Thanks, it worked!

I tried rotating around x-axis, but I did not know that I had to clear the Rotation.

I don't get it.

I have a cylinder representing a line. And on building it, I want to translate it to a certain point (working) and rotate it, that it looks into the same direction as a given vector. The last thing does not work.
When I give the vector
* (1/0/0), the cylinder's direction is the z-axis (or -z, I could not see),
* (0/1/0) the cylinder's direction is also the z-axis (or -z)
* (0/0/1) the cylinde's direction is the x-axis.

I changed the coordinate system to an "upright" as needed in school.

public static void addGerade(Gerade g){
Object3D gt = Primitives.getCylinder(6, 0.1f, 150);

// Changing the ccordinates from the calculated line to the ones needed to draw it
double ax = g.getA().getX1();
double ay = -g.getA().getX3();
double az = g.getA().getX2();

double rx = g.getV().getX();
double ry = -g.getV().getZ();
double rz = g.getV().getY();

SimpleVector Aufpunkt = new SimpleVector (ax, ay, az);
SimpleVector Richtung = new SimpleVector(rx, ry, rz);
Matrix r = Richtung.getRotationMatrix();
gt.setRotationMatrix(r);
gt.translate(Aufpunkt);

gt.setTexture("linet");
gt.build();
world.addObject(gt);

buffer.clear(java.awt.Color.DARK_GRAY);
world.renderScene(buffer);
// world.drawWireframe(buffer, Color.WHITE);
world.draw(buffer);
buffer.update();
}

Almost the same code works fine with points (as already said, translating works) and even planes (translating and rotating so that the normal vector looks into a given direction.

Can anybody help?

Ok, that is much shorter, and the axis could be set as in my source by a cross product.

Thanks a lot!

Are planes in wireframe view only visible from the upper side? When I move my camera blow a plane, it disappears.

Ok, got it. I'm sure, there is a easier way
I used a rotation matrix that rotates the camera position around a normalized cross-vector of the camera position and the y-axis. That stops working when I'm directly above the origin, but that does not matter to me. 

public static void rotateupdown(float v){
SimpleVector cam = world.getCamera().getPosition();
SimpleVector y = new SimpleVector(0,1,0);
SimpleVector rot = cam.calcCross(y);
rot = rot.normalize();
float n1 = rot.x;
float n2 = rot.y;
float n3 = rot.z;
float r = v*(float)Math.PI/30;
float c =(float) Math.cos(r);
float s =(float) Math.sin(r);
Matrix m = new Matrix();
m.set(0, 0, n1*n1*(1-c) + c);
m.set(0,1, n1*n2*(1-c) - n3*s);
m.set(0,2, n1*n3*(1-c) + n2*s);
m.set(1,0, n1*n2*(1-c) + n3*s);
m.set(1,1, n2*n2*(1-c) + c);
m.set(1,2, n2*n3*(1-c)- n1*s);
m.set(2,0, n1*n3*(1-c)- n2*s);
m.set(2,1, n2*n3*(1-c) + n1*s);
m.set(2,2, n3*n3*(1-c) + c);

cam.rotate(m);

world.getCamera().setPosition(cam);
world.getCamera().lookAt(new SimpleVector(0,0,0));

buffer.clear(java.awt.Color.DARK_GRAY);
world.renderScene(buffer);
world.drawWireframe(buffer, Color.WHITE);
buffer.update();
}

Ok, I'm blind - just found the RotateCameraAxis() Method.

Edit: Nope, that's not it. The camera rotates around itself instead around the origin. 

I could also implement the action listener into the class, where the world and the frame buffer reside?

Eclipse tells me so, when I write the rotation method and put it in the Actionlistener.

I have Objects siting at the origin and want to rotate the camera around that point.

Rotating left and right is no problem, as it is always a rotation around the y-axis. But Rotating up and down is quite difficult, as it is no rotation around a fixed axis. I looked into the methods of the camera, the SimpleVector and the Matrixc, but did not really find something to work with.

Can anyone give me a tip?

With the permission of Egon, I could put it into the wiki.

Got it working

There are two problems I still have:
1. Camera rotation left-right is ok, as it is a rotation around the z-axis, but rotation up-down is quite difficult. I will open up a new thread for this.
2. Why do the world and the frame buffer to be static?



