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• 2D camera perspective projection from 3D coordinates -- HOW?

  - by Jack

  I am developing a camera for a 2D game with a top-down view that has depth. It's almost a 3D camera. Basically, every object has a Z even though it is in 2D, and similarly to parallax layers their position, scale and rotation speed vary based on their Z. I guess this would be a perspective projection. But I am having trouble converting the objects' 3D coordinates into the 2D space of the screen so that everything has correct perspective and scale. I never learned matrices though I did dig the topic a bit today. I tried without using matrices thanks to this article but every attempt gave awkward results. I'm using ActionScript 3 and Flash 11+ (Starling), where the screen coordinates work like this: Left-handed coordinates system illustration I can explain further what I did if you want to help me sort out what's wrong, or you can directly tell me how you would do it properly. In case you prefer the former, read on. These are images showing the formulas I used: upload.wikimedia.org/math/1/c/8/1c89722619b756d05adb4ea38ee6f62b.png upload.wikimedia.org/math/d/4/0/d4069770c68cb8f1aa4b5cfc57e81bc3.png (Sorry new users can't post images, but both are from the wikipedia article linked above, section "Perspective projection". That's where you'll find what all variables mean, too) The long formula is greatly simplified because I believe a normal top-down 2D camera has no X/Y/Z rotation values (correct ?). Then it becomes d = a - c. Still, I can't get it to work. Maybe you could explain what numbers I should put in a(xyz), c(xyz), theta(xyz), and particularly, e(xyz) ? I don't quite get how e is different than c in my case. c.z is also an issue to me. If the Z of the camera's target object is 0, should the camera's Z be something like -600 ? ( = focal length of 600) Whatever I do, it's wrong. I only got it to work when I used arbitrary calculations that "looked" right, like most cameras with parallax layers seem to do, but that's fake! ;) If I want objects to travel between Z layers I might as well do it right. :) Thanks a lot for your help!

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• Pixmaps, ByteBuffers, and Textures....Oh my

  - by odaymichael

  My ultimate goal is to take a specific region of the screen, and redraw it somewhere else. For example, take a square from the upper left hand corner of the screen and redraw it on the lower right hand corner, so that it is basically a copy of that screen section; kind of like a minimap, but at the same scale as the original. I have looked in to pixmaps and bytebuffers. Also maybe copying that region from the backbuffer somehow. Wondering the best way to go about this. Any help is appreciated. I am using opengl es and libgdx for what it's worth.

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• JavaScript 3D space ship rotation

  - by user36202

  I am working with a fairly low-level JavaScript 3D API (not Three.js) which uses euler angles for rotation. In most cases, euler angles work quite well for doing things like aligning buildings, operating a hovercraft, or looking around in the first-person. However, in space there is no up or down. I want to control the ship's roll, pitch, and yaw. To do that, some people would use a local coordinate system or a permenant matrix or quaternion or whatever to represent the ship's angle. However, since I am not most people and am using a library that deals exclusively in euler angles, I will be using relative angles to represent how to rotate the ship in space and getting the resulting non-relative euler angles. For you math nerds, that means I need to convert 3 euler angles (with Y being the vertical axis, X representing the pitch, and Z representing a roll which is unaffected by the other angles, left-handed system) into a 3x3 orientation matrix, do something fancy with the matrix, and convert it back into the 3 euler angles. Euler to matrix to euler. Somebody has posted something similar to this on SO (http://stackoverflow.com/questions/1217775/rotating-a-spaceship-model-for-a-space-simulator-game) but he ended up just working with a matrix. This will not do for me. Also, I am using JavaScript, not C++. What I want essentially are the functions do_roll, do_pitch, and do_yaw which only take in and put out euler angles. Many thanks.

