development approach - Page 432

Turn-based tile game dynamic item/skill/command script files

- by user1542

I want to create a mechanism that could read text script, for example some kind of custom script such as ".skill" or ".item", which maybe contain some sort of simple script like .item Item.Name = "Strength Gauntlet"; Character.STR += 20; .. .skill Skill.Name = "Poison Attack"; Skill.Description = "Steal HP and inflict poison"; Player.HP += 200; Enemy.HP -= 200; Enemy.Status += Status.POISON; It may be different from this, but just want to give some idea of what I desire. However, I do not know how to dynamically parse these things and translate it into working script. For example, in battle scenerio, I should make my game read one of this ".skill" file and apply it to the current enemy, or the current player. How would I do this? Should I go for String parsing? It is like a script engine, but I prefer C# than creating new language, so how would I parse custom files into appropiate status commands? Another problem is, I have also created a command engine which would read String input and parse it into action such as "MOVE (1,2)" would move character to tile (1,2). Each command belong to separate class, and provide generic parsing method that should be implemented by hand. This is for the reason of custom number/type of arguments per each command. However, I think this is not well designed, because I desire it to automatically parse the parameters according to specify list of types. For example, MOVE command in "MOVE 1 2" would automatically parse the parameters into int, int and put it into X and Y. Now, this form can change, and we should be able to manually specify all type of formats. Any suggestion to this problem? Should I change from string parsing to some hardcode methods/classes?

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Why do meshes show up as bones in the Model class?

- by Itamar Marom

Right now I'm working on a 3D game and I've come across something very weird. When I created the model in Blender, I added an armature named "MyBone" to the stage and attached a cube ("MyCube") to it, so that when I move the armature, the cube moves with it. I exported this as an FBX and loaded it as a Model object. What I expected to see was: But what I got was this: I'm really confused. Why is the mesh I created showing up in the bone list? And what's Root Node? Here are the .blend and .fbx files: here or here. Thanks.

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Setting Anchor Point

- by Siddharth

I want to set anchor point for the sprite like cocos2d has done for their implementation. I do not found any thing like that in andengine so please provide guidance on that. I want to move the sprite on touch so I use following code but that does not work for me. super.setPosition(pX - this.getWidthScaled() / 2, pY - this.getHeightScaled() / 2); Because I touch on the corner of the image but automatically it comes at center of the image because of above code. I want to remain the touch at desire position and drag it. For me the anchor point became useful. But I don't found anything in andengine.

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how to move the camera behind a model with the same angle? in XNA

- by Mehdi Bugnard

I meet are having difficulty in moving my camera behind an object in a 3D world. I would create two view mode. 1: for fps (first person). 2nd: external view behind the character (second person). I searched the net some example but it does not work in my project. Here is my code used to change view if F2 is pressed //Camera double X1 = this.camera.PositionX; double X2 = this.player.Position.X; double Z1 = this.camera.PositionZ; double Z2 = this.player.Position.Z; //Verify that the user must not let the press F2 if (!this.camera.IsF2TurnedInBoucle) { // If the view mode is the second person if (this.camera.ViewCamera_type == CameraSimples.ChangeView.SecondPerson) { this.camera.ViewCamera_type = CameraSimples.ChangeView.firstPerson; //Calcul position - ?? Here my problem double direction = Math.Atan2(X2 - X1, Z2 - Z1) * 180.0 / 3.14159265; //Calcul angle - ?? Here my problem this.camera.position = .. this.camera.rotation = .. this.camera.MouseRadian_LeftrightRot = (float)direction; } //IF mode view is first person else { //....

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Exporting XNA class library as a DLL file

- by Will Bagley

I have downloaded an open source project that I intend to use with my current game. The download came with all the class files from the original project as well as a pre-compiled DLL file representing the project. I was able to easily link this DLL with my current project and get it working just fine, no problems there. The problem I now have is that I want to make a couple of changes to the original libraries (extend its functionality a bit to better suit my needs) and re-export the class library as a DLL again, but I have no clue how to do this. Is there some simple way in VS where I can just take the class library and export/compile it as a DLL file again or is there more to it than that? This seems like something that should be pretty simple but my efforts to find an answer have so far come up with nothing. Thanks in advance.

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How to blend multiple normal maps?

