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  • Maya and Game Engines (i.e. Environment Testing)

    - by DiscreteGenius
    What does it mean if I'm designing an environment and I want to test it in the game engine, to see what its like to "run" [or fly] around my environment? I heard an instructor say that exact thing in a Maya training video and I'd like to know more about "How Game Engines and Maya are related to each other." He stated this would be done to see how things look in "size" (e.g. I assume he meant: 'How big is the cathedral, bridge, wall, building, etc.'). I've tried to research such information but it's too complicated, and detailed. I just want a simplistic response to my query. Thanks to everyone willing to help and not criticize my question.

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  • How to program a cutting tool for 3D model in game

    - by Jesse S
    I'm looking for a resource to figure out how to program a function to cut a 3d model in game. Example: Enemy/NPC is sliced into 2 pieces with a sword. His body is not hollow, you can see bloody texture where normally a 'polygon hole' would be. The first step is to actually 'cut/slice' the model, then add in polygons to fill the hole in the model. I know this can be done in 3D modelling software, but I'm not sure how to go about doing this in a game, code-wise. I do not wish to use 'pre cut-up" models, the code will determine where the cut is. Any pointers in the right direction would be greatly appreciated.

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  • Path Modifier in Tower Of Defense Game

    - by Siddharth
    I implemented PathModifier for path of each enemy in my tower of defense game. So I applied fixed time to path modifier in that enemy complete their path. Like following code describe. new PathModifier(speed, path); Here speed define the time to complete the path. But in tower of defense game my problem is, there is a tower which slow down the movement of the enemy. In that particular situation I was stuck. please someone provide me some guidance what to do in this situation. EDIT : Path path = new Path(wayPointList.size()); for (int j = 0; j < wayPointList.size(); j++) { Point point = grid.getCellPoint(wayPointList.get(j).getRow(), wayPointList.get(j).getCol()); path.to(point.x, point.y); }

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  • C++ Game Engine Book/Tutorial/Anything recent?

    - by TheNoob
    Before I get flamed, please understand that I have been looking for a while now. Yes, I have found a good amount of game engine tutorials...except filled with errors, out of date syntax, missing crucial information, and so on. Is there anywhere with a recent tutorial, or a book, anything at all? I'm not asking for an opinion in graphics API's, just a point in the right direction to get started on game engine development. I just want to make it clear, I have googled/stacked like crazy. Any help appreciated. Thank you.

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  • Multiple weapons for android game

    - by Z3r0
    I am trying to make a 3D game for android using the Rajawali engine to render the 3D graphics and blender for designing my models(exporting as .md2), and I want my character to be able to change weapons, armor, helm, etc. Rendering every possible animation would be too much: if I had 10 different weapons, 10 armor and 10 helm, I would have to create 1000 animations with every possible equipment and if I add boots to list it would be even worse. I read somewhere you can use bones for this; but in Android, I only get the object itself to work with. Does anyone has an idea how i can solve this? If I make the weapon a different object how do I parent it to my models in my game?

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  • Adding multiplayer to an HTML5 game

    - by espais
    I am interested in making a game that I currently have a co-op experience, however I'm curious as to the best method of implementing this in HTML5. I have made games before using straight C sockets, and also with the Net library for SDL. What are some of my best options for doing this in a canvas-based environment? At present, all I can come up with are either AJAX/database solutions (with a high refresh rate), or somehow implementing a PHP server that would funnel the data through sockets. The overall gameplay would be a 2.5D platformer-ish type of game, so both clients would need to be continually updated with player positions, enemy positions, projectiles, environmental data, etc.

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  • First Steps. Windows Phone game development

    - by anatoliiG
    I'm pretty new in game development. Have a couple ideas wich could be cool. First that comes to mind is to develop a 2D game (kinda puzzles) for Windows Phone Mango. You may ask: "Why Windows Phone?". I answer - I've got solid experience in Silverlight and C#. For me, this is a major advantage compared to other platforms. Please, give advice and suggestions about: What should I read? Best practices. Third party libraries. Silverlight(Only) vs XNA. Whatever I should pay attention to.

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  • engine for responsive gameplay

    - by zaftcoAgeiha
    Many games have been praised for its responsive gameplay, where each user action input correspond to a quick and precise character movement (eg: super meat boy, shank...) What makes those games responsive? and what prevents other games from achieving the same? How much of it is due to the game framework used to queue mouse/keyboard events and render/update the game and how much is attributed to better coding?

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  • android game: how to approach mutliplayer

    - by willmer
    I'm making a single player game that is near completion, and I am already starting to think about giving the game multiplayer. The multiplayer would basically be finding someone to play against, likely in a waiting room or just have a match-making function, and then having a pokemon style battle between the people in real time. I think it would be relatively simple as I'm just sending information about each attack(move chosen and damage) and what it did back and forth, but I'm not sure what resources to consult for this. I am very new to Android/Java development and really just learning as I go. I have heard a bit about Skiller, but I'm still unfamiliar with using other SDK's and how easy it may be. Does anyone have any suggestions as to what SDK's or methods for accomplishing this. I currently have no money to spend on software development, but I'd like to get started on learning how to do this.

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  • Protecting the integrity of a game state while minimizing amount of data sent

    - by espais
    I'm developing a game in PHP/jQuery, and naturally have to be wary of any sort of data coming from the client. At present, I have tables of data representing the map (2D roguelike), monsters, items, and player(s). Initially, my thought was to simply package it all in a JSON object and send it every game tick, however when actually looking at the data I realized that's quite a large packet to be sending. So, my question is what is a good approach for minimizing data sent to the client? Obviously I would need to figure out some way of validating whatever it sends back. Initially we'd hoped to do some minimal verification on the client-side, but each time we thought of one thing we could do it is immediately invalidated with tools like Firebug. Kind of an open question I realize, but we want to get this right before we move on with our implementation so we don't have to shoehorn in bugfixes later on.

