Update README.md

Updated readme

README.md

@@ -1,39 +1,37 @@
-MyAddon (rename to your addon's name)
+ofxSpatialHash
 =====================================
-
-*This is a template of a README file for your addon. Fill in the relevant sections, and it should already give users a pretty good overview over your awesome addon!*
-We chose the [Markdown format](http://daringfireball.net/projects/markdown/syntax) since it can present good formatting where available (e.g. on Github) while still staying human-readable with a plain text editor.
-Don't forget, before announcing your addon to the world, you should replace `README.md` with this file and remove `README_AUTHOR.md`.
-
-Introduction
-------------
-Describe what your addon is about
+Fast nearest neighbour lookup for 2d particle systems
 
 License
 -------
-State which license you offer your addon under. openFrameworks is distributed under the [MIT License](https://en.wikipedia.org/wiki/MIT_License), and you might consider using this for your repository. By default, `license.md` contains a copy of the MIT license to which you can add your name and the year.
+[MIT License](https://en.wikipedia.org/wiki/MIT_License)
 
 Installation
 ------------
-Any steps necessary to install your addon. Optimally, this means just dropping the folder into the `openFrameworks/addons/` folder.
+Git clone or copy into `openFrameworks/addons/` folder.
 
-Dependencies
+Usage
 ------------
-What other addons are needed to properly work with this one?
+#### First use
+First initialise the hash with the correct dimensions `ofxSpatialHash::init()` <br />
+Points can be added to the hash with `ofxSpatialHash::addPoint(float x, float y, T value)` <br />
+Search for points `getNearestPoints(float x, float y, float radius)` and test for distance if necessary <br />
 
-Compatibility
-------------
-Which versions of OF does this addon work with?
+#### Update points
+Clear hash `ofxSpatialHash::clear()` <br />
+Add points `ofxSpatialHash::addPoint(float x, float y, T value)` <br />
 
-Known issues
-------------
-Any specific (and long-living) issues/limitations you want to mention? For bugs, etc. you should use the issue tracker of your addon's repository
-
-Version history
-------------
-It make sense to include a version history here (newest releases first), describing new features and changes to the addon. Use [git tags](http://learn.github.com/p/tagging.html) to mark release points in your repo, too!
-
-### Version 0.1 (Date):
-Describe relevant changes etc.
+#### Example
+All points contained in the green squares will be returned from a call to `ofxSpatialHash::getNearestPoints(float x, float y, float radius)`<br />
+Users need to test the returned points to see if they are inside the radius with a call to `ofVec2f::distance` or `glm::distaance`
 
+![Example](https://github.com/skell999/ofxSpatialHash/blob/main/docs/example.jpg?raw=true)
 
+Known issues
+------------
+- 2d only.
+- Points must be positive in x and y. 
+- The spatial hash top left corner is anchored to 0,0.
+- The class needs a predefined space width and height. Points outside this space will cause errors.
+- The returned points from a nearest neighbour search will contain points outside of the search radius.
+- An extra distance check provided by the user is needed to make sure you have points contained inside the radius.