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Index › Programming Questions & Help › OpenGL and 3D Libraries › JOGL for dummies

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JOGL for dummies (Read 1849 times)

nardove

JOGL for dummies
Jul 20^th, 2009, 4:02am

Hi, can you help me to understand this, basically I just trow an arrow here to see what happens, obviously nothing...

I try to follow this tutorial http://jerome.jouvie.free.fr/OpenGl/Tutorials/Tutorial4.php

but I am missing something, can you tell me how to get this sample working, and what I am doing wrong?
Code:

import javax.media.opengl.*;
import processing.opengl.*;

void setup() {
  size(800, 600, OPENGL);
}

void draw() {
  background(255);

  PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;
  GL gl = pgl.beginGL();
  gl.glBegin(GL.GL_TRIANGLE_FAN);
    gl.glColor3f(1.0f,0.0f,0.0f); 
    gl.glVertex3f( 0.0f, 1.0f, 0.0f);
    gl.glColor3f(0.0f,1.0f,0.0f); 
    gl.glVertex3f(-1.0f,-1.0f, 1.0f);
    gl.glColor3f(0.0f,0.0f,1.0f); 
    gl.glVertex3f( 1.0f,-1.0f, 1.0f);
    gl.glColor3f(0.0f,1.0f,0.0f); 
    gl.glVertex3f( 1.0f,-1.0f,-1.0f);
    gl.glColor3f(0.0f,0.0f,1.0f); 
    gl.glVertex3f(-1.0f,-1.0f,-1.0f);
    gl.glColor3f(0.0f,1.0f,0.0f); 
    gl.glVertex3f(-1.0f,-1.0f, 1.0f);
  gl.glEnd();
  pgl.endGL();

}

Please note that I have no idea of JOGL, OPENGL at all

Cheers
rS

« Last Edit: Feb 16^th, 2010, 1:06am by nardove »

threesixty3d

Re: JOGL for dummies
Reply #1 - Jul 20^th, 2009, 5:20am

it's missing a bit of camera setup

Quote:

import javax.media.opengl.*;
import processing.opengl.*;
import javax.media.opengl.*;
import javax.media.opengl.glu.*;

GLU glu = new GLU();

void setup() {
  size(800, 600, OPENGL);
}

void draw() {
  background(0);

  PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;
  GL gl = pgl.beginGL();

  gl.glMatrixMode( GL.GL_PROJECTION );
  gl.glLoadIdentity();
  glu.gluPerspective( 45.0, (float)width/(float)height, 0.1, 10000.0 );
  gl.glMatrixMode( GL.GL_MODELVIEW );
  gl.glLoadIdentity();
  glu.gluLookAt( 0.0, 1.0, 10.0,  // position
  0.0, 0.0, 0.0,                  // interest
  0.0, 1.0, 0.0 );                // upvector

  gl.glBegin(GL.GL_TRIANGLE_FAN);
  gl.glColor3f(1.0f,0.0f,0.0f);
  gl.glVertex3f( 0.0f, 1.0f, 0.0f);
  gl.glColor3f(0.0f,1.0f,0.0f);
  gl.glVertex3f(-1.0f,-1.0f, 1.0f);
  gl.glColor3f(0.0f,0.0f,1.0f);
  gl.glVertex3f( 1.0f,-1.0f, 1.0f);
  gl.glColor3f(0.0f,1.0f,0.0f);
  gl.glVertex3f( 1.0f,-1.0f,-1.0f);
  gl.glColor3f(0.0f,0.0f,1.0f);
  gl.glVertex3f(-1.0f,-1.0f,-1.0f);
  gl.glColor3f(0.0f,1.0f,0.0f);
  gl.glVertex3f(-1.0f,-1.0f, 1.0f);
  gl.glEnd();
  pgl.endGL();
}

nardove

Re: JOGL for dummies
Reply #2 - Jul 20^th, 2009, 5:29am

Hi, that is good it works fine, but why that camera setup is not present in this code and it still renders fine?

Code:

import javax.media.opengl.*;
import processing.opengl.*;

float a; 

void setup() {
  size(800, 600, OPENGL);
}

void draw() {
  background(255);
  
  PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;
  GL gl = pgl.beginGL();
  
  gl.glColor4f(0.7, 0.7, 0.7, 0.8);
  gl.glTranslatef(width/2, height/2, 0);
  gl.glRotatef(a, 1, 0, 0);
  gl.glRotatef(a*2, 0, 1, 0);
  gl.glRectf(-200, -200, 200, 200);
  gl.glRotatef(90, 1, 0, 0);
  gl.glRectf(-200, -200, 200, 200);
  
  pgl.endGL();
  
  a += 0.5;
}

That code is a sample code from the processing opengl library page

Cheers
rS

threesixty3d

Re: JOGL for dummies
Reply #3 - Jul 20^th, 2009, 5:47am

You need to learn how the modelview matrix works.
You can think of that in terms of cameras or in terms objects or both.
In my code I usually prefer to setup the camera first, using a lookat, and then I place the objects, but it's not a rule.
In that example, gl.glTranslatef is used to change the modelview matrix (that's the matrix you're changing by default)

To be completely clear: the first code you posted it's working and rendering, but you can't see it because the triangles might be behind the camera (or beyond the znear / zfar limits)

nardove Full Member Offline Posts: 189 UK	Re: JOGL for dummies Reply #4 - Jul 20^th, 2009, 6:02am Brilliant! Thanks for the explanation, do you now any good JOGL Processing tutorials, link, ect? rS

threesixty3d YaBB Newbies Offline Posts: 22 Italy	Re: JOGL for dummies Reply #5 - Jul 20^th, 2009, 7:04am The usual ones: gamedev.net, opengl.org, lighthouse3d.com, the red book, the orange book, etc. Btw don't look for JOGL processing tutorials unless you need something specific to OpenGL integration within processing. Look for OpenGL tutorials instead. -m

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