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  • Displaying text letter by letter

    - by Evi
    I am planing to Write a Text adventure and I don't know how to make the text draw letter by letter in any other way than changing the variable from h to he to hel to hell to hello That would be a terrible amount of work since there are tons of dialogue. Here is the source code so far { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; Texture2D sampleBG; Texture2D TextBG; SpriteFont defaultfont; KeyboardState keyboardstate; public bool spacepress = false; public bool mspress = false; public int textheight = 425; public int rowspace = 40; public string namebox = "(null)"; public string Row1 = "(null)"; public string Row2 = "(null)"; public string Row3 = "(null)"; public string Row4 = "(null)"; public int Dialogue = 0; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; graphics.PreferredBackBufferHeight = 600; graphics.PreferredBackBufferWidth = 800; IsMouseVisible = true; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); // TODO: use this.Content to load your game content here sampleBG = Content.Load <Texture2D>("SampleBG"); defaultfont = Content.Load<SpriteFont>("SpriteFont1"); TextBG = Content.Load<Texture2D>("textbg"); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { KeyboardState keyboardstate = Keyboard.GetState(); MouseState mousestate = Mouse.GetState(); // Changes Dialgue by pressing Left Mouse Button or Space #region Dialogue changer if (mousestate.LeftButton == ButtonState.Pressed && mspress == false) { mspress = true; Dialogue = Dialogue + 1; } if (mousestate.LeftButton == ButtonState.Released && mspress == true) { mspress = false; } if (keyboardstate.IsKeyDown(Keys.Space) && spacepress == false) { spacepress = true; Dialogue = Dialogue + 1; } if (keyboardstate.IsKeyUp(Keys.Space) && spacepress == true) { spacepress = false; } #endregion // ------------------------------------------------------ // Dialgue Content #region Dialgue if (Dialogue == 1) { Row1 = "Input Text 1 Here."; Row2 = "Input Text 2 Here."; Row3 = "Input Text 3 Here."; Row4 = "Input Text 4 Here."; } if (Dialogue == 2) { Row1 = "Text 1"; Row2 = "Text 2"; Row3 = "Text 3"; Row4 = "Text 4"; } #endregion // ------------------------------------------------------ base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); // TODO: Add your drawing code here spriteBatch.Begin(); spriteBatch.Draw(sampleBG, new Rectangle(0, 0, 800, 600), Color.White); spriteBatch.Draw(TextBG, new Rectangle(0, 400, 800, 200), Color.White); spriteBatch.DrawString(defaultfont, Row1, new Vector2(10, (textheight + (rowspace * 0))), Color.Black); spriteBatch.DrawString(defaultfont, Row2, new Vector2(10, (textheight + (rowspace * 1))), Color.Black); spriteBatch.DrawString(defaultfont, Row3, new Vector2(10, (textheight + (rowspace * 2))), Color.Black); spriteBatch.DrawString(defaultfont, Row4, new Vector2(10, (textheight + (rowspace * 3))), Color.Black); spriteBatch.End(); base.Draw(gameTime); } } }

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  • Which are the cons of using only non-member functions and POD?

    - by Miro
    I'm creating my own game engine. I've read these articles and this question about DOD and it was written to not use member functions and classes. I also heard some criticism to this idea. I can write it using member functions or non-member functions it would be similar. So what are the benefits/cons of that approach or when the project grows, does any of these approaches give clearer and better manageable code? With POD & non-member functions I don't have to make struct members public I can still use object id outside of engine like OpenGL does with all it's stuff, so It's not about encapsulation. POD - plain old data DOD - data oriented design

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  • Algorithm to shift the car