GUI:
package jPCT;

import java.awt.EventQueue;

public class HelloGui extends JFrame {

private JPanel contentPane;

/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
HelloGui frame = new HelloGui();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}



public HelloGui() throws Exception {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 800, 600);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);

JButton btnTest = new JButton("Test 1");
btnTest.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
RenderPanel.rotateleft();
repaint();
}
});
btnTest.setBounds(10, 11, 89, 23);
contentPane.add(btnTest);

JButton btnTest_1 = new JButton("Test 2");
btnTest_1.setBounds(10, 45, 89, 23);
contentPane.add(btnTest_1);

JButton btnTest_2 = new JButton("Test 3");
btnTest_2.setBounds(10, 79, 89, 23);
contentPane.add(btnTest_2);

JPanel panel = new JPanel();
panel.setBounds(109, 11, 665, 540);
contentPane.add(panel);
panel.setLayout(new BorderLayout(0, 0));

RenderPanel panel_1 = new RenderPanel();
panel.add(panel_1, BorderLayout.CENTER);


}
}


RenderPanel Class
package jPCT;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JPanel;

import com.threed.jpct.FrameBuffer;
import com.threed.jpct.Matrix;
import com.threed.jpct.Object3D;
import com.threed.jpct.Primitives;
import com.threed.jpct.SimpleVector;
import com.threed.jpct.World;

public class RenderPanel extends JPanel {
private static final long serialVersionUID = 1L;

static World world;
static FrameBuffer buffer;
Object3D box;
{

world = new World();
// world.setAmbientLight(200, 255, 200);

// TextureManager.getInstance().addTexture("box", new Texture("box.jpg"));

box = Primitives.getBox(3f, 2f);
// box.setTexture("box");
// box.setEnvmapped(Object3D.ENVMAP_ENABLED);
box.build();
world.addObject(box);

world.getCamera().setPosition(50, -20, -5);
world.getCamera().lookAt(box.getTransformedCenter());
buffer = new FrameBuffer(660, 530, FrameBuffer.SAMPLINGMODE_NORMAL);}


public RenderPanel() {
setPreferredSize(new Dimension(buffer.getOutputWidth(), buffer.getOutputHeight()));
setFocusable(true);
setLayout(null);

buffer.clear(java.awt.Color.DARK_GRAY);
world.renderScene(buffer);
world.drawWireframe(buffer, Color.WHITE);
buffer.update();
}

public static void rotateleft(){
SimpleVector temp = world.getCamera().getPosition();
float rotation = (float) Math.PI/30;
temp.rotateY(-rotation);


world.getCamera().setPosition(temp);
world.getCamera().lookAt(new SimpleVector(0,0,0));

buffer.clear(java.awt.Color.DARK_GRAY);
world.renderScene(buffer);
world.drawWireframe(buffer, Color.WHITE);
buffer.update();
}


@Override
    public void paintComponent(Graphics g) {
        buffer.display(g);
    }
   
}


Yeah, you are right, I want to rotate at least the camera around the scene ...

Ok, then I will go this way further. Mysteriously WindowBuilder opens the GUI correctly.   

How do I update the component, e.g. when I add new objects or rotate something? How do I force the paint-method of my component?

Is there a way to do it without extending a JPanel or JLabel or ...
because otherwise I cannot use WindowsBuilder ...

Got it at least working :
package jPCT;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JPanel;

import com.threed.jpct.FrameBuffer;
import com.threed.jpct.Object3D;
import com.threed.jpct.Primitives;
import com.threed.jpct.World;

public class RenderPanel extends JPanel {
private static final long serialVersionUID = 1L;

private World world;
private FrameBuffer buffer;
private Object3D box;


public RenderPanel() {
world = new World();
// world.setAmbientLight(200, 255, 200);

// TextureManager.getInstance().addTexture("box", new Texture("box.jpg"));

box = Primitives.getBox(3f, 2f);
// box.setTexture("box");
// box.setEnvmapped(Object3D.ENVMAP_ENABLED);
box.build();
world.addObject(box);

world.getCamera().setPosition(50, -50, -5);
world.getCamera().lookAt(box.getTransformedCenter());
buffer = new FrameBuffer(660, 530, FrameBuffer.SAMPLINGMODE_NORMAL);

setPreferredSize(new Dimension(buffer.getOutputWidth(), buffer.getOutputHeight()));
setFocusable(true);
setLayout(null);

buffer.clear(java.awt.Color.DARK_GRAY);
world.renderScene(buffer);
world.drawWireframe(buffer, Color.WHITE);
buffer.update();

}
   
@Override
    public void paintComponent(Graphics g) {
        buffer.display(g);
    }
   
}


I thought the framebuffer method getGraphics does the job ...

so the jPCT Class has to be an extension of an component?