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• Need help understanding Mocks and Stubs

  - by Theomax

  I'm new to use mocking frameworks and I have a few questions on the things that I am not clear on. I'm using Rhinomocks to generate mock objects in my unit tests. I understand that mocks can be created to verify interactions between methods and they record the interactions etc and stubs allow you to setup data and entities required by the test but you do not verify expectations on stubs. Looking at the recent unit tests I have created, I appear to be creating mocks literally for the purpose of stubbing and allowing for data to be setup. Is this a correct usage of mocks or is it incorrect if you're not actually calling verify on them? For example: user = MockRepository.GenerateMock<User>(); user.Stub(x => x.Id = Guid.NewGuid()); user.Stub(x => x.Name = "User1"); In the above code I generate a new user mock object, but I use a mock so I can stub the properties of the user because in some cases if the properties do not have a setter and I need to set them it seems the only way is to stub the property values. Is this a correct usage of stubbing and mocking? Also, I am not completely clear on what the difference between the following lines is: user.Stub(x => x.Id).Return(new Guid()); user.Stub(x => x.Id = Guid.NewGuid());

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• Should I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority?

  - by JonathonG

  Can I build a multi-threaded system that handles events from a game and sorts them, independently, into different threads based on priority, and is it a good idea? Here's more info: I am about to begin work on porting a mid-sized game from Flash/AS3 to Java so that I can continue development with multi-threading capabilities. Here's a small bit of background about the game: The game contains numerous asynchronous activities, such as "world updating" (the game environment is constantly changing based on a set of natural laws and forces), procedural generation of terrain, NPCs, quests, items, etc., and on top of that, the effects of all of the player's interactions with his environment are programmatically calculated in real time, based on a set of constantly changing "stats" and once again, natural laws and forces. All of these things going on at once, in an asynchronous manner, seem to lend themselves to multi-threading very well. My question is: Can I build some kind of central engine that handles the "stacking" of all of these events as they are triggered, and dynamically sorts them out amongst the available threads, and would it be a good idea? As an example: Essentially, every time something happens (IE, a magic missile being generated by a spell, or a bunch of plants need to grow to their next stage), instead of just processing that task right then and adding the new object(s) to a list of managed objects, send a reference to that event to a core "event handler" that throws it into a stack of all other currently queued events, which then sorts them out and orders them according to urgency, splits them between a number of available threads for as-fast-as-possible multithreaded execution.

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• Take a snapshot with JavaFX!

  - by user12610255

  JavaFX 2.2 has a "snapshot" feature that enables you to take a picture of any node or scene. Take a look at the API Documentation and you will find new snapshot methods in the javafx.scene.Scene class. The most basic version has the following signature: public WritableImage snapshot(WritableImage image) The WritableImage class (also introduced in JavaFX 2.2) lives in the javafx.scene.image package, and represents a custom graphical image that is constructed from pixels supplied by the application. In fact, there are 5 new classes in javafx.scene.image: PixelFormat: Defines the layout of data for a pixel of a given format. WritablePixelFormat: Represents a pixel format that can store full colors and so can be used as a destination format to write pixel data from an arbitrary image. PixelReader: Defines methods for retrieving the pixel data from an Image or other surface containing pixels. PixelWriter: Defines methods for writing the pixel data of a WritableImage or other surface containing writable pixels. WritableImage: Represents a custom graphical image that is constructed from pixels supplied by the application, and possibly from PixelReader objects from any number of sources, including images read from a file or URL. The API documentation contains lots of information, so go investigate and have fun with these useful new classes! -- Scott Hommel

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• Authenticate with Django 1.5

