window OpenGL nya:

mungkin anda ingin sedikit bermain-main dengan warna seperti berikut ini:

atau

berikut ini source codenya:

private void renderGL() {
GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
GL11.glLoadIdentity(); // Reset The View
GL11.glTranslatef(-1.5f, 0.0f, -6.0f);

GL11.glTranslatef(3.0f, 0.0f, 0.0f); // Move Right 3 Units
GL11.glBegin(GL11.GL_QUADS); // Draw A Quad
GL11.glColor3f(243.0f/255.0f, 156.0f/255.0f, 18.0f/255.0f);
GL11.glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
GL11.glColor3f(211.0f/255.0f, 84.0f/255.0f, 0.0f/255.0f);
GL11.glVertex3f(1.0f, 1.0f, 0.0f); // Top Right
GL11.glColor3f(192.0f/255.0f, 57.0f/255.0f, 43.0f/255.0f);
GL11.glVertex3f(1.0f, -1.0f, 0.0f); // Bottom Right
GL11.glColor3f(39.0f/255.0f, 174.0f/255.0f, 96.0f/255.0f);
GL11.glVertex3f(-1.0f, -1.0f, 0.0f); // Bottom Left
GL11.glEnd(); // Done Drawing The Quad
}


lihat semua tutorial

Referensi:
- http://nehe.gamedev.net/
- http://computergraphicsindonesia.blogspot.com/2015/01/cglwjgl0004-menggambar-segitiga.html