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• Moving objects colliding when using unalligned collision avoidance (steering)

  - by James Bedford

  I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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• "Walking" along a rotating surface in LimeJS

  - by Dave Lancea

  I'm trying to have a character walk along a plank (a long, thin rectangle) that works like a seesaw, being rotated around a central point by box2d physics (falling objects). I want the left and right arrow keys to move the player up and down the plank, regardless of it's slope, and I don't want to use real physics for the player movement. My idea for achieving this was to compute the coordinate based on the rotation of the plank and the current location "up" or "down" the board. My math is derived from here: http://math.stackexchange.com/questions/143932/calculate-point-given-x-y-angle-and-distance Here's the code I have so far: movement = 0; if(keys[37]){ // Left movement = -3; } if(keys[39]){ // Right movement = 3; } // this.plank is a LimeJS sprite. // getRotation() Should return an angle in degrees var rotation = this.plank.getRotation(); // this.current_plank_location is initialized as 0 this.current_plank_location += movement; var x_difference = this.current_plank_location * Math.cos(rotation); var y_difference = this.current_plank_location * Math.sin(rotation); this.setPosition(seesaw.PLANK_CENTER_X + x_difference, seesaw.PLANK_CENTER_Y + y_difference); This code causes the player to swing around in a circle when they are out of the center of the plank given a slight change in rotation of the plank. Any ideas on how I can get the player position to follow the board position?

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• Confused about implementing Single Responsibility Principle

  - by HichemSeeSharp

  Please bear with me if the question looks not well structured. To put you in the context of my issue: I am building an application that invoices vehicles stay duration in a parking. In addition to the stay service there are some other services. Each service has its own calculation logic. Here is an illustration (please correct me if the design is wrong): public abstract class Service { public int Id { get; set; } public bool IsActivated { get; set; } public string Name { get; set } public decimal Price { get; set; } } public class VehicleService : Service { //MTM : many to many public virtual ICollection<MTMVehicleService> Vehicles { get; set; } } public class StayService : VehicleService { } public class Vehicle { public int Id { get; set; } public string ChassisNumber { get; set; } public DateTime? EntryDate { get; set; } public DateTime? DeliveryDate { get; set; } //... public virtual ICollection<MTMVehicleService> Services{ get; set; } } Now, I am focusing on the stay service as an example: I would like to know at invoicing time which class(es) would be responsible for generating the invoice item for the service and for each vehicle? This should calculate the duration cost knowing that the duration could be invoiced partially so the like is as follows: not yet invoiced stay days * stay price per day. At this moment I have InvoiceItemsGenerator do everything but I am aware that there is a better design.

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• Rope Colliding with a Rectangle

  - by Colton

  I have my rope, and I have my rectangles. The rope is similar to the implementation found here: http://nehe.gamedev.net/tutorial/rope_physics/17006/ Now, I want to make the rope properly collide with the rectangle such that the rope will not pass through a rectangle, and wrap around the rectangle and all that good stuff. Currently, I have it set so no rope node can pass through a rect (successfully), however, this means a rope segment can still pass through a block. Ex: So the question is, what can I do to fix this? What I have tried: I create a rectangle between two nodes of a rope, calculate rotation between the nodes, and get myself a transformed rectangle. I can successfully detect a collision between rope segments and a (non-transformed) rectangle. Create a new node or pivot point around the corner of the block, and rearrange nodes to point to the corner node. Trouble is determining what corner the rope segment is passing through. And then the current rope setup goes wonky (based on verlet integration, so a sudden change in position causes the rope to wiggle like a seismograph during a magnitude 8 earth quake.) Among other issues that might be solvable, but its turning into a case by case thing, which doesn't seem right. I think the best answer here would just be a link to a tutorial (I simply can't find any, most lead to box2D or farseer, but I want to at least learn how it works before I hide behind an engine).

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• Japanese Multiplication simulation - is a program actually capable of improving calculation speed?