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  • Framework to implement an in game gui editor

    - by momboco
    I need to do an in game gui editor. The game engine has his own widgets elements and I don't want a gui library that substitute it. The most difficult task is the implementation of the functionality that makes usable to artists and designers. Positioning Resize Alignment between some elements Multiselection Relationship between children and parents Add guides Magnet to place elements quickly Use of layers Undo / Redo ... I'm searching a framework or something like, with these functionalities implemented. And a form of append my own engine to make use of it. It would be ideally a mixing between a tool like Photoshop and libRocket ( engine rendering independent ).

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  • How to begin serious game development (in C++) [closed]

    - by Rondogiannis Aristophanes
    I would like to start developing games. I have tried before Game Maker 8, which was a very easy way to start creating games, if you were new in game development. Then, I tried Unity 3D, which was a much more serious and complete tool to create computer-games, and required some experience. And now, I would like to start creating games, and don't use any special environment or developer, but just code (in C++ preferably). So, here is my question: from where should I begin, if I would like to start programming games? Thanks in advance. Note: I work in ubuntu 10.04, I can also use windows 7, but I prefer ubuntu.

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  • Code for Controlling the Bike in a bike game

    - by user1489257
    I'm new(ish) to Actionscript 3 and I was wondering what the code what would be like for controlling the bike in a game. I have a two main questions: Is Box2D the best physics engine to go with for this type of game? How would the animation of the bike work. Would I have to create a bike animation of the wheels moving and make it start and stop when the key to go forward is pressed. How would I go about it slowly stopping when the key to go forward is released? Thanks.

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  • Separate parts of a game engine [on hold]

    - by user272716
    I'm pretty new in developing videogames. By now I only used SDL with C/C++ to create games. I'm currently learning OpenGL and I realized that to be fluid and easy to maintain the code must be logically separated. Since I want to use OpenGLES on iOS and Android I was wondering how the engine must be imagined in a technical way, some questions came up: Do I have to separate input/update functions from draw functions in different threads? Is there only one proper way to think a game engine/loop? What kind of assets should I use to create a 3D game using openGl ES to get better performance?

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  • How to draw a map for the game?

    - by user36689
    I wanted to make a small game, it will be about space. But I had a couple of questions, how to draw a map for the game? I would like to have lots of planets, possible consolidation of the system (as the solar system) But how to draw these planets? Is it really necessary to draw them by hand? I plan to give the names of the planets, but maybe I will not do what is best to do? Prompt Council Help me, please) I'm sorry if that is not the case)) Thanks in advance!

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  • Android / IPhone / Desktop C++ Game Template

    - by OriginalDaemon
    I was wondering if anyone has come across any articles detailing how to set up a basic game in C++ for use in Android / IPhone / Desktop applications. My thoughts just now are that I would like to make my game as a library and have a different project for each device which just interfaces with this library. You know the kind of thing, bootstrap the program, call some library initialize, load and run routines and occasionally pass some information to the library like input. I was hoping someone would have made a template for this kind of thing but I just had no luck finding one. It seems to me that it's the kind of thing you really only have to do once, so I was hoping someone would have done it for me already.

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  • Header Guard Issues - Getting Swallowed Alive

