I'm trying to build a small application for a specific problem in cartography. The workflow is like this:
in the field, use a compass and tape measure to obtain terrain data.
also in the field, sketch the plot being surveyed
using inkscape, create a vector drawing of that sketch
crunch the data to obtain the relevant information (implemented already)
put the vector and the data together (mostly warping and scaling the drawing - implemented already)
Now, I'd like to do the vectorizing, which I'm doing in inkscape now, directly in my custom application - this helps me characterize the sketch faster.
I had a look at the Inkscape and Karbon codebases, but the code responsible for the widgets that draw curves and paths, along with the whole user interaction parts, is quite involved. I'd like to stick to number crunching and make sure that works properly.
In short, I'm looking for something like Qwt (whichs provides plotting utilities), but directed to adding vector drawing/sketching functionality to an application. Then it'd be a matter of putting the GUI pieces together, and i'd be free to worry about the number crunching. So far I couldn't find anything like this - Inkscape, Karbon, Libreoffice, Printdesign, Gimp, they all implement their own path, curve widgets, using the graphics primitives of their frameworks and adding all the code that shows the curve moving with the mouse, the control points, etc.
Does anyone have an idea if such a pre-made framework for higher-level graphics - that lets me forget about the GUI code - exists?
Thanks!
QGraphicsScene and QGraphicsView provide enough for you to fairly simply implement the rest of it. Do note that Qt has a rather rich set of graphics primitives that you can trivially reuse, like bezier curves, paths, etc. You need to implement the application-specific bits, but the basics are done.
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Recently I explored some libraries where I can visualize graphs from Neo4j, but didn't get a clear view wich one to choose, so I have a couple thought I'd like to share.
My requirements and wishes - after search throught REST API with cypher query visualize graphs with all relationships, nodes. And result make interactive - able to drag/drop... opportunity to reveal other nodes/rels on click. Import nodes throught json data and be able to show quickly up to at least 400 elements.
So I more or less explored further libraries:
Three.js - mostly for 3D. (If I don't need 3D then better not to choose this one)
Arbor.js - drawing leaves up to you, mostly layout library
VivaGraphJS - easy to use, but almost no documentation :(
D3.js - Looks fine, but uses SVG
Cytoscape.js - looks fine, but I read that I can't use it with Neo4j. Is D3.js the right choice for real-time visualization of Neo4j Graph DB data why?
Processing.js - have it's own language similar to Java. I'm not so much in Java-like language (yet).
And I have a couple questions:
1) Whats your experience - benefits, weakneses of libraries?
2) I suppose I want to use canvas insted of SVG? (a lot of small elements on the screen).
3) Arbor is special library for layout, but others don't have layout algorithms or what?
I'll appreciate any opinion! :-)
I pondered a similar situation. I chose sigma.js.
1) Whats your experience - benefits, weakneses of libraries?
sigma.js is specific to graph rendering. d3 is a full on toolbox for visualization. Since I only want to draw graphs, the concise sigma.js interface was easier to work with. I think this is the video where the creator talks about how sigma.js is able to do incremental rendering and thus perform better and handle more vertices/edges smoothly.
2) I suppose I want to use canvas insted of SVG? (a lot of small
elements on the screen).
sigma.js renders to the canvas.
Here are the sigma.js examples. The "hide nodes" example shows mouse interactions. Additionaly, here is a blog post showing how one can easily integrate neo4j w/ sigma using a very minimal amount of data massaging code written in node.js. It would be easy to port this to any server language.
I don't see sigma.js in that list which you might want to take a look at as it is very useful (example)
You will have to somehow handle the rendering of the received data (i.e. go from a data structure to its visual representation) and this depends on what are you trying to show / say with that visualisation, how you want to do it and how you want it to look like.
As a starting point, i would go with D3 and Sigma.
I note that Gephi is not on your list. As a standalone visualiser/editor, its the best that I have used (you just get the neo4j plugin, and it will import the source files of the database and let you view it). Its also Open Source, so you can include it as part of a project.
Also missing from your list is the yFiles family of graph visualization libraries.
The JavaScript variant of if uses both Canvas, WebGL, and SVG. This can give very good performance and high-quality visualizations at the same time. For hair-ball-like graphs (thousands of dots and lines, but probably no text) you can use WebGL and Canvas and when you zoom in to actually make sense of the data, you can use SVG to get detailed high-quality visualizations with labels, icons, data-bound visualizations, etc. You can use both techniques in the same visualization, even at the same time, benefiting from the best of both worlds (demo).
Connecting yFiles to Neo4j is easy using the JavaScript Bolt driver.
Aiming at 400 elements in the view is a good idea. While larger graphs tend to look really nice, most of the time you won't gain a lot of insights by looking at "hair-balls". These almost artistic visualizations all look very similar and as such carry little to no information. Often you could just as well display a static image showing the first google image search hit for a "hairball graph" query :-)
In order to better support the user during exploration, filtering, grouping, nesting, and dynamic interaction should be added to the viewer application. How this can be implemented, very much depends on the business domain in the visualization, though and there are only very few generic approaches that work for generic graphs.
Disclaimer: I work for the company that creates the above mentioned visualization library. I do not represent it on SO, though.
Is there a way to create and use a simple 3d model on the Unreal Engine?
Your best bet would be to create the initial 3D asset in a third party tool and import it into the IDE. From there you can change the texture map, and manipulate the aesthetics in one way or another, but the initial 3D model should be in an external 3D format, and then placed as a prefab into your world.