  - by jt0dd

  On SuperUser, I asked a (possibly silly) question about processors using mathematical shortcuts and would like to have a look at the possibility at the software application of that concept. I'd like to write a simulation of Japanese Multiplication to get benchmarks on large calculations utilizing the shortcut vs traditional CPU multiplication. I'm curious as to whether it makes sense to try this. My Question: I'd like to know whether or not a software math shortcut, as described above is actually a shortcut at all. This is a question of programming concept. By utilizing the simulation of Japanese Multiplication, is a program actually capable of improving calculation speed? Or am I doomed from the start? The answer to this question isn't required to determine whether or not the experiment will succeed, but rather whether or not it's logically possible for such a thing to occur in any program, using this concept as an example. My theory is that since addition is computed faster than multiplication, a simulation of Japanese multiplication may actually allow a program to multiply (large) numbers faster than the CPU arithmetic unit can. I think this would be a very interesting finding, if it proves to be true. If, in the multiplication of numbers of any immense size, the shortcut were to calculate the result via less instructions (or faster) than traditional ALU multiplication, I would consider the experiment a success.

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• Defining formula through user interface in user form

  - by BriskLabs Pakistan

  I am a student and developing a simple assignment - windows form application in visual studio 2010. The application is suppose to construct formulas as per user requirement. The process: It has to pick data from columns of Microsoft Access database and the user should be able to pick the data by column name like we do in a drop down menu. and create reusable formulas in it ( configure it once and can change it again). followings are column titles from database that can be picked for example. e.g Col -1 : Marks in Maths Col -2 : Total Marks in Maths Col -3 : Marks in science Col -4 : Total marks in science Finally we should be able to construct any formula in the UI like (Col 1 + Col 3 ) / ( col 2 + col 4) = Formula 1 once this is formula is set saved and a name is assigned to it by user. he/she can use the formula and results shall appear in a window below. i.e He would be able to calculate his desired figures (formula) by only manipulating underlying data on the UI layer....choose the data for a period and apply the formula and get the answer Problem: It looks like I have to create an app where rules are set through UI....... this means no stored procedures are required in SQL.... please suggest the right approach.

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• Two Copies of "Silverlight 5 In Action" to Give Away and a FREE chapter!

  - by Dave Campbell

  I know most of you have seen my post from Tuesday where I talked about giving away 2 copies of Pete's book on Monday morning July 18th. Well... I'm repeating it, because it's a smoking deal... for the cost of an email you too can take a shot at getting Pete's latest released "Silverlight 5 In Action" free. 2 Important Pieces of Information 1) The deadline: midnight Sunday night, July 17, 2012, Arizona time... if you know me, you know I've lived here too long and am timezone stupid... so don't make me calculate it out :) 2) The how: I have a special email address for submittals: mailto:[email protected]?Subject=Giveaway. 3) oh yeah... I lied about only 2 pieces of info... number 3 ... there may be other surprises on Monday morning... 'nuff said 4) and just to pump up the volume on the book... how about a Free chapter you can read right here on Working with RSS and Atom! 5) send me an email and Stay in the 'Light!

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• "unresolvable problem" error when upgrading from 12.04 to 14.04

  - by flyingfisch

  So I have solved this issue, but now I have another problem: An unresolvable problem occurred while calculating the upgrade. This can be caused by: * Upgrading to a pre-release version of Ubuntu * Running the current pre-release version of Ubuntu * Unofficial software packages not provided by Ubuntu If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. I am not upgrading to a pre-release version of Ubuntu and I am not running a pre-release either. I have unchecked all my 3rd-party packages using Ubuntu Software Manager, EditSoftware Sources... What else might be wrong? UPDATE After doing sudo update-manager -d and sudo apt-get update;sudo apt-get dist-upgrade as per JimB's post, and then running sudo do-release-upgrade, here what I get: Err http://extras.ubuntu.com trusty/main Translation-en Err http://extras.ubuntu.com trusty/main Translation-en_US Err http://extras.ubuntu.com trusty/main Translation-en Ign http://extras.ubuntu.com trusty/main Translation-en_US Ign http://extras.ubuntu.com trusty/main Translation-en Fetched 0 B in 0s (0 B/s) Checking package manager Reading package lists... Done Building dependency tree Reading state information... Done Building data structures... Done Calculating the changes Calculating the changes Could not calculate the upgrade An unresolvable problem occurred while calculating the upgrade. This can be caused by: * Upgrading to a pre-release version of Ubuntu * Running the current pre-release version of Ubuntu * Unofficial software packages not provided by Ubuntu If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. Restoring original system state Aborting Reading package lists... Done Building dependency tree Reading state information... Done Building data structures... Done === Command detached from window (Mon Aug 18 23:53:10 2014) === === Command terminated with exit status 1 (Mon Aug 18 23:53:10 2014) ===