    - by Simran kaur
    I have a track that can be divided into n number of tracks and a car as GamObject. The track has transforms such that some part of the track's width lies in negative x axis and other in positive. Requirement: One move should cross one track. On every move(left or right), I want the car to reach exact centre of the next track on either sides i.e left or right. My code: Problem: : Because of negative values , somewhere I am missing out something that is making car move not in desirable positions and that's because of negative values only. variable tracks is the number of tracks the whole track is divided in. variable dist is the total width of the complete track. On left movement: if (Input.GetKeyDown (KeyCode.LeftArrow)) { if (this.transform.position.x < r.renderer.bounds.min.x + box.size.x) { this.transform.position = new Vector3 (r.renderer.bounds.min.x + Mathf.FloorToInt(box.size.x), this.transform.position.y, this.transform.position.z); } else { int tracknumber = Mathf.RoundToInt(dist - transform.position.x)/tracks; float averagedistance = (tracknumber*(dist/tracks) + (tracknumber-1)*(dist/tracks))/2; if(transform.position.x > averagedistoftracks) { amountofmovement = amountofmovement + (transform.position.x - averagedistance); } else { amountofmovement = amountofmovement - (averagedistance - transform.position.x); } this.transform.position = new Vector3 (this.transform.position.x - amountofmovement, this.transform.position.y, this.transform.position.z); } }

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  • OpenGL: Want to keep gun on top of car and be able to control angle. Having difficulties.

    - by Blair
    So I am making a simple game. I want to put a gun on top of a car so basically like a long rod in the middle of a black is how I am modelling it right now. I want to be able to control the angle of the gun. Basically it can go forward all the way so that it is parallel to the ground facing the direction the car is moving or it can point behind the car and any of the angles in between these positions. I have something like the following right now but its not really working. Is there an better way to do this that I am not seeing? #This will place the car glPushMatrix() glTranslatef(self.position.x,1.5,self.position.z) glRotated(self.rotation, 0.0, 1.0, 0.0) glScaled(0.5, 0.5, 0.5) glCallList(self.model.gl_list) glPopMatrix() #This will place the gun on top glPushMatrix() glTranslatef(self.position.x,2.5,self.position.z) glRotated(self.tube_angle, self.direction.z, 0.0, self.direction.x) print self.direction.z glRotated(45, self.position.z, 0.0, self.position.x) glScaled(1.0, 0.5, 1.0) glCallList(self.tube.gl_list) glPopMatrix() This almost works. It moves the gun up and down. But when the car moves around the angle of the gun changes. Not what I want.

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  • Including slick2d or slick-util in maven build?

    - by BotskoNet
    I'm converting a project to lwjgl and trying to use slick-util as well. There's no slick-util maven repo anywhere (nor slick2d itself anymore). I've included local dependancies before using <dependency> <groupId>org.newdawn</groupId> <artifactId>slick</artifactId> <version>237</version> <scope>system</scope> <systemPath>${project.basedir}/lib/slick-util.jar</systemPath> </dependency> The maven package process runs without issue, but when I try to run the jar, it errors out with a ClassNotFoundException. There's no mention of slick-util in the manifest and I can't find out how to make my game load that jar properly. Side question: how do I ensure when I distribute my applications, the game properly installs these libraries?

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  • How to use the zoom gesture in libgdx?

    - by user3452725
    I found the example code for the GestureListener class, but I don't understand the zoom method: private float initialScale = 1; public boolean zoom (float originalDistance, float currentDistance) { float ratio = originalDistance / currentDistance; //I get this camera.zoom = initialScale * ratio; //This doesn't make sense to me because it seems like every time you pinch to zoom, it resets to the original zoom which is 1. So basically it wouldn't 'save' the zoom right? System.out.println(camera.zoom); //Prints the camera zoom return false; } Am I not interpreting this right?

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  • how to implement motion blur effect?

    - by PlayerOne
    I wanted to know how one would implement this motion blur or fade effect behind the soccer ball . Here is what I was thinking . You have the balls current position and you also keep its previous position(couple of sec back). and you draw a "streak" sprite between the 2 points. I have seen this effect lots of time implemented for projects in various 2d games and wanted to know if there is a standard technique. http://i45.tinypic.com/2n24j7r.png

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  • How to stop camera from rotating in 2.5d platformer

    - by Artem Suchkov
    I'm stuck with a problem: I can not make my camera stop rotating after character. What I already have tried: using empty game object with rigid body and locked rotation and make it parent of camera, while player being the parent of object. Also, I've tried using few scripts from web, that did not help. Right now I'm bad with using JS in Unity (can handle JS on website, but I dont know how to integrate it for now) and practicing the basics, making easy 2.5d platformer with basic features, so I can not write code for now.