- by János Turánszki

I want to achieve a distortion effect which distorts the full screen. For that I spawn a couple of images with normal maps. I render their normal map part on some camera facing quads onto a rendertarget which is cleared with the color (127,127,255,255). This color means that there is no distortion whatsoever. Then I want to render some images like this one onto it: If I draw one somewhere on the screen, then it looks correct because it blends in seamlessly with the background (which is the same color that appears on the edges of this image). If I draw another one on top of it then it will no longer be a seamless transition. For this I created a blendstate in directX 11 that keeps the maximum of two colors, so it is now a seamless transition, but this way, the colors lower than 127 (0.5f normalized) will not contribute. I am not making a simulation and the effect looks quite convincing and nice for a game, but in my spare time I am thinking how I could achieve a nicer or a more correct effect with a blend state, maybe averaging the colors somehow? I I did it with a shader, I would add the colors and then I would normalize them, but I need to combine arbitrary number of images onto a rendertarget. This is my blend state now which blends them seamlessly but not correctly: D3D11_BLEND_DESC bd; bd.RenderTarget[0].BlendEnable=true; bd.RenderTarget[0].SrcBlend = D3D11_BLEND_SRC_ALPHA; bd.RenderTarget[0].DestBlend = D3D11_BLEND_INV_SRC_ALPHA; bd.RenderTarget[0].BlendOp = D3D11_BLEND_OP_MAX; bd.RenderTarget[0].SrcBlendAlpha = D3D11_BLEND_ONE; bd.RenderTarget[0].DestBlendAlpha = D3D11_BLEND_ZERO; bd.RenderTarget[0].BlendOpAlpha = D3D11_BLEND_OP_MAX; bd.RenderTarget[0].RenderTargetWriteMask = 0x0f; Is there any way of improving upon this? (PS. I considered rendering each one with a separate shader incementally on top of each other but that would consume a lot of render targets which is unacceptable)

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Box2D physics editor for complex bodies

- by Paul Manta

Is there any editor out there that would allow me to define complex entities, with joins connecting their multiple bodies, instead of regular single body entities? For example, an editor that would allow me to 'define' a car as having a main body with two circles as wheels, connected through joints. Clarification: I realize I haven't been clear enough about what I need. I'd like to make my engine data-driven, so all entities (and therefore their Box2D bodies) should be defined externally, not in code. I'm looking for a program like Code 'N' Web's PhysicsEditor, except that one only handles single body entities, no joints or anything like that. Like PhysicsEditor, the program should be configurable so that I can save the data in whatever format I want to. Does anyone know of any such software?

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SpriteFont Exception, no such character?

- by Michal Bozydar Pawlowski

I have such spriteFont: <?xml version="1.0" encoding="utf-8"?>  <XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics"> <Asset Type="Graphics:FontDescription">  <FontName>Segoe UI</FontName>  <Size>20</Size>  <Spacing>0</Spacing>  <UseKerning>true</UseKerning>  <Style>Regular</Style>    <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>Ұ</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> It has the character regions (32-1200) And I get this exception: A first chance exception of type 'System.ArgumentException' occurred in Microsoft.Xna.Framework.Graphics.ni.dll The character '?' (0x0441) is not available in this SpriteFont. If applicable, adjust the font's start and end CharacterRegions to include this character. Parameter name: character Why? I'm drawing the string like this: spriteBatch.DrawString(font24, zasadyText, zasadyTextPos, kolorCzcionki1, -0.05f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.5f) I even changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception -- EDIT -- Ok, I got the solution. It was a letter mistake in language. I had this: if (jezyk == "ru_RU") { font14 = Content.Load<SpriteFont>("ru_font14"); font24 = Content.Load<SpriteFont>("ru_font24"); font12 = Content.Load<SpriteFont>("ru_czcionkaFloty"); font10 = Content.Load<SpriteFont>("ru_font10"); font28 = Content.Load<SpriteFont>("ru_font28"); font20 = Content.Load<SpriteFont>("ru_font20"); } else { font14 = Content.Load<SpriteFont>("font14"); font24 = Content.Load<SpriteFont>("font24"); font12 = Content.Load<SpriteFont>("czcionkaFloty"); font10 = Content.Load<SpriteFont>("font10"); font28 = Content.Load<SpriteFont>("font28"); font20 = Content.Load<SpriteFont>("font20"); } and there should be not "ru_RU" but "ru-RU" I have no idea. I changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception

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Fitting a rectangle into screen with XNA

- by alecnash

I am drawing a rectangle with primitives in XNA. The width is: width = GraphicsDevice.Viewport.Width and the height is height = GraphicsDevice.Viewport.Height I am trying to fit this rectangle in the screen (using different screens and devices) but I am not sure where to put the camera on the Z-axis. Sometimes the camera is too close and sometimes to far. This is what I am using to get the camera distance: //Height of piramid float alpha = 0; float beta = 0; float gamma = 0; alpha = (float)Math.Sqrt((width / 2 * width/2) + (height / 2 * height / 2)); beta = height / ((float)Math.Cos(MathHelper.ToRadians(67.5f)) * 2); gamma = (float)Math.Sqrt(beta*beta - alpha*alpha); position = new Vector3(0, 0, gamma); Any idea where to put the camera on the Z-axis?

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Time calculation between openGL update calls.

- by Vijayendra

In XNA, the system calls update and draw function with the time information. This contains information such as how much time has passed since last update was called. This makes easy to integrate time and do animation calculation accordingly. But I dont see any such mechanism in openGL. I see openGL requires programmers to have their own implementation which could be buggy or inefficient. Is there any standard (and efficient) code that demonstrate this practice in openGL?

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How to build a 4x game?

- by Marco

I'm trying to study how succefully implement a 4x game. Area of interest: 1) map data: how to store stellars systems (graphs?), how to generate them and so on.. 2) multiplayer: how to organize code in a non graphical server and a client to display it 3) command system: what are patters to catch user and ai decisions and handle them, adding at first "explore" and "colonize" then "combat", "research", "spy" and so on (commands can affect ships, planets, research, etc..) 4) ai system: ai can use commands to expand, upgrade planets and ship I know is a big questions, so help is appreciated :D 1) Map data Best choice is have a graph to model a galaxy. A node is a stellar system and every system have a list of planets. Ship cannot travel outside of predefined paths, like in Ascendancy: http://www.abandonia.com/files/games/221/Ascendancy_2.png Every connection between two stellar systems have a cost, in turns. Generate a galaxy is only a matter of: - dimension: number of stellar systems, - variety: randomize number of planets and types (desertic, earth, etc..), - positions of each stellar system on game space - connections: assure that exist a path between every node, so graph is "connected" (not sure if this a matematically correct term) 2) Multiplayer Game is organized in turns: player 1, player 2, ai1, ai2. Server take care of all data and clients just diplay it and collect data change. Because is a turn game, latency is not a problem :D 3) Command system I would like to design a hierarchy of commands to take care of this aspect: abstract Genericcommand (target) ExploreCommand (Ship) extends genericcommand colonizeCommand (Ship) buildcommand(planet, object) and so on. In my head all this commands are stored in a queue for every planets, ships or reasearch center or spy, and each turn a command is sent to a server to apply command and change data state 4) ai system I don't have any idea about this. Is a big topic and what I want is a simple ai. Something like "expand and fight against everyone". I think about a behaviour tree to control ai moves, so I can develop an ai that try to build ships to expand and then colonize planets, upgrade them throught science and combat enemies. Could be done with a finite state machine too ? any ideas, resources, article are welcome!

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Pathfinding in multi goal, multi agent environment

- by Rohan Agrawal

I have an environment in which I have multiple agents (a), multiple goals (g) and obstacles (o). . . . a o . . . . . . . o . g . . a . . . . . . . . . . o . . . . o o o o . g . . o . . . . . . . o . . . . o . . . . o o o o a What would an appropriate algorithm for pathfinding in this environment? The only thing I can think of right now, is to Run a separate version of A* for each goal separately, but i don't think that's very efficient.

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What's wrong with this turn to face algorithm?

