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Search found 418 results on 17 pages for 'convex polygon'.

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• Delayed "rendering" of WPF/Silverlight Dependency Properties?

  - by Aardvark

  Is there a way to know the first time a Dependency Property is accessed through XAML binding so I can actually "render" the value of the property when needed? I have an object (class derived from Control) that has several PointCollection Dependency Properties that may contain 100's or 1000's of points. Each property may arrange the points differently for use in different types shapes (Polyline, Polygon, etc - its more complicated then this, but you get the idea). Via a Template different XAML objects use TemplateBinding to access these properties. Since my object uses a Template I never know what XAML shapes may be in use for my object - so I never know what Properties they may or may not bind to. I'd like to only fill-in these PointCollections when they are actually needed. Normally in .NET I'd but some logic in the Property's getter, but these are bypassed by XAML data binding. I need a WPF AND Silverlight compatible solution. I'd love a solution that avoids any additional complexities for the users of my object.

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• How do I prevent jagged edges alongside the surfaces of my 3d model?

  - by badcodenotreat

  Lets say I've implemented in openGL a crude model viewer with shading which renders a series of blocks, such that I have something that looks like this. http://i.imgur.com/TsF7K.jpg Whenever I rotate my model to the side, it causes an unwanted jagged effect along any surface with a steep viewing angle. http://i.imgur.com/Bgl9o.jpg I'm pretty sure this is due to the polygon offset I used to prevent z-fighting between the model and the wireframe, however I'm not able to find the factor/unit parameters in openGL which prevent this unwanted effect. what are the best values of factor and unit for glPolygonOffset to prevent this? would implementing anti-aliasing alleviate the problem? is the trade off in performance trivial/significant? is this perhaps a shading issue? should i try a solution along this line of thought?

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• Why use multiple OpenGL context

  - by Luca

  For rendering I have a current GL context, associated to a window. In the case the application render multiple scenes (for example using accumulation or different viewports) I think it is ok to reuse the same context. My question, indeed, is: why should I use multiple GL context? I red on ARB_framebuffer_object extension spec that MakeCurrent call could be expansive, and in the case the ARB_framebuffer_object extension is present I can render on a generic buffer without using MakeCurrent. Apparently the only reason to use multiple GL context is to avoid to setup context state (pixel store, transfer, point size, polygon stipple...) or to have avaialable multiple render buffers configuration (one context with accumulation, another without). How to determine when is better an alternative context instead of setting context state? Thankyou all!

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• iPhone - Drawing 2D Shapes

  - by Hawdon

  Hi guys! I have an array of 2D points which make an irregular polygon. What I want to do is draw the borders of it and then fill it with a color. I am using Cocos2d to code the game around, but I have not found a fill function in Cocos2d, only the ccDrawLine and such. Is there a simple way to draw filled shapes in Cocos2? I have also noted that Core Graphics would work beautifully for this purpose, but I am not able to integrate it with Cocos2d. I put this in to the draw function of my CCLayer: CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextClearRect(ctx, [[UIScreen mainScreen] bounds]); And every time I run it i get this error: <Error>: CGContextClearRect: invalid context I really need to get this working... Any ideas?

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• How to Convert ILayer to IPolygon In ArcObjects

  - by Scott

  Having trouble converting an Ilayer to an IPolygon. I am developing a toolbar for ArcMap and I grab a layer via code from the side table of contents. The Layer is a Polygon, but the code won't convert it to a IPolygon. Can anyone help me out? This is the code I am using to try and convert it to a IPolygon... IPolygon poly = m_document.Maps.get_Item(0).get_Layer(0) as IPolygon; I can do this: ILayer layer = m_document.Maps.get_Item(0).get_Layer(0) as ILayer; And that works, just not converting it to a IPloygon..

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• textures and vertex arrays with OpenGL?

  - by user146780

  Basically what I'd like to do is make textured NGONS. I also want to use a tesselator (GLU) to make concave and multicontour objects. I was wondering how the texture comes into play though. I think that the tesselator will return verticies so I will add these to my array, that's fine. But my vertex array will contain more than one polygon object so then how can I tell it when to bind the texture like in immediate mode? Right now I feel stuck with one call to bind. How can this be done? Thanks

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• WPF - Binding a variable in an already bound ListBox?

  - by Corey Ogburn

  I really don't know how to title this question, but I need some help with binding to a ListBox. I have an object, that contains (among other information) 2 properties that need to be bound in one ListBox. One of these is an ObservableCollection of objects, called Layers, and the other property holds an enum value of either Point, Line or Polygon, called SpatialType. These are to act as a legend to a map application. I have bound Layers to a ListBox, no problem, but inside the ListBox.ItemTemplate, I need to bind the single variable SpatialType to every Item in the ListBox. The problem I'm running into is that when I try to bind while inside the ListBox, the only variables I have access to are the properties of each Layer and I can't access any properties of the original bound class that holds the Layers (and the needed SpatialType property). What can I do to get that piece of information bound inside the ItemTemplate without messing up a good MVVM architecture?