    - by gjnave
    I'm totally at wit's end: I can't figure out how my dependency issues. I've read countless posts and blogs and reworked my code so many times that I can't even remember what almost worked and what didnt. I continually get not only redefinition errors, but class not defined errors. I rework the header guards and remove some errors simply to find others. I somehow got everything down to one error but then even that got broke while trying to fix it. Would you please help me figure out the problem? card.cpp #include <iostream> #include <cctype> #include "card.h" using namespace std; // ====DECL====== Card::Card() { abilities = 0; flavorText = 0; keywords = 0; artifact = 0; classType = new char[strlen("Card") + 1]; classType = "Card"; } Card::~Card (){ delete name; delete abilities; delete flavorText; artifact = NULL; } // ------------ Card::Card(const Card & to_copy) { name = new char[strlen(to_copy.name) +1]; // creating dynamic array strcpy(to_copy.name, name); type = to_copy.type; color = to_copy.color; manaCost = to_copy.manaCost; abilities = new char[strlen(to_copy.abilities) +1]; strcpy(abilities, to_copy.abilities); flavorText = new char[strlen(to_copy.flavorText) +1]; strcpy(flavorText, to_copy.flavorText); keywords = new char[strlen(to_copy.keywords) +1]; strcpy(keywords, to_copy.keywords); inPlay = to_copy.inPlay; tapped = to_copy.tapped; enchanted = to_copy.enchanted; cursed = to_copy.cursed; if (to_copy.type != ARTIFACT) artifact = to_copy.artifact; } // ====DECL===== int Card::equipArtifact(Artifact* to_equip){ artifact = to_equip; } Artifact * Card::unequipArtifact(Card * unequip_from){ Artifact * to_remove = artifact; artifact = NULL; return to_remove; // put card in hand or in graveyard } int Card::enchant( Card * to_enchant){ to_enchant->enchanted = true; cout << "enchanted" << endl; } int Card::disenchant( Card * to_disenchant){ to_disenchant->enchanted = false; cout << "Enchantment Removed" << endl; } // ========DECL===== Spell::Spell() { currPower = basePower; currToughness = baseToughness; classType = new char[strlen("Spell") + 1]; classType = "Spell"; } Spell::~Spell(){} // --------------- Spell::Spell(const Spell & to_copy){ currPower = to_copy.currPower; basePower = to_copy.basePower; currToughness = to_copy.currToughness; baseToughness = to_copy.baseToughness; } // ========= int Spell::attack( Spell *& blocker ){ blocker->currToughness -= currPower; currToughness -= blocker->currToughness; } //========== int Spell::counter (Spell *& to_counter){ cout << to_counter->name << " was countered by " << name << endl; } // ============ int Spell::heal (Spell *& to_heal, int amountOfHealth){ to_heal->currToughness += amountOfHealth; } // ------- Creature::Creature(){ summoningSick = true; } // =====DECL====== Land::Land(){ color = NON; classType = new char[strlen("Land") + 1]; classType = "Land"; } // ------ int Land::generateMana(int mana){ // ... // } card.h #ifndef CARD_H #define CARD_H #include <cctype> #include <iostream> #include "conception.h" class Artifact; class Spell; class Card : public Conception { public: Card(); Card(const Card &); ~Card(); protected: char* name; enum CardType { INSTANT, CREATURE, LAND, ENCHANTMENT, ARTIFACT, PLANESWALKER}; enum CardColor { WHITE, BLUE, BLACK, RED, GREEN, NON }; CardType type; CardColor color; int manaCost; char* abilities; char* flavorText; char* keywords; bool inPlay; bool tapped; bool cursed; bool enchanted; Artifact* artifact; virtual int enchant( Card * ); virtual int disenchant (Card * ); virtual int equipArtifact( Artifact* ); virtual Artifact* unequipArtifact(Card * ); }; // ------------ class Spell: public Card { public: Spell(); ~Spell(); Spell(const Spell &); protected: virtual int heal( Spell *&, int ); virtual int attack( Spell *& ); virtual int counter( Spell*& ); int currToughness; int baseToughness; int currPower; int basePower; }; class Land: public Card { public: Land(); ~Land(); protected: virtual int generateMana(int); }; class Forest: public Land { public: Forest(); ~Forest(); protected: int generateMana(); }; class Creature: public Spell { public: Creature(); ~Creature(); protected: bool summoningSick; }; class Sorcery: public Spell { public: Sorcery(); ~Sorcery(); protected: }; #endif conception.h -- this is an "uber class" from which everything derives class Conception{ public: Conception(); ~Conception(); protected: char* classType; }; conception.cpp Conception::Conception{ Conception(){ classType = new char[11]; char = "Conception"; } game.cpp -- this is an incomplete class as of this code #include <iostream> #include <cctype> #include "game.h" #include "player.h" Battlefield::Battlefield(){ card = 0; } Battlefield::~Battlefield(){ delete card; } Battlefield::Battlefield(const Battlefield & to_copy){ } // =========== /* class Game(){ public: Game(); ~Game(); protected: Player** player; // for multiple players Battlefield* root; // for battlefield getPlayerMove(); // ask player what to do addToBattlefield(); removeFromBattlefield(); sendAttack(); } */ #endif game.h #ifndef GAME_H #define GAME_H #include "list.h" class CardList(); class Battlefield : CardList{ public: Battlefield(); ~Battlefield(); protected: Card* card; // make an array }; class Game : Conception{ public: Game(); ~Game(); protected: Player** player; // for multiple players Battlefield* root; // for battlefield getPlayerMove(); // ask player what to do addToBattlefield(); removeFromBattlefield(); sendAttack(); Battlefield* field; }; list.cpp #include <iostream> #include <cctype> #include "list.h" // ========== LinkedList::LinkedList(){ root = new Node; classType = new char[strlen("LinkedList") + 1]; classType = "LinkedList"; }; LinkedList::~LinkedList(){ delete root; } LinkedList::LinkedList(const LinkedList & obj) { // code to copy } // --------- // ========= int LinkedList::delete_all(Node* root){ if (root = 0) return 0; delete_all(root->next); root = 0; } int LinkedList::add( Conception*& is){ if (root == 0){ root = new Node; root->next = 0; } else { Node * curr = root; root = new Node; root->next=curr; root->it = is; } } int LinkedList::remove(Node * root, Node * prev, Conception* is){ if (root = 0) return -1; if (root->it == is){ root->next = root->next; return 0; } remove(root->next, root, is); return 0; } Conception* LinkedList::find(Node*& root, const Conception* is, Conception* holder = NULL) { if (root==0) return NULL; if (root->it == is){ return root-> it; } holder = find(root->next, is); return holder; } Node* LinkedList::goForward(Node * root){ if (root==0) return root; if (root->next == 0) return root; else return root->next; } // ============ Node* LinkedList::goBackward(Node * root){ root = root->prev; } list.h #ifndef LIST_H #define LIST_H #include <iostream> #include "conception.h" class Node : public Conception { public: Node() : next(0), prev(0), it(0) { it = 0; classType = new char[strlen("Node") + 1]; classType = "Node"; }; ~Node(){ delete it; delete next; delete prev; } Node* next; Node* prev; Conception* it; // generic