- by Chan

I implement a torpedo object that chases a rotating planet. Specifically, it will turn toward the planet each update. Initially my implement was: void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (to_target * speed); } which works perfectly for torpedo that is a solid sphere. Now my torpedo is actually a model, which has a forward vector, so using this method looks odd because it doesn't actually turn toward but jump toward. So I revised it a bit to get, double get_rotation_angle(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); double cosine_theta = u.dot(v); // domain of arccosine is [-1, 1] if (cosine_theta > 1) { cosine_theta = 1; } if (cosine_theta < -1) { cosine_theta = -1; } return math3d::to_degree(acos(cosine_theta)); } vector3<float> get_rotation_axis(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); // fix linear case if (u == v || u == -v) { v[0] += 0.05; v[1] += 0.0; v[2] += 0.05; v.normalize(); } vector3<float> axis = u.cross(v); return axis.normal(); } void turn_to_face() { vector3<float> to_target = (target - position); vector3<float> axis = get_rotation_axis(get_forward(), to_target); double angle = get_rotation_angle(get_forward(), to_target); double distance = math3d::distance(position, target); gl_matrix_mode(GL_MODELVIEW); gl_push_matrix(); { gl_load_identity(); gl_translate_f(position.get_x(), position.get_y(), position.get_z()); gl_rotate_f(angle, axis.get_x(), axis.get_y(), axis.get_z()); gl_get_float_v(GL_MODELVIEW_MATRIX, OM); } gl_pop_matrix(); move(); } void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (get_forward() * speed); } The logic is simple, I find the rotation axis by cross product, the angle to rotate by dot product, then turn toward the target position each update. Unfortunately, it looks extremely odds since the rotation happens too fast that it always turns back and forth. The forward vector for torpedo is from the ModelView matrix, the third column A: MODELVIEW MATRIX -------------------------------------------------- R U A T -------------------------------------------------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 -------------------------------------------------- Any suggestion or idea would be greatly appreciated.

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Audio Panning using RtAudio

- by user1801724

I use Rtaudio library. I would like to implement an audio program where I can control the panning (e.g. shifting the sound from the left channel to the right channel). In my specific case, I use a duplex mode (you can find an example here: duplex mode). It means that I link the microphone input to the speaker output. I seek on the web, but I did not find anything useful. Should I apply a filter on the output buffer? What kind of filter? Can anyone help me? Thanks

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Multiple volumetric lights

- by notabene

I recently read this GPU GEMS 3 article Volumetric Light Scattering as a Post-Process. I like the idea to add volumetric light property to realtime render i'm working on. Question is will it work for multiple lights? Our renderer uses one render pass per light and uses additive blending to sum incoming light. I'm mostly convinced that it have to work nice. Do you agree? Maybe there can be problem where light rays crosses each other.

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Maya .IFF plugins for Gimp

- by Kara Marfia

Maya's preferred format for saving off a UV Snapshot is its own .IFF format, so I was hoping to find a plugin allowing Gimp 2 (Windows) to read it. I've found plenty of plugins for different linux distros, but none are win-friendly (that I can discern - admittedly I'm no whiz with Gimp). Does anyone know of one? Alternately, .tiff seems to work just fine, so if there's no good reason to bother fiddling with IFFs, I'd appreciate the input there, too. (sorry if this isn't on-topic)

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Modern Shader Book?

- by Michael Stum

I'm interested in learning about Shaders: What are they, when/for what would I use them, and how to use them. (Specifically I'm interested in Water and Bloom effects, but I know close to 0 about Shaders, so I need a general introduction). I saw a lot of books that are a couple of years old, so I don't know if they still apply. I'm targeting XNA 4.0 at the moment (which I believe means HLSL Shaders for Shader Model 4.0), but anything that generally targets DirectX 11 and OpenGL 4 is helpful I guess.

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What methods should save/load a game state

- by vedi

There are a lot of articles about how to save a state of a game and they are pretty good. But I have one conceptual misunderstanding where should I save the state? My game has number of screens and pair of them are MainMenuScreen and MainSceneScreen these are inherited from Screen class. MainMenuScreen is shown at start of the game the MainSceneScreen little later. What is the problem? I navigated to MainSceneScreen, forced Android to stop the application (I change a language settings on the device to achieve it, please let me know if I'm wrong). After that I select the application again and I can see MainMenuScreen is shown. But I want MainSceneScreen to be shown. I suppose I should override resume method. But what class I should override? I have class PsGame that extends Game class of libgdx. I put breakpoints to its resume method and it turned out that method was not called. I investigated the problem and I've found little strange code in onResume method of AndroidApplication class of libgdx: if (!firstResume) graphics.resume(); else firstResume = false; My debugger said firstResume was true and didn't go to *graphics.resume()*line. Sorry for a lot of words but could you answer following question: What did I do wrong? What methods should I override? Thank you in advance.