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• Microeconomical simulation: coordination/planning between self-interested trading agents

  - by Milton Manfried

  In a typical perfect-information strategy game like Chess, an agent can calculate its best move by searching the state tree for the best possible move, while assuming that the opponent will also make the best possible move (i.e. Mini-max). I would like to use this approach in a "game" modeling economic activity, where the possible "moves" would be to buy or sell for a given price, and the goal, rather than a specific class of states (e.g. Checkmate), would be to maximize some function F of the agent's state (e.g. F(money, widget) = 10*money + widget). How to handle buy/sell actions that require coordination between both parties, at the very least agreement upon a price? The cheap way out would be to set the price beforehand, maybe based upon the current supply -- but the idea of this simulation is to examine how prices emerge when freely determined by "perfectly rational" agents. A great example of what I do not want is the trading algorithm in SugarScape -- paraphrasing from Growing Artificial Societies p101-102: when a pair of agents interact to trade, they each compute their internal valuations of the goods, then a bargaining process is conducted and a price is agreed to. If this price makes both agents better off, they complete the transaction The protocol itself is beautiful, but what it cannot capture (as far as I can tell) is the ability for an agent to pay more than it might otherwise for a good, because it knows that it can sell it for even more at a later date -- what appears to be called "strategic thinking" in this pape at Google Books Multi-Agent-Based Simulation III: 4th International Workshop, MABS 2003... to get realistic behavior like that, it seems one would either (1) have to build an outrageously-complex internal valuation system which could at best only cover situations that were planned for at compile-time, or otherwise (2) have some mechanism to search the state tree... which would require some way of planning future trades. Note: The chess analogy only works as far as the state-space search goes; the simulation isn't intended to be "zero sum", so a literal mini-max search wouldn't be appropriate -- and ideally, it should work with more than two agents.

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• Clean MVC design when there is viewer latency

  - by Tony Suffolk 66

  It isn't clear if this question has already been answered, so apologies in advance if this is a duplicate : I am implementing a game and trying to design around a clean MVC pattern - so my Control plane will implement the rules of the game (but not how the game is displayed), and the View plane implements how the game is displayed, and user iteraction - i.e. what game items or controls the user has activated. The challenge that I have is this : In my game the Control Plane can move game items more or less instaneously (The decision about what item to place where - and some of the initial consequences of that placement are reasonably trivial to calculate), but I want to design the Control Plane so that the View plane can display these movements either instaneously or using movement animations. The other complication is that player interaction must be locked out while those game items are moving (similar to chess - you can't attack an opposing piece as it moves past one of your pieces) So do I : Implement all the logic in the Control Plane asynchronously - and separate the descision making from the actions - so the Control plane decides piece 'A' needs to move to a given place - tells the view plane, and but does not implement the move in data until the view plane informs the control plane that the move/animation is complete. A lot of interlock points between the two layers. Implement all the control plane logic in one place - decisions and movement (keeping track of what moved where), and pass all the movements in one go to the View plane to do with what it will. Control Plane is almost fire and forget here. A hybrid of 1 & 2 - The control plane implements all the moves in a temporary data store - but maintains a second store which reflects what is actually visible to the viewer, based on calls and feedback from the View plane. All 3 are relatively easy to implement (target language is python), but having never done a clean MVC pattern with view latency before - I am not sure which design is best

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• Java : 2D Collision Detection

  - by neko

  I'm been working on 2D rectangle collision for weeks and still cannot get this problem fixed. The problem I'm having is how to adjust a player to obstacles when it collides. I'm referencing this link. The player sometime does not get adjusted to obstacles. Also, it sometimes stuck in obstacle guy after colliding. Here, the player and the obstacle are inheriting super class Sprite I can detect collision between the two rectangles and the point by ; public Point getSpriteCollision(Sprite sprite, double newX, double newY) { // set each rectangle Rectangle spriteRectA = new Rectangle( (int)getPosX(), (int)getPosY(), getWidth(), getHeight()); Rectangle spriteRectB = new Rectangle( (int)sprite.getPosX(), (int)sprite.getPosY(), sprite.getWidth(), sprite.getHeight()); // if a sprite is colliding with the other sprite if (spriteRectA.intersects(spriteRectB)){ System.out.println("Colliding"); return new Point((int)getPosX(), (int)getPosY()); } return null; } and to adjust sprites after a collision: // Update the sprite's conditions public void update() { // only the player is moving for simplicity // collision detection on x-axis (just x-axis collision detection at this moment) double newX = x + vx; // calculate the x-coordinate of sprite move Point sprite = getSpriteCollision(map.getSprite().get(1), newX, y);// collision coordinates (x,y) if (sprite == null) { // if the player is no colliding with obstacle guy x = newX; // move } else { // if collided if (vx > 0) { // if the player was moving from left to right x = (sprite.x - vx); // this works but a bit strange } else if (vx < 0) { x = (sprite.x + vx); // there's something wrong with this too } } vx=0; y+=vy; vy=0; } I think there is something wrong in update() but cannot fix it. Now I only have a collision with the player and an obstacle guy but in future, I'm planning to have more of them and making them all collide with each other. What would be a good way to do it? Thanks in advance.