object }; // ---------------------- class LinkedList : public Conception { public: LinkedList(); ~LinkedList(); LinkedList(const LinkedList&); friend bool operator== (Conception& thing_1, Conception& thing_2 ); protected: virtual int delete_all(Node*); virtual int add( Conception*& ); // virtual Conception* find(Node *&, const Conception*, Conception* ); // virtual int remove( Node *, Node *, Conception* ); // removes question with keyword int display_all(node*& ); virtual Node* goForward(Node *); virtual Node* goBackward(Node *); Node* root; // write copy constrcutor }; // ============= class CircularLinkedList : public LinkedList { public: // CircularLinkedList(); // ~CircularLinkedList(); // CircularLinkedList(const CircularLinkedList &); }; class DoubleLinkedList : public LinkedList { public: // DoubleLinkedList(); // ~DoubleLinkedList(); // DoubleLinkedList(const DoubleLinkedList &); protected: }; // END OF LIST Hierarchy #endif player.cpp #include <iostream> #include "player.h" #include "list.h" using namespace std; Library::Library(){ root = 0; } Library::~Library(){ delete card; } // ====DECL========= Player::~Player(){ delete fname; delete lname; delete deck; } Wizard::~Wizard(){ delete mana; delete rootL; delete rootH; } // =====Player====== void Player::changeName(const char[] first, const char[] last){ char* backup1 = new char[strlen(fname) + 1]; strcpy(backup1, fname); char* backup2 = new char[strlen(lname) + 1]; strcpy(backup1, lname); if (first != NULL){ fname = new char[strlen(first) +1]; strcpy(fname, first); } if (last != NULL){ lname = new char[strlen(last) +1]; strcpy(lname, last); } return 0; } // ========== void Player::seeStats(Stats*& to_put){ to_put->wins = stats->wins; to_put->losses = stats->losses; to_put->winRatio = stats->winRatio; } // ---------- void Player::displayDeck(const LinkedList* deck){ } // ================ void CardList::findCard(Node* root, int id, NodeCard*& is){ if (root == NULL) return; if (root->it.id == id){ copyCard(root->it, is); return; } else findCard(root->next, id, is); } // -------- void CardList::deleteAll(Node* root){ if (root == NULL) return; deleteAll(root->next); root->next = NULL; } // --------- void CardList::removeCard(Node* root, int id){ if (root == NULL) return; if (root->id = id){ root->prev->next = root->next; // the prev link of root, looks back to next of prev node, and sets to where root next is pointing } return; } // --------- void CardList::addCard(Card* to_add){ if (!root){ root = new Node; root->next = NULL; root->prev = NULL; root->it = &to_add; return; } else { Node* original = root; root = new Node; root->next = original; root->prev = NULL; original->prev = root; } } // ----------- void CardList::displayAll(Node*& root){ if (root == NULL) return; cout << "Card Name: " << root->it.cardName; cout << " || Type: " << root->it.type << endl; cout << " --------------- " << endl; if (root->classType == "Spell"){ cout << "Base Power: " << root->it.basePower; cout << " || Current Power: " << root->it.currPower << endl; cout << "Base Toughness: " << root->it.baseToughness; cout << " || Current Toughness: " << root->it.currToughness << endl; } cout << "Card Type: " << root->it.currPower; cout << " || Card Color: " << root->it.color << endl; cout << "Mana Cost" << root->it.manaCost << endl; cout << "Keywords: " << root->it.keywords << endl; cout << "Flavor Text: " << root->it.flavorText << endl; cout << " ----- Class Type: " << root->it.classType << " || ID: " << root->it.id << " ----- " << endl; cout << " ******************************************" << endl; cout << endl; // ------- void CardList::copyCard(const Card& to_get, Card& put_to){ put_to.type = to_get.type; put_to.color = to_get.color; put_to.manaCost = to_get.manaCost; put_to.inPlay = to_get.inPlay; put_to.tapped = to_get.tapped; put_to.class = to_get.class; put_to.id = to_get.id; put_to.enchanted = to_get.enchanted; put_to.artifact = to_get.artifact; put_to.class = to_get.class; put.to.abilities = new char[strlen(to_get.abilities) +1]; strcpy(put_to.abilities, to_get.abilities); put.to.keywords = new char[strlen(to_get.keywords) +1]; strcpy(put_to.keywords, to_get.keywords); put.to.flavorText = new char[strlen(to_get.flavorText) +1]; strcpy(put_to.flavorText, to_get.flavorText); if (to_get.class = "Spell"){ put_to.baseToughness = to_get.baseToughness; put_to.basePower = to_get.basePower; put_to.currToughness = to_get.currToughness; put_to.currPower = to_get.currPower; } } // ---------- player.h #ifndef player.h #define player.h #include "list.h" // ============ class CardList() : public LinkedList(){ public: CardList(); ~CardList(); protected: virtual void findCard(Card&); virtual void addCard(Card* ); virtual void removeCard(Node* root, int id); virtual void deleteAll(); virtual void displayAll(); virtual void copyCard(const Conception*, Node*&); Node* root; } // --------- class Library() : public CardList(){ public: Library(); ~Library(); protected: Card* card; int numCards; findCard(Card&); // get Card and fill empty template } // ----------- class Deck() : public CardList(){ public: Deck(); ~Deck(); protected: enum deckColor { WHITE, BLUE, BLACK, RED, GREEN, MIXED }; char* deckName; } // =============== class Mana(int amount) : public Conception { public: Mana() : displayTotal(0), classType(0) { displayTotal = 0; classType = new char[strlen("Mana") + 1]; classType = "Mana"; }; protected: int accrued; void add(); void remove(); int displayTotal(); } inline Mana::add(){ accrued += 1; } inline Mana::remove(){ accrued -= 1; } inline Mana::displayTotal(){ return accrued; } // ================ class Stats() : public Conception { public: friend class Player; friend class Game; Stats() : wins(0), losses(0), winRatio(0) { wins = 0; losses = 0; if ( (wins + losses != 0) winRatio = wins / (wins + losses); else winRatio = 0; classType = new char[strlen("Stats") + 1]; classType = "Stats"; } protected: int wins; int losses; float winRatio; void int getStats(Stats*& ); } // ================== class Player() : public Conception{ public: Player() : wins(0), losses(0), winRatio(0) { fname = NULL; lname = NULL; stats = NULL; CardList = NULL; classType = new char[strlen("Player") + 1]; classType = "Player"; }; ~Player(); Player(const Player & obj); protected: // member variables char* fname; char* lname; Stats stats; // holds previous game statistics CardList* deck[]; // hold multiple decks that player might use - put ll in this private: // member functions void changeName(const char[], const char[]); void shuffleDeck(int); void seeStats(Stats*& ); void displayDeck(int); chooseDeck(); } // -------------------- class Wizard(Card) : public Player(){ public: Wizard() : { mana = NULL; rootL = NULL; rootH = NULL}; ~Wizard(); protected: playCard(const Card &); removeCard(Card &); attackWithCard(Card &); enchantWithCard(Card &); disenchantWithCard(Card &); healWithCard(Card &); equipWithCard(Card &); Mana* mana[]; Library* rootL; // Library Library* rootH; // Hand } #endif