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State / Screen management in Entity Component Systems

- by David Lively

My entity/component system is happily humming along and, despite some performance concerns I initially had, everything is working fine. However, I've realized that I missed a crucial point when starting this thing: how do you handle different screens? At the moment, I have a GameManager class which owns a component manager and entity manager. When I create an entity, the entity manager assigns it an ID and makes sure it's tracked. When I modify the components that are assigned to an entity. an UpdateEntity method is called, which alerts each of the systems that they may need to add or remove the entity from their respective entity lists. A problem with this is that the collection of entities operated on by each system is determined solely by the individual Systems, typically based on a "required component" filter. (An entity has to have a Renderable component to be rendered, for instance.) In this situation, I can't just keep collections of entities per screen and only Update/Draw those collections. They'd have to either be added and removed depending on their applicability to the current screen, which would cause their associated components to be removed, or enable/disable entities in a group per screen to hide what's not supposed to be visible. These approaches seem like really, really crappy kludges. What's a good way to handle this? A pretty straightforward way that comes to mind is to create a separate GameManager (which in my implementation owns all of the systems, entities, etc.) per screen, which means that everything outside of the device context would be duplicated. That's bothersome because some things are always visible, or I might want to continue to display the game under a translucent menu window. Another option would be to add a "layer" key to the GameManager class, which could be checked against a displayable layer stack held by the game manager. *System.Draw() would be called for each active layer, in the required order as determined by the stack. When the systems request an iterator for their respective entity collections, it would be pre-filtered to a (cached) set of those entities that participate in the active layer. Those collections could be updated from the same UpdateEntity event that's already used to maintain each system's entity collections. Still, kinda feels like a hack. If I've coded myself into a corner, feel free to throw tomatoes as long as they're labeled with a helpful suggestion. Hooray for learning curves.

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How to use batch rendering with an entity component system?

- by Kiril

I have an entity component system and a 2D rendering engine. Because I have a lot of repeating sprites (the entities are non-animated, the background is tile based) I would really like to use batch rendering to reduce calls to the drawing routine. What would be the best way to integrate this with an engtity system? I thought about creating and populating the sprite batche every frame update, but that will probably be very slow. A better way would be to add a reference to an entity's quad to the sprite batch at initialization, but that would mean that the entity factory has to be aware of the Rendering System or that the sprite batch has to be a component of some Cache entity. One case violates encapsulation pretty heavily, while the other forces a non-game object entity in the entity system, which I am not sure I like a lot. As for engine, I am using Love2D (Love2D website) and FEZ ( FEZ website) as entity system(so everything is in Lua). I am more interested in a generic pattern of how to properly implement that rather than a language/library specific solution. Thanks in advance!

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3D Studio Max biped restrictions?

- by meds

I have a stock biped character in 3D studio max which has a jump animation. The problem I have with the jump animation is that there is actual y offset happening inside it which makes it awkward to play while the character is jumping since it's not only jumping in the game world but the jump animation is adding its own height offset. I'm tryuing to remove the jump animations height offset, so far I've found the root node and deleted all its key frames which has helped a bit. The problem I'm having now is that the character still has some height offset and if I try to lower it it has a fake 'ground' that isn't at 0 and the limbs sort of bend on the imaginary floor, si there a way to remove this restriction just for the jump animation? Here's what I mean: http://i.imgur.com/qoWIR.png Any idea for a fix? I'm using Unity 3D if that opens any other possibilities...

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Server-side Architecture for Online Game

- by Draiken

Hi, basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks !

