Hello,

I have a problem with rotation. I have the solution in c++/opengl but I want to use P3D in processing to do the same thing. (I dont want to use opengl shapes coz I want to export it with an .STL exporter)

I want to draw cylinders in 3d by having 2 PVectors as the start and the end point. length is the distance between the PVectors. I have search the forum and the web (as you can see my code has many examples from the forum) with no luck.

C++/openGL
Code:

void mpee::renderCylinder(float x1, float y1, float z1, float x2,float y2, float z2, float radius,int subdivisions,GLUquadricObj *quadric)
{
    float vx = x2-x1;
    float vy = y2-y1;
    float vz = z2-z1;

    //handle the degenerate case of z1 == z2 with an approximation
    if(vz == 0)
        vz = .00000001;

    float v = sqrt( vx*vx + vy*vy + vz*vz );
    float ax = 57.2957795*acos( vz/v );
    if ( vz < 0.0 )
        ax = -ax;
    float rx = -vy*vz;
    float ry = vx*vz;
    glPushMatrix();

    //draw the cylinder body
    glTranslatef( x1,y1,z1 );
    glRotatef(ax, rx, ry, 0.0);
    gluQuadricOrientation(quadric,GLU_OUTSIDE);
    gluCylinder(quadric, radius, radius, v, subdivisions, 1);

    //draw the first cap
    gluQuadricOrientation(quadric,GLU_INSIDE);
    gluDisk( quadric, 0.0, radius, subdivisions, 1);
    glTranslatef( 0,0,v );

    //draw the second cap
    gluQuadricOrientation(quadric,GLU_OUTSIDE);
    gluDisk( quadric, 0.0, radius, subdivisions, 1);
    glPopMatrix();
}
 

and many attempts in processing:
Code:

   for( int i=1; i < renderPath.size(); i++ ) {
      DLAParticle p = (DLAParticle)renderPath.get(i);
      if(p.parent == null) break;

      DLAParticle p1 = p.parent;
      //stroke(5, 10, 50);
      fill(200,50,200,p.size+10);
      float h = p.pos.dist(p1.pos);
      float w = p.size;
      float ramt = TWO_PI/30.f;



      // test 1 ////////////
      float vx = p.pos.x-p1.pos.x;
      float vy = p.pos.y-p1.pos.y;
      float vz = p.pos.z-p1.pos.z;

      //handle the degenerate case of z1 == z2 with an approximation
      if(vz == 0)
        vz = .00000001;

      float v = sqrt( vx*vx + vy*vy + vz*vz );
      float ax = 57.2957795*acos( vz/v );

      if ( vz < 0.0 ) ax = -ax;

      float rx = -vy*vz;
      float ry = vx*vz;

      // test 2 ///////////////

      PVector location1 = new PVector(p.pos.x, p.pos.y, p.pos.z);
      PVector location2 = new PVector(p1.pos.x, p1.pos.y, p1.pos.z);
      PVector d = PVector.sub(location2, location1);
      PVector polar = cartesianToPolar(d);

      stroke(255,0,0);
      line(p.pos.x, p.pos.y, p.pos.z,p1.pos.x, p1.pos.y, p1.pos.z);
      stroke(0);
      
      pushMatrix();

      translate(location1.x, location1.y, location1.z);
      rotateY(polar.y);
      rotateZ(polar.z);
      //rotateZ(d.z);
      /////////
     
      
      // openGL
      //
      //gl.glPushMatrix();
      //gl.glTranslatef( p1.pos.x,p1.pos.y,p1.pos.z );
      //gl.glRotatef(ax, rx, ry, 0);
      //gl.glTranslatef( p1.pos.x,p1.pos.y,p1.pos.z );

      //rotateX(ax);
      //rotateY(ax);
      //translate(rx,ry,0.0f);
      //rotate(PVector.angleBetween(p.pos,p1.pos));
 
 
      beginShape(QUADS);
      for( float r = 0; r < TWO_PI; r += ramt )
      {
        vertex( cos(r)*w, -h, sin(r)*w );
        vertex( cos(r+ramt)*w, -h, sin(r+ramt)*w );
        vertex( cos(r+ramt)*w, h, sin(r+ramt)*w );
        vertex( cos(r)*w, h, sin(r)*w );
      }
      endShape();
      
      //gl.glPopMatrix();
      
      popMatrix();


    }
 

 

give me a hand if you can please!

Tasos

would be easier to help if you'd pasted a full example so we can just cut and paste and run it.

anyway i think your problem is with
glRotatef(ax, rx, ry, 0.0);
which is a rotation of ax, around the vector rx, ry, 0 which doesn't have an equivalent (afaik) in processing.

that said, the opengl man page pretty much gives you the matrix for said transformation:
http://www.opengl.org/documentation/specs/man_pages/hardcopy/GL/html/gl/rotate.html

i'm still slightly puzzled by "having 2 PVectors as the start and the end point". what about the radius? ah, ok, constant.

ie

Code:

// lazy cylinder, circular in x and y, height = z, no caps
void cylinder(int divisions, float radius, float len) {
  for (int i = 0 ; i < divisions ; i++) {
    float angle1 = i * (TWO_PI / divisions);    
    line(radius * cos(angle1), radius * sin(angle1), 0,
	  radius * cos(angle1), radius * sin(angle1), len);
  }
}