hello i need to rotate an element in its own center. I need to use glRotatef , if i use rotateZ(aumenta_rota) if works fine , but if i use gl.glRotatef(aumenta_rota , 0, 0, 1); it doenst rotate in its own center, it seems it also translate , why is that? which is the difference between both ? how can i make to rotate in its own center using glRotate?

here is the code so you can see the difference ,comment and uncomment  each of these lines to see  the difference gl.glRotatef(aumenta_rota , 0, 0, 1);
 //rotateZ(aumenta_rota);


here is the code:

Code:

import codeanticode.glgraphics.*;
import processing.opengl.*;

import javax.media.opengl.GL;

GL gl;
float aumenta = 0;
float aumenta_rota = 0;

float x1;
float y1;
float cx1;
float cy1;
float cx2;
float cy2;
float x2;
float y2;

void setup() {
  
  size(640, 480, GLConstants.GLGRAPHICS);
  aumenta_rota = 0;
  background(250, 250 , 250);
  x1 = 0;
  y1 = random(200) + 200 * 2;
  cx1 = 322  * 2 ;
  cy1 =  322  * 2;     //random(200) ; //+ 100;
  cx2 =   222 * 2    ;//random(200) - 100;
  cy2 = 222  * 2 ;
  x2 = random(200) + 400 * 2  ;
  y2 = random(200) + 400  * 2 ;
 
}


void draw(){
  aumenta_rota = aumenta_rota + 0.1;
    
  GLGraphics renderer = (GLGraphics)g;
  gl = renderer.beginGL();
  background(250, 250 , 250);
  noFill();
  
  bezier(0, y1, cx1, cy1, cx2, cy2, x2, y2 );
  
  aumenta = aumenta + 0.003;
  float x = bezierPoint(0, cx1, cx2, x2, aumenta);
  float y = bezierPoint(y1, cy1, cy2, y2, aumenta);
  
  gl.glPushMatrix();
  gl.glTranslatef(x, y, 0);
  
    
   
   //comment the line below and uncomment rotateZ(aumenta_rota); to see the differece.
   gl.glRotatef(aumenta_rota , 0, 0, 1);
  //rotateZ(aumenta_rota);
  
  
  ellipse(0, 0, 10, 25);
  gl.glPopMatrix();
  
  renderer.endGL();
  
 }





 

because rotateZ doesnt work with the library glgraphics, glgraphics just work with pure opengl commands. And yes i thouth glRotatef was the same as rotateZ but im having wierd results, i cant rotate in its own center with glRotate , any idea?

the code above is just example, when you use the class glmodel from glgraphics you cant use standard transformation commands from processing like translate and rotate.