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Collision Resolution

- by ultifinitus

Hey all, I'm making a simple side-scrolling game, and I would appreciate some input! My collision detection system is a simple bounding box detection, so it's really easy to implement. However my collision resolution is ridiculous! Currently I have a little formula like this: if (colliding(firstObject,secondObject)) firstObject.resolve_collision(yAxisOffset); if (colliding(firstObject,secondObject)) firstObject.resolve_collision(xAxisOffset); where yAxisOffset is only set if the first object's previous y position was outside the second object's collision frame, respectively xAxisOffset as well. Now this is working great, in general. However there is a single problem. When I have a stack of objects and I push the first object against that stack, the first object get's "stuck," on the stack. What's I think is happening is the object's collision system checks and resolves for collisions based on creation time, so If I check one axis, then the other, the object will "sink" object directly along the checking axis. This sinking action causes the collision detection routine to think there's a gap between our position and the other object's position, and when I finally check the object that I've already sunk into, my object's position is resolved to it's original position... All this is great, and I'm sure if I bang my head against a wall long enough i'll come up with a working algorithm, but I'd rather not =). So what in the heck do you think I should do? How could I change my collision resolution system to fix this? Here's the program (temporary link, not sure how long it'll last) (notes: arrow keys to navigate, click to drop block, x to jump) I'd appreciate any help you can offer!

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Calculating collision force with AfterCollision/NormalImpulse is unreliable when IgnoreCCD = false?

- by Michael

I'm using Farseer Physics Engine 3.3.1 in a very simple XNA 4 test game. (Note: I'm also tagging this Box2D, because Farseer is a direct port of Box2D and I will happily accept Box2D answers that solve this problem.) In this game, I'm creating two bodies. The first body is created using BodyFactory.CreateCircle and BodyType.Dynamic. This body can be moved around using the keyboard (which sets Body.LinearVelocity). The second body is created using BodyFactory.CreateRectangle and BodyType.Static. This body is static and never moves. Then I'm using this code to calculate the force of collision when the two bodies collide: staticBody.FixtureList[0].AfterCollision += new AfterCollisionEventHandler(AfterCollision); protected void AfterCollision(Fixture fixtureA, Fixture fixtureB, Contact contact) { float maxImpulse = 0f; for (int i = 0; i < contact.Manifold.PointCount; i++) maxImpulse = Math.Max(maxImpulse, contact.Manifold.Points[i].NormalImpulse); // maxImpulse should contain the force of the collision } This code works great if both of these bodies are set to IgnoreCCD=true. I can calculate the force of collision between them 100% reliably. Perfect. But here's the problem: If I set the bodies to IgnoreCCD=false, that code becomes wildly unpredictable. AfterCollision is called reliably, but for some reason the NormalImpulse is 0 about 75% of the time, so only about one in four collisions is registered. Worse still, the NormalImpulse seems to be zero for completely random reasons. The dynamic body can collide with the static body 10 times in a row in virtually exactly the same way, and only 2 or 3 of the hits will register with a NormalImpulse greater than zero. Setting IgnoreCCD=true on both bodies instantly solves the problem, but then I lose continuous physics detection. Why is this happening and how can I fix it? Here's a link to a simple XNA 4 solution that demonstrates this problem in action: http://www.mediafire.com/?a1w242q9sna54j4

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Friction not working for Vehicle in BulletPhysics

