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  • World Location issues with camera and particle

    - by Joe Weeks
    I have a bit of a strange question, I am adapting the existing code base including the tile engine as per the book: XNA 4.0 Game Development by example by Kurt Jaegers, particularly the aspect that I am working on is the part about the 2D platformer in the last couple of chapters. I am creating a platformer which has a scrolling screen (similar to an old school screen chase), I originally did not have any problems with this aspect as it is simply a case of updating the camera position on the X axis with game time, however I have since added a particle system to allow the players to fire weapons. This particle shot is updated via the world position, I have translated everything correctly in terms of the world position when the collisions are checked. The crux of the problem is that the collisions only work once the screen is static, whilst the camera is moving to follow the player, the collisions are offset and are hitting blocks that are no longer there. My collision for particles is as follows (There are two vertical and horizontal): protected override Vector2 horizontalCollisionTest(Vector2 moveAmount) { if (moveAmount.X == 0) return moveAmount; Rectangle afterMoveRect = CollisionRectangle; afterMoveRect.Offset((int)moveAmount.X, 0); Vector2 corner1, corner2; // new particle world alignment code. afterMoveRect = Camera.ScreenToWorld(afterMoveRect); // end. if (moveAmount.X < 0) { corner1 = new Vector2(afterMoveRect.Left, afterMoveRect.Top + 1); corner2 = new Vector2(afterMoveRect.Left, afterMoveRect.Bottom - 1); } else { corner1 = new Vector2(afterMoveRect.Right, afterMoveRect.Top + 1); corner2 = new Vector2(afterMoveRect.Right, afterMoveRect.Bottom - 1); } Vector2 mapCell1 = TileMap.GetCellByPixel(corner1); Vector2 mapCell2 = TileMap.GetCellByPixel(corner2); if (!TileMap.CellIsPassable(mapCell1) || !TileMap.CellIsPassable(mapCell2)) { moveAmount.X = 0; velocity.X = 0; } return moveAmount; } And the camera is pretty much the same as the one in the book... with this added (as an early test). public static void Update(GameTime gameTime) { position.X += 1; }

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  • Impact Earth Lets You Simulate Asteroid Impacts

    - by Jason Fitzpatrick
    If you’re looking for a little morbid simulation to cap off your Friday afternoon, this interactive asteroid impact simulator makes it easy to the results of asteroid impacts big and small. The simulator is the result of a collaboration between Purdue University and the Imperial College of London. You can adjust the size, density, impact angle, and impact velocity of the asteroid as well as change the target from water to land. The only feature missing is the ability to select a specific location as the point of impact (if you want to know what a direct strike to Paris would yield, for example, you’ll have to do your own layering). Once you plug all that information in, you’re treated to a little 3D animation as the simulator crunches the numbers. After it finishes you’ll see a breakdown of a variety of effects including the size of the crater, the energy of the impact, seismic effects, and more. Hit up the link below to take it for a spin. Impact Earth [via Boing Boing] How To Delete, Move, or Rename Locked Files in Windows HTG Explains: Why Screen Savers Are No Longer Necessary 6 Ways Windows 8 Is More Secure Than Windows 7

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  • Slopes in 2D Platformer

    - by Carlosrdz1
    I'm dealing with Slopes in a 2D platformer game I'm developing in XNA Game Studio. I was really tired of trying without success, until I found this post: 45° Slopes in a Tile based 2D platformer, and I solved part of the problem with the bummzack answer. Now I'm dealing with 2 more problems: 1) Inverted slopes: The post says: If you're only dealing with 45 degree angles, then it gets even simpler: y1 = y + (x1 - x) If the slope is the other way round, it's: y1 = y + (v - (x1 - x)) My question is, what if I'm dealing with slopes with less than 45 degree angles? Does y1 = y + (v - (x1 - x)) work? 2) Going down the slope: I can't find a better way to handle the "going down through the slope" situation, considering that my player can accelerate its velocity. Edit: I was about to post a image but I guess I need to have more reputation he he he... What I'm trying to say with "going down" is like walking towards the opposite direction, assuming that if you are walking to the right, you are incrementing your Y position because you are climbing the slope, but if you are walking to the left, you are decrementing your Y position.

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  • Pure functional programming and game state

    - by Fu86
    Is there a common technique to handle state (in general) in a functional programming language? There are solutions in every (functional) programming language to handle global state, but I want to avoid this as far as I could. All state in a pure functional manner are function parameters. So I need to put the whole game state (a gigantic hashmap with the world, players, positions, score, assets, enemies, ...)) as a parameter to all functions which wants to manipulate the world on a given input or trigger. The function itself picks the relevant information from the gamestate blob, do something with it, manipulate the gamestate and return the gamestate. But this looks like a poor mans solution for the problem. If I put the whole gamestate into all functions, there is no benefit for me in contrast to global variables or the imperative approach. I could put just the relevant information into the functions and return the actions which will be taken for the given input. And one single function apply all the actions to the gamestate. But most functions need a lot of "relevant" information. move() need the object position, the velocity, the map for collision, position of all enemys, current health, ... So this approach does not seem to work either. So my question is how do I handle the massive amount of state in a functional programming language -- especially for game development?