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  • Game Sound Effects Availability

    - by Ben
    Is there a need in the community for affordable game-focused sound effect packs? I am considering putting together some effects specifically geared toward games and indie developers that desire to get a working prototype quickly off the ground. Is there a need for this, or is there another standard "go-to" spot for this kind of thing? I want to offer value to the community but wanted to assess the need first. If anyone has thoughts, insight, or personal opinions on this I would love to hear it!

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  • What tools should I consider if my aim is to make a game available to as many platforms as possible?

    - by Kenji Kina
    We're planning on developing a 2D, grid-based puzzle game, and although it's still very early in the planning stages, we'd like to make our decisions well from the beginning. Our strategy will be to make the game available to as many platforms as possible, for example PCs (Windows, Mac and/or Linux), mobile phones (iPhone and/or Android based phones), game consoles (XBLA and/or PSN) PC will have an emphasis, but I believe that's the most flexible platform so that shouldn't be a problem. So, what programming language, game engine, frameworks and all around tools would be best suited for our goal? P.S.: I'm betting a set of tools won't cover ALL of them, and that there will still be some kind of "translating" effort for some platforms, but we'd like to know what the most far reaching are.

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  • Realistic planetary terrain generation with weights

    - by Programmdude
    I need terrain generation for a planet. The planet will be divided up into several hundred hexes, and I need it to be realistic and based on weights. I have dabbled in terrain generation before, but nothing like this. So I figure it would be a good idea to ask the community for answers, recommended articles or the like. By realistic, I mean not just random hexes, but continent shaped things with a few islands. More desert around the equator and more ice around the poles. I also have two weights I need to base it around: ice percentage and water percentage. That means that around XX% of the planet will need to be water. Does anyone have any advice or places to start? Generating arbitrary terrain is easy, but something a bit more "organic" like this seems rather difficult. It also needs to be seamless. Should be obvious since it's a planet, but no harm in pointing it out.

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  • Execute code at specific intervals, only once?

    - by Mathias Lykkegaard Lorenzen
    I am having an issue with XNA, where I want to execute some code in my Update method, but only at a given interval, and only once. I would like to avoid booleans to check if I've already called it once, if possible. My code is here: if ((gameTime.TotalGameTime.TotalMilliseconds % 500) == 0) { Caret.Visible = !Caret.Visible; } As you may have guessed, it's for a TextBox control, to animate the caret between invisible and visible states. I just have reason to believe that it is called twice or maybe even 3 times in a single update-call, which is bad, and makes it look unstable and jumpy.

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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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  • Cool examples of procedural pixel shader effects?

    - by Robert Fraser
    What are some good examples of procedural/screen-space pixel shader effects? No code necessary; just looking for inspiration. In particular, I'm looking for effects that are not dependent on geometry or the rest of the scene (would look okay rendered alone on a quad) and are not image processing (don't require a "base image", though they can incorporate textures). Multi-pass or single-pass is fine. Screenshots or videos would be ideal, but ideas work too. Here are a few examples of what I'm looking for (all from the RenderMonkey samples): PS - I'm aware of this question; I'm not asking for a source of actual shader implementations but instead for some inspirational ideas -- and the ones at the NVIDIA Shader Library mostly require a scene or are image processing effects. EDIT: this is an open-ended question and I wish there was a good way to split the bounty. I'll award the rep to the best answer on the last day.

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  • What light attenuation function does UDK use?

    - by ananamas
    I'm a big fan of the light attenuation in UDK. Traditionally I've always used the constant-linear-quadratic falloff function to control how "soft" the falloff is, which gives three values to play with. In UDK you can get similar results, but you only need to tweak one value: FalloffExponent. I'm interested in what the actual mathematical function here is. The UDK lighting reference describes it as follows: FalloffExponent: This allows you to modify the falloff of a light. The default falloff is 2. The smaller the number, the sharper the falloff and the more the brightness is maintained until the radius is reached. Does anyone know what it's doing behind the scenes?

