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Topics - Knuffi

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Support / Rotating a cylinder in a direction given by a simple vector
« on: April 16, 2012, 10:40:51 pm »
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.

Code: [Select]
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();


// world.drawWireframe(buffer, Color.WHITE);

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?

Support / Planes only visible from the upper side?
« on: April 08, 2012, 07:27:00 pm »
Are planes in wireframe view only visible from the upper side? When I move my camera blow a plane, it disappears.

Support / Rotating the Camera up an down around the Origin
« on: April 08, 2012, 12:42:34 pm »
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?


I searched this site, but did not find any hint. I read the examples which render the "Hello World" in software, OpenGL and AWTGL, but I don't get the clue.
I have two problems:
1. I want to render a scene in a JPanel. As it is not very GPU demanding, software renderer will be enough - as I read, it is the only one really working with SWING components. Can someone give me an example? I thought, I've seen one somewhere in the wiki, but I can't find it anymore.

2. Is it possible to swap the HelloWorld class out of the "GUI class"?
As the GUI of the programme I want to write is very complex, I use WindowsBuilder in Eclipse, so I want to write a jPCT class and then just call it in the GUI. Is this possible?

Thanks in advance!

Projects / 3D Geometry Programme
« on: April 05, 2012, 12:45:29 am »
Hi, I'm about to write a 3D geometry programme. It is supposed to help teachers and older students with vectors, points, lines, planes and squares and their intersections.
Most work is done in Java Swing (entering the objects, calculating and checking their intersections), I will try to get the visualisation done with jPCT. I hope I will be good enough to do so.

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