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  • is there a way to have VIM do incremental search on text files?

    - by Alex
    Is there a way to have VIM do incremental search on text files? Vim already does incremental search within the currently open file. Examples of programs that demonstrate the type of search I'm trying to accomplish are Notational Velocity for MacOS, Resop for windows or SimpleNote for the web. These apps do an instant or incremental search in the files of a specific directory and make it easy/fast to narrow down the file you are looking for or create a new file. I use both but would rather live in one editor.(that being VIM) Is there some plug in that would do this?

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  • How to perform game object smoothing in multiplayer games

    - by spaceOwl
    We're developing an infrastructure to support multiplayer games for our game engine. In simple terms, each client (player) engine sends some pieces of data regarding the relevant game objects at a given time interval. On the receiving end, we step the incoming data to current time (to compensate for latency), followed by a smoothing step (which is the subject of this question). I was wondering how smoothing should be performed ? Currently the algorithm is similar to this: Receive incoming state for an object (position, velocity, acceleration, rotation, custom data like visual properties, etc). Calculate a diff between local object position and the position we have after previous prediction steps. If diff doesn't exceed some threshold value, start a smoothing step: Mark the object's CURRENT POSITION and the TARGET POSITION. Linear interpolate between these values for 0.3 seconds. I wonder if this scheme is any good, or if there is any other common implementation or algorithm that should be used? (For example - should i only smooth out the position? or other values, such as speed, etc) any help will be appreciated.

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  • 2D Tile Collision free movement

    - by andrepcg
    I'm coding a 3D game for a project using OpenGL and I'm trying to do tile collision on a surface. The surface plane is split into a grid of 64x64 pixels and I can simply check if the (x,y) tile is empty or not. Besides having a grid for collision, there's still free movement inside a tile. For each entity, in the end of the update function I simply increase the position by the velocity: pos.x += v.x; pos.y += v.y; I already have a collision grid created but my collide function is not great, i'm not sure how to handle it. I can check if the collision occurs but the way I handle is terrible. int leftTile = repelBox.x / grid->cellSize; int topTile = repelBox.y / grid->cellSize; int rightTile = (repelBox.x + repelBox.w) / grid->cellSize; int bottomTile = (repelBox.y + repelBox.h) / grid->cellSize; for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { if (grid->getCell(x, y) == BLOCKED){ Rect colBox = grid->getCellRectXY(x, y); Rect xAxis = Rect(pos.x - 20 / 2.0f, pos.y - 20 / 4.0f, 20, 10); Rect yAxis = Rect(pos.x - 20 / 4.0f, pos.y - 20 / 2.0f, 10, 20); if (colBox.Intersects(xAxis)) v.x *= -1; if (colBox.Intersects(yAxis)) v.y *= -1; } } } If instead of reversing the direction I set it to false then when the entity tries to get away from the wall it's still intersecting the tile and gets stuck on that position. EDIT: I've worked with Flashpunk and it has a great function for movement and collision called moveBy. Are there any simplified implementations out there so I can check them out?

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  • Space Invaders-type game: Keeping the enemies aligned with each other as they turn around?

    - by CorundumGames
    OK, so here's the lowdown of the problem I'm trying to solve. I'm developing a game in PyGame that's a cross between Space Invaders and Columns. I'm trying to make the motion of the enemies similar to that of the aliens in Space Invaders; that is, they're all clustered in a grid, and if even one hits the side of the screen, the entire formation moves down and turns around. However, the motion of these aliens is continuous (as continuous as a monitor can be, anyway), not on a discrete grid like in the original. The enemies are instances of an Enemy class, and in turn they're held by a 2D array in a enemysquadron module (which, if you don't use Python, is in this case essentially a singleton due to the way Python modules work). Inside the Enemy class I have a class-scope velocity vector that is reversed every time an Enemy object touches the edge of the screen. This won't do, though, because as time goes on the enemies just become disorganized and jumbled (i.e. not in a grid as planned). I haven't implemented the Enemies going downward yet, so let's not worry about that right now. Any tips?

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  • How do you do incremental search across multiple text files in VIM?

    - by Alex
    Is there a way to have VIM do incremental search on text files? Vim already does incremental search within the currently open file. Examples of programs that demonstrate the type of search I'm trying to accomplish are Notational Velocity for MacOS, Resop for windows or SