Deciding Camera Altitude for view field

QA_2 · 10-23-2009, 07:40 PM

Hey, all. I have a pair of lat/long points, and want to zoom in/out to the point where they're in opposite corners of the view field. Does anyone know how to go from that to a camera altitude number I can feed into a FlyToOrbitViewAnimator?

I know enough trigonometry to picture the problem as an isosceles triangle where the bottom side is the line between my two points, and I'm looking to calculate the height, but I'd need to know the top angle (i.e. the angle between edges of the camera's field of view). Besides, I feel like there must be a call for this somewhere.

patmurris · 10-25-2009, 04:30 AM

The eye field of view is the angle between the eye and both sides (left and right) of the viewport.

From your two locations you can devive an angular distance between the two - see LatLon.greatCircleDistance(), and a center location - see LatLon.greatCircleEndPosition(). You can then think of the circle encompassing the two points and determine the proper eye altitude to fit that circle in the viewport rectangle... There are certainly different ways to do that.

I think i briefly glanced something related in the SDK but can't remember exactly what and where.

QA_2 · 10-25-2009, 10:01 AM

Don't suppose you know a way to get the eye field angle, do you? Even if not, this should help a lot, since now I know what the number I'm called is looking for! And once I have that number, the math shouldn't be a problem.

Thanks!

patmurris · 10-25-2009, 02:41 PM

view.getFieldOfView() : Angle

QA_2 · 10-25-2009, 11:06 PM

Great. Thanks a lot!

10-23-2009, 07:40 PM	#1
QA_2 Junior Member Join Date: Oct 2009 Posts: 17	Deciding Camera Altitude for view field Hey, all. I have a pair of lat/long points, and want to zoom in/out to the point where they're in opposite corners of the view field. Does anyone know how to go from that to a camera altitude number I can feed into a FlyToOrbitViewAnimator? I know enough trigonometry to picture the problem as an isosceles triangle where the bottom side is the line between my two points, and I'm looking to calculate the height, but I'd need to know the top angle (i.e. the angle between edges of the camera's field of view). Besides, I feel like there must be a call for this somewhere.

10-25-2009, 04:30 AM	#2
patmurris WWJ Consultant Join Date: Jun 2005 Location: Saint-Paul de Vence, Alpes Maritimes, France Posts: 3,412	The eye field of view is the angle between the eye and both sides (left and right) of the viewport. From your two locations you can devive an angular distance between the two - see LatLon.greatCircleDistance(), and a center location - see LatLon.greatCircleEndPosition(). You can then think of the circle encompassing the two points and determine the proper eye altitude to fit that circle in the viewport rectangle... There are certainly different ways to do that. I think i briefly glanced something related in the SDK but can't remember exactly what and where. __________________ My World Wind Java Blog & WW.net Plugins page

10-25-2009, 02:41 PM	#4
patmurris WWJ Consultant Join Date: Jun 2005 Location: Saint-Paul de Vence, Alpes Maritimes, France Posts: 3,412	view.getFieldOfView() : Angle __________________ My World Wind Java Blog & WW.net Plugins page

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10-25-2009, 10:01 AM	#3
QA_2 Junior Member Join Date: Oct 2009 Posts: 17	Don't suppose you know a way to get the eye field angle, do you? Even if not, this should help a lot, since now I know what the number I'm called is looking for! And once I have that number, the math shouldn't be a problem. Thanks!

10-25-2009, 11:06 PM	#5
QA_2 Junior Member Join Date: Oct 2009 Posts: 17	Great. Thanks a lot!

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