Goodmorning everybody,
I searched in the web for this problem for something like an hour an nobody seemed to have my same difficulty, so here I am. I'll explain you my problem: I have four states (but in future they can become much more the four) A, B, C and D between which a particle can do transitions. Suppose I know exactly how many times the particle undergoes the A->B, B->C, C->D, A->C (... and so on) transitions. I want to represent my states as dots on a circle and the transitions as arrows between states, which are wider (the arrows, not the dots!) proportionally to the number of transitions. I hope I made myself clear. Is this possible on Gnuplot 4.6? Otherwise: do you know other programs able to do that? Because I saw maps like this before, but sincerly I don't even know how to search for them!!
Thank you very much for your help.
A much more suitable tool for your problem would be Graphviz. You can use the Graphviz “DOT” language to express your transition map directly, and then use the Graphviz tools to perform various types of automated layout (including circular ones) and to produce image files showing the nodes and edges in the graph. If none of the automated layouts are what you want, you can compute them yourself and set the positions explicitly, and still use graphviz's renderer.
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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.
As I delve into SVG, I find myself trying to round corners in <path>s.
Contemplating web examples and looking at the answers to similar but more specific questions, I see that the most common ways to do so are using curves or arcs of some sort.
The idea behind arcs (A/a) seems pretty straight forward, but a blog post on how to figure out the maths was nowhere to be easily found or in not well-organized websites.
After seeing examples that use C/c I was pretty lost, and I couldn't find a well formatted and united blog post.
The world would be greatful if there was an SO answer with a few resources on nice posts for rounding edges or explaining the maths and implementation directly
The answer should assume:
no libraries (maybe as extra references, but not library-only answers)
paths with corners at non-orthogonal angles (non-90deg)
how it would be easier at certain specific angles/lengths
differences in efficiency between using arcs and curves (which one is best size-wise to use for what purpose and in what case)
generic examples (specific but not-hard-to-visualize values, out of 100 for example, are fine)
The answer can just list well-presented and introduced resources, and need to explain what is expected to find in the link along with a short description and summary
What maths are you trying to figure out?
Assuming you want "round" corners, meaning circular, then in most cases arcs will be what you want to use. And it has the advantage that there is normally no maths to figure out. You will have the start point of the arc (where the incoming path segment stopped). Then to add an arc, you just need to provide it with:
the radius of the curve you want
the rotation of the arc relative to the X axis. This will be 0 for circular arcs, and therefore for your case also.
the large arc flag. For every arc there will be two potential arcs: the shortest arc between the two points, or the "long way" around the circle
the sweep flag. This is the direction: clockwise or anti-clockwise
the end point of the arc
All pretty straightforward really. You may need some maths to work out where the end of the arc will be, but that's pretty much it.
The full explanation for all these parameters to the A command can be found in the Paths section of the SVG spec.
https://www.w3.org/TR/SVG/paths.html#PathDataEllipticalArcCommands
Basically, I'm looking for something like this awesome research project: Gmap, which was referenced in this related SO question.
It's a rather novel data visualization that combines a network graph with an imaginary set of regions that looks like a map. Basically, the map-ification helps humans comprehend the enormous data set better.
Cool, huh? GMap doesn't appear to be open source, though I plan to contact the authors.
I already know how to create a network graph with a force-directed layout (currently using Prefuse/Flare), so an answer could be a way to layer a mapping algorithm on top of an existing graph. I'm also not concerned about the client-side at all right now - this would be a backend process, and I am flexible about technology stack and data output at this stage.
There's also this paper that describes the algorithm backing GMap. If you have heard of Voronoi diagrams (which rock, but make my head hurt), this paper is for you. I quit after Calc 1, though, so I'm hoping to avoid remembering what sigmas and epsilons are.
As a start, could you do a simple closest point sort of an algorithm? So it looks something like this: You have your force directed layout and have computed some sort of bounding box. Now you want to render it. Adjust your bounding box to line up to the origin and then as you calculate the color of each pixel, find it's closest point. This should generate some semblance of regions and should be quite simple to try out. Of course, it isn't going to be as pretty as GMap, but maybe a start? The runtime would be awful, but... I don't know about you but computing boundary lines directly sounds a lot harder to me.
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I'm interested in creating poster-sized images that contain repeating patterns, similar to the two (public domain) images below, the Flower of Life and a Penrose tiling:
My questions:
How do people usually create images like these on a computer? I'm hoping the answer isn't, "Open Adobe Illustrator and guess at intersection points," since such points can be defined mathematically. But I also imagine that not everyone with an interest in geometric patterns is also familiar with programming.
