I'm creating a navigation app and want the map to show the users location at the bottom of the map, like in Maps app when routing/navigating. However you can only determine which coordinate to focus on by using the centre coordinate.
Therefore I need to calculate an offset distance and bearing and calculate a coordinate that this represents the central coordinate that will allow the displaying of the users location at the bottom of the map.
This is all complicated by the 3D view where the camera pitch and altitude affects the relationship of distance between the offset coordinate and the users location.
Is there an easier way to do this or does someone know how to calculate this?
Thanks (a lot!)
D
Related
A project I've been working on for the past few months is calculating the top area of an object taken with a 3D depth camera from top view.
workflow of my project:
capture a group of objects image(RGB,DEPTH data) from top-view
Instance Segmentation with RGB image
Calculate the real area of the segmented mask with DEPTH data
Some problem on the project:
All given objects have different shapes
The side of the object, not the top, begins to be seen as it moves to the outside of the image.
Because of this, the mask area to be segmented gradually increases.
As a result, the actual area of an object located outside the image is calculated to be larger than that of an object located in the center.
In the example image, object 1 is located in the middle of the angle, so only the top of the object is visible, but object 2 is located outside the angle, so part of the top is lost and the side is visible.
Because of this, the mask area to be segmented is larger for objects located on the periphery than for objects located in the center.
I only want to find the area of the top of an object.
example what I want image:
Is there a way to geometrically correct the area of an object located on outside of the image?
I tried to calibrate by multiplying the area calculated according to the angle formed by Vector 1 connecting the center point of the camera lens to the center point of the floor and Vector 2 connecting the center point of the lens to the center of gravity of the target object by a specific value.
However, I gave up because I couldn't logically explain how much correction was needed.
fig 3:
What I would do is convert your RGB and Depth image to 3D mesh (surface with bumps) using your camera settings (FOVs,focal length) something like this:
Align already captured rgb and depth images
and then project it onto ground plane (perpendicul to camera view direction in the middle of screen). To obtain ground plane simply take 3 3D positions of the ground p0,p1,p2 (forming triangle) and using cross product to compute the ground normal:
n = normalize(cross(p1-p0,p2-p1))
now you plane is defined by p0,n so just each 3D coordinate convert like this:
by simply adding normal vector (towards ground) multiplied by distance to ground, if I see it right something like this:
p' = p + n * dot(p-p0,n)
That should eliminate the problem with visible sides on edges of FOV however you should also take into account that by showing side some part of top is also hidden so to remedy that you might also find axis of symmetry, and use just half of top side (that is not hidden partially) and just multiply the measured half area by 2 ...
Accurate computation is virtually hopeless, because you don't see all sides.
Assuming your depth information is available as a range image, you can consider the points inside the segmentation mask of a single chicken, estimate the vertical direction at that point, rotate and project the points to obtain the silhouette.
But as a part of the surface is occluded, you may have to reconstruct it using symmetry.
There is no way to do this accurately for arbitrary objects, since there can be parts of the object that contribute to the "top area", but which the camera cannot see. Since the camera cannot see these parts, you can't tell how big they are.
Since all your objects are known to be chickens, though, you could get a pretty accurate estimate like this:
Use Principal Component Analysis to determine the orientation of each chicken.
Using many objects in many images, find a best-fit polynomial that estimates apparent chicken size by distance from the image center, and orientation relative to the distance vector.
For any given chicken, then, you can divide its apparent size by the estimated average apparent size for its distance and orientation, to get a normalized chicken size measurement.
I would like to make a game where I use a camera with infrared tracking, so that I can track peoples heads (from top view). For example each player will get a helmet so that the camera or infrared sensor can track him/her.
After that I need to know the exact positions of that person in unity, to place a 3D gameobject at the players position.
Maybe there is another workaround to get peoples positions in unity. I know I could use a kinect, but I need to track at least 10 people at the same time.
Thanks
Note: This is not really a closed answer, just a collection of my thoughts regarding your question on how to transfer recorded positions into unity.
If you really need full 3D positions, I believe you won't be happy when using only one sensor. In order to obtain depth information, which can further be used to calculate 3D positions in a reference coordinate system, you would have to use at least 2 sensors.
Another thing you could do is fixing the camera position and assuming, that all persons are moving in the same plane (e.g. fixed y-component), which would allow you to determine 3D positions utilizing the projection formula given the camera parameters (so camera has to be calibrated).