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  • Smooth animation when using fixed time step

    - by sythical
    I'm trying to implement the game loop where the physics is independent from rendering but my animation isn't as smooth as I would like it to be and it seems to periodically jump. Here is my code: // alpha is used for interpolation double alpha = 0, counter_old_time = 0; double accumulator = 0, delta_time = 0, current_time = 0, previous_time = 0; unsigned frame_counter = 0, current_fps = 0; const unsigned physics_rate = 40, max_step_count = 5; const double step_duration = 1.0 / 40.0, accumulator_max = step_duration * 5; // information about the circ;e (position and velocity) int old_pos_x = 100, new_pos_x = 100, render_pos_x = 100, velocity_x = 60; previous_time = al_get_time(); while(true) { current_time = al_get_time(); delta_time = current_time - previous_time; previous_time = current_time; accumulator += delta_time; if(accumulator > accumulator_max) { accumulator = accumulator_max; } while(accumulator >= step_duration) { if(new_pos_x > 1330) velocity_x = -15; else if(new_pos_x < 70) velocity_x = 15; old_pos_x = new_pos_x; new_pos_x += velocity_x; accumulator -= step_duration; } alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; al_clear_to_color(al_map_rgb(20, 20, 40)); // clears the screen al_draw_textf(font, al_map_rgb(255, 255, 255), 20, 20, 0, "current_fps: %i", current_fps); // print fps al_draw_filled_circle(render_pos_x, 400, 15, al_map_rgb(255, 255, 255)); // draw circle // I've added this to test how the program will behave when rendering takes // considerably longer than updating the game. al_rest(0.008); al_flip_display(); // swaps the buffers frame_counter++; if(al_get_time() - counter_old_time >= 1) { current_fps = frame_counter; frame_counter = 0; counter_old_time = al_get_time(); } } I have added a pause during the rendering part because I wanted to see how the code would behave when a lot of rendering is involved. Removing it makes the animation smooth but then I'll have to make sure that I don't let the frame rate drop too much and that doesn't seem like a good solution. I've been trying to fix this for a week and have had no luck so I'd be very grateful if someone can read through my code. Thank you! Edit: I added the following code to work out the actual velocity (pixels per second) of the ball each time the ball is rendered and surprisingly it's not constant so I'm guessing that's the issue. I'm not sure why it's not constant. alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; cout << (render_pos_x - old_render_pos) / delta_time << endl; old_render_pos = render_pos_x;

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  • C++ Game engine time scale

    - by I Phantasm I
    i have begun creating a very simple game engine and i am trying to work out how to create a time scale for the game.by time scale i mean some way of increasing and decreasing the speed of the game(not the fps) like creating a slow motion effect ... i have no idea how this could be accomplished so any help would be appreciated. if this help im using windows, Opengl and C++ in the game engine... How my engine is setup i have an update and draw function...update is called 25 times per second while display is called as much as possible.

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  • GUI device for throwing a ball

    - by Fredrik Johansson
    The hero has a ball, which shall be thrown with accuracy in a court on iPhone/iPad. The player is seen from above, in a 2D view. In game play, the player reach is between 1/15 and 1/6 of the height of the iPhone screen. The player will run, and try to outmaneuver his opponent, and then throw the ball at a specific location, which is guarded by the opponent (which is also shown on the screen). The player is controlled by a joystick, and that works ok, but how shall I control the stick? Maybe someone can propose a third control method? I've tried the following two approaches: Joystick: Hero has a reach of 1 meter, and this reach is marked with a semi-opaque circle around the player. The ball can be moved by a joystick. When the joystick is moved south, the ball is moved south within the reach circle. There is a direct coupling with the joystick and the position of the ball. I.e. when the joystick is moved max south, the ball is max south within the player reach. At each touch update the speed is calculated, and the Box2d ball position and ball speed are updated. NB, the ball will never be moved outside the reach as long as the player push the joystick. The ball is thrown by swiping the joystick to make the ball move, and then releasing the joystick. At release, the ball will get a smoothed speed of the joystick. Joystick Problem: The throwing accuracy gets bad, because the joystick can not be that big, and a small movement results in quite a large movement of the ball. If the user does not release before the end of the joystick maximum end point, the ball will stop, and when the user releases the joystick the speed of the ball will be zero. Bad... Touch pad A force is applied to the ball by a sweep on a touchpad. The ball is released when the sweep is ended, or when the ball is moved outside the player reach. As there is no one to one mapping between the swipe and the ball position, the precision can be improved. A large swipe can result in a small ball movement. Touch Pad Problem A touchpad is less intuitive. Users do not seem to know what to do with the touch pad. Some tap the touchpad, and then the ball just falls to the ground. As there is no one-to-one mapping, the ball can be moved outside the reach, and then it will just fall to the ground. It's a bit hard to control the ball, especially if the player also moves.