What is the best environment for creating such images? In particular, what's the best way to get high-resolution images out of Java, Python, Processing, etc? Or, is Mathematica the best tool?
Actually calculating the points and doing the math isn't the hard part, in my mind (at least, it's not the focus of this question). I'm interested in the best way to get a high-quality visual product out of a program.
The best way to create images like these is to learn to write PostScript. It's a clean language, easy to learn, and quite powerful once you know it well.
Bill Casselman's manuals are by far the best reference for high quality mathematical illustration.
Use a vector image format like SVG. This will scale perfectly to any resolution.
Inkscape is a great tool for creating these.
Once you have a vector image format, there are many options for using it in programming languages, depending on your language of choice.
For example -
.NET - SvgNet
ActionScript - svgweb
C++ - LeadTools
XAML for WPF/Silverlight - ViewerSVG (Converts SVG to XAML)
I don't know how those images were created, I would guess they were scanned from a book, but, in my work with fractals, I tend to start with just using the <canvas> tag, mainly so that I can change the size of the element and see it drawn more iterations, so I can get the highest resolution.
That is the problem with something like SVG is that you would need to pick a resolution and then create it, and it will scale well up and down, but if you developed it at one resolution, then you go to a higher resolution to demo, you may see more gaps than you would like.
If you want to just do it and save it as a static image then any GUI will work, as you are saving a GIF at that point, but if you want it, for example, on a web page, and have it look as good as it can on that browser then you may want to look at using javascript.
The math part isn't hard, and so drawing the image is fairly easy, once you derive the recursive algorithm that is needed. I tend to go to the next iteration until the size is below a threshold, for example, a radius of < 3, then it exits.
Well, #2 is going to be kind of a holy war so I'll address #1. :)
The key to images of this nature is recursion. Basically they are the same image repeated over and over in a controlled way to get an intersting result. Take the flower of life for example. You repeat the center petal six times (the method to do the petals is up to you). Then you create six more flowers using the petals tip as the center and overlapping one of the petals. You then recursively move outward. After a few "rounds" you stop and draw the containing circle. Basically the recusion simulates the stamp, move and rotate that would be required if you were doing it by hand.
When I have played around with these kinds of things I have always found that experimentation is the best way to get cool new things. Of course that could be just my lack of imagination. :)
I know I am not very math heavy in this answer but that is up to you and experimentation. Just remember that COS and SIN are your friends and there are 360 degrees in a cricle (or 2pi radians depending on your math package).
EDIT: Adding some math for the "Flower"
Starting with a center of (Xo, Yo) and a flower radius of r...
The tips of the petals (P0, P1, etc) are determined by...
X = Xo + (sin((n * pi)/3 + (pi / 6)) * r)
Y = Yo - (cos((n * pi)/3 + (pi / 6)) * r)
where n is the petal number (0..5)
Once you compute a petal tip, just draw the petal and then start a new flower at the tip. You would also set a bounding circle so that any point outside that circle would not be drawn.
I would try to create a PDF with iText in Java. PDF supports vector graphics, so it should scale without problems. I don't know how well iText scales w.r.t. performance when you have a really big number of graphic elements.
A1. You might want to look at turtle-graphics, l-systems, iterated function systems, space filling curves, and probably a lot of other approaches I'm not familiar with or haven't thought of yet.
A2. You can program any of these with any of the languages you suggest. I like Mathematica, but I know that not everyone has a copy of it and I have a copy 'cos I work in number-crunching and get to play with it for making pretty pictures. But Processing, which is free, was designed to be artist-friendly and might be a better starting point for you. Both Mathematica and Processing do the graphics right there and then, no calls to external libraries (or worrying which ones to use).
And, while I agree with everyone who says that vectors are the way to go, don't forget that the final productions step, onto paper or screen, is rendering so give some thought to how that will be done. This might, for example, lead you to Postscript or PDF for an output format.
Have fun
Mark
Well, I used to draw flowers of life with a compass, back then in junior school ... very simple actually ... but I don't think that's the answer you're looking for.
Basically it consists of drawing a circle of the same radius, from every point, until you encounter the big circle (limit).
I am IT student and I have to make a project in VB6, I was thinking to make a 3D Software Renderer but I don't really know where to start, I found a few tutorials but I want something that goes in depth with the maths and algorithms, I will like something that shows how to make 3D transformations, Camera, lights, shading ...
It does not matter the programing language used, I just need some resources that shows me exactly how to make this.