What also comes to my mind is: You could try to simulate your real camera with a virtual camera in unity. This way you can use the virtual camera to project image coordinates (coming from the real camera) into unity's 3D world. I haven't tried this myself, but there was someone who tried it, you can have a look at that: https://community.unity.com/t5/Editor/How-to-simulate-Unity-Pinhole-Camera-from-its-intrinsic/td-p/1922835
Edit given your comment:
Okay, sticking to your soccer example, you could proceed as follows:
Setup: Say you define your playing area to be rectangular with its origin in the bottom left corner (think of UVs). You set these points in the real world (and in unitys representation of it) as (0,0) (bottom left) and (width, height) (top right), choosing whichever measure you like (e.g. meters, as this is unitys default unit). As your camera is stationary, you can assign the corresponding corner points in image coordinates (pixel coordinates) as well. To make things easier, work with normalized coordinates instead of pixels, thus bottom left is (0,0) ans top right is (1,1).
Tracking: When tracking persons in the image, you can calculate their normalized position (x,y) (with x and y in [0,1]). These normalized positions can be transferred into unitys 3D space (in unity you will have a playable area of the same width and height) by simply calculating a Vector3 as (x*widht, 0, y*height) (in unity x is pointing right, y is pointing up and z is pointing forward).
Edit on Tracking:
For top-view tracking in a game, I would say you are on the right track with using some sort of helmet, which enables you to use some sort of marker based tracking (in my opinion markerless multi-target tracking is not reliable enough for use in a video game) (if you want learn more about object tracking, there are lots of resources in the field of computer vision).
Independent of the sensor you are using (IR or camera), you would go create some unique marker for each helmet, thus enabling you to identify each helmet (and also the player). A marker in that case is some sort of unique pattern, that can be recognized by an algorithm for each recorded frame. In IR you can arrange quadratic IR markers to form a specific pattern and for normal cameras you can use markers like QR codes (there are also libraries for augmented reality related content, that offer functionality for creating and recognizing markers, e.g. ArUco or ARToolkit, although I don't know if they offer C# libraries, I have only used ArUco with c++ a while ago).
When you have your markers of choice, the tracking procedure is then pretty straightforward, for each recorded image:
- detect all markers in the current image (these correspond to all players currently visible)
- follow the steps from my last edit using the detected positions
I hope that helps, feel free to contact me again.
In my windows phone app I have a map object which points to the position longitude and latitude. I track the position changed event for every few meters threshold value. It works fine and shows the data correctly on map with puhpins when I am moving from point A to point B.
But when I am moving from point B to point A, it shows the map in the same direction as earlier which is A to B with pushpin values moving from B to A.
I want to change this behavior that is when a person is moving from point B to A the B point should face the person holding the mobile and pushpins should move towards A i.e. away from the person who is holding the phone.. currently I rotate my mobile 180 degress to see the pushpins are pointing towards A from B.
Bing Maps doesn't support rotating PushPins or perspective on WP7/WP8. You can only rotate the full Bing Maps control. Which causes a lot of problems if you have unidirectional items (such as text) as they'll show up rotated alongside with the map.
If you're on WP8, you can use the new Nokia Map control and set the Pitch & Heading properties to rotate the map for turn-by-turn navigation. See examples of setting Pitch, Heading and other properties at this Nokia article # http://www.developer.nokia.com/Resources/Library/Lumia/#!maps-tutorial.html;#toc_Mapproperties
For example, here's the WP8 Map control with Heading=0:
And here is the same place rotated with all the text and items appearing as they should with Heading=180.
And here's the Map control after setting the Pitch property.
The reason Bing Maps can't do rotations and Pitch correctly is because it has Bitmap tiles. Which means the data it gets from the server is an bunch of images it lays out in a grid. The reason Nokia Maps can do rotations and pitch correctly is because it uses vector tiles. It gets data from the server about what's in each location and the map control itself draws the topographic layout.
This code worked for me- http://j2i.net/blogEngine/post/2010/12/15/Calculating-Distance-from-GPS-Coordinates.aspx
You should save the last coordinate (or get the next one you are heading to) and compare them using the Bearing method, then set
myMap.Heading property to the received value.
Given the 3D vector of the direction that the camera is facing and the orientation/direction vector of a 3D object in the 3D space, how can I calculate the 2-dimensional slope that the mouse pointer must follow on the screen in order to visually be moving along the direction of said object?