  - by gorjuce

  I'm currently testing django 1.5 and a custom User model, but I've some problems. I've created a User class in my account app, which looks like: class User(AbstractBaseUser): email = models.EmailField() activation_key = models.CharField(max_length=255) is_active = models.BooleanField(default=False) is_admin = models.BooleanField(default=False) USERNAME_FIELD = 'email' I can correctly register a user, who is stored in my account_user table. Now, how can I log in? I've tried with: def login(request): form = AuthenticationForm() if request.method == 'POST': form = AuthenticationForm(request.POST) email = request.POST['username'] password = request.POST['password'] user = authenticate(username=email, password=password) if user is not None: if user.is_active: login(user) else: message = 'disabled account, check validation email' return render( request, 'account-login-failed.html', {'message': message} ) return render(request, 'account-login.html', {'form': form}) I can correctly register a new User My forms.py which contains my register form class RegisterForm(forms.ModelForm): """ a form to create user""" password = forms.CharField( label="Password", widget=forms.PasswordInput() ) password_confirm = forms.CharField( label="Password Repeat", widget=forms.PasswordInput() ) class Meta: model = User exclude = ('last_login', 'activation_key') def clean_password_confirm(self): password = self.cleaned_data.get("password") password_confirm = self.cleaned_data.get("password_confirm") if password and password_confirm and password != password_confirm: raise forms.ValidationError("Password don't math") return password_confirm def clean_email(self): if User.objects.filter(email__iexact=self.cleaned_data.get("email")): raise forms.ValidationError("email already exists") return self.cleaned_data['email'] def save(self): user = super(RegisterForm, self).save(commit=False) user.password = self.cleaned_data['password'] user.activation_key = generate_sha1(user.email) user.save() return user My question is: Why does authenticate give me None? I know I'm trying to authenticate() with an email as username but is that not one of the reasons to use a custom User model?

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• Must all AI states be able to react to any event?

  - by Prog

  FSMs implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. How is this used in games to design AI agents? Consider a simplified class Monster, representing an AI agent: class Monster { State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses implementing execute() differently. So far, classic State pattern. AI agents are subject to environmental effects and other objects communicating with them. For example, an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Is this correct? If correct, how is this done? Are all states obligated by their superclass to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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• C# XNA 2D Multiple boxes collision detection and movement

  - by zini

  Hi, I've been making simple game where you shoot boxes that are coming towards you. All game objects are simple rectangles. Now I have problem with collision detection; how to check where the collision comes so I can change the coordinates right? I have this kind of situation: http://imgur.com/8yjfW Imagine that all of those blocks are moving towards you (green box). If those orange boxes collide with each other, they should "avoid" themselves and not go through each other. I have class Enemy which has properties x, y and such. Now I'm doing the collision like this: // os.Count is an amount of other enemies colliding with this enemy if (os.Count == 0) { // If enemy doesn't collide with other enemy lasty = y; lastx = x; slope = (x - player.x) / (y - player.y); x += slope * l; // l is "movement speed" of enemy (float) if (y > player.y) { y = lasty; } else if (y < player.y) { y += l; } } else { foreach(Enemy b in os) { if (b.y > this.y) { // If some colliding enemy is closer player than this enemy, that closer one will be moved towards the player b.lasty = b.y; if (!BiggestY(os)) { // BiggestY returns true if this enemy has the biggest Y b.y += b.l; } b.x = b.lastx; } } } But this is very, very bad way to do this. I know it, but I just can't figure out other way. And as a matter in fact, this method doesn't even work pretty good; if multiple enemies are colliding same enemy they go through each other. I explained this pretty badly, but I hope that you understand this. And to sum up, as I said: How to check where the collision comes so I can change the coordinates right?

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• How do I interpolate air drag with a variable time step?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• Encapsulate standard C functions?

  - by Jack Stout

  While studying the C programming language and learning safe practices, I'm inclined to write a layer of functionality over several parts of the standard library. This would serve two purposes: I could use standard parts of the language in ways that feel more familiar or rational to me, and I could easily replace that functionality with my own, if I needed to. I could benefit from this, but should I do it? As an example, we can consider memory management. If I've written malloc() into the constructors of each of my objects, then decide that I need to handle memory allocation on my own, I have to edit the constructor associated with every object. By referencing my own function, I can change the contents of that function without writing a new constructors. It seems obvious that I should do this, but I'm used to Python. I'm extremely comfortable in that environment and have no problem linking to any part of the standard library from any part of my program because I know I will almost certainly leave that relationship untouched for the life of the project. The situation I'm running into with C feels like I'm trying to hide the language from myself. Will writing a layer of functionality over the C standard library help me in learning the language and developing a codebase, or will it stifle my understanding going forward?

