android – The best way to exchange data from one to several phones nearby

I want to create an application where several people close to an Android or iOS phone can exchange a small amount of data with one person. Thus, one person is the group leader and passes the name of the group to the other participants. I was thinking of using NFC but I have not been able to know if iphones can transmit a value (it seems they can now read NFC tags – but I have never seen writing this data). I could use QR codes (the manager then displays the QR image and the others scan this image). Or I believe there are blue-tooth and wifi options. But I want it to be a very simple action – to activate the bluetooth / wifi and connect the sound as if they were too long. Alternatives, suggestions?

My camera does not focus on nearby objects

The minimum focus distance is the closest you can get to a subject and get the focus on that subject. This is a property of your lens, not your camera.

Please see the specifications of this Canon 24-105mm lens:

You will notice that the MFD is 1.48 feet tall. This means that you can not physically focus on an object closer to you than 1.48 ft.

If you are trying to approach a very small object, this type of photography calls Macrophotography. There are macro lenses specifically designed for closer-to-average tuning. For example, the MFD of this 100mm macro lens is 11.81 inches:

In addition to obtaining a dedicated macro lens, one can use extension tubes with any purpose to allow for more precise focus, at the cost of not being able to focus too far. Your distance depends on the length of the tube and the lens you are using. The calculations become quite complex, especially with the zooms. The normal advice is simply: experiment.

lighting – Simulates the appearance of an aircraft illuminated by a nearby point source

I would like to simulate the appearance of a reflective flat surface illuminated by a nearby point source.

Graphics3D[{Lighting -> {{"Point", White, {0, 0, 1}}},
     {{-10, -10, 0}, 
      {-10, 10, 0}, 
      {10, 10, 0}, 
      {10, -10, 0}, 
      {-10, -10, 0}}]}
PlotRange -> {{-10, 10}, {-10, 10}, {0, 10}},
Axes -> True,
AxesLabel -> {"x", "y", "z"}]

plane illuminated by a point source

Note that the single point source is {0,0,1}, just above the surface at its center. What should appear is that the center the plane must appear bright (because it is close to the source just above the center and for geometric reasons), while the edges (distant parts) of the plane must appear dark. It does not happen

I've adjusted the properties of specularity and so on, never managed to get the bright region expected in the center.

bluetooth – Unable to get data attachments tags with the help of Google Nearby API on Android

I am a newcomer to tags and am having problems with the Message API near Google. I did it as shown on their page ( but it does not get any attachments of the tags.

It connects to the Google API client, it subscribes successfully but never gets to "onFound" or "onLost". I am able to successfully register the lighthouse and locate it in the "Tag Tools" application.

bluetooth – Nearby iPhone / Android file sharing systems on multiple platforms

In the past, I was excluded from group discussions, I was not allowed to join groups and I was generally discriminated against because I had an Android while almost all the people I know own an iPhone. I've been trying to find ways to integrate the features of the iPhone and Android to bring the two platforms closer together. I had found the "WeMessage" application that would allow an Android user to use iMessage, but I have not configured it yet. Then I wondered if there was a way to send and receive messages using the AirDrop feature of the iPhone on an Android. My phone, a Huawei Mate SE, has a feature called Huawei Share, but it only works with other Huawei phones. Does anyone know how AirDrop works or how to use a file-sharing system close to one platform at the other?

How can I stream audio to another nearby Android device?

I have tried the RTSP server over LAN, but the delay is too long. Is there a more efficient way to achieve this?

polygon-edge unit allowing only nearby points to be listed

I'm trying to create code to allow the addition of nodes only to an area close to an EdgeCollider2D in Unity.

I have polygons without holes (Ferr2D objects) and I need to reduce the number of nodes that I add to my routing algorithm. My thought is to create lines from collider points. Then ONLY if my node is close to a collider line, to add it to my list of obstacles for tracking. Reducing the number of nodes added. That is to say. Do not add nodes in the middle of large polygons or far from large polygons. But only around the edges of the collider.

                                                foreach (EdgeCollider2D ec in edgeColliders) {
for (int y = 0; y <gridElemCntY; y ++) {
for (int x = 0; x <gridElemCntX; x ++) {
Vector2[] pts = ec.points;
for (int i = 1; i <pts.Length; i ++) {
Vector2 nodePt = new Vector2 (nodes[x, y].pixX, nodes[x, y].fairy);
Vector2 worldSpacePoint1 = ec.transform.TransformPoint (pts[i - 1])
Vector2 worldSpacePoint2 = ec.transform.TransformPoint (pts[i])
Point pt1 = new Point (worldSpacePoint1.x, worldSpacePoint1.y);
Point pt2 = new Point (worldSpacePoint2.x, worldSpacePoint2.y);
Point pt3 ​​= new Point (nodePt.x, nodePt.y);
double dist = PointToLine.DistanceFromPointToLine (pt1, pt2, pt3);
if (dist <0.005) {
obsNodesAsVectorList.Add (nodePt);