Basically I'd like to be able to click on an arrow and make it move back and forth by dragging it, but only if the mouse pointer drags (roughly) along the length of the arrow, i.e. in the direction that it's pointing to.
thank you
I'm not sure I 100% understand your question. Would you mind posting a diagram?
You might find these of interest. I answered previous questions to calculate a local X Y Z axis given a camera direction (look at) vector, and also a question to translate an object in a plane parallel to the camera.
Both of these examples use Vector dot product, Vector cross product to compute the required vectors. In your example the vector dot product can be also used to output the angle between two vectors once you have found them.
It depends to an extent on the transformation that you are using to convert your 3d real world coordinates to 2d screen coordinates, e.g. perspective, isometric, etc... You will typically have a forward (3d -> 2d) and backward (2d -> 3d) transformation in play, where the backward transformation loses information. (i.e. going forward each 3d point will map to a unique 2d point, but going back from the point may not yield the same 3d point). You can often project the mouse point onto the object to get the missing dimension.
For mouse dragging, you typically get the user to specify an operation (translation on the plane of projection, zooming in or out, or rotating about an anchor point). Your input is the mouse coordinate at the start and end of the drag, which you transform into your 3d coordinate system to get two 3d coordinates, which will give you dx, dy, dz for dragging / translation etc...
I'd like to implement a dragging feature where users can drag objects around the workspace. That of course is the easy bit. The hard bit is to try and make it a physically correct drag which incorporates rotation due to torque moments (imagine dragging a book around on a table using only one finger, how does it rotate as you drag?).
Does anyone know where I can find explanations on how to code this (2D only, rectangles only, no friction required)?
Much obliged,
David
EDIT:
I wrote a small app (with clearly erroneous behaviour) that I hope will convey what I'm looking for much better than words could. C# (VS 2008) source and compiled exe here
EDIT 2:
Adjusted the example project to give acceptable behaviour. New source (and compiled exe) is available here. Written in C# 2008. I provide this code free of any copyright, feel free to use/modify/whatever. No need to inform me or mention me.
Torque is just the applied force projected perpendicular to a vector between the point where the force is applied and the centroid of the object. So, if you pull perpendicular to the diameter, the torque is equal to the applied force. If you pull directly away from the centroid, the torque is zero.
You'd typically want to do this by modeling a spring connecting the original mouse-down point to the current position of the mouse (in object-local coordinates). Using a spring and some friction smooths out the motions of the mouse a bit.
I've heard good things about Chipmunk as a 2D physics package:
http://code.google.com/p/chipmunk-physics/
Okay, It's getting late, and I need to sleep. But here are some starting points. You can either do all the calculations in one coordinate space, or you can define a coordinate space per object. In most animation systems, people use coordinate spaces per object, and use transformation matrices to convert, because it makes the math easier.
The basic sequence of calculations is:
On mouse-down, you do your hit-test,
and store the coordinates of the
event (in the object coordinate
space).
When the mouse moves, you create a
vector representing the distance
moved.
The force exterted by the spring is k * M, where M is the amount of distance between that initial mouse-down point from step 1, and the current mouse position. k is the spring constant of the spring.
Project that vector onto two direction vectors, starting from the initial mouse-down point. One direction is towards the center of the object, the other is 90 degrees from that.
The force projected towards the center of the object will move it towards the mouse cursor, and the other force is the torque around the axis. How much the object accelerates is dependent on its mass, and the rotational acceleration is dependent on angular momentum.
The friction and viscosity of the medium the object is moving in causes drag, which simply reduces the motion of the object over time.
Or, maybe you just want to fake it. In that case, just store the (x,y) location of the rectangle, and its current rotation, phi. Then, do this:
Capture the mouse-down location in world coordinates
When the mouse moves, move the box according to the change in mouse position
Calculate the angle between the mouse and the center of the object (atan2 is useful here), and between the center of the object and the initial mouse-down point. Add the difference between the two angles to the rotation of the rectangle.
This would seem to be a basic physics problem.
You would need to know where the click, and that will tell you if they are pushing or pulling, so, though you are doing this in 2D, your calculations will need to be in 3D, and your awareness of where they clicked will be in 3D.
Each item will have properties, such as mass, and perhaps information for air resistance, since the air will help to provide the motion.
You will also need to react differently based on how fast the user is moving the mouse.
So, they may be able to move the 2 ton weight faster than is possible, and you will just need to adapt to that, as the user will not be happy if the object being dragged is slower than the mouse pointer.
Which language?
Here's a bunch of 2d transforms in C