Processing 1.0 - Processing Discourse - Rotating about fixed axes

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Index › Programming Questions & Help › OpenGL and 3D Libraries › Rotating about fixed axes

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Rotating about fixed axes (Read 1276 times)

Rotating about fixed axes
Nov 7^th, 2009, 3:21pm

This has most probably been asked before. But a search for 'fixed axes, static axes etc' did not bring up anything I wanted.

I want to rotate an object about fixed axes in 3d. In the usual examples on rotating about the x and y and z axes, the rotation about one axis changes the other axes and therefore subsequent rotations will be about the new rotated axes.

Here is what I could come up with( seeing some opengl program I had written long ago):

Quote:

PMatrix3D m3d;
void setup(){
size(400, 400, P3D);
m3d = new PMatrix3D();
}
void draw(){
background(150);
translate(width/2, height/2, 200);
applyMatrix(m3d);
box(50, 50, 50);
}

void keyPressed(){
if ( key == CODED)
{
  if (keyCode == UP )
  {
    resetMatrix();
    rotate(2*PI/180.0,1.0,0.0,0.0);
    applyMatrix(m3d);
    getMatrix(m3d);
  }
  else if (keyCode == RIGHT)
  {
    resetMatrix();
    rotate(2*PI/180.0,0.0,1.0,0.0);
    applyMatrix(m3d);
    getMatrix(m3d);
  }
}
}

Now I have read that applyMatrix() is to be avoided. Can this sort of thing be done any other way in Processing?
Please do excuse me if this has been discussed in another post.

nardove Full Member Offline Posts: 189 UK	Re: Rotating about fixed axes Reply #1 - Nov 17^th, 2009, 7:22am Hi, I am new to this field as well, I think the solution is to use quaternions, they allow to rotate around each axis without effecting the rotation of the other axis Search for quaternions, gamedev.net is a good source, if I get a working sketch, I will post it here Cheers rS

Cedric

Re: Rotating about fixed axes
Reply #2 - Nov 17^th, 2009, 8:56am

something like this ?

float x = 0;
float y = 0;
void setup(){
size(400, 400, P3D);

}
void draw(){
background(150);
translate(width/2, height/2, 200);
rotateX(x);
rotateY(y);

box(50, 50, 50);
}

void keyPressed(){
if ( key == CODED){

if (keyCode == UP ){
x+=(2*PI/180.0 );
}

if (keyCode == RIGHT){
y+=(2*PI/180.0 );
}

if (keyCode == LEFT){
y-=(2*PI/180.0 );
}

if (keyCode == DOWN){
x-=(2*PI/180.0 );
}

}
}

twitter.com/CedricKiefer

rj Ex Member	Re: Rotating about fixed axes Reply #3 - Nov 22^nd, 2009, 10:51am Thanks, but no, this doesn't work. The rotation about the x- axis is about a 'fixed' x-axis because in your 'draw' that comes first. But the rotation about the y-axis is not about a fixed y-axis because the y-axis also rotates when you rotate the x-axis. Your website is quite inspiring.

Re: Rotating about fixed axes
Reply #4 - Nov 22^nd, 2009, 11:20am

nardove wrote on Nov 17^th, 2009, 7:22am:

Hi, I am new to this field as well, I think the solution is to use quaternions, they allow to rotate around each axis without effecting the rotation of the other axis

Search for quaternions, gamedev.net is a good source, if I get a working sketch, I will post it here

Cheers
rS

Thanks. Will look into quaternions.

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