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  • 3Ds Max is exporting model with more normals than vertices

    - by Delta
    I made a simple teapot with the "Create Standard Primitives" option and exported it as a collada file, ended up with this: < float_array id="Teapot001-POSITION-array" count="1590" < float_array id="Teapot001-Normal0-array" count="9216" For what I know there should be only one normal per vertex, am I wrong? What am I supposed to do with that much normals? Just put them on the normal buffer all at once normally?

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  • Making a game "resize-safe"

    - by CPP_Person
    It's one thing to get the graphics aligned perfectly, it's another to do this for every single resolution and not take too much time and/or make the code unreadable due to size. Games like Battlefield 3 and Minecraft seem to manage this. But what do they do to keep things from stretching or going off the screen? I don't know any algorithms to do this. I'd like some help on this topic. I've always programmed games that only handle a single resolution, so help would be appreciate.

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  • Fixed timestep and interpolation question

    - by Eric
    I'm following Glenn Fiedlers excellent Fix Your Timestep! tutorial to step my 2D game. The problem I'm facing is in the interpolation phase in the end. My game has a Tween-function which lets me tween properties of my game entites. Properties such as scale, shear, position, color, rotation etc. Im curious of how I'd interpolate these values, since there's a lot of them. My first thought is to keep a previous value of every property (colorPrev, scalePrev etc.), and interpolate between those. Is this the correct method? To interpolate my characters I use their velocity; renderPostion = position + (velocity * interpolation), but I cannot apply that to color for example. So what is the desired method to interpolate various properties or a entity? Is there any rule of thumb to use?

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  • Data-driven animation states