Creating an object dynamically in UDK is cumbersome and requires lots of tweaking, and won't save much in terms of cost of resources. Especially if you want it to look good and more than just 3D meshes thrown together rudimentarily. It is possible, but almost not worth it, especially if you have 3DSMax, Maya, Cinema4D, MotionBuilder, or one of the other hundred tools available to do the grunt work for you.
Most 3D Engines (IE Unity, UDK, Torque, Cry and now Havok) support many formats, and especially the unversal FBX. You could even use google sketchup and export to DAE or FBX format to get it into your Engine. Grant it you lose a lot of the elements, but the basic 3D mesh stays relatively in tact.
I'm currently evaluating the possibilities to implement a navigable 3D scene which allows to render multiple 2D layers. To be a bit more precise, I would like to display multiple graphs in a 3D environment in order to pinpoint simularities and differences between those graphs. Considering the following screenshot, there would be two graphs (one black, one grey), which are equivalent - for different graphs, deviant nodes might, i.e, be highlighted in red.
I am working with Qt's Graphic View Framework and established an editable graph editor using QGraphicsScene and several QGraphicsItems, which I separately from this project.
Qt provides OpenGL support, e.g., the QGLWidget and I had a look at the provided examples. Given, that I have not worked with OpenGL (I did some work with Java3D though) I would love if some people can share their experience.
Several solutions came to my mind:
Render every QGraphicsView to a QPixmap and display them in 3D, which would make the graphs navigatable but would prohibit any picking of elements etc.
Create an equivalent 3D element for every 2D graph element and "transform" every QGraphicsView into an 3D representation. I guess this would be quite some work (espacially as I have not worked with OpenGL)
Maybe there is an easy way to "place" the QGraphicScenes, the view, or just the QGraphicsItems in a QGLWidget without many adaptions and still register the usual "mouseclickevents" etc.
For a first implementation a plain navigable "viewer" which displayes multiple graphs in different layers would sufficient. But I would like to keep it extendable in order to add, e.g., picking, in the future.
The Qt3D project provides a class called QGraphicsEmbedScene which does exactly what you are asking for.
Currently I'm trying to develop some simple plot prototype and I'm struggling with some kind of white/empty sheet syndrome.
I'm back to Qt after 2 years, so I feel quite retarded.
My application should:
plot and manage custom layers of data
plot on custom canvas background
manage markers on plot
My plan is to use following design:
QGraphicsScene /View/Item as a sprite like management widgets for background, markers, pointers and other "bitmap" objects etc.
QPainter/ Qpixmap or QPicture for actual data layers - and if possible set them as QGraphicItem to simplify management of dynamic graphics
I don't want to use Qwt or similar library, unless I can plot with it on custom background (I don't like the look of the qwt's graphic style).
Is my plan proper in scope of qt class usage and composition?
I'd like to have at least clear overview of the classes which should be involved for this kind of prototype.
Thanks in advance.
P.
I think you have the basic idea with QGraphicsView. Here are a few resources which might help:
Graphics View
Diagram Scene
If you want to use the new animation and state set classes:
Stickman
Also, take a look at gunnar's labs blog. He recently did a series on graphics performance.
All of these are strictly Qt (animation and state set are in 4.6). They are in C++ but hopefully you can translate what you need to python.
You don't say much about your project for me to propose a more helpful answer, but have a look at the Qt demos involving the graphics view, especially diagram scene and 40000 chips. I think you will find them inspiring for what you want to do.
May be MathGL is appropriate for you. It have Qt widget or you can use RGBA image directly to combine it with any background in your widget.
I recommend you to use QCustomPlot which is a Qt C++ library. It focuses on making good looking, publication quality 2D plots, graphs and charts and also has high performance for realtime visualization applications. You get it here: http://www.qcustomplot.com/
You may want to take a look at the Core Plot framework. Core Plot is OS X specific, but it is built on the the OS X Core Animation system which has a lot of conceptual similarity to the Qt Graphics View Framework. You'll have to learn to visually parse the Objective-C (a less-than-two day process for any competent C++ developer), but you should be able to see the general architecture relatively easily. The Core Plot wiki has some nice high-level documentation that might set you on your way without even needing to look at the code.
In working on a shortest path algorithm across a network I would like to generate a picture of the network. I'd like to represent nodes (circles), links (lines), cost to traverse the link (number in the middle of the link line), and capacity of the link (number on the link line next to the node it represents) in the picture. Is there any library/software out there that would help to automate creating this picture?
I can do this manually in Visio or with some drawing application but I'd like to generate them from code as I change/tweak the network.
Sounds like a job for GraphViz , it generates graphs from a short text description file. I've used it to produce connected node graphs and I believe it should be possible to add link labels, as you require.
If you're using python, Nodebox draws pretty graphs.
One of the big problems in displaying networks like this is figuring out where to put the nodes on the display screen. If arranging nodes is logically simple given your network, then an off-the-shelf product is likely to suit your needs.
If the arrangements are much more complicated, you may have to accept a certain amount of manual intervention to get this to work with off-the-shelf stuff, or byte the bullet and program the whole thing yourself.
.NET is one choice, and once you've mastered the Graphics class it's easy to use and plenty fast for something like this. However, there are probably better languages/platforms than .NET for something graphics-oriented like this.
Update: .NET is much better for 2D graphics than I knew. The key is finding a fast workaround to the pitifully slow GetPixel() and SetPixel() methods in the Bitmap class. Once you can read and write individual pixels easily and quickly, you can do whatever you want as a programmer.
Did you by chance check out the R programming language? I'm not positive but I believe that you can make images and such out of graphs. r-project.org
There are a bunch of visualizations of various algorithms here: Algorithmics Animation Workshop