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  • Runge-Kutta (RK4) integration for game physics

    - by Kai
    Gaffer on Games has a great article about using RK4 integration for better game physics. The implementation is straightforward but the math behind it confuses me. I understand derivatives and integrals on a conceptual level but I haven't manipulated equations in a long time. Here's the brunt of Gaffer's implementation: void integrate(State &state, float t, float dt) { Derivative a = evaluate(state, t, 0.0f, Derivative()); Derivative b = evaluate(state, t+dt*0.5f, dt*0.5f, a); Derivative c = evaluate(state, t+dt*0.5f, dt*0.5f, b); Derivative d = evaluate(state, t+dt, dt, c); const float dxdt = 1.0f/6.0f * (a.dx + 2.0f*(b.dx + c.dx) + d.dx); const float dvdt = 1.0f/6.0f * (a.dv + 2.0f*(b.dv + c.dv) + d.dv) state.x = state.x + dxdt * dt; state.v = state.v + dvdt * dt; } Can anybody explain in simple terms how RK4 works? Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? After reading the accepted answer below, and several other articles, I have a grasp on how RK4 works. To answer my own questions: Can anybody explain in simple terms how RK4 works? RK4 takes advantage of the fact that we can get a much better approximation of a function if we use its higher-order derivatives rather than just the first or second derivative. That's why the Taylor series converges much faster than Euler approximations. (take a look at the animation on the right side of that page) Specifically, why are we averaging the derivatives at 0.0f, 0.5f, 0.5f, and 1.0f? The Runge-Kutta method is an approximation of a function that samples derivatives of several points within a timestep, unlike the Taylor series which only samples derivatives of a single point. After sampling these derivatives we need to know how to weigh each sample to get the closest approximation possible. An easy way to do this is to pick constants that coincide with the Taylor series, which is how the constants of a Runge-Kutta equation are determined. This article made it clearer for me: http://web.mit.edu/10.001/Web/Course%5FNotes/Differential%5FEquations%5FNotes/node5.html. Notice how (15) is the Taylor series expansion while (17) is the Runge-Kutta derivation. How is averaging derivatives up to the 4th order different from doing a simple euler integration with a smaller timestep? Mathematically it converges much faster than doing many Euler approximations. Of course, with enough Euler approximations we can gain equal accuracy to RK4, but the computational power needed doesn't justify using Euler.

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  • Card Shuffling in C#

    - by Jeff
    I am trying to write a code for a project that lists the contents of a deck of cards, asks how much times the person wants to shuffle the deck, and then shuffles them. It has to use a method to create two random integers using the System.Random class. These are my classes: Program.cs: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication3 { class Program { static void Main(string[] args) { Deck mydeck = new Deck(); foreach (Card c in mydeck.Cards) { Console.WriteLine(c); } Console.WriteLine("How Many Times Do You Want To Shuffle?"); } } } Deck.cs: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication3 { class Deck { Card[] cards = new Card[52]; string[] numbers = new string[] { "2", "3", "4", "5", "6", "7", "8", "9", "J", "Q", "K" }; public Deck() { int i = 0; foreach(string s in numbers) { cards[i] = new Card(Suits.Clubs, s); i++; } foreach (string s in numbers) { cards[i] = new Card(Suits.Spades, s); i++; } foreach (string s in numbers) { cards[i] = new Card(Suits.Hearts, s); i++; } foreach (string s in numbers) { cards[i] = new Card(Suits.Diamonds, s); i++; } } public Card[] Cards { get { return cards; } } } } classes.cs: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication3 { enum Suits { Hearts, Diamonds, Spades, Clubs } } Card.cs: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication3 { class Card { protected Suits suit; protected string cardvalue; public Card() { } public Card(Suits suit2, string cardvalue2) { suit = suit2; cardvalue = cardvalue2; } public override string ToString() { return string.Format("{0} of {1}", cardvalue, suit); } } } Please tell me how to make the cards shuffle as much as the person wants and then list the shuffled cards. Sorry about the formatting im new to this site.

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  • physics game programming box2d - orientating a turret-like object using torques

    - by egarcia
    This is a problem I hit when trying to implement a game using the LÖVE engine, which covers box2d with Lua scripting. The objective is simple: A turret-like object (seen from the top, on a 2D environment) needs to orientate itself so it points to a target. The turret is on the x,y coordinates, and the target is on tx, ty. We can consider that x,y are fixed, but tx, ty tend to vary from one instant to the other (i.e. they would be the mouse cursor). The turret has a rotor that can apply a rotational force (torque) on any given moment, clockwise or counter-clockwise. The magnitude of that force has an upper limit called maxTorque. The turret also has certain rotational inertia, which acts for angular movement the same way mass acts for linear movement. There's no friction of any kind, so the turret will keep spinning if it has an angular velocity. The turret has a small AI function that re-evaluates its orientation to verify that it points to the right direction, and activates the rotator. This happens every dt (~60 times per second). It looks like this right now: function Turret:update(dt) local x,y = self:getPositon() local tx,ty = self:getTarget() local maxTorque = self:getMaxTorque() -- max force of the turret rotor local inertia = self:getInertia() -- the rotational inertia local w = self:getAngularVelocity() -- current angular velocity of the turret local angle = self:getAngle() -- the angle the turret is facing currently -- the angle of the like that links the turret center with the target local targetAngle = math.atan2(oy-y,ox-x) local differenceAngle = _normalizeAngle(targetAngle - angle) if(differenceAngle <= math.pi) then -- counter-clockwise is the shortest path self:applyTorque(maxTorque) else -- clockwise is the shortest path self:applyTorque(-maxTorque) end end ... it fails. Let me explain with two illustrative situations: The turret "oscillates" around the targetAngle. If the target is "right behind the turret, just a little clock-wise", the turret will start applying clockwise torques, and keep applying them until the instant in which it surpasses the target angle. At that moment it will start applying torques on the opposite direction. But it will have gained a significant angular velocity, so it will keep going clockwise for some time... until the target will be "just behind, but a bit counter-clockwise". And it will start again. So the turret will oscillate or even go in round circles. I think that my turret should start applying torques in the "opposite direction of the shortest path" before it reaches the target angle (like a car braking before stopping). Intuitively, I think the turret should "start applying torques on the opposite direction of the shortest path when it is about half-way to the target objective". My intuition tells me that it has something to do with the angular velocity. And then there's the fact that the target is mobile - I don't know if I should take that into account somehow or just ignore it. How do I calculate when the turret must "start braking"?