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• Polygon is rotating too fast

  - by Manderin87

  I am going to be using a polygon collision detection method to test when objects collide. I am attempting to rotate a polygon to match the sprites rotation. However, the polygon is rotating too fast, much faster than the sprite is. I feel its a timing issue, but the sprite rotates like it is supposed to. Can anyone look at my code and tell me what could be causing this issue? public void rotate(float x0, float y0, double angle) { for(Point point : mPoints) { float x = (float) (x0 + (point.x - x0) * Math.cos(Utilities.toRadians(angle)) - (point.y - y0) * Math.sin(Utilities.toRadians(angle))); float y = (float) (y0 + (point.x - x0) * Math.sin(Utilities.toRadians(angle)) + (point.y - y0) * Math.cos(Utilities.toRadians(angle))); point.x = x; point.y = y; } } This algorithm works when done singly, but once I plug it into the update method the rotation is too fast. The Points used are: P1 608, 368 P2 640, 464 P3 672, 400 Origin x0 is: 640 400 The angle goes from 0 to 360 as the sprite rotates. When the codes executes the triangle looks like a star because its moving so fast. The rotation is done in the sprites update method. The rotation method just increases the sprites degree by .5 when it executes. public void update() { if(isActive()) { rotate(); mBounding.rotate(mPosition.x, mPosition.y, mDegree); } }

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• Returning a flexible datatype from a C++ function

  - by GavinH

  I'm developing for a legacy C++ application which uses ODBC for it's data access. Coming from a C# background, I really miss the ADO style of data access. I'm writing a wrapper (because we can't actually use ADO) to make our data access less painful. This means no char arrays, no manual text blob streaming, and no declaritive column binding. I'm struggling with how to store / return data values. In C# at least, you can declare an object and cast it to whatever (as long as the type is convertable). My current C++ solution is to use boost::any to store the data value in a custom DataColumnValue object. This class has conversion and assignment operators to the various types used in our app (more than 10). There's a bit of complexity here because if you store an int in the boost::any and try to boost::any_cast<long> you get a boost::bad_any_cast. Client objects shouldn't have to know how the value is stored internally. Does anyone have any experience trying to store / return values whose types are only known at runtime? Is there a better / cleaner way?

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• MVC design patterns

  - by insane-36

  I have an application and it does not use a very good structure. However it seems to me that I have tried to stick to mvc design pattern but a senior engineer claims that I have no design patterns and code are mesh. How I have structured the code : I have couple of nsmanagedobject model classes which represents model in my case and a reskit library which encapsulates the nsurlconnection and url request. I fetch the request from the view controller itself and then when the request get completed I create predicate and then populate it in tableview. Wherever I need custom view either I create it in nib or create in a custom subclass of UIView. I have use delegation pattern and notification to communication to view controller, views and block callback with restkit. But, the senior engineer is very new to ios. He has been doing it for 2 months now but he is a good java programmer. So, what is mvc pattern ? Is core data model not working as a model objects, view controller as controller and views. I dont seem to find any other places or any other cases to create my own model object since the most of the models are used as NSManagedObject subclass.

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• Guidelines for creating referentially transparent callables

  - by max

  In some cases, I want to use referentially transparent callables while coding in Python. My goals are to help with handling concurrency, memoization, unit testing, and verification of code correctness. I want to write down clear rules for myself and other developers to follow that would ensure referential transparency. I don't mind that Python won't enforce any rules - we trust ourselves to follow them. Note that we never modify functions or methods in place (i.e., by hacking into the bytecode). Would the following make sense? A callable object c of class C will be referentially transparent if: Whenever the returned value of c(...) depends on any instance attributes, global variables, or disk files, such attributes, variables, and files must not change for the duration of the program execution; the only exception is that instance attributes may be changed during instance initialization. When c(...) is executed, no modifications to the program state occur that may affect the behavior of any object accessed through its "public interface" (as defined by us). If we don't put any restrictions on what "public interface" includes, then rule #2 becomes: When c(...) is executed, no objects are modified that are visible outside the scope of c.__call__. Note: I unsuccessfully tried to ask this question on SO, but I'm hoping it's more appropriate to this site.