- by Manmohan Bishnoi

I am creating a vehicle using bullet-physics engine (v 2.82). I created a ground ( btBoxShape ), a box and a vehicle (following the demo). But friction between ground and vehicle wheels seems not working. As soon as the vehicle is placed in 3d world, it starts moving forward. START : Steering works for the vehicle, but engineForce and brakingForce does not work (i.e. I cannot speed-up or stop the vehicle) : I create physics world like this : void initPhysics() { broadphase = new btDbvtBroadphase(); collisionConfiguration = new btDefaultCollisionConfiguration(); dispatcher = new btCollisionDispatcher(collisionConfiguration); solver = new btSequentialImpulseConstraintSolver(); dynamicsWorld = new btDiscreteDynamicsWorld(dispatcher, broadphase, solver, collisionConfiguration); dynamicsWorld->setGravity(btVector3(0, -9.81, 0)); // Debug Drawer bulletDebugugger.setDebugMode(btIDebugDraw::DBG_DrawWireframe); dynamicsWorld->setDebugDrawer(&bulletDebugugger); //groundShape = new btStaticPlaneShape(btVector3(0, 1, 0), 1); groundShape = new btBoxShape(btVector3(50, 3, 50)); fallShape = new btBoxShape(btVector3(1, 1, 1)); // Orientation and Position of Ground groundMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(0, -3, 0))); btRigidBody::btRigidBodyConstructionInfo groundRigidBodyCI(0, groundMotionState, groundShape, btVector3(0, 0, 0)); groundRigidBody = new btRigidBody(groundRigidBodyCI); dynamicsWorld->addRigidBody(groundRigidBody); /////////////////////////////////////////////////////////////////////// // Vehicle Setup /////////////////////////////////////////////////////////////////////// vehicleChassisShape = new btBoxShape(btVector3(1.f, 0.5f, 2.f)); vehicleBody = new btCompoundShape(); localTrans.setIdentity(); localTrans.setOrigin(btVector3(0, 1, 0)); vehicleBody->addChildShape(localTrans, vehicleChassisShape); localTrans.setOrigin(btVector3(3, 0.f, 0)); vehicleMotionState = new btDefaultMotionState(localTrans); //vehicleMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(3, 0, 0))); btVector3 vehicleInertia(0, 0, 0); vehicleBody->calculateLocalInertia(vehicleMass, vehicleInertia); btRigidBody::btRigidBodyConstructionInfo vehicleRigidBodyCI(vehicleMass, vehicleMotionState, vehicleBody, vehicleInertia); vehicleRigidBody = new btRigidBody(vehicleRigidBodyCI); dynamicsWorld->addRigidBody(vehicleRigidBody); wheelShape = new btCylinderShapeX(btVector3(wheelWidth, wheelRadius, wheelRadius)); { vehicleRayCaster = new btDefaultVehicleRaycaster(dynamicsWorld); vehicle = new btRaycastVehicle(vehicleTuning, vehicleRigidBody, vehicleRayCaster); // never deactivate vehicle vehicleRigidBody->setActivationState(DISABLE_DEACTIVATION); dynamicsWorld->addVehicle(vehicle); float connectionHeight = 1.2f; bool isFrontWheel = true; vehicle->setCoordinateSystem(rightIndex, upIndex, forwardIndex); // 0, 1, 2 // add wheels // front left btVector3 connectionPointCS0(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // front right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, 2*CUBE_HALF_EXTENT-wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); isFrontWheel = false; // rear right connectionPointCS0 = btVector3(-CUBE_HALF_EXTENT+(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); // rear left connectionPointCS0 = btVector3(CUBE_HALF_EXTENT-(0.3*wheelWidth), connectionHeight, -2*CUBE_HALF_EXTENT+wheelRadius); vehicle->addWheel(connectionPointCS0, wheelDirectionCS0, wheelAxleCS, suspensionRestLength, wheelRadius, vehicleTuning, isFrontWheel); for (int i = 0; i < vehicle->getNumWheels(); i++) { btWheelInfo& wheel = vehicle->getWheelInfo(i); wheel.m_suspensionStiffness = suspensionStiffness; wheel.m_wheelsDampingRelaxation = suspensionDamping; wheel.m_wheelsDampingCompression = suspensionCompression; wheel.m_frictionSlip = wheelFriction; wheel.m_rollInfluence = rollInfluence; } } /////////////////////////////////////////////////////////////////////// // Orientation and Position of Falling body fallMotionState = new btDefaultMotionState(btTransform(btQuaternion(0, 0, 0, 1), btVector3(-1, 5, 0))); btScalar mass = 1; btVector3 fallInertia(0, 0, 0); fallShape->calculateLocalInertia(mass, fallInertia); btRigidBody::btRigidBodyConstructionInfo fallRigidBodyCI(mass, fallMotionState, fallShape, fallInertia); fallRigidBody = new btRigidBody(fallRigidBodyCI); dynamicsWorld->addRigidBody(fallRigidBody); } I step physics world like this : // does not work vehicle->applyEngineForce(maxEngineForce, WHEEL_REARLEFT); vehicle->applyEngineForce(maxEngineForce, WHEEL_REARRIGHT); // these also do not work vehicle->setBrake(gBreakingForce, WHEEL_REARLEFT); vehicle->setBrake(gBreakingForce, WHEEL_REARRIGHT); // this works vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTLEFT); vehicle->setSteeringValue(gVehicleSteering, WHEEL_FRONTRIGHT); dynamicsWorld->stepSimulation(1 / 60.0f, 10); However If I apply brakingForce to all 4 wheels (i.e. including WHEEL_FRONTLEFT and WHEEL_FRONTRIGHT), then my vehicle stops, but keeps sliding/moving forward very very slowly. How do I fix this ?

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