I have a region table in oracle 12c, the table include 9 region that each of them defined by a polygon.
Polygon defined by 4 points in 2D.
I give a point from client and I must find out that this point is in which polygon. can anyone help me with this problem?
by the way I use Oracle 12c.
Ray casting algorithm is a popular solution to your problem https://en.wikipedia.org/wiki/Point_in_polygon. You can find pseudo-code easily and can start from that.
If you want to have solution in a specific language, then sorry I can't be of help.
I am trying to render a mvt (Mapbox Vector Tile) containing OSM data using Mapbox GL js, but I keep getting some ugly polygons like they were simplified (like in the Simplification section of this documentation!). I don't want those polygons to be simplified. At least I would like the best resolution to be as close as possible from reality.
First, I checked if it could come from OSM data. But OSM data is good.
So I looked into the tile server and more precisely into the mvt encoder (code). The extent value, which controls how detailed the coordinates are encoded in the vector tile, is 4096. 4096 is a very good value. So I don't understand why I don't get proper polygons.
I suppose that this issue comes from Mapbox GL js which might perform an additional simplification.
What extent value could I use in the encoder?
Is there a way to configure a resolution with mapbox gl js ?
I would appreciate some help !
Thanks!
Mapbox GL JS does not do any additional simplification on vector tile sources. If you are seeing simplified geometries, this is most likely done during vector tile generation.
I was finding the same thing. I got better results when, rather than importing the polygons as a geojson as I had been doing, I converted the file to a shape file, zipped it, and imported that into mapbox. There was then no simplification to the shape.
Ok, here is the thing. Recently i decided i wanted to understand how Random map generation works. I found some papers and some arguments. The most interesting one was "Diamond Square algorithm" and "Midpoint Displacement". I still have to try to apply those to a software, but other than that, i ran into this site: http://www-cs-students.stanford.edu/~amitp/game-programming/polygon-map-generation/
As you can see, the idea is to use polygons. But i have no idea how to apply that a Tile-Based map, not even how to create those polygons using the tools i have (c++ and sdl). I am assuming there is no way to do it ( please correct me if i am wrong.) But if i am not, how does a non-tile map works, and how are these polygons generated?
This answer will not give you directly the answers you're looking for, but hopefully will get you close enough!
The Problem
I think what blocks you is how to represent the data. You're probably used to a 2D grid that simply represent the type of each tile. As you know, this is fine to handle a tile-based map, but doesn't properly allow you to model worlds where tiles are of a different shape.
Graphs
What I suggest to you, is to see the problem a bit differently. A grid is nothing more than a graph (more info) with nodes that have 4 (or 8 if you allow diagonals) implicit neighbor nodes. So first, what I would do if I was you, would be to move from your strict standard 2D grid to a more "loose" graph, where each node has a position, a position, a list of neighbors (in most cases you'll have corners with 2 neighbors, borders with 3 and "middle" tiles with 4) and finally a rendering component which simply draws your tile on screen at the given position. Once this is done, you should be able to have the exact same results on screen that you currently have with your "2D Tile-Based" engine by simply calling the rendering component with each node who's bounding box (didn't touch it in what you should add to your node, but I'll get back to this later) intersects with the camera's frustum (in a 2D world, it would most likely if the position +/- the size intersects the RECT currently being drawn).
Search
The more generic approach will also help you doing stuff like pathfinding with generic algorithms that explore nodes until they find a valid path (see A* or Dijkstra). Even if you decided to stick to a good old 2D Tile Map game, these techniques would still be useful!
Yeah but I want Polygons
I hear you! So, if you want polygons, basically all you need to do, is add to your nodes a list of vertices and the appropriate data that you might need to render your polygons (either vertex color, textures and U/V maps, etc...) and update your rendering component to do the appropriate OpenGL (this for example should help) calls to draw your nodes. Once again, the first step to iteratively upgrade your 2D Tile Engine to a polygon map engine would be to, for each tile in your map, give each of your nodes two triangles, a texture resource (the tile), and U/V mappings (0,0 - 0,1 - 1,0 and 1,1). Once again, when this step is done, you should have a "generic" polygon based tile map engine. The creation of most of this data can be created procedurally by calculating coordinates based on tile position, tile size, etc...
Convex Polygons
If you decide that you ever might need NPCs to navigate on your map or want to allow your player to navigate by clicking the map, I would suggest that you always use convex polygons (the triangle being the simplest for of a convex polygon). This allows your code that assume that two different positions on the same polygon can be navigated to in straight line.
Complex Maps
Based on the link you provided, you want to have rather complex maps. In this case, the author used Voronoi Diagrams to generate the polygons of the map. There are already solutions to do triangulation like that, but you might also want to use other techniques that are easier to work with if you're just switching to 3D like this one for example. Once you have interesting results, you should consider implementing serialization to save/open your map data from the game. If you want to create an editor, be aware that it might be a lot of work but can be worth it if you want people to help you creating maps or to add elements to the maps (like geometry that's not part of the terrain).
I went all over the place with this answer, but hopefully it helps!
Just iterate over all the tiles, and do a hit-test from the centre of the tile to the polys. Turn the type of the tile into the type of the polygon. Did you need more than that?
EDIT: Sorry, I realize that probably isn't helpful. Playing with procedural algorithms can be fun and profitable. Start with a loop that iterates over all tiles and chooses randomly whether or not the tile is occupied. Then, iterate over them again and choose whether it is occupied or its neighbour is.
Also, check out the source code for this: http://dustinfreeman.org/toys/wall7-dustin.html
I would like to draw sector of circle on map defined by point, radius, startAngle and stopAngle. I found lots of exmaples but with polygons etc whitch was too complicated for my case.
Thanks for any help!
a Circle is an object with no defined sides. Only a radius and a center point.
You are required to use a polygon to build a semi circle as it is a two sied object
There is not always an easy way out in coding, and typicaly they are the bad ways to do things (unless your talking about somthing like JQ/Bootstrap)
Here is a fairly stright forware implementation
http://googlemaps.googlermania.com/google_maps_api_v3/en/draw-semi-circle.html
This was refered in this question
Google Maps Polygon Incorrectly Rendered
they even provide a working example for you to rip apart
http://maps.forum.nu/temp/gm_bearing.html
Given an arbitary polygon with vertices stored in either clockwise/counterclockwise fashion (depicted as a black rectangle in the diagram), I need to be able to subtract an arbitrary number of circles (in red on the diagram) from that polygon. Removing a circle could possibly split the polygon into two seperate polygons (as depicted by the second line in the diagram).
I'm not sure where to start.
Example http://www.freeimagehosting.net/uploads/89a0276d9d.jpg
Warning: getting code to do this absolutely right is tricky. (Conceptually it's fine, but you can quickly get bogged down in numerical errors and edge cases.) You're basically asking for a 2D version of Constructive Solid Geometry. You might want to see if you can use an existing library written by an expert in computational geometry. There are some libraries here that will probably do what you want, but you'll have to choose a representation that suits you best and convert what you have into that representation.
Here's a freeware polygon clipping library (written in Delphi and C++) that does what you're asking: http://sourceforge.net/projects/polyclipping/