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• Classes as a compilation unit

  - by Yannbane

  If "compilation unit" is unclear, please refer to this. However, what I mean by it will be clear from the context. Edit: my language allows for multiple inheritance, unlike Java. I've started designing+developing my own programming language for educational, recreational, and potentially useful purposes. At first, I've decided to base it off Java. This implied that I would have all the code be written inside classes, and that code compiles to classes, which are loaded by the VM. However, I've excluded features such as interfaces and abstract classes, because I found no need for them. They seemed to be enforcing a paradigm, and I'd like my language not to do that. I wanted to keep the classes as the compilation unit though, because it seemed convenient to implement, familiar, and I just liked the idea. Then I noticed that I'm basically left with a glorified module system, where classes could be used either as "namespaces", providing constants and functions using the static directive, or as templates for objects that need to be instantiated ("actual" purpose of classes in other languages). Now I'm left wondering: what are the benefits of having classes as compilation units? (Also, any general commentary on my design would be much appreciated.)

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• Are super methods in JavaScript limited to functional inheritance, as per Crockford's book?

  - by kindohm

  In Douglas Crockford's "JavaScript: The Good Parts", he walks through three types of inheritance: classical, prototypal, and functional. In the part on functional inheritance he writes: "The functional pattern also gives us a way to deal with super methods." He then goes on to implement a method named "superior" on all Objects. However, in the way he uses the superior method, it just looks like he is copying the method on the super object for later use: // crockford's code: var coolcat = function(spec) { var that = cat(spec), super_get_name = that.superior('get_name'); that.get_name = function (n) { return 'like ' + super_get_name() + ' baby'; }; return that; }; The original get_name method is copied to super_get_name. I don't get what's so special about functional inheritance that makes this possible. Can't you do this with classical or prototypal inheritance? What's the difference between the code above and the code below: var CoolCat = function(name) { this.name = name; } CoolCat.prototype = new Cat(); CoolCat.prototype.super_get_name = CoolCat.prototype.get_name; CoolCat.prototype.get_name = function (n) { return 'like ' + this.super_get_name() + ' baby'; }; Doesn't this second example provide access to "super methods" too?

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• Achieve anisotropic filtering

  - by fedab

  I want to set anisotropic filtering to my scene. I use SharpDX (DirectX 11) and C#. How do i set up anisotropic filtering in my shader? Currently i try that in the shader: Texture2D tex; sampler textureSampler = sampler_state { Texture = (tex); MipFilter = Anisotropic; MagFilter = Anisotropic; MinFilter = Anisotropic; MaxAnisotropy = 16; }; float4 PShader(float4 position : SV_POSITION, float4 color:COLOR, float2 tex0 : TEXCOORD0) : SV_TARGET { float4 textureColor; textureColor = tex.Sample(textureSampler, tex0) * color; return textureColor; } I get my object, textured, but it is not filtered anisotropic. I can write everything in the Parameters, even invalid things and i don't get any errors. The result is the same, objects without applied anisotropic filtering. Do i have to set that in the shader? Can i do that also with SamplerState? I tested that but i didn't get a result too. Some steps what i have to set would be helpful.

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• How to choose between Tell don't Ask and Command Query Separation?

  - by Dakotah North

  The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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• Problems moving a rectangle in Pygame.

  - by Yann Core

  Hi guys! I'm making a game in Pygame and I want to be able to target enemy unit. I made it so when I click on them a variable "targeted" becomes true, and stays true until I click somewhere else on the screen. I also want targeted units to have a small green circle around them, so I made it in GEDIT. I have made a function that draws everything on the screen (the background, the player, objects, etc) and in the part where it draws the units it checks if the variable "targeted" is true and if it is it should move that little green circle over the enemy units. here is the code that does that: screen.blit(enemy_unit.pic, enemy_unit.rect) #draw the unit if enemy_unit.targeted == True: #if the unit has been targeted then draw a circle over it target_rect.move_ip(enemy_unit.pos) #move the circle to the unit target_rect.fit(enemy_unit.rect) #there are some bigger units and some smaller ones, so we have to "scale" the circle screen.blit(target_pic, target_rect) #actually draw the circle This doesn't work, when I target the unit the circle just appears for a 1/5 of second next (not on, but just next) to the unit and then disappears. I am sure that I am keeping a good track of "enemy_unit.pos" because I tested it (I added a piece of code that would print one units position and mouse's position every time i clicked the mouse and when i was near him the numbers were same). If you could give me a hint about what I'm doing wrong. I think its in move_ip function, but I tried just move and it didn't work either (the circle didn't even show at all)!

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• What's the point of the Prototype design pattern?

