zooming to the mouse

[FreeMind]

So. Ive been trying to achieve this for two days, but i just can't get it right.
Ok, so i have a script right here that draws a triangle:

Code:

 TheImage.canvas.MoveTo(round((100*zoom-moved.x)), round((100*zoom-moved.y)));
 TheImage.canvas.LineTo(round((200*zoom-moved.x)), round((200*zoom-moved.y)));
 TheImage.canvas.LineTo(round(100*zoom-moved.x)), round((200*zoom-moved.y)));
 TheImage.canvas.LineTo(round((100*zoom-moved.x)), round((100*zoom-moved.y)));

Zoom is the distance. When i roll my mouse wheel, it gets multyplied by 1.1 or 0.9 to increase or decrease the size.

moved.x and moved.y is the distance the view is shifted. Like, if i take a hand tool, i can shift the view.

Now, how should i do the math so the view could zoom to the mouse instead of the 0 0 position? Embarrassed

[chronozphere]

You could do something like this (not tested though):

Compute the vector between your mouse and the center of the view, like this:

Vec.X := Center.X - Mouse.X;
Vec.Y := Center.Y - Mouse.Y;

And now you have to move along that vector when you zoom in or out. For example, you can do this when you zoom in:

Moved.X := Moved.X + Vec.X * 0.1;
Moved.Y := Moved.Y + Vec.Y * 0.1;

And when you zoom out:

Moved.X := Moved.X - Vec.X * 0.1;
Moved.Y := Moved.Y - Vec.Y * 0.1;

I don't know if it works. Just try it.

Ok, so i have a script right here that draws a triangle

FYI, Pascal is code, not script (no pun ofcourse )

Hope this helps.

[FreeMind]

not working.

As far as i understand, in this case the distance it moves is allways the same if i keep my mouse steady, as i understand, the more i'm zoomed in, the more it has to move.

[chronozphere]

The more you are zoomed in the higher "Zoom" is. You said:

the more i'm zoomed in, the more it has to move.

So you could try this:

Moved.X := Moved.X - Vec.X * Zoom;
Moved.Y := Moved.Y - Vec.Y * Zoom;

The ammount of movement now depends on how much you zoomed.

It would be good if you wrote short comprehensible sentences instead of this:

As far as i understand, in this case the distance it moves is allways the same if i keep my mouse steady, as i understand, the more i'm zoomed in, the more it has to move.

I had to read it 4 times to figure out what you ment.

[FreeMind]

I figured it out. Actually your first code was close to what should have been done, though i only notice that after i achieved it.

mousewheel up:

  if zoom<6 then begin
  zoom:=zoom*1.1;
  moved.x:=round(moved.x+(moved.x+pt.x)*0.1) ;
  moved.y:=round(moved.y+(moved.y+pt.y)*0.1);
  end;

mousewheel down:

  if zoom>0.02 then begin
  zoom:=zoom*10/11;
  moved.x:=round(moved.x+(moved.x+pt.x)*(10/11-1)) ;
  moved.y:=round(moved.y+(moved.y+pt.y)*(10/11-1));
  end;

Thanks a lot for your time! Appreciate.

edit: pt.x and pt.y is the mouse position.

[chronozphere]

I'm glad you figured it out...