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• Material, Pass, Technique and shaders

  - by Papi75

  I'm trying to make a clean and advanced Material class for the rendering of my game, here is my architecture: class Material { void sendToShader() { program->sendUniform( nameInShader, valueInMaterialOrOther ); } private: Blend blendmode; ///< Alpha, Add, Multiply, … Color ambient; Color diffuse; Color specular; DrawingMode drawingMode; // Line Triangles, … Program* program; std::map<string, TexturePacket> textures; // List of textures with TexturePacket = { Texture*, vec2 offset, vec2 scale} }; How can I handle the link between the Shader and the Material? (sendToShader method) If the user want to send additionals informations to the shader (like time elapsed), how can I allow that? (User can't edit Material class) Thanks!

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• Elliptical orbit modeling

  - by Nathon

  I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every frame as appropriate given Newton's law of universal gravitation. The point masses don't move (there's only 1 right now) so I would expect an elliptical orbit. Instead, I see this: I've tried with nearly circular orbits, and I've tried making the masses vastly different (a factor of a million) but I always get this rotated orbit. Here's some (D) code, for context: void accelerate(Vector delta) { velocity = velocity + delta; // Velocity is a member of the ship class. } // This function is called every frame with the fixed mass. It's a // method of the ship's. void fall(Well well) { // f=(m1 * m2)/(r**2) // a=f/m // Ship mass is 1, so a = f. float mass = 1; Vector delta = well.position - loc; float rSquared = delta.magSquared; float force = well.mass/rSquared; accelerate(delta * force * mass); }

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• Water Simulation in LIBGDX [on hold]

  - by Noah Huppert

  I am doing some R&D for a game and am now tackling the topic of water. The goal Make water that can flow. Aka you can have an origin point that water shoots out from or a downhill slope. Make it so water splashes, so when an object hits the water there is a splash. Aka: Actual physics water sim. The current way I know how to do it I know how to create a shader that makes an object look like its water by making waves. Combined with that you can check to see if an object is colliding and apply an upwards force to simulate buoyancy. What is wrong with that way The water does not flow No splashes Possible solutions Have particles that are fairly large that interact with each other to simulate water Possible drawbacks Performance. Question: Is there a better way to do water or is using particles as described the only way?

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• How to model interentity membership in entity-component architecture?

  - by croxis

  I'm falling in love with simple grace of entity-component design, although I still have issues breaking from MVC and OOP practices. Some of my game entities have membership relationships with each other (ex: a player is a member of a city, a city is a member of a nation), and I am unsure on the best way to implement it. My initial reaction is to have a a MemberOfCity component that points to the appropriate city component, but components are suppose to have no references to each other. My other option is to have a System do it, but that would require the system to persist data outside of a component. Is there a clean way to do this in an entity-component design, or am I trying to use a hammer on a screw and should use a hybrid/another approach?

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• Android: how do I switch between game scenes in a game? Any tutorials?

  - by Flavio

  I am trying to create a simple game using the Android SDK without using AndEngine (or any other game engine). I have plenty of experience designing games from the past, but I'm having lots of trouble trying to use the Android SDK to make my game. By far my biggest hurdle right now is switching between views. That is, for example, going from the menu to the first level, etc. I am using a traditional model I learned (I think it's called a scene stack or something?) in which you push the current scene onto a stack and the game's main loop runs the top item of the stack. This model seems non-trivial to implement in the Android SDK, mostly because Android seems to be picky about which thread instantiates which view. My issue is that I want the first level to show up when you press a button on the main menu, but when I instantiate the first level (the level class extends SurfaceView and implements SurfaceHolder.Callback) I get a runtime error complaining that the thread that runs the main menu can't instantiate this class. Something about calling Looper.prepare(). I figured at this point I was probably doing things wrong. I'm not sure how to specifically phrase my issue into a question, so maybe I should leave it as either 1) Does anybody know a good way (or the 'proper' way) to switch between scenes in an Android game? or 2) Are there any tutorials out there which show how to create a game that doesn't take place entirely in one scene? (I have googled for a while to no avail... maybe someone else knows of one?) Thanks!

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• What is the practical use of IBOs / degenerate vertex in OpenGL?