  - by user1905391

  So I'm learning about design patterns in school. Many of them are silly little ideas, but nevertheless solve some recurring problems(singleton, adapters, asynchronous polling, ect). But today I was told about the so called 'Prototype' design pattern. I must be missing something, because I don't see any benefits from it. I've seen people online say it's faster than using "new"' but this is doesn't make any sense, since at some point, regardless how the new object is created, memory needs to be allocated for it ect. Furthermore, doesn't this pattern run in the same circles as the 'chicken or egg' problem? By this I mean, since the prototype pattern essentially is just cloning objects, at some point the original object must be created itself (ie, not cloned). So this would mean, that I would need to have an existing copy of every object that I would ever want to clone already ready to clone? Seems stupid to me. Can anyone explain what the use of this pattern is? Original post: http://stackoverflow.com/questions/13887704/whats-the-point-of-the-prototype-design-pattern

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• How do I find actors in an area on a poly-precise basis?

  - by Almo

  Ok, I've been asking various questions and getting some good answers, but I think I need to rethink my method, so I'll describe the problem. I have a player who has a big blue box in front of him. This box shows which KActors will be pushed when he pulls the trigger: Currently, the blue box spawns a descendant of Actor which checks collision to see which KActors are touching it: foreach Owner.TouchingActors(class'DynamicSMActor', DynamicActorItt) { // do stuff } The problem is, if you check for touching between Actors and KActors, it looks like it does a plain axis-aligned bounding-box collision. The power will push the box on the lower right, when it's clear it's not touching the blue box. How should I do this properly? I just need a way to find out which KActors are touching that area, on a poly-by-poly level. These collisions are only done with rectangular boxes and simple sphere collision; we are aware of the potential for performance issues with complex objects and poly-collision. I've tried making the collision checker a KActor, but it doesn't report any TouchingActors. This issue is causing us trouble in a lot of other places as well. So solving this problem is a core issue in our game.

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• What's wrong performing unit test against concrete implementation if your frameworks are not going to change?

  - by palm snow

  First a bit of background: We are re-architecting our product suite that was written 10 years ago and served its purpose. One thing that we cannot change is the database schema as we have 500+ client base using this system. Our db schema has over 150+ tables. We have decided on using Entity Framework 4.1 as DAL and still evaluating various frameworks for storing our business logic. I am investigation to bring unit testing into the mix but I also confused as to how far I need to go with setting up a full blown TDD environment. One aspect of setting up unit testing is by getting into implementing Repository, unit of work and mocking frameworks etc. This mean there will be cost and investment on the code-bloat associated with all these frameworks. I understand some of this could be auto-generated but when it comes to things like behaviors, that will be mostly hand written. Just to be clear, I am not questioning the important of unit testing your code. I am just not sure we need all its components (like repository, mocking etc.) when we are fairly certain of storage mechanism/framework (SQL Server/Entity Framework). All that code bloat with generic repositories make sense when you need a generic layers with ability to change this whenever you like however its very likely a YAGNI in our case. What we need is more of integration testing where we can unit-test our code with concrete repository objects and test data in database. In this scenario, just running integration test seem to be more beneficial in our case. Any thoughts if I am missing any thing here?

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• How to configure Bullet for LookAt?

  - by AllCoder

  I'm having problems positioning Bullet objects. I am doing: ToolVec3 origin = ToolVec3( obj_posx, obj_posy, obj_posz ); ToolVec3 vmod = ToolVec3( object_sizex / 2.0f, object_sizey / 2.0f, object_sizez / 2.0f ); btTransform shapeTransform = btTransform::getIdentity(); shapeTransform.setOrigin( btVector3(origin.x+vmod.x, origin.y+vmod.y, origin.z+vmod.z) ); btDefaultMotionState* myMotionState = new btDefaultMotionState(shapeTransform); btRigidBody::btRigidBodyConstructionInfo rbInfo(mass,myMotionState,m_collisionShapes[2],localInertia); btRigidBody* body = new btRigidBody(rbInfo); I then do: btCollisionObject* colObj = m_dynamicsWorld->getCollisionObjectArray()[i]; btRigidBody* body = btRigidBody::upcast(colObj); if(body && body->getMotionState()) { btDefaultMotionState* myMotionState = (btDefaultMotionState*)body->getMotionState(); myMotionState->m_graphicsWorldTrans.getOpenGLMatrix(m); } else { colObj->getWorldTransform().getOpenGLMatrix(m); } And after obtaining the matrix m, I paste it as model matrix. I am observing few things: I must add some weird "size / 2" to object's position, to have it drawed normally, I have following "up" look at vector defined: "0.0f, -1.0f, 0.0f" – basically, Y grows up, Z grows forward (to monitor), BUT – x grows LEFT, I think there is some conflict with the X direction.. I cannot obtain consistent positioning having world setup like this How to configure this in Bullet? Why the weird + size/2 requirement?