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• How can Agile methodologies be adapted to High Volume processing system development?

  - by luckyluke

  I am developing high volume processing systems. Like mathematical models that calculate various parameters based on millions of records, calculated derived fields over milions of records, process huge files having transactions etc... I am well aware of unit testing methodologies and if my code is in C# I have no problem in unit testing it. Problem is I often have code in T-SQL, C# code that is a SQL stored assembly, and SSIS workflow with a good amount of logic (and outcomes etc) or some SAS process. What is the approach YOu use when developing such systems. I usually develop several tests as Stored procedures in a designed schema(TEST) and then automatically run them overnight and check out the results. But this is only for T-SQL. And Continous integration IS hard. But the problem is with testing SSIS packages. How do You test it? What is Your preferred approach for stubbing data into tables (especially if You need a lot data initialization). I have some approach derived over the years but maybe I am just not reading enough articles. So Banking, Telecom, Risk developers out there. How do You test your mission critical apps that process milions of records at end day, month end etc? What frameworks do You use? How do You validate that Your ssis package is Correct (as You develop it)/ How do You achieve continous integration in such an environment (Personally I never got there)? I hope this is not to open-ended question. How do You test Your map-reduce jobs for example (i do not use hadoop but this is quite similar). luke Hope that this is not too open ended

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• Track sales and commission with third-party tool

  - by Andrew

  I have a clothing website where I link to various clothing retailers. I have reached an agreement with one of the retailers whereby they will pay a commission to us for every sale they make from traffic that was referred by our site. I need a mechanism for tracking how much commission should be paid to us, that involves as little work as possible to implement from their side. We both have Google Analytics. Option 1: They record a goal in their GA account whenever someone makes a purchase on their site. They see how many completed goals are marked as referral traffic from our site and calculate commission accordingly. The problem with this is that the whole process of calculating and paying commission will be manual. They will need to frequently check how many sales were generated by referral traffic from our site, and probably we will have to chase them for commission payments. Also - since we won't have access to their GA data - we will need to trust that they report all sales accurately. Option 2: Sign them up to an affiliate network like Commission Junction or Google's Affiliate Network, and connect to them through this network. The problem with this solution is that it seems too heavyweight; ideally we don't want to ask a retailer to go through the whole sign up process just to deal with us and pay us commission. I am assuming that there must be some lightweight service that tracks the number of sales by one site and pays commission accordingly to the other site, where the sign up and installation procedure is simple and fast.

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• Parsing mathematical experssions with two values that have parenthesis and minus signs

  - by user45921

  I'm trying to parse equations like these which only has two values or the square root of a certain value from a text file: 100+100 -100-100 -(100)+(-100) sqrt(100) by the minues signs, parenthesis and the operator symbol in the middle and the square root, and I have no idea how to start off... I've got the file part done and the simple calculation parts except that I couldnt get my program to solve the equations in the above. #include <stdio.h> #include <string.h> #include <stdlib.h> #include <math.h> main(){ FILE *fp; char buff[255], sym,sym2,del1,del2,del3,del4; double num1, num2; int ret; fp = fopen("input.txt","r"); while(fgets(buff,sizeof(buff),fp)!=NULL){ char *tok = buff; sscanf(tok,"%lf%c%lf",&num1,&sym,&num2); switch(sym){ case '+': printf("%lf\n", num1+num2); break; case '-': printf("%lf\n", num1-num2); break; case '*': printf("%lf\n", num1*num2); break; case '/': printf("%lf\n", num1/num2); break; default: printf("The input value is not correct\n"); break; } } fclose(fp); } that is what have I written for the other basic operations without parenthesis and the minus sign for the second value and it works great for the simple ones. I'm using a switch method to calculate the add, sub, mul and divide but I'm not sure how to properly use the sscanf function (if I am not using it properly) or if there is another way using a function like strtok to properly parse the parenthesis and the minus signs. Any kind help?