  - by 0xFAIL

  Vertices in 3D models CAN get cut in the process of optimizing 3D geometry, (degenerate vertices) by 3D graphics software (Blender, ...) when exporting because they aren't needed when reusing a vertex for multiple triangles. (In the current case 3D data is exported from Blender as .ply and read by a simple application that displays the 3D model) Every vertex has a few attributes like position, color, normal, tangent,... But the data for each vertex that is cut through the vertex sharing is lost and is missing in the vertex shader. Modern shader techniques like Bump or Normal mapping require normals/tangents per vertex which are also cut. To use complex shader techniques IBOs must not be used? Or is there a way to use IBOs and retain the data per vertex that was origionally lost?

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• Setting Krypton Light to Screen Pixels

  - by Adam Jerrett

  So a few days back, I started playing around with Krypton XNA for 2D lighting in my game. I noticed in general, that spawning a light at (0,0) with Krypton causes the light to appear in, pretty much, the centre of the game screen. Is there any way to change this so a Krypton light's "starting point" at [0,0] would spawn at the top left of the screen, and thus follow the standard screen co-ordinates for position? I ask because currently I'm busy working on my game where my spawn point is [512,512]. With hard code, the closest I've got to the light being "central" to this point is the vector position [12,-20], which makes no sense and is impossible to craft, mathematically, if I want the light to move with the camera (the position [480,512] maps roughly to [10,-20]). So, is there any way to "normalise" the krypton lights to use standard screen co-ordinates? If you guys can, play around with the demo from the site and please see if you can find anything out about it. Documentation on the engine is rather scarce, so it's difficult to find anything relevant to my "pixel-perfect" need. It might just also be something in the code with regards to the matrices that I'm not fully understanding. Any help would be useful. Thanks.

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• 2D Car Simulation with Throttle Linear Physics

  - by James

  I'm trying to make a simulation game for an automatic cruise control system. The system simulates a car on varying inclinations and throttle speeds. I've coded up to the car physics but these do note make sense. The dynamics of the simulation are specified as follows: a = V' - V T = (k1)V + ?(k2) + ma V' = (1 - (k1 / m) V) + T - ( k2 / m) * ? Where T = throttle position k1 = viscous friction V = speed V' = next speed ? = angle of incline k2 = m g sin ? a = acceleration m = mass Notice that the angle of incline in the equation is not chopped up by sin or cos. Even the equation for acceleration isn't right. Can anyone correct them or am I misinterpreting the physics?

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• HLSL: Pack 4 values into 32 bit float.

  - by TheBigO

  I can't find any useful information on packing 4 values into a 32 bit float in HLSL. Ideally, what I want to be able to do in HLSL is: float4 values = ... // Some values where each component is between 0 and 1. float packedValues = pack32R(values); float4 values2 = unpack32R(packedValues); I realize that there will be precision limitations, and performance tradeoffs between different precisions in different methods. I'm just wondering what ideas are out there.

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• Inverse projection: question about w coordinate

  - by fayeWilly

  I have to perform in shader an inverse projection from a u/v of a render target. What I do is: Get NDC as 2*(u,v,depth) - 1 Then world space as tmp = (P*V)^-1 * (NDC,1.0); world space = tmp/tmp.w; This apparently works, but I am confused about the w division there. Why this work? Shouldn't be a multiplication by a w somewhere (as in the "forward" pipeline there is the perpsective division?) Thank you, Faye

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• How do I create a curved line or filled circle or generally a circle using C++/SDL?

