Creating an OpenGL Cube Class

[Hiura]

I would have done something like

Code: [Select]

class Cube {
Position pos; Rotation rot; Size size;
setPosition/Rotation/Size(newValue) { pos/rot/size = newValue; }
draw() {
 // save state
 glPushMatrix();
 glPushAttrib(...);

 // use pos, rot, size here
 glTranslate(..);
 glRotation(..);
 glColor(..)
 :
 :

 glVertex..(..);
 :
 :

 // restore state
 glPopAttrib();
 glPopMatrix();
}
};

It's the way most of the students did their project this semester – and the way they were taught.

[Fierce_Dutch]

I would have done something like

Code: [Select]

class Cube {
Position pos; Rotation rot; Size size;
setPosition/Rotation/Size(newValue) { pos/rot/size = newValue; }
draw() {
 // save state
 glPushMatrix();
 glPushAttrib(...);

 // use pos, rot, size here
 glTranslate(..);
 glRotation(..);
 glColor(..)
 :
 :

 glVertex..(..);
 :
 :

 // restore state
 glPopAttrib();
 glPopMatrix();
}
};

It's the way most of the students did their project this semester – and the way they were taught.

What? I am confused, can you give me like a full example?

[Hiura]

I don't have light example on my computer so here is only the part between the glPush/PopMatrix :

Code: [Select]

glBegin(GL_TRIANGLES);
    glColor3ub(0,0,255);
glVertex3d(Position[0],Position[1],Position[2]);
glVertex3d(Position[0],Position[1],Position[2]);
glVertex3d(Position[0],Position[1],Position[2]);
    glEnd();
In this example there are (obviously) no dynamic size nor rotation.

What puzzles you exactly ? I'll try to be more understandable if I can.

[Fierce_Dutch]

I don't have light example on my computer so here is only the part between the glPush/PopMatrix :

Code: [Select]

glBegin(GL_TRIANGLES);
    glColor3ub(0,0,255);
glVertex3d(Position[0],Position[1],Position[2]);
glVertex3d(Position[0],Position[1],Position[2]);
glVertex3d(Position[0],Position[1],Position[2]);
    glEnd();
In this example there are (obviously) no dynamic size nor rotation.

What puzzles you exactly ? I'll try to be more understandable if I can.

Well I was wondering why you rotate adn translate it inside the function. The whole point of this is so that I can set the position of this shape and draw it in two different ends of the code.

[Hiura]

But you can draw and set rotation/position/whatever-you-like with my approach.  :wink: Look at this pseudo-code:

Code: [Select]


void f(void) {
  // Setting up some stuff.
  mySquare.SetPosition(0, 0);
  mySquare.SetRotation(pi/4); // or 45°

  // Some code
  :
  :
 
  // Drawing our beautiful square.
  mySquare.Draw();
}


with something like this implementation of Square :

Code: [Select]


Square::SetPosition(x, y) { myX = x, myY = y }
Square::SetRotation(alpha) { myAlpha = alpha }
Square::Draw() {
  glPushMatrix();

  glTranslate(myX, myY)
  glRotate(myAlpha)

  glVertex(-1, -1)
  glVertex(-1, 1)
  glVertex(1, 1)
  glVertex(1, -1)

  glPopMatrix(); // Restore previous coordinate system
}


[Fierce_Dutch]

i kinda understand, but not how to it

[Hiura]

Well, what's your main concern ? How to create the class ? How to display many objects ? (Just try, something we have to go that way.)

BTW : you don't have to quote everything/every time.  :wink:

[Fierce_Dutch]

Well, how is this class not going to get confused with other classes say if I call it like this..

block a1, a2;
a1.roatate(sfksuda)
a2.draw
a2.rotate
a1.draw.

Wont it get confused withing the class?

[Hiura]

If «Block::Rotate» from your example only store the new rotation (like in the example above) you won't mix up anything.

Look at the doc of glPush/PopMatrix too.  :wink:

[Fierce_Dutch]

If «Block::Rotate» from your example only store the new rotation (like in the example above) you won't mix up anything.

Look at the doc of glPush/PopMatrix too.  :wink:

but you are pushing the same matrix right?

[Hiura]

yes.

Did you try ? You'll see  :wink:

[Terrydil]

Its the same (modelview) matrix but basically you are resetting it, then changing it and drawing with those changes, then resetting it again and changing it in a different way and drawing something with those changes, then resetting it again ...etc...etc...

[Fierce_Dutch]

Its the same (modelview) matrix but basically you are resetting it, then changing it and drawing with those changes, then resetting it again and changing it in a different way and drawing something with those changes, then resetting it again ...etc...etc...

Thanks a bunch, it works great! LOOK! But now I have another problem(below pic)



anything sfml doesnt draw right... Its really weird..