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  • Moving a unit precisely along a path in x,y coordinates

    - by Adam Eberbach
    I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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  • Performance issues in android game

    - by user1446632
    I am making an android game, but however, the game is functioning like it should, but i am experiencing some performance issues. I think it has something to do with the sound. Cause each time i touch the screen, it makes a sound. I am using the standard MediaPlayer. The method is onTouchEvent() and onPlaySound1(). Could you please help me with an alternate solution for playing the sound? Thank you so much in advance! It would be nice if you also came up with some suggestions on how i can improve my code. Take a look at my code here: package com.mycompany.mygame; import java.util.ArrayList; import android.content.Context; import android.content.Intent; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.media.MediaPlayer; import android.os.Handler; import android.os.Message; import android.util.Log; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.MotionEvent; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View; import android.webkit.WebView; import android.widget.TextView; import android.widget.Toast; public class ExampleView extends SurfaceView implements SurfaceHolder.Callback { class ExampleThread extends Thread { private ArrayList<Parachuter> parachuters; private Bitmap parachuter; private Bitmap background; private Paint black; private boolean running; private SurfaceHolder mSurfaceHolder; private Context mContext; private Context mContext1; private Handler mHandler; private Handler mHandler1; private GameScreenActivity mActivity; private long frameRate; private boolean loading; public float x; public float y; public float x1; public float y1; public MediaPlayer mp1; public MediaPlayer mp2; public int parachuterIndexToResetAndDelete; public int canvasGetWidth; public int canvasGetWidth1; public int canvasGetHeight; public int livesLeftValue; public int levelValue = 1; public int levelValue1; public int parachutersDown; public int difficultySet; public boolean isSpecialAttackAvailible; public ExampleThread(SurfaceHolder sHolder, Context context, Handler handler) { mSurfaceHolder = sHolder; mHandler = handler; mHandler1 = handler; mContext = context; mActivity = (GameScreenActivity) context; parachuters = new ArrayList<Parachuter>(); parachuter = BitmapFactory.decodeResource(getResources(), R.drawable.parachuteman); black = new Paint(); black.setStyle(Paint.Style.FILL); black.setColor(Color.GRAY); background = BitmapFactory.decodeResource(getResources(), R.drawable.gamescreenbackground); running = true; // This equates to 26 frames per second. frameRate = (long) (1000 / 26); loading = true; mp1 = MediaPlayer.create(getContext(), R.raw.bombsound); } @Override public void run() { while (running) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas(); synchronized (mSurfaceHolder) { long start = System.currentTimeMillis(); doDraw(c); long diff = System.currentTimeMillis() - start; if (diff < frameRate) Thread.sleep(frameRate - diff); } } catch (InterruptedException e) { } finally { if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } protected void doDraw(Canvas canvas) { canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), black); //Draw for (int i = 0; i < parachuters.size(); i++) { canvas.drawBitmap(parachuter, parachuters.get(i).getX(), parachuters.get(i).getY(), null); parachuters.get(i).tick(); } //Remove for (int i = 0; i < parachuters.size(); i++) { if (parachuters.get(i).getY() > canvas.getHeight()) { parachuters.remove(i); onPlaySound(); checkLivesLeftValue(); checkAmountOfParachuters(); } else if(parachuters.get(i).isTouched()) { parachuters.remove(i); } else{ //Do nothing } } } public void loadBackground(Canvas canvas) { //Load background canvas.drawBitmap(background, 0, 0, black); } public void checkAmountOfParachuters() { mHandler.post(new Runnable() { @Override public void run() { if(parachuters.isEmpty()) { levelValue = levelValue + 1; Toast.makeText(getContext(), "New level! " + levelValue, 15).show(); if (levelValue == 3) { drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); drawParachutersGroup4(); } else if (levelValue == 5) { drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); drawParachutersGroup4(); drawParachutersGroup5(); } else if (levelValue == 7) { drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); drawParachutersGroup4(); drawParachutersGroup5(); drawParachutersGroup6(); } else if (levelValue == 9) { //Draw 7 groups of parachuters drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); drawParachutersGroup4(); drawParachutersGroup5(); drawParachutersGroup6(); drawParachutersGroup1(); } else if (levelValue > 9) { //Draw 7 groups of parachuters drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); drawParachutersGroup4(); drawParachutersGroup5(); drawParachutersGroup6(); drawParachutersGroup1(); } else { //Draw normal 3 groups of parachuters drawParachutersGroup1(); drawParachutersGroup2(); drawParachutersGroup3(); } } else { //Do nothing } } }); } private void checkLivesLeftValue() { mHandler.post(new Runnable() { @Override public void run() { Log.d("checkLivesLeftValue", "lives = " + livesLeftValue); // TODO Auto-generated method stub if (livesLeftValue == 3) { //Message to display: "You lost! Log.d("checkLivesLeftValue", "calling onMethod now"); parachuters.removeAll(parachuters); onMethod(); } else if (livesLeftValue == 2) { Toast.makeText(getContext(), "Lives left=1", 15).show(); livesLeftValue = livesLeftValue + 1; Log.d("checkLivesLeftValue", "increased lives to " + livesLeftValue); } else if (livesLeftValue == 1) { Toast.makeText(getContext(), "Lives left=2", 15).show(); livesLeftValue = livesLeftValue + 1; Log.d("checkLivesLeftValue", "increased lives to " + livesLeftValue); } else { //Set livesLeftValueText 3 Toast.makeText(getContext(), "Lives left=3", 15).show(); livesLeftValue = livesLeftValue + 1; Log.d("checkLivesLeftValue", "increased lives to " + livesLeftValue); } } }); } public void onMethod() { mHandler.post(new Runnable() { @Override public void run() { try { Toast.makeText(getContext(), "You lost!", 15).show(); livesLeftValue = 0; //Tell the user that he lost: android.content.Context ctx = mContext; Intent i = new Intent(ctx, playerLostMessageActivity.class); i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); i.putExtra("KEY","You got to level " + levelValue + " And you shot down " + parachutersDown + " parachuters"); i.putExtra("levelValue", levelValue); ctx.startActivity(i); System.exit(0); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); //Exit activity and start playerLostMessageActivity Toast.makeText(getContext(), "You lost!", 15).show(); livesLeftValue = 0; //Tell the user that he lost: android.content.Context ctx = mContext; Intent i = new Intent(ctx, playerLostMessageActivity.class); i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); i.putExtra("KEY","You got to level " + levelValue + " And you