  - by NoobScratcher

  Hello I've been trying for ages to make a pixel circle using the putpixel function provided by SDL main website here is that function : void putpixel(int x,int y , int color , SDL_Surface* surface) { unsigned int *ptr = static_cast <unsigned int *> (surface->pixels); int offset = y * (surface->pitch/sizeof(unsigned int)); ptr[offset + x] = color; } and my question is how do I curve a line or create an circle arc of pixels or any other curved shape then a rectangle or singular pixel or line. for example here are some pictures filled pixel circle below enter link description here now my idea was too change the x and y value of the pixel position using + and - to create the curves but in practice didn't provide the correct results what my results are in this is to be able to create a circle that is made out of pixels only nothing else. thank you for anyone who takes the time to read this question thanks! :D

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• Creating a level editor event system

  - by Vaughan Hilts

  I'm designing a level editor for game, and I'm trying to create sort of an 'event' system so I can chain together things. If anyone has used RPG Maker, I'm trying to do similar to their system. Right now, I have an 'EventTemplate' class and a bunch of sub-classed 'EventNodes' which basically just contain properties of their data. Orginally, the IAction and IExecute interface performed logic but it was moved into a DLL to share between the two projects. Question: How can I abstract logic from data in this case? Is my model wrong? Isn't cast typing expensive to parse these actions all the time? Should I write a 'Processor' class to execute these all? But then these actions that can do all sorts of things need to interact with all sorts of sub-systems.

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• Ideas for time-keeping in a webbased RPG?

  - by ashy_32bit

  I'm assigned a task of doing the preliminary research stuff for a web-based MMO RPG. Now my buggiest problem here is "web based" vs "MMO RPG". I did some research about time keeping systems and I'm totally confused as how exactly something as real-time as an MMO-RPG can work on some pull-only (unidirectional) platform like HTTP. I know there is also a turn-based alternative to time keeping but can it work in an MMO setting ? EDIT: Take a battle for example, player A (human) wants to attack Player B (also human) in the open. How does it work when when player A issues the "attack" command on player B ? how do I inform player B that he is being attacked ? and then how exactly the battle goes on between the two in an HTTP based communication channel? To my knowledge this is impossible unless you resort to another technology (HTML is 1-way, that is you can just ask server and get response, server can't update you unless being asked to. this is very well-known and simply explained). So I though maybe I can somehow change the whole timekeeping model from real-time to a more non-real-time model (towards a turn based RPG for example) and somehow work around the whole problem of "interactivity". EDIT2: It is not that I don't wanna use any server side technologies. For sure it is not gonna work client-side-only even for the most trivial of the multi-player games, let alone an RPG. So sure there would be a (probably complex) server side component to it (the so called Game Engine I suppose). The problem is not the technology that implements the logic (game mechanics) bits but the communication technology and how it limits the game mechanics abilities (like how real-time or turn based it is gonna be). HTTP is a request-response protocol meaning you get served only if you ask for it (explicitly send a GET or POST request to the server). HTTP server can not inform you if anything of interest happens in the game world unless you refresh the page (as some suggested) or you use some bi-directional tech (totally different animals) like Flash, WebSock, HTML5 etc etc. So maybe the question is: Is it possible to implement a MMORPG using only HTML5/PHP and no periodic page refreshes? if so what would be rules to make it an MMO-RPG? Can't explain it any clearer. Sorry :D

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• Creating an interactive grid for a puzzle game

  - by Noupoi

  I am trying to make a slitherlink game, and am not too sure how to approach creating the game, more specifically the grid structure on which the puzzle will be played on. This is what a empty and completed slitherlink grid would look like: The numbers in the squares are sort of clues and the areas between the dots need to be clickable: I would like to create the game in VB .NET. What data structures should I try to use, and would it be beneficial using any frameworks such as XNA?

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• Drawing a sprite or text causes the OpenGl rendering to 'disappear' in SFML

  - by Ken

  I'm using some SFML built in functions to draw sprites and text as an overlay on top of some OpenGL rending in an SFML RenderWindow. The opengl rendering appears fine until I add the code to draw the sprites or text. The sprite or text drawing causes the OpenGL stuff to disappear. The follow code show what I'm trying to do sf::RenderWindow window(sf::VideoMode(viewport.width,viewport.height,32), "SFML Window"); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0,viewport.width,0,viewport.height,0,1); while (window.pollEvent(Event)) { //event handling... //begin drawing glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glBegin(GL_TRIANGLES); glColor3f(col.x,col.y,col.z); for(int i=0;i<3;i++) glVertex2f(pos.x+verts[i].x,pos.y+verts[i].y); glEnd(); // adding this line causes all the previous opengl triangles not to appear window.draw("Sometext"); window.display(); }

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• Any significant performance cost to using BlendState.Premultiplied?

  - by Donutz

  Normally I guess you'd use BlendState.AlphaBlend because normally when you load your textures through the pipeline they're already premultiplied. However, if you're loading textures at runtime from PNGs or some such, you have to loop through the pixels and premultiply them, which can take a long time if you've got a lot of textures to load. So it looks (haven't tried it) like using BlendState.Premultiplied instead of BlendState.AlphaBlend should handle non-premultiplied textures and produce the same visual result, without all the startup costs. I have to wonder if there's a non-obvious cost to doing this, like a huge drop in performance or something. Anyone know?

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• How to create a reasonably sized urban area manually but efficiently

  - by Overv

  I have a game concept that only really works in an urban area that is of reasonable scale and diversity. In terms of what it should look like, think GTA, in terms of the size think more like a small neighbourhood with residents and a few local shops, perhaps a supermarket. I'm mostly experienced in programming and not at all with modelling, texturing or drawing, but I've found that SketchUp allows me to design interesting looking buildings that I model after real world buildings in my own neighbourhood. Designing these buildings and other objects can take from a few tens of minutes to a few hours. My question is: what is the best approach for a one man army like me who does manage to model buildings to create an interesting city environment in a reasonable amount of time? My game will not be based on procedural generation, the environment will actually be modelled like GTA cities.

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• Procedural terrains in 3D: what has been done ? Are there common algo and/or theories about it ?

  - by jokoon

  Besides programming, modeling an environment takes a great deal of time. I don't know about the work time involved, for example, in a WoW dungeon level, or other beautiful city-like, future environment, jungles, fantasy, etc, but this kind of work is made from scratch by artists. What are the techniques involved in the TorchLight level randomizer, and does other titles have similarities with this ? Is there a family name for such techniques ?

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• How to design a separated tutorial mode?

  - by Sylpheed

  I'm working on a "social" game that's about 90% completion. One of the remaining features is the tutorial mode. Basically, the tutorial mode will restrict the user to access some parts of UI and limit the features (like store items). The tutorial will only progress if a certain event is triggered, specifically following the tutorial. The code is ready and we already have an "almost" working game. The problem is I haven't foreseen the tutorial mode while I was doing those 90%. My requirement is there shouldn't be any loading/transition from tutorial mode to normal mode. This means I have to pick up the progress from the tutorial (no re-rendering of assets and stuff). How should I design this in a way where I won't touch anything from my old code? I want it to be as easy as just plugging it in. I don't want to jam the tutorial in my old code since this will lead to many bugs.

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• FBX Importer - Texture Name

  - by CmasterG

  I have a problem with the FBX SDK. I read in the data for the vertex position and the uv coordinates. It works fine, but now I want to read for each polygon to which texture it belongs, so that I can have models with multiple textures. Can anyone tell me how I can get the texture name (file name) for my polygon. My code to read in vertex position and uv coordinates is the following: int i, j, lPolygonCount = pMesh->GetPolygonCount(); FbxVector4* lControlPoints = pMesh->GetControlPoints(); int vertexId = 0; for (i = 0; i < lPolygonCount; i++) { int lPolygonSize = pMesh->GetPolygonSize(i); for (j = 0; j < lPolygonSize; j++) { int lControlPointIndex = pMesh->GetPolygonVertex(i, j); FbxVector4 pos = lControlPoints[lControlPointIndex]; current_model[vertex_index].x = pos.mData[0] - pivot_offset[0]; current_model[vertex_index].y = pos.mData[1] - pivot_offset[1]; current_model[vertex_index].z = pos.mData[2]- pivot_offset[2]; FbxVector4 vertex_normal; pMesh->GetPolygonVertexNormal(i,j, vertex_normal); current_model[vertex_index].nx = vertex_normal.mData[0]; current_model[vertex_index].ny = vertex_normal.mData[1]; current_model[vertex_index].nz = vertex_normal.mData[2]; //read in UV data FbxStringList lUVSetNameList; pMesh->GetUVSetNames(lUVSetNameList); //get lUVSetIndex-th uv set const char* lUVSetName = lUVSetNameList.GetStringAt(0); const FbxGeometryElementUV* lUVElement = pMesh->GetElementUV(lUVSetName); if(!lUVElement) continue; // only support mapping mode eByPolygonVertex and eByControlPoint if( lUVElement->GetMappingMode() != FbxGeometryElement::eByPolygonVertex && lUVElement->GetMappingMode() != FbxGeometryElement::eByControlPoint ) return; //index array, where holds the index referenced to the uv data const bool lUseIndex = lUVElement->GetReferenceMode() != FbxGeometryElement::eDirect; const int lIndexCount= (lUseIndex) ? lUVElement->GetIndexArray().GetCount() : 0; FbxVector2 lUVValue; //get the index of the current vertex in control points array int lPolyVertIndex = pMesh->GetPolygonVertex(i,j); //the UV index depends on the reference mode //int lUVIndex = lUseIndex ? lUVElement->GetIndexArray().GetAt(lPolyVertIndex) : lPolyVertIndex; int lUVIndex = pMesh->GetTextureUVIndex(i, j); lUVValue = lUVElement->GetDirectArray().GetAt(lUVIndex); current_model[vertex_index].tu = (float)lUVValue.mData[0]; current_model[vertex_index].tv = (float)lUVValue.mData[1]; vertex_index ++; } } float v1[3], v2[3], v3[3]; v1[0] = current_model[vertex_index - 3].x; v1[1] = current_model[vertex_index - 3].y; v1[2] = current_model[vertex_index - 3].z; v2[0] = current_model[vertex_index - 2].x; v2[1] = current_model[vertex_index - 2].y; v2[2] = current_model[vertex_index - 2].z; v3[0] = current_model[vertex_index - 1].x; v3[1] = current_model[vertex_index - 1].y; v3[2] = current_model[vertex_index - 1].z; collision_model->addTriangle(v1,v2,v3);

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• Is there an application that converts a PC into a video game kiosk/arcade machine?

  - by Rahil627

  Sorry to make the question so vague. What I ultimately want is software that allows people to play independent video games on a PC and not have to worry about maintaining it. Imagine a game that was made in a few hours that does not have a restart button and crashes often. It should be able to handle these kinds of things and do more! The software should: allow the game to be restarted manually handle game crashes (likely by restarting the game) restrict the user from doing anything crazy later... offer a UI to select the game from a list handle pre-configured key bindings cross-platform (start with windows) I just want to know if this exists already before I start creating one. As of now AutoHotKey is being used to do this sloppily. If such software does not exist then perhaps someone could recommend a general open source Kiosk software? Open Kiosk? I'll take anything. (I also could not find a related tag. Not even sure if this question should be here rather than stackoverflow)

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• Using SQL tables for storing user created level stats. Is there a better way?

  - by Ivan

  I am developing a racing game in which players can create their own tracks and upload them to a server. Players will be able to compare their best track times to their friends and see world records. I was going to generate a table for each track submitted to store the best times of each player who plays the track. However, I can't predict how many will be uploaded and I imagine too many tables might cause problems, or is this a valid method? I considered saving each player's best times in a string in a single table field like so: level1:00.45;level2:00.43;level3:00.12 If I did this I wouldn't need a separate table for each level (each level could just have a row in a 'WorldRecords' table). However, this just causes another problem because the text would eventually reach the limit for varchar length. I also considered storing the times data in XML files. This would avoid database issues and server disk space can be increased if needed. But I imagine this would be very slow. To update one players best time on one level, I would have to check every node in the file to find their time record to update. Apologies for the wall of text. Any suggestions would be appreciated.

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