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• Qt - invalid conversion to child class

  - by David Davidson

  I'm drawing polygons using the Graphics View framework. I added a polygon to the scene with this: QGraphicsPolygonItem *poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); poly->setPos(some_point); But I need to implement some custom behaviour like selection, mouse over indicator, and other similar stuff on the graphics item. So I declared a class that inherits QGraphicsPolygonItem: #include <QGraphicsPolygonItem> class GridHex : public QGraphicsPolygonItem { public: GridHex(QGraphicsItem* parent = 0); }; GridHex::GridHex(QGraphicsItem* parent) : QGraphicsPolygonItem(parent) { } Not doing much with that class so far, as you can see. But shouldn't replacing QGraphicsPolygonItem with my GridHex class? This is throwing a " invalid conversion from 'QGraphicsPolygonItem*' to 'GridHex*' " error: GridHex* poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); What am I doing wrong?

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• How can I display characters in a map by mapfile?

  - by sirius

  Hello. I'm trying to show a map using postGIS+Mapserver.And I've displayed a PNG picture in my WEB. However, I want to show some charactors in the map, just like this: this is the example from Mapserver Now I'm using database(postgreSQL), but not a shape file. How can I add the charactors then? Here is a part of my mapfile: LAYER CONNECTIONTYPE postgis NAME "state" //Connect to a remote spatial database CONNECTION "user=postgres dbname=*** host=*** password=***" PROCESSING "CLOSE_CONNECTION=DEFER" DATA "the_geom from province" STATUS ON TYPE POLYGON CLASS STYLE COLOR 122 122 122 OUTLINECOLOR 0 0 0 END LABEL COLOR 132 31 31 SHADOWCOLOR 218 218 218 SHADOWSIZE 2 2 TYPE TURETYPE FONT arial-bold SIZE 12 ANTIALIAS TRUE POSITION CL PARTIALS FALSE MINDISTANCE 300 BUFFER 4 END END Some said adding a "TEXT ([*])" in "LABEL", but I don't know howto? Thanks for your help!

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• Nesting maximum amount of shapes on a surface

  - by Fuu

  In industry, there is often a problem where you need to calculate the most efficient use of material, be it fabric, wood, metal etc. So the starting point is X amount of shapes of given dimensions, made out of polygons and/or curved lines, and target is another polygon of given dimensions. I assume many of the current CAM suites implement this, but having no experience using them or of their internals, what kind of computational algorithm is used to find the most efficient use of space? Can someone point me to a book or other reference that discusses this topic?

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• Plotting 3D Polygons in python-matplotlib

  - by Developer

  I was unsuccessful browsing web for a solution for the following simple question: How to draw 3D polygon (say a filled rectangle or triangle) using vertices values? I have tried many ideas but all failed, see: from mpl_toolkits.mplot3d import Axes3D from matplotlib.collections import PolyCollection import matplotlib.pyplot as plt fig = plt.figure() ax = Axes3D(fig) x = [0,1,1,0] y = [0,0,1,1] z = [0,1,0,1] verts = [zip(x, y,z)] ax.add_collection3d(PolyCollection(verts),zs=z) plt.show() I appreciate in advance any idea/comment. Updates based on the accepted answer: import mpl_toolkits.mplot3d as a3 import matplotlib.colors as colors import pylab as pl import scipy as sp ax = a3.Axes3D(pl.figure()) for i in range(10000): vtx = sp.rand(3,3) tri = a3.art3d.Poly3DCollection([vtx]) tri.set_color(colors.rgb2hex(sp.rand(3))) tri.set_edgecolor('k') ax.add_collection3d(tri) pl.show() Here is the result:

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• Can I show a single country (masked out) in GoogleMaps?

  - by NIclas Lindbegr

  Hello! Is it possible to mask away neighbor countries in GoogleMap? In my case I just want to show Sweden on one view. On a second view just Norway, Denmark etc etc... I know it is possible to draw polygon lines and fill them accordingly on to Maps API. Problem is that or the result sets get huge or the lines get very rough etc... Would be nice if GoogleMaps could deliver a country at the time without neighbors. Does anyone know about a good coordinate database with country borders? Best best regards, Niclas

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• manually create a plot frame in R

  - by tfarkas

  I need to control the style of a basic xy plot in R, and so have build the plotting area like this: frame() plot.window(xlim=c(0,1), ylim=c(-.6, .8)) axis(1, at=c(0, .2, .4, .6, .8, 1.0), lwd=2) axis(2, at=c(-.6, -.4, -.2, 0, .2, .4, .6, .8), lwd=2) I cannot, however, figure out how to create a physical frame around this plot (with lwd = 2). Is it possible (necessary?) to use line() or polygon()? Or is there something more built-in for this? I'm also interested in how to change the frame and axis weights for a plot created using the plot() function.