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• How to use mount points in MilkShape models?

  - by vividos

  I have bought the Warriors & Commoners model pack from Frogames and the pack contains (among other formats) two animated models and several non-animated objects (axe, shield, pilosities, etc.) in MilkShape3D format. I looked at the official "MilkShape 3D Viewer v2.0" (msViewer2.zip at http://www.chumba.ch/chumbalum-soft/ms3d/download.html) source code and implemented loading the model, calculating the joint matrices and everything looks fine. In the model there are several joints that are designated as the "mount points" for the static objects like axe and shield. I now want to "put" the axe into the hand of the animated model, and I couldn't quite figure out how. I put the animated vertices in a VBO that gets updated every frame (I know I should do this with a shader, but I didn't have time to do this yet). I put the static vertices in another VBO that I want to keep static and not updated every frame. I now tried to render the animated vertices first, then use the joint matrix for the "mount joint" to calculate the location of the static object. I tried many things, and what about seems to be right is to transpose the joint matrix, then use glMatrixMult() to transform the modelview matrix. For some objects like the axe this is working, but not for others, e.g. the pilosities. Now my question: How is this generally implemented when using bone/joint models, and especially with MilkShape3D models? Am I on the right track?

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• Calculating up-vector to avoid gimbal lock using euler angles

  - by jessejuicer

  I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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• Frame Independent Movement

  - by ShrimpCrackers

  I've read two other threads here on movement: Time based movement Vs Frame rate based movement?, and Fixed time step vs Variable time step but I think I'm lacking a basic understanding of frame independent movement because I don't understand what either of those threads are talking about. I'm following along with lazyfoo's SDL tutorials and came upon the frame independent lesson. http://lazyfoo.net/SDL_tutorials/lesson32/index.php I'm not sure what the movement part of the code is trying to say but I think it's this (please correct me if I'm wrong): In order to have frame independent movement, we need to find out how far an object (ex. sprite) moves within a certain time frame, for example 1 second. If the dot moves at 200 pixels per second, then I need to calculate how much it moves within that second by multiplying 200 pps by 1/1000 of a second. Is that right? The lesson says: "velocity in pixels per second * time since last frame in seconds. So if the program runs at 200 frames per second: 200 pps * 1/200 seconds = 1 pixel" But...I thought we were multiplying 200 pps by 1/1000th of a second. What is this business with frames per second? I'd appreciate if someone could give me a little bit more detailed explanation as to how frame independent movement works. Thank you.

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• How do I apply 2 rotations about different points to a single primitive using OpenGL

  - by Fenoec

  I'm working on a 2D top-down shooter game that has a rotation feature like Realm Of The Mad God such that if you press e the camera rotates around the character in a clockwise direction and q rotates the camera around the character in a counterclockwise direction. I have this working with my floors and walls by translating to the character, doing the screen rotation, and drawing everything with the character as the origin. The problem arises when I shoot projectiles which need to both rotate around the character and rotate around themselves (shooting uses the mouse cursor so I can shoot at any angle). For example, if the screen is not rotated and I'm shooting rectangular projectiles, I want them to face in the direction I'm shooting (rotation around themselves). However if I only do this rotation, when I then rotate the screen the projectiles will always shoot at the same position because my cursor position does not change. Therefore I need to also either rotate the projectiles around the character or rotate the mouse cursor position to get the correct position (which would then totally screw up all of the collision detection). Likewise if I only do the screen rotation on projectiles, the rectangles will always be facing the same way and they would only look correct if I were shooting straight up or straight down. So my question is, how can I perform 2 rotations on a primitive around 2 different points? The only way I can think of is to translate to the character and do the screen rotation, then somehow calculate the translation required to move back to the middle of the projectile (seeing as how my axes are now rotated) and do its rotation. Or am I thinking about this in the wrong way and there is a different solution to accomplishing this effect?