shot down " + parachutersDown + " parachuters"); i.putExtra("levelValue", levelValue); System.exit(0); ctx.startActivity(i); System.exit(0); } } }); } public void onPlaySound() { try { mp1.start(); } catch (Exception e) { e.printStackTrace(); mp1.release(); } } public void onDestroy() { try { parachuters.removeAll(parachuters); mp1.stop(); mp1.release(); } catch (Exception e) { e.printStackTrace(); } } public void onPlaySound1() { try { mp2 = MediaPlayer.create(getContext(), R.raw.airriflesoundeffect); mp2.start(); } catch (Exception e) { e.printStackTrace(); mp2.release(); } } public boolean onTouchEvent(MotionEvent event) { if (event.getAction() != MotionEvent.ACTION_DOWN) releaseMediaPlayer(); x1 = event.getX(); y1 = event.getY(); checkAmountOfParachuters(); removeParachuter(); return false; } public void releaseMediaPlayer() { try { mp1.release(); } catch (Exception e) { e.printStackTrace(); } } public void removeParachuter() { try { for (Parachuter p: parachuters) { if (x1 > p.getX() && x1 < p.getX() + parachuter.getWidth() && y1 > p.getY() && y1 < p.getY() + parachuter.getHeight()) { p.setTouched(true); onPlaySound1(); parachutersDown = parachutersDown + 1; p.setTouched(false); } } } catch (Exception e) { e.printStackTrace(); } } public void initiateDrawParachuters() { drawParachutersGroup1(); } public void drawParachutersGroup1() { // TODO Auto-generated method stub //Parachuter group nr. 1 //Parachuter nr. 2 x = 75; y = 77; Parachuter p1 = new Parachuter(x, y); parachuters.add(p1); //Parachuter nr.1 x = 14; y = 28; Parachuter p = new Parachuter(x, y); parachuters.add(p); //Parachuter nr. 3 x = 250; y = 94; Parachuter p3 = new Parachuter(x, y); parachuters.add(p3); //Parachuter nr. 3 x = 275; y = 80; Parachuter p2 = new Parachuter(x, y); parachuters.add(p2); //Parachuter nr. 5 x = 280; y = 163; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 125; y = 118; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 126; y = 247; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 123; y = 77; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachutersGroup2() { // TODO Auto-generated method stub //Parachuter group nr. 2 //Parachuter nr. 5 x = 153; y = 166; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 133; y = 123; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 170; y = 213; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 190; y = 121; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachutersGroup3() { // TODO Auto-generated method stub //Parachuter group nr. 3 //Parachuter nr. 2 x = 267; y = 115; Parachuter p1 = new Parachuter(x, y); parachuters.add(p1); //Parachuter nr.1 x = 255; y = 183; Parachuter p = new Parachuter(x, y); parachuters.add(p); //Parachuter nr. 3 x = 170; y = 280; Parachuter p3 = new Parachuter(x, y); parachuters.add(p3); //Parachuter nr. 3 x = 116; y = 80; Parachuter p2 = new Parachuter(x, y); parachuters.add(p2); //Parachuter nr. 5 x = 67; y = 112; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 260; y = 89; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 260; y = 113; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 178; y = 25; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachutersGroup4() { // TODO Auto-generated method stub //Parachuter group nr. 1 //Parachuter nr. 2 x = 75; y = 166; Parachuter p1 = new Parachuter(x, y); parachuters.add(p1); //Parachuter nr.1 x = 118; y = 94; Parachuter p = new Parachuter(x, y); parachuters.add(p); //Parachuter nr. 3 x = 38; y = 55; Parachuter p3 = new Parachuter(x, y); parachuters.add(p3); //Parachuter nr. 3 x = 57; y = 18; Parachuter p2 = new Parachuter(x, y); parachuters.add(p2); //Parachuter nr. 5 x = 67; y = 119; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 217; y = 113; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 245; y = 234; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 239; y = 44; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachutersGroup5() { // TODO Auto-generated method stub //Parachuter group nr. 1 //Parachuter nr. 2 x = 59; y = 120; Parachuter p1 = new Parachuter(x, y); parachuters.add(p1); //Parachuter nr.1 x = 210; y = 169; Parachuter p = new Parachuter(x, y); parachuters.add(p); //Parachuter nr. 3 x = 199; y = 138; Parachuter p3 = new Parachuter(x, y); parachuters.add(p3); //Parachuter nr. 3 x = 22; y = 307; Parachuter p2 = new Parachuter(x, y); parachuters.add(p2); //Parachuter nr. 5 x = 195; y = 22; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 157; y = 132; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 150; y = 183; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 130; y = 20; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachutersGroup6() { // TODO Auto-generated method stub //Parachuter group nr. 1 //Parachuter nr. 2 x = 10; y = 10; Parachuter p1 = new Parachuter(x, y); parachuters.add(p1); //Parachuter nr.1 x = 20; y = 20; Parachuter p = new Parachuter(x, y); parachuters.add(p); //Parachuter nr. 3 x = 30; y = 30; Parachuter p3 = new Parachuter(x, y); parachuters.add(p3); //Parachuter nr. 3 x = 60; y = 60; Parachuter p2 = new Parachuter(x, y); parachuters.add(p2); //Parachuter nr. 5 x = 90; y = 90; Parachuter p5 = new Parachuter(x, y); parachuters.add(p5); x = 120; y = 120; Parachuter p4 = new Parachuter(x, y); parachuters.add(p4); //Parachuter nr. 7 x = 150; y = 150; Parachuter p7 = new Parachuter(x, y); parachuters.add(p7); //Parachuter nr. 6 x = 180; y = 180; Parachuter p6 = new Parachuter(x, y); parachuters.add(p6); } public void drawParachuters() { Parachuter p = new Parachuter(x, y); parachuters.add(p); Toast.makeText(getContext(), "x=" + x + " y=" + y, 15).show(); } public void setRunning(boolean bRun) { running = bRun; } public boolean getRunning() { return running; } } /** Handle to the application context, used to e.g. fetch Drawables. */ private Context mContext; /** Pointer to the text view to display "Paused.." etc. */ private TextView mStatusText; /** The thread that actually draws the animation */ private ExampleThread eThread; public ExampleView(Context context) { super(context); // register our interest in hearing about changes to our surface SurfaceHolder holder = getHolder(); holder.addCallback(this); // create thread only; it's started in surfaceCreated() eThread = new ExampleThread(holder, context, new Handler() { @Override public void handleMessage(Message m) { // mStatusText.setVisibility(m.getData().getInt("viz")); // mStatusText.setText(m.getData().getString("text")); } }); setFocusable(true); } @Override public boolean onTouchEvent(MotionEvent event) { return eThread.onTouchEvent(event); } public ExampleThread getThread() { return eThread; } @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } public void surfaceCreated(SurfaceHolder holder) { if (eThread.getState() == Thread.State.TERMINATED) { eThread = new ExampleThread(getHolder(), getContext(), getHandler()); eThread.start(); } else { eThread.start(); } } @Override public void surfaceDestroyed(SurfaceHolder holder) { boolean retry = true; eThread.setRunning(false); while (retry) { try { eThread.join(); retry = false; } catch (InterruptedException e) { } } } }