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• Calculate angle of moving ball after collision with angled or sloped wall that is a 2D line segment

  - by Ben Mc

  If you have a "ball" inside a 2D polygon, made up of say, 4 line segments that act as bounding walls, how do you calculate the angle of the ball after the collision with the irregularly sloped wall? I know how to make the ball bounce if the wall is horizontal, vertical, or at a 45 degree angle. I also have my code setup to detect a collision with the wall. I've read about dot products and normals, but I cannot figure out how to implement these in Java / Android. I'm completely stumped and feel like I've looked up everything 10 pages deep in Google 10 times now. I'm burned out trying to figure this out, I hope someone can help.

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• How to initialize an array of structures within a function?

  - by drtwox

  In the make_quad() function below, how do I set the default values for the vertex_color array in the quad_t structure? /* RGBA color */ typedef { uint8_t r,g,b,a; } rgba_t; /* Quad polygon - other members removed */ typedef { rgba_t vertex_color[ 4 ] } quad_t; Elsewhere, a function to make and init a quad: quad_t *make_quad() { quad_t *quad = malloc( sizeof( quad_t ) ); quad->vertex_color = ??? /* What goes here? */ return ( quad ); } Obviously I can do it like this: quad->vertex_color[ 0 ] = { 0xFF, 0xFF, 0xFF, 0xFF }; ... quad->vertex_color[ 3 ] = { 0xFF, 0xFF, 0xFF, 0xFF }; but this: quad->vertex_color = { { 0xFF, 0xFF, 0xFF, 0xFF }, { 0xFF, 0xFF, 0xFF, 0xFF }, { 0xFF, 0xFF, 0xFF, 0xFF }, { 0xFF, 0xFF, 0xFF, 0xFF } }; ...results in "error: expected expression before '{' token".

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• How to change the coordinate of a point that is inside a GraphicsPath?

  - by Ben

  Is there anyway to change the coordinates of some of the points within a GraphicsPath object while leaving the other points where they are? The GraphicsPath object that gets passed into my method will contain a mixture of polygons and lines. My method would want to look something like: void UpdateGraphicsPath(GraphicsPath gPath, RectangleF regionToBeChanged, PointF delta) { // Find the points in gPath that are inside regionToBeChanged // and move them by delta. // gPath.PathPoints[i].X += delta.X; // Compiles but doesn't work } GraphicsPath.PathPoints seems to be readonly, so does GraphicsPath.PathData.Points. So I am wondering if this is even possible. Perhaps generating a new GraphicsPath object with an updated set of points? How can I know if a point is part of a line or a polygon? If anyone has any suggestions then I would be grateful.

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• Fitting maximum amount of shapes on a surface

  - by Fuu

  In industry, there is often a problem where you need to calculate the most efficient use of material, be it fabric, wood, metal etc. So the starting point is X amount of shapes of given dimensions, made out of polygons and/or curved lines, and target is another polygon of given dimensions. I assume many of the current CAM suites implement this, but having no experience using them or of their internals, what kind of computational algorithm is used to find the most efficient use of space? Can someone point me to a book or other reference that discusses this subject?

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• Python. Draw rectangle in basemap

  - by user2928318

  I need to add several rectangles in my basemap. I nee four rectangles with lat and log ranges as below. 1) llcrnrlon=-10, urcrnrlon=10, llcrnrlat=35,urcrnrlat=60 2) llcrnrlon=10.5, urcrnrlon=35, llcrnrlat=35,urcrnrlat=60 3) llcrnrlon=35.5, urcrnrlon=52, llcrnrlat=30,urcrnrlat=55 4) llcrnrlon=-20, urcrnrlon=35, llcrnrlat=20,urcrnrlat=34.5 My script is below. I found "polygon" packages to add lines but I do not exactly know how to do. Please help me!! Thanks a lot for your help in advance! from mpl_toolkits.basemap import Basemap m=basemaputpart.Basemap(llcrnrlon=-60, llcrnrlat=20, urcrnrlon=60, urcrnrlat=70, resolution='i', projection='cyl', lon_0=0, lat_0=45) lon1=np.array([[-180.+j*0.5 for j in range(721)] for i in range(181)]) lat1=np.array([[i*0.5 for j in range(721)] for i in range(181) ]) Nx1,Ny1=m(lon1,lat1,inverse=False) toplot=data[:,:] toplot[data==0]=np.nan toplot=np.ma.masked_invalid(toplot) plt.pcolor(Nx1,Ny1,np.log(toplot),vmin=0, vmax=5) cbar=plt.colorbar() m.drawcoastlines(zorder=2) m.drawcountries(zorder=2) plt.show()

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• Is this possible with OpenGL?

