# Calculate the arc distance between 2 points on a sphere

 0 Hello Everyone, I have an issue here, its related to math but some hints are appretiated. The player has to position 3d models on a sphere which is the globe. For example a building.. and after plotting I have to display the distance between his poltted position and the accurate position. I am getting the player chosen point by a raycast, so on mouse down the model will be plotted and I save have the hit point and the other point is defined by me. I have positioned small sphere's at the accurate position, so the position of these sphere's have to be compared to the hit point(position) to get the distance(arc distance) I think to get the arc distance I need a third point which is the center of the sphere(globe) and hence I can get the radus, since the hit point and the original position is the on surface of the globe. I really appretiate any help! more ▼ asked Jun 22 '12 at 08:03 AM moghes 660 ● 17 ● 30 ● 44 whydoidoit 33.1k ● 12 ● 23 ● 101 add new comment (comments are locked) 10|3000 characters needed characters left ▼ Viewable by all users

 0 Using the center point sounds right. Run a "spoke" from the center to one point; find the angle to the other; you know 360 degrees is a distance of 2xPIxR; find the percent. Untested: ``````Vector3 spokeToActual = playerPos-sphereCenter, spokeToCorrect = correctPos-sphereCenter; float angleFromCenter = Vector3.Angle(spokeToActual, spokeToCorrect); // NOTE: angle inputs don't need normalize. In degrees(!!) float D = 2*Mathf.PI*radius * (angleFromCenter/360); ``````As a check, print that along with `playerPos-correctPos).magnitude`. It should only be a little bit bigger, if the player is remotely close. more ▼ answered Jun 22 '12 at 02:14 PM Owen Reynolds 11.5k ● 1 ● 7 ● 45 sounds to be the solutoins, i'll try this out then comment! thanks alot btw Jun 22 '12 at 04:36 PM moghes add new comment (comments are locked) 10|3000 characters needed characters left ▼ Viewable by all users
 0 Hi, I think that you need to compute great circle distance:http://en.wikipedia.org/wiki/Great-circle_distance more ▼ answered Jun 22 '12 at 02:57 PM add new comment (comments are locked) 10|3000 characters needed characters left ▼ Viewable by all users

By Email:

Topics:

x355
x212
x199
x35
x25

asked: Jun 22 '12 at 08:03 AM

Seen: 674 times

Last Updated: Jun 22 '12 at 04:36 PM