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• Estimate angle to launch missile, maths question

  - by Jonathan

  I've been working on this for an hour or two now and my maths really isn't my strong suit which is definitely not a good thing for a game programmer but that shouldn't stop me enjoying a hobby surely? After a few failed attempts I was hoping someone else out there could help so here's the situation. I'm trying to implement a bit of faked intelligence when the A.I fires it's missiles at a target in a 2D game world. By predicting the likely position the target will be in given it's current velocity and the time it will take the missile to reach it's target. I created an image to demonstrate my thinking: http://i.imgur.com/SFmU3.png which also contains the logic I use for accelerating the missile after launch. The ship that fires the missile can fire within a total of 40 degree angle, 20 either side of itself, but this could likely become variable. My current attempt was to break the space between the two lines into segments which match the targets width. Then calculate the time it would take the missile to get to that location using the formula. So for each iteration of this we total up the values and that tells us the distance travelled, ad it would then just need compared to distance to the segment. startVelocity * ((startVelocity * acceleration)^(currentframe-1) So for example. If we start at a velocity of 1f/frame with an acceleration of 0.1f the formula, at frame 4, would be 1 * (1.1^3) = 1.331 But I quickly realized I was getting lost when trying to put this into practice. Does this seem like a correct starting point or am I going completely the wrong way about it? Any pointers would help me greatly. Maths really isn't my strong suit so I get easily lost in these matters and don't even really know a good phrase to search for with this. So I guess in summary my question is more about the correct way to approach this problem and any additional code samples on top of that would be great but I'm not averse to working out the complete code from helpful pointers.

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• Optimal communication pattern to update subscribers

  - by hpc

  What is the optimal way to update the subscriber's local model on changes C on a central model M? ( M + C - M_c) The update can be done by the following methods: Publish the updated model M_c to all subscribers. Drawback: if the model is big in contrast to the change it results in much more data to be communicated. Publish change C to all subscribes. The subscribers will then update their local model in the same way as the server does. Drawback: The client needs to know the business logic to update the model in the same way as the server. It must be assured that the subscribed model stays equal to the central model. Calculate the delta (or patch) of the change (M_c - M = D_c) and transfer the delta. Drawback: This requires that calculating and applying the delta (M + D_c = M_c) is an cheap/easy operation. If a client newly subscribes it must be initialized. This involves sending the current model M. So method 1 is always required. Think of playing chess as a concrete example: Subscribers send moves and want to see the latest chess board state. The server checks validity of the move and applies it to the chess board. The server can then send the updated chessboard (method 1) or just send the move (method 2) or send the delta (method 3): remove piece on field D4, put tower on field D8.

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• Calculating a child object's Position, Rotation and Scale values?

  - by Sergio Plascencia

  I am making my own game editor, but have encountered the following problem: I have two objects, A and B. A's initial values: Position: (3,3,3), Rotation: (45,10,0), Scale(1,2,2.5) B's initial values: Position: (1,1,1), Rotation: (10,34,18), Scale(1.5,2,1) If I now make B a child of A, I need to re-calculate the B's Position, Rotation and Scale relative to A such that it maintains its current position, rotation and scale in world coordinates. So B's position would now be (-2, -2, -2) since now A is its center and (-2, -2, -2) will keep B in the same position. I think I got the Position and scale figured out, but not rotation. So I opened Unity and ran the same example and I noticed that when making a child object, the child object did not move at all. but had its Position, Rotation and Scale values changed relative to the parent. For example: Unity (Parent Object "A"): Position: (0,0,0) Rotation: (45,10,0) Scale: (1,1,1) Unity (Child Object "B"): Position: (0,0,0) Rotation: (0,0,0) Scale: (1,1,1) When B becomes a child of A, it's rotation values become: X: -44.13605 Y: -14.00195 Z: 9.851074 If I plug the same rotation values into the B object in my editor, the object does not move at all. How did Unity arrive at those rotation values for the child? What are the calculations? If you can put all the equations for the Position, Rotation or Scale then I can double check I am doing it correctly but the Rotation is what I really need.

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• Cutting out smaller rectangles from a larger rectangle

  - by Mauro Destro

  The world is initially a rectangle. The player can move on the world border and then "cut" the world via orthogonal paths (not oblique). When the player reaches the border again I have a list of path segments they just made. I'm trying to calculate and compare the two areas created by the path cut and select the smaller one to remove it from world. After the first iteration, the world is no longer a rectangle and player must move on border of this new shape. How can I do this? Is it possible to have a non rectangular path? How can I move the player character only on path? EDIT Here you see an example of what I'm trying to achieve: Initial screen layout. Character moves inside the world and than reaches the border again. Segment of the border present in the smaller area is deleted and last path becomes part of the world border. Character moves again inside the world. Segments of border present in the smaller area are deleted etc.