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  • mvc design in a card game

    - by Hong
    I'm trying to make a card game. some classes I have are: CardModel, CardView; DeckModel, DeckView. The deck model has a list of card model, According to MVC, if I want to send a card to a deck, I can add the card model to the deck model, and the card view will be added to the deck view by a event handler. So I have a addCard(CardModel m) in the DeckModel class, but if I want to send a event to add the card view of that model to the deck view, I only know let the model has a reference to view. So the question is: If the card model and deck model have to have a reference to their view classes to do it? If not, how to do it better? Update, the code: public class DeckModel { private ArrayList<CardModel> cards; private ArrayList<EventHandler> actionEventHandlerList; public void addCard(CardModel card){ cards.add(card); //processEvent(event x); //must I pass a event that contain card view here? } CardModel getCards(int index){ return cards.get(index); } public synchronized void addEventHandler(EventHandler l){ if(actionEventHandlerList == null) actionEventHandlerList = new ArrayList<EventHandler>(); if(!actionEventHandlerList.contains(l)) actionEventHandlerList.add(l); } public synchronized void removeEventHandler(EventHandler l){ if(actionEventHandlerList!= null && actionEventHandlerList.contains(l)) actionEventHandlerList.remove(l); } private void processEvent(Event e){ ArrayList list; synchronized(this){ if(actionEventHandlerList!= null) list = (ArrayList)actionEventHandlerList.clone(); else return; } for(int i=0; i<actionEventHandlerList.size(); ++i){ actionEventHandlerList.get(i).handle(e); } } }

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  • One letter game problem?

    - by Alex K
    Recently at a job interview I was given the following problem: Write a script capable of running on the command line as python It should take in two words on the command line (or optionally if you'd prefer it can query the user to supply the two words via the console). Given those two words: a. Ensure they are of equal length b. Ensure they are both words present in the dictionary of valid words in the English language that you downloaded. If so compute whether you can reach the second word from the first by a series of steps as follows a. You can change one letter at a time b. Each time you change a letter the resulting word must also exist in the dictionary c. You cannot add or remove letters If the two words are reachable, the script should print out the path which leads as a single, shortest path from one word to the other. You can /usr/share/dict/words for your dictionary of words. My solution consisted of using breadth first search to find a shortest path between two words. But apparently that wasn't good enough to get the job :( Would you guys know what I could have done wrong? Thank you so much. import collections import functools import re def time_func(func): import time def wrapper(*args, **kwargs): start = time.time() res = func(*args, **kwargs) timed = time.time() - start setattr(wrapper, 'time_taken', timed) return res functools.update_wrapper(wrapper, func) return wrapper class OneLetterGame: def __init__(self, dict_path): self.dict_path = dict_path self.words = set() def run(self, start_word, end_word): '''Runs the one letter game with the given start and end words. ''' assert len(start_word) == len(end_word), \ 'Start word and end word must of the same length.' self.read_dict(len(start_word)) path = self.shortest_path(start_word, end_word) if not path: print 'There is no path between %s and %s (took %.2f sec.)' % ( start_word, end_word, find_shortest_path.time_taken) else: print 'The shortest path (found in %.2f sec.) is:\n=> %s' % ( self.shortest_path.time_taken, ' -- '.join(path)) def _bfs(self, start): '''Implementation of breadth first search as a generator. The portion of the graph to explore is given on demand using get_neighboors. Care was taken so that a vertex / node is explored only once. ''' queue = collections.deque([(None, start)]) inqueue = set([start]) while queue: parent, node = queue.popleft() yield parent, node new = set(self.get_neighbours(node)) - inqueue inqueue = inqueue | new queue.extend([(node, child) for child in new]) @time_func def shortest_path(self, start, end): '''Returns the shortest path from start to end using bfs. ''' assert start in self.words, 'Start word not in dictionnary.' assert end in self.words, 'End word not in dictionnary.' paths = {None: []} for parent, child in self._bfs(start): paths[child] = paths[parent] + [child] if child == end: return paths[child] return None def get_neighbours(self, word): '''Gets every word one letter away from the a given word. We do not keep these words in memory because bfs accesses a given vertex only once. ''' neighbours = [] p_word = ['^' + word[0:i] + '\w' + word[i+1:] + '$' for i, w in enumerate(word)] p_word = '|'.join(p_word) for w in self.words: if w != word and re.match(p_word, w, re.I|re.U): neighbours += [w] return neighbours def read_dict(self, size): '''Loads every word of a specific size from the dictionnary into memory. ''' for l in open(self.dict_path): l = l.decode('latin-1').strip().lower() if len(l) == size: self.words.add(l) if __name__ == '__main__': import sys if len(sys.argv) not in [3, 4]: print 'Usage: python one_letter_game.py start_word end_word' else: g = OneLetterGame(dict_path = '/usr/share/dict/words') try: g.run(*sys.argv[1:]) except AssertionError, e: print e

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