Hi Davide,

I recently a rotating 2d sprite class.  Select  File|Examples|Basics|Sprite and replace the example code with that below to see it work.

There seems to be a minor problem in the 0148 ode.  You need to save before running or you'll get a message saying "The constructor Sprite(PImage) is undefined".  I'll report this if its not already in bugzilla.
--
Tom

/**
* Rotating Sprite
* by Tom Blackwell.
* Based on sprite example
* by James Patterson.
*
* Demonstrates loading and displaying a transparent GIF image.
*/

PImage teddy;
Sprite sprite;

float xpos;
float ypos;
float rotation = 0;
float drag = 30.0;

void setup()
{
 size(200,200, P3D);
 teddy = loadImage("teddy.gif");
 sprite = new Sprite(teddy);

 xpos = width/2;
 ypos = height/2;
 frameRate(60);
}

void draw()
{
 background(102);
 
 float difx = mouseX - xpos-teddy.width/2;
 if(abs(difx) > 1.0) {
   xpos = xpos + difx/drag;
   xpos = constrain(xpos, 0, width-teddy.width);
 }  
 
 float dify = mouseY - ypos-teddy.height/2;
 if(abs(dify) > 1.0) {
   ypos = ypos + dify/drag;
   ypos = constrain(ypos, 0, height-teddy.height);
 }  
 
 sprite.draw(xpos, ypos, 0, rotation);
 rotation += PI/32;
}

class Sprite {
 PImage img;
 Float size = 1.0;
 Float half_w, half_h;

 Sprite(PImage im) {
   img = im;
   half_w = float(im.width/2);  half_h = float(im.height/2);
 }

 void  draw(float x, float y, float z, float angle)
 {
   Boolean stroke_state = g.stroke;
   noStroke();
   pushMatrix();
   //translate(x+half_w, y+half_h, z);
   translate(x, y, z);
   rotate(angle);
   beginShape();
     textureMode(NORMALIZED);
     texture(img);
     vertex(-half_w, -half_h, 0, 0);
     vertex(half_w, -half_h, 1, 0);
     vertex(half_w, half_h, 1, 1);
     vertex(-half_w, half_h, 0, 1);
   endShape();
   popMatrix();
   g.stroke = stroke_state;
 }
}