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Zooming and swiping with OpenGL ES

Riens Esperado · 2013-08-29T22:33:26

Hello! I am making a 2D puzzle for iOS and currently I`m trying to implement zooming and scrolling with UIPinchGestureRecognizer. Zooming is done this way: I have a target 2D vector which is a "zooming point". The code is: glTranslatef(target.x, target.y, 0); glScalef(scale, scale, 0); glTranslatef(-target.x, -target.y, 0); Target is being selected with gesture recognizer this way: -(void)handlePinchGesture:(UIPinchGestureRecognizer*)recognizer { if (UIGestureRecognizerStateBegan == [recognizer state]) { view->setTarget([recognizer locationInView:self]); } // Rest of the code omitted } Everything works just fine. Initially the game was designed for iPAD, but I want it to work on iPhone and iPOD too. But iPhone and iPOD have different aspect ratio. To keep initial picture proportions I decided to make initial Y scale a bit bigger. Also this made possible to swipe the game field up and down with initial zoom factor. The code is: glTranslatef(target.x, target.y, 0); glScalef(scale, scale * aspectRatio, 0); glTranslatef(-target.x, -target.y, 0); This works just fine IF the game field is "centered" at the screen(e.g. when there are equal space in bot swipe directions(up and down)). But if we swipe the field up or down and begin pinch gesture, the game field jumps to the centre again. I understand that I need to translate the gesture position by some offset, but I cannot figure how exactly for 3 days.

General and Gameplay Programming Programming

Started by riens April 23, 2012 11:10 AM

16 comments, last by Jekahy 10 years, 7 months ago

riens

100

Author

May 04, 2012 12:50 PM

No, i want to translate the image to some point, zoom it and then translate back

JoJoSim1

173

May 04, 2012 03:44 PM

like this ?



glTranslatef(target.x*scale, target.y*scale * aspectRatio, 0);

glScalef(scale, scale * aspectRatio, 0);

glTranslatef(-target.x, -target.y, 0);

riens

100

Author

May 08, 2012 12:09 PM

I`ll check this now.

P.S. Sorry for late response, I was on vacation

riens

100

Author

May 08, 2012 02:54 PM

Nope, this does not work properly either

JoJoSim1

173

May 08, 2012 03:13 PM

ah ok i guess it's like this.
You move scale - it works
you move a second time and the image jumps correct ?
could you write down a sequence of actions you want to do ?

for example moveto (1,0) scaleto (1.5,1.5) moveto(-1,0) scaleto(1,1)
btw if you have icq message me and i'll add you

riens

100

Author

May 10, 2012 07:40 AM

You move scale - it works
you move a second time and the image jumps correct ?[/quote]
I don`t move scale - it works
I move scale - it jumps back before zoom

could you write down a sequence of actions you want to do ?[/quote]
swipe, pinch zoom
this corresponds to: moveby(1, 0), scaleby(delta, delta)

btw if you have icq message me and i'll add you[/quote]
I can create a new ICQ account if you have no jabber or skype

JoJoSim1

173

May 10, 2012 08:57 AM

I have skype at home so PN me your skype name.
Maybe we could chat later the day.

Jekahy

120

August 29, 2013 10:33 PM

Hi! I'm having almost the same issue with zooming and scrolling! Can you post your solution?

Zooming and swiping with OpenGL ES

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