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• Flickering problem with world matrix

  - by gnomgrol

  I do have a pretty wierd problem today. As soon as I try to change my translation- or rotationmatrix for an object to something else than (0,0,0), the object starts to flicker (scaling works fine). It rapid and randomly switches between the spot it should be in and a crippled something. I first thought that the problem would be z-fighting, but now Im pretty sure it isn't. I have now clue at all what it could be, here are two screenshots of the two states the plant is switching between. I already used PIX, but could find anything of use (Im not a very good debugger anyway) I would appreciate any help, thanks a lot! Important code: D3DXMatrixIdentity(&World); D3DXVECTOR3 rotaxisX = D3DXVECTOR3(1.0f, 0.0f, 0.0f); D3DXVECTOR3 rotaxisY = D3DXVECTOR3(0.0f, 1.0f, 0.0f); D3DXVECTOR3 rotaxisZ = D3DXVECTOR3(0.0f, 0.0f, 1.0f); D3DXMATRIX temprot1, temprot2, temprot3; D3DXMatrixRotationAxis(&temprot1, &rotaxisX, 0); D3DXMatrixRotationAxis(&temprot2, &rotaxisY, 0); D3DXMatrixRotationAxis(&temprot3, &rotaxisZ, 0); Rotation = temprot1 *temprot2 * temprot3; D3DXMatrixTranslation(&Translation, 0.0f, 10.0f, 0.0f); D3DXMatrixScaling(&Scale, 0.02f, 0.02f, 0.02f); //Set objs world space using the transformations World = Translation * Rotation * Scale; shader: cbuffer cbPerObject { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix);

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• Searching for entity awareness in 3D space algorithm and data structure

  - by Khanser

  I'm trying to do some huge AI system just for the fun and I've come to this problem. How can I let the AI entities know about each other without getting the CPU to perform redundant and costly work? Every entity has a spatial awareness zone and it has to know what's inside when it has to decide what to do. First thoughts, for every entity test if the other entities are inside the first's reach. Ok, so it was the first try and yep, that is redundant and costly. We are working with real time AI over 10000+ entities so this is not a solution. Second try, calculate some grid over the awareness zone of every entity and test whether in this zones are entities (we are working with 3D entities with float x,y,z location coordinates) testing every point in the grid with the indexed-by-coordinate entities. Well, I don't like this because is also costly, but not as the first one. Third, create some multi linked lists over the x's and y's indexed positions of the entities so when we search for an interval between x,y and z,w positions (this interval defines the square over the spatial awareness zone) over the multi linked list, we won't have 'voids'. This has the problem of finding the nearest proximity value if there isn't one at the position where we start the search. I'm not convinced with any of the ideas so I'm searching for some enlightening. Do you people have any better ideas?

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• GLES2.0 3D Android game performance and multi threading the update?

  - by Ofer

  I have profiled my mixed Java\C++ Android game and I got the following result: https://dl.dropbox.com/u/8025882/PompiDev/AndroidProfile.png As you can see, the pink think is a C++ functions that updates the game. It does things like updating the logic but it mostly it generates a "request list" for rendering. The thing is, I generate DrawLists on C++ and then send them to Java to process and draw using GLES2.0. Since then I was able to improve update from 9ms down to about 7ms, but I would like to ask if I would benefit from multi threading the update? As I understand from that diagram is that the function that takes the most time is the one you see it's color on the timeline. So the pink area is taken mostly by update. The other area has MainOpenGL.Handle as it's main contributor(whch is my java function), but since it's not drawn to the top of the diagram I can conclude other things are happening at the same time that use the CPU? Or even GPU stuff that isn't shown in this diagram. I am not sure how the GPU works on this. Does it calculate stuff in parallel to the CPU? Or is it part of the CPU usage as in SoC? I am not sure. Anyway, in case GPU things DO happen in parallel to CPU, then I would guess that if I do this C++ Update in parallel to the thread that makes the OpenGL calls, I might make use of "dead CPU time" due to GPU stalling or maybe have the GPU calls getting processed earlier because it won't have to wait for Update to finish? How do you suggest to improve performance based on that? Thanks.

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