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• Fast, accurate 2d collision

  - by Neophyte

  I'm working on a 2d topdown shooter, and now need to go beyond my basic rectangle bounding box collision system. I have large levels with many different sprites, all of which are different shapes and sizes. The textures for the sprites are all square png files with transparent backgrounds, so I also need a way to only have a collision when the player walks into the coloured part of the texture, and not the transparent background. I plan to handle collision as follows: Check if any sprites are in range of the player Do a rect bounding box collision test Do an accurate collision (Where I need help) I don't mind advanced techniques, as I want to get this right with all my requirements in mind, but I'm not sure how to approach this. What techniques or even libraries to try. I know that I will probably need to create and store some kind of shape that accurately represents each sprite minus the transparent background. I've read that per pixel is slow, so given my large levels and number of objects I don't think that would be suitable. I've also looked at Box2d, but haven't been able to find much documentation, or any examples of how to get it up and running with SFML.

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• Why am I seeing so many instantiable classes without state?

  - by futlib

  I'm seeing a lot of instantiable classes in the C++ and Java world that don't have any state. I really can't figure out why people do that, they could just use a namespace with free functions in C++, or a class with a private constructor and only static methods in Java. The only benefit I can think of is that you don't have to change most of your code if you later decide that you want a different implementation in certain situations. But isn't that a case of premature design? It could be turned into a class later, when/if it becomes appropriate. Am I getting this wrong? Is it not OOP if I don't put everything into objects (i.e. instantiated classes)? Then why are there so many utility namespaces and classes in the standard libraries of C++ and Java? Update: I've certainly seen a lot examples of this in my previous jobs, but I'm struggling to find open source examples, so maybe it's not that common after all. Still, I'm wondering why people do it, and how common it is.

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• Android Bitmap: Collision Detecting

  - by Aekasitt Guruvanich

  I am writing an Android game right now and I would need some help in the collision of the Pawns on screen. I figured I could run a for loop on the Player class with all Pawn objects on the screen checking whether or not Width*Height intersects with each other, but is there a more efficient way to do this? And if you do it this way, many of the transparent pixel inside the rectangular area will also be considered as collision as well. Is there a way to check for collision between Bitmap on a Canvas that disregard transparent pixels? The class for player is below and the Pawn class uses the same method of display. Class Player { private Resources res; // Used for referencing Bitmap from predefined location private Bounds bounds; // Class that holds the boundary of the screen private Bitmap image; private float x, y; private Matrix position; private int width, height; private float velocity_x, velocity_y; public Player (Resources resources, Bounds boundary) { res = resources; bounds = boundary; image = BitmapFactory.decodeResource(res, R.drawable.player); width = image.getWidth(); height = image.getHeight(); position = new Matrix(); x = bounds.xMax / 2; // Initially puts the Player in the middle of screen y = bounds.yMax / 2; position.preTranslate(x,y); } public void draw(Canvas canvas) { canvas.drawBitmap(image, position, null); } }

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• Strategy to store/average logs of pings

  - by José Tomás Tocino

  I'm developing a site to monitor web services. The most basic type of check is sending a ping, storing the response time in a CheckLog object. By default, PingCheck objects are triggered every minute, so in one hour you get 60 CheckLogs and in one day you get 1440 CheckLogs. That's a lot of them, I don't need to store such level of detail, so I've set a up collapsing mechanism that periodically takes the uncollapsed CheckLogs older than 24h and collapses (averages) them in intervals of 30 minutes. So, if you have 360 CheckLogs that have been saved from 0:00 to 6:00, after collapsing you retain just 12 of them. The problem.. well, is this: After averaging the response times, the graph changes drastically. What can I do to improve this? Guess one option could be narrowing the interval duration to 15 min. I've seen the graphs at the GitHub status page and they do not seem to suffer from this problem. I'd appreciate any kind of information you could give me about this area.

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