  - by user146780

  Basically what I'd like to do is make textured NGONS. I also want to use a tesselator (GLU) to make concave and multicontour objects. I was wondering how the texture comes into play though. I think that the tesselator will return verticies so I will add these to my array, that's fine. But my vertex array will contain more than one polygon object so then how can I tell it when to bind the texture like in immediate mode? Right now I feel stuck with one call to bind. How can this be done? Thanks

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• Structure of Astar (A*) graph search data in C#

  - by Shawn Mclean

  How do you structure you graphs/nodes in a graph search class? I'm basically creating a NavMesh and need to generate the nodes from 1 polygon to the other. The edge that joins both polygons will be the node. I'll then run A* on these Nodes to calculate the shortest path. I just need to know how to structure my classes and their properties? I know for sure I wont need to create a fully blown undirected graph with nodes and edges.

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• Help with memory leak (malloc)

  - by user146780

  I'v followed a tutorial to use OGL tesselaton. In one of the callbacks there is a malloc and it creates a leak every time I render a new frame. void CALLBACK combineCallback(GLdouble coords[3], GLdouble *vertex_data[4], GLfloat weight[4], GLdouble **dataOut) { GLdouble *vertex; vertex = (GLdouble *) malloc(6 * sizeof(GLdouble)); vertex[0] = coords[0]; vertex[1] = coords[1]; vertex[2] = coords[2]; for (int i = 3; i < 6; i++) { vertex[i] = weight[0] * vertex_data[0][i] + weight[1] * vertex_data[0][i] + weight[2] * vertex_data[0][i] + weight[3] * vertex_data[0][i]; } *dataOut = vertex; } I'v tried to free(vertex) but then the polygons did not render. I also tried allocating on the heap then doing delete(vertex) but then the polygon rendered awkwardly. I'm not sure what to do. Thanks

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• box2d resize bodies arround point

  - by philipp

  I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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• Crash when using datablocks

  - by scorcher24

  I have really throughly searched the net and could not find any solution for this so I ask for help here. Anyway, I have this datablock in datablocks.cs: datablock t2dSceneObjectDatablock(EnemyShipConfig) { canSaveDynamicFields = "1"; Layer = "3"; size = "64 64"; CollisionActiveSend = "1"; CollisionActiveReceive = "1"; CollisionCallback = true; CollisionLayers = "3"; CollisionDetectionMode = "POLYGON"; CollisionPolyList = "0.00 -0.791 0.756 0.751 -0.746 0.732"; UsesPhysics = "0"; Rotation = "-90"; WorldLimitMode = "KILL"; WorldLimitMax = "880 360"; WorldLimitMin = "-765 -436"; minFireRate = "2000"; maxFireRate = "1200"; laserSpeed = "800"; minSpeed = "100"; maxSpeed = "150"; }; This is an exact reproduction of an object that I have manually edited in the editor. So far, I just used clone() to get as many enemies as I need, while it was out of sight. It is a r-type style shooter, so I need a variable amount of enemies. Since clone() spams my log, I decided to use datablocks, since it is also more flexible. That's what I get when I use clone(): Con::execute - 0 has no namespace: onRemoveFromScene However, once spawning begins, my game freezes and crashes: function SpawnEnemy() { //%spawnedEnemy = EnemyShipMaster.clone(true); %spawnedEnemy = new t2dStaticSprite() { class = "EnemyShip"; sceneGraph = $global_sceneGraph; datablock = "EnemyShipConfig"; imageMap = "starshipImageMap"; layer = 3; }; %speed = getRandom(%spawnedEnemy.minSpeed, %spawnedEnemy.maxSpeed); %y = getRandom(-320, 320); // Set Properties %spawnedEnemy.setPositionX(700); %spawnedEnemy.setPositionY(%y); %spawnedEnemy.setVisible(true); %spawnedEnemy.setLinearVelocityX( -%speed ); %spawnedEnemy.setTimerOn( getRandom( %spawnedEnemy.maxFireRate, %spawnedEnemy.minFireRate ) ); } // Definition of $global_sceneGraph from game.cs: $global_sceneGraph = sceneWindow2D.loadLevel(%level); As I said, it works fine when I use clone() (which is commented out here), but my log gets spammed. I really hope someone can shed some light for me, this is driving me crazy.

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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• Sparse (Pseudo) Infinite Grid Data Structure for Web Game

  - by Ming

  I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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