Added test function to find an intersection between circle and curve

Added test function to find an intersection between circle and curve

The main file to change is IntersectionPoint.java

[manu_chaud, 2017-12-08 11:43:09]

@Biwen, Wei: if you have time I put some comments to help you figure out my code

The main file is IntersectionPoint.java

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
File wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java
(right):

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:8: public
class IntersectionPoint {
Feel free of course to copy this class to a new project and call it from the
entry point through: IntersectionPoint.test();
(or make this class the entry point of your project directly)

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:22: public
static void test() {
The function implementing the R code is this one.

Reminder of the problem to solve:

Links are already created between, A<->B and B<->C. We want to reduce the path
between A and C. To achiev this, we create a new node D which is on the path
B<->C. We try to find the intersection between the circle of radius "the maximum
distance allowed" (== the constraint) and the path B<->C

  /--B_ D <-- new node
 / ___/\_
A-/      \C
    Λ
    |
    |
 the path right above is the new path proposed by Dijkstra

PS: if the circle has no intersection with the path B<->C, we don't create a
node. If it goes beyond the path BC (i.e. if the constraint distance is higher
than AB and than AC), it means that we can create a link from A to C directly,
in which case we just create it and do not need to find the intersection point

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:72: // x
<- (a0 + (b0-a0) %o% t) * radian  // Columns are (lat, lon)
The code that has yet to be translated is here

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:78:
double[][] x = new double[2][tl.size()];
Feel free to add some System.out.println() in the end to display the
intersection pooint in the console, and look on Google Maps if the coordinates
correspond actually to a point that is on the way between two points, and that
could reduce the path if we would create a link between a third point and this
point of intersection.

[manu_chaud, 2017-12-11 02:21:15]

Finally finished to translate that R code into Java, so as to have a function to
determine the intersection between a circle and a line on a sphere.
- Hopefully considering the Earth as a sphere is reasonable enough for the
purpose of our project (it should be, yet we need to see the result on the world
map)
- for the moment there is just a test function that prints the coordinates to
the standard output; the result should be ultimately integrated in the modified
graph on which Dijkstra will be run before being returned to the client

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
File wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java
(right):

https://codereview.appspot.com/334210043/diff/20001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:56: alpha
= Math.sqrt(u.get("lat")) + Math.sqrt(u.get("lng"));
I was using sqrt for computing the square, one of the reasons some inexpected
behaviors happened

https://codereview.appspot.com/334210043/diff/40001/wan_server/src/main/java/...
File wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java
(right):

https://codereview.appspot.com/334210043/diff/40001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:9: /*
The main information about this java class/code is written below

https://codereview.appspot.com/334210043/diff/40001/wan_server/src/main/java/...
wan_server/src/main/java/net/wancom/wan_server/IntersectionPoint.java:24: *
https://gis.stackexchange.com/questions/36841/line-intersection-with-circle-o...
The links here explains the rationale behind this code, better than I could do