So I just want to know where to find some resources, or you can show me some source code and tell me where to start from.
Or if any of you have a better idea for a VB6 project.
Thanks.
I disagree with the previous posts, a 3D renderer is actually pretty simple. A high-quality 3D renderer is hard however.
Get a bunch of 3D data, triangles are simplest.
Learn about homogenous coordinates and the great 4x4 matrix for transforms.
Define a camera by a position and a rotation (expressed in the 4x4 matrix).
Transform your 3D geometry by this camera.
Perform the perspective divide and scale to your window. This converts your 3D data to 2D.
Render the data as 2D.
Now you're going to lose out on a depth buffer, so stick to wireframes in the beginning. :-)
Don't listen to these nay-sayers, go out and have some fun!
Many years ago I made a shaded triangle renderer that used library calls to draw the triangles. It's a rather naive approach but you would be able to achieve the same result using VB6. I got all the maths & techniques from "Computer Graphics principles and practice" by Foley et al. Some parts are out of date now but I think you'd find it very helpful for this project and it can be bought 2nd hand at reasonable prices from Amazon for example.
One simple approach could be:
Read model file as triangles
Transform each triangle using matrices to account for camera position
Project triangle points onto 2D
Draw 2D triangle (probably using GDI)
This covers wireframe viewing. To extend this to hidden surface removal you need to work out which triangles are in front. Two possible ways:
Z-order sorting the triangles and drawing the ones furthest from the camera first. This is simple but inefficient if there are a lot of triangles and can give overlapping triangle effects when the order is not quite correct. You also have to decide how to sort the triangles - e..g by centroid, by extents...
Using a software depth buffer. This will give better results but is more work to implement. You will have to write your own triangle drawing code so cannot rely on GDI. See bresenham's line algorithm and related algorithms for doing filled triangles for how to do this.
After this you'd also need some kind of shading based on lighting. The calculations are covered in Computer Graphics principles and practice. For simple shading you can stick with drawing triangles using gdi , but if you want to do gouraud or phong shading the colour values vary across a triangle. One way around this is to sub-divide the triangle into smaller triangles, but this is inefficient and won't give very nice looking results. Better would be to draw the triangles yourself as required above for the software depth buffer.
A good extension would be to support primitives other than triangles. Basic approach would be to split primitives into triangles as you read them.
Good luck - could be an interesting project.
VB6 is not the best suited language to do maths and 3D graphics, and given that you have no previous knowledge about the subject either, I would recommend you to choose something different (and easier).
As it's Visual Basic, you could try something more form-oriented, that is the original intent of the language.
There is the 3D engine list which lists three engine in pure basic (an oxymoron) + Source code and of them one is in Visual Basic (Dex3D)
DeX3D is an open source 3D engine
coded entirely in Visual Basic from
Jerry Chen ( -onlyuser#hotmail.com ).
Gouraud shading
Transparency
Fogging
Omni and spot lights
Hierarchical meshes
Support for 3D Studio files
Particle systems
Bezier curve segments
2.5 D text
Visual Basic source
More information, screenshots and the
source can be found on the Dex3D
Homepage. (<= Dead Link)
EGL25 by Erkan Sanli is a fast open source VB 6 renderer that can render, rotate, animate, etc. complex solid shapes made of thousands of polygons. Just Windows API calls – no DirectX, no OpenGL.
VBMigration.com chose EGL25 as a high-quality open-source VB6 project to demonstrate their VB6 to VB.Net upgrade tool.
A 3D software renderer as a whole project is fairly complex if you've never done it before. I would suggest something smaller - like just doing the 3D portion and using lines to do the rendering OR just write a shaded triangle renderer (which is the underpinnings of 3D renderers anyway).
Something a little simpler rather than trying to write a full-blown 3D software renderer on the first go - especially in VB.
A software renderer is a very difficult project and the language VB6 is not indicated at all ( for a task like this c++ is the way.. ), anyway I can suggest you some great books I used:
Shaders: http://wiki.gamedev.net/index.php/D3DBook:Introduction_%28Volume%29
Math: 3D Math Primer for Graphics and Game Development
There are other 2 books. Even if they are for VB.NET you can find some useful code:
.NET Game Programming with DirectX 9.0
Beginning .NET Game Programming in VB .NET
I think you can take two ways either go the Direct X way and use DirectX 8 that has VB 5-6 support. I found a page http://www.gamedev.net/reference/articles/article1308.asp
You can always write a engine group up but by doing so you will need some basic linear algebra like Frank Krueger suggests.