    - by user8363
    I'm trying to handle animations in a 2D game engine hobby project, without hard-coding them. Hard coding animation states seems like a common but very strange phenomenon, to me. A little background: I'm working with an entity system where components are bags of data and subsystems act upon them. I chose to use a polling system to update animation states. With animation states I mean: "walking_left", "running_left", "walking_right", "shooting", ... My idea to handle animations was to design it as a data driven model. Data could be stored in an xml file, a rdbms, ... And could be loaded at the start of a game / level/ ... This way you can easily edit animations and transitions without having to go change the code everywhere in your game. As an example I made an xml draft of the data definitions I had in mind. One very important piece of data would simply be the description of an animation. An animation would have a unique id (a descriptive name). It would hold a reference id to an image (the sprite sheet it uses, because different animations may use different sprite sheets). The frames per second to run the animation on. The "replay" here defines if an animation should be run once or infinitely. Then I defined a list of rectangles as frames. <animation id='WIZARD_WALK_LEFT'> <image id='WIZARD_WALKING' /> <fps>50</fps> <replay>true</replay> <frames> <rectangle> <x>0</x> <y>0</y> <width>45</width> <height>45</height> </rectangle> <rectangle> <x>45</x> <y>0</y> <width>45</width> <height>45</height> </rectangle> </frames> </animation> Animation data would be loaded and held in an animation resource pool and referenced by game entities that are using it. It would be treated as a resource like an image, a sound, a texture, ... The second piece of data to define would be a state machine to handle animation states and transitions. This defines each state a game entity can be in, which states it can transition to and what triggers that state change. This state machine would differ from entity to entity. Because a bird might have states "walking" and "flying" while a human would only have the state "walking". However it could be shared by different entities because multiple humans will probably have the same states (especially when you define some common NPCs like monsters, etc). Additionally an orc might have the same states as a human. Just to demonstrate that this state definition might be shared but only by a select group of game entities. <state id='IDLE'> <event trigger='LEFT_DOWN' goto='MOVING_LEFT' /> <event trigger='RIGHT_DOWN' goto='MOVING_RIGHT' /> </state> <state id='MOVING_LEFT'> <event trigger='LEFT_UP' goto='IDLE' /> <event trigger='RIGHT_DOWN' goto='MOVING_RIGHT' /> </state> <state id='MOVING_RIGHT'> <event trigger='RIGHT_UP' goto='IDLE' /> <event trigger='LEFT_DOWN' goto='MOVING_LEFT' /> </state> These states can be handled by a polling system. Each game tick it grabs the current state of a game entity and checks all triggers. If a condition is met it changes the entity's state to the "goto" state. The last part I was struggling with was how to bind animation data and animation states to an entity. The most logical approach seemed to me to add a pointer to the state machine data an entity uses and to define for each state in that machine what animation it uses. Here is an xml example how I would define the animation behavior and graphical representation of some common entities in a game, by addressing animation state and animation data id. Note that both "wizard" and "orc" have the same animation states but a different animation. Also, a different animation could mean a different sprite sheet, or even a different sequence of animations (an animation could be longer or shorter). <entity name="wizard"> <state id="IDLE" animation="WIZARD_IDLE" /> <state id="MOVING_LEFT" animation="WIZARD_WALK_LEFT" /> </entity> <entity name="orc"> <state id="IDLE" animation="ORC_IDLE" /> <state id="MOVING_LEFT" animation="ORC_WALK_LEFT" /> </entity> When the entity is being created it would add a list of states with state machine data and an animation data reference. In the future I would use the entity system to build whole entities by defining components in a similar xml format. -- This is what I have come up with after some research. However I had some trouble getting my head around it, so I was hoping op some feedback. Is there something here what doesn't make sense, or is there a better way to handle these things? I grasped the idea of iterating through frames but I'm having trouble to take it a step further and this is my attempt to do that.

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  • How can I use iteration to lead targets?

    - by e100
    In my 2D game, I have stationary AI turrets firing constant speed bullets at moving targets. So far I have used a quadratic solver technique to calculate where the turret should aim in advance of the target, which works well (see Algorithm to shoot at a target in a 3d game, Predicting enemy position in order to have an object lead its target). But it occurs to me that an iterative technique might be more realistic (e.g. it should fire even when there is no exact solution), efficient and tunable - for example one could change the number of iterations to improve accuracy. I thought I could calculate the current range and thus an initial (inaccurate) bullet flight time to target, then work out where the target would actually be by that time, then recalculate a more accurate range, then recalculate flight time, etc etc. I think I am missing something obvious to do with the time term, but my aimpoint calculation does not currently converge after the significant initial correction in the first iteration: import math def aimpoint(iters, target_x, target_y, target_vel_x, target_vel_y, bullet_speed): aimpoint_x = target_x aimpoint_y = target_y range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) time_to_target = range / bullet_speed time_delta = time_to_target n = 0 while n <= iters: print "iteration:", n, "target:", "(", aimpoint_x, aimpoint_y, ")", "time_delta:", time_delta aimpoint_x += target_vel_x * time_delta aimpoint_y += target_vel_y * time_delta range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) new_time_to_target = range / bullet_speed time_delta = new_time_to_target - time_to_target n += 1 aimpoint(iters=5, target_x=0, target_y=100, target_vel_x=1, target_vel_y=0, bullet_speed=100)

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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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  • runtime error: invalid memory address or nil pointer dereference

