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  Camera zooming on specific point  (Read 1803 times)
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Offline Mads

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« Posted 2013-02-12 13:17:11 »

I'm using LibGDX, and I'd very much like to zoom in on something specific in my game.
Using the OrthographicCamera, changing the zoom field works wonders, but it zooms in on the center of the screen.

I'd like to move the camera while zooming, so that the point I'm zooming in on, remains on the same window-coordinate.

This would require some magic, figuring out how much I need to move the camera and in what direction, based on a point.

Offline Mads

JGO Ninja

Medals: 26
Projects: 3
Exp: 6 years

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« Reply #1 - Posted 2013-02-12 14:09:14 »

This is my attempt at it. Needless to say, it doesn't work as expected.
public void zoomMaintainPoint(int x, int y, float zoom, OrthographicCamera camera) {
      Vector3 pointToMaintain = new Vector3(x, y, 0);
      camera.zoom = zoom;
      Vector3 pointNewPos = new Vector3(pointToMaintain);
      int deltaX = (int) (pointNewPos.x - pointToMaintain.x);
      int deltaY = (int) (pointNewPos.y - pointToMaintain.y);
      camera.translate(deltaX, deltaY);

Offline cheatsguy

Junior Devvie

Medals: 3

Gamer turned Pixel Artist turned Programmer

« Reply #2 - Posted 2013-02-12 15:03:28 »

I'm as clueless as you, and I also need this :/

Busy between school, work, life, games, programming and general screwing around.
If you'd like some pixel art for your game, send me a PM, i'll see what I can do.
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Offline Roquen
« Reply #3 - Posted 2013-02-12 15:48:09 »

Orthographic projections don't have a real can only scale & translate.
Offline Mads

JGO Ninja

Medals: 26
Projects: 3
Exp: 6 years

One for all!

« Reply #4 - Posted 2013-02-12 17:35:52 »

Orthographic projections don't have a real can only scale & translate.

I'm quite aware. I think you can see through that flaw in my statement, to help me though. Smiley
I think you know what I meant with the original question.

Offline Mike

« JGO Spiffy Duke »

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« Reply #5 - Posted 2013-02-12 19:35:42 »

final Point2DFloat before = getMouseCoordInGame();
final Point2DFloat after = getMouseCoordInGame();
Camera.setCameraPos2D(Camera.getLookingAt().getX() + before.getX() - after.getX(), Camera.getLookingAt().getY() + before.getY() - after.getY());

This is the code in the State of Profit map that handles that. In general, check where the mouse was (in the game, not in the applet), do the zoom, check where it is after and move the camera the difference. Smiley


My current game, Minecraft meets Farmville and goes online Smiley
State of Fortune | Discussion thread @ JGO
Offline Mads

JGO Ninja

Medals: 26
Projects: 3
Exp: 6 years

One for all!

« Reply #6 - Posted 2013-02-12 20:31:28 »

That is what I was doing, and I'm confident I can make it work now.
I think my only problem was that I did not update the camera after zooming it. Obviously, project/unproject isn't going to work, if it's not updated.

Thanks again.

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