I'm currently working on project that uses json file with points & polygons.
All input data are a Lat/Lon format. I wish to draw these on a map (Which should be able to pan). I'm able to draw these objects on a JavaFx Pane or Canvas.
The issue is the data line between two coordinates is a straight line while it actually should follow stereographic projection .
I looked into ArcGis and other GeoTools but these tools all build upon tile maps something I don't need for my project.
You will have to create something what we call a LineDrawer. First you have to determine what line type you want to use. Standard line types are great-circle, rhumb and just straight lines. Second you have to define the projection you want to use. So if you now want to draw a line between two points A and B you have to split this up into small enough sections and compute intermediate points according to the formula for your chosen line type and then you have to project these points into your drawing pane.
But that's basically what every GIS software can do for you and you don't have to re-invent the wheel here.
Related
I'm currently rendering a 3D model (Wavefront .obj format) in my Qt program. Right now, I'm rendering the model using Scene3D in QML, and I'm able to get it to display in the viewing area. What I would like to do is have a user click on the model and generate a 2D cross section of the slice that I would like to plot on a different window. I'm quite new to 3D rendering, and a lot of Qt documentation isn't very descriptive. I've been reading Qt documentation, experimenting, and searching online with no luck. How can I create 2D slices of a 3D object Model in Qt 3D, preferably in QML? What Qt libraries or classes can I use to achieve this?
Unfortunately, the fact that models are stored as a set of surfaces makes this hard. QT probably doesn't have a built in method for this.
Consider, for example, that a model made of faces might be missing a face. What now? can you interpolate across that gap consistently from different angles? What about the fact that a cross-section probably won't contain any vertices?
But, of course, it can be solved. First, just don't allow un-closed surfaces (meshes with holes). Second, for finding the vertices of your cross-section, perform an intersection between every edge in your model and the plane you're using, and if there's an intersection, there's a point there. Third, to find the edges, look at the list of vertices, and any two that are from an edge on the same polygon in the mesh should be connected by an edge in the cross section. To find which direction the edge should go, project the normal of the polygon onto the plane your using. For filling, I don't really know what to do. I guess that's whatever you want it to be.
I have a GPX file with locations and altitude data.
I would like to create a 3D model and show this model using SceneKit.
I already tried the method using a NSBezierPath, but the problem is, that I can not add the Z data and it is more like a 2D route.
Right now I am creating a SCNBox for every single trackpoint - well, it works but it's not really that pretty and it kinda seems wrong.
I also thought about creating a 3D model (obj file) programatically, but this is too hard.
So, long story short: What is the best way to create a 3D geometry object with SceneKit when I got a list of points with X/Y/Z data?
Is there a way to "connect" SCNBoxes?
Regards,
Sascha
Try the SCNShape class. It allows you to create a 3D shape following a bezier path while controlling the Z axis as well:
"SceneKit creates a three-dimensional geometry by extruding a Bézier path, which extends in the x- and y-axis directions of its local coordinate space, along the z-axis by a specified amount."
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
these vector or raster files being classic files without geocoordinates. They are lat/long projection, I want to import them into QGIS, scale them up/down, place them to their right place, and they become reusable shp or raster geocoordinated layers.
Edit: I'am from the wikipedia Graphic Lab>Map workshop, we want to work more using GIS. We litteraly have hundreds maps to migrate to GIS technologies....
File:Chinese_plain_5c._BC-en.svg
File:Vignobles_basse_loire.svg
Partial Solution: load SVG into Inkscape, Save as DXF file, then you can load this into QGIS. This should at least get you most of the linework into QGIS.
However, it won't yet be properly georeferenced or styled, and different layers may be in different places because the SVG has some scaling and translating operators on parts of the map data that QGIS or Inkscape is ignoring. You'll probably need to work with a layer at a time. This probably isn't a problem since maybe you are only interested in the added data on the map, and not the base map (country outlines etc) since you will probably want to overlay your data onto standard map base layer (natural earth, OpenStreetMap tiles).
The only way I see to do the transformation at present is to work out the affine transformation parameters and use the QgsAffine plugin, but that does require you to work out the parameters beforehand by fitting known source coordinates to known target coordinates.
But to do hundreds? You might be better off writing some custom SVG parsing code for each one...
If you only want to display it in the correct place, scale and rotation treat it as an SVG icon.
1. create a point layer and put a single point at the georeferenced centre of the SVG you will load.
2. edit the symbology and load the SVG as an icon
3. set the size units to map units
4. supply the appropriate dimensions
5. rotate as necessary
The redraw is very slow and painful, but if you use Project>import/Export>Export map as image you can make a georeferenced raster.
I am completely new to 3D and started with Jeff Lamarche's tutorials as an introduction to openGL ES for iPhone, then so far, I am able to draw a spinning sphere, which will the base of my application.
What I want to do is render a planet Earth, thanks to 2D GIS vector data (polygones, lines or points with latitude/longitude or x/y coord).
I want to be able to turn different layers on/off and maybe able to identify an object that wold be touched.
My questions are :
would it be easier to rasterize my vector data to use them as image texture or apply the vector data onto the sphere (keeping in mind that I want to turn on/off the layers, the touch-enabled objects being optional)?
would it be easier to use a software like blender to draw the planet and add the layers rather than starting with the sphere I already have (procedural sphere)?
do the export tool from blender to opengl work well?
This kind of question is difficult to answer in general. Technically your intention sounds a lot like if you would like to write a program like Google Earth or KDE Marble. Since you're referring to GIS data you will require very high resolution. Textures only make sense for limited resolution data.
GIS applications usually work using hybrid approaches where some vector data are rendered directly (roads, waters, borders), while others are rendered to texture and the texture, or more accurately texture tiles, being used as caches, for example for building outlines in dense cities or the like. However data as it comes from say OSM can be directly rendered as vector data, since they are not very dense.