    - by Klink
    I want to learn OpenGL 3.0 with golang. But when i try to compile some code, i get many errors. package main import ( "os" //"errors" "fmt" //gl "github.com/chsc/gogl/gl33" //"github.com/jteeuwen/glfw" "github.com/go-gl/gl" "github.com/go-gl/glfw" "runtime" "time" ) var ( width int = 640 height int = 480 ) var ( points = []float32{0.0, 0.8, -0.8, -0.8, 0.8, -0.8} ) func initScene() { gl.Init() gl.ClearColor(0.0, 0.5, 1.0, 1.0) gl.Enable(gl.CULL_FACE) gl.Viewport(0, 0, 800, 600) } func glfwInitWindowContext() { if err := glfw.Init(); err != nil { fmt.Fprintf(os.Stderr, "glfw_Init: %s\n", err) glfw.Terminate() } glfw.OpenWindowHint(glfw.FsaaSamples, 1) glfw.OpenWindowHint(glfw.WindowNoResize, 1) if err := glfw.OpenWindow(width, height, 0, 0, 0, 0, 32, 0, glfw.Windowed); err != nil { fmt.Fprintf(os.Stderr, "glfw_Window: %s\n", err) glfw.CloseWindow() } glfw.SetSwapInterval(1) glfw.SetWindowTitle("Title") } func drawScene() { for glfw.WindowParam(glfw.Opened) == 1 { gl.Clear(gl.COLOR_BUFFER_BIT) vertexShaderSrc := `#version 120 attribute vec2 coord2d; void main(void) { gl_Position = vec4(coord2d, 0.0, 1.0); }` vertexShader := gl.CreateShader(gl.VERTEX_SHADER) vertexShader.Source(vertexShaderSrc) vertexShader.Compile() fragmentShaderSrc := `#version 120 void main(void) { gl_FragColor[0] = 0.0; gl_FragColor[1] = 0.0; gl_FragColor[2] = 1.0; }` fragmentShader := gl.CreateShader(gl.FRAGMENT_SHADER) fragmentShader.Source(fragmentShaderSrc) fragmentShader.Compile() program := gl.CreateProgram() program.AttachShader(vertexShader) program.AttachShader(fragmentShader) program.Link() attribute_coord2d := program.GetAttribLocation("coord2d") program.Use() //attribute_coord2d.AttribPointer(size, typ, normalized, stride, pointer) attribute_coord2d.EnableArray() attribute_coord2d.AttribPointer(0, 3, false, 0, &(points[0])) //gl.DrawArrays(gl.TRIANGLES, 0, len(points)) gl.DrawArrays(gl.TRIANGLES, 0, 3) glfw.SwapBuffers() inputHandler() time.Sleep(100 * time.Millisecond) } } func inputHandler() { glfw.Enable(glfw.StickyKeys) if glfw.Key(glfw.KeyEsc) == glfw.KeyPress { //gl.DeleteBuffers(2, &uiVBO[0]) glfw.Terminate() } if glfw.Key(glfw.KeyF2) == glfw.KeyPress { glfw.SetWindowTitle("Title2") fmt.Println("Changed to 'Title2'") fmt.Println(len(points)) } if glfw.Key(glfw.KeyF1) == glfw.KeyPress { glfw.SetWindowTitle("Title1") fmt.Println("Changed to 'Title1'") } } func main() { runtime.LockOSThread() glfwInitWindowContext() initScene() drawScene() } And after that: panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x0 pc=0x41bc6f74] goroutine 1 [syscall]: github.com/go-gl/gl._Cfunc_glDrawArrays(0x4, 0x7f8500000003) /tmp/go-build463568685/github.com/go-gl/gl/_obj/_cgo_defun.c:610 +0x2f github.com/go-gl/gl.DrawArrays(0x4, 0x3, 0x0, 0x45bd70) /tmp/go-build463568685/github.com/go-gl/gl/_obj/gl.cgo1.go:1922 +0x33 main.drawScene() /home/klink/Dev/Go/gogl/gopher/exper.go:85 +0x1e6 main.main() /home/klink/Dev/Go/gogl/gopher/exper.go:116 +0x27 goroutine 2 [syscall]: created by runtime.main /build/buildd/golang-1/src/pkg/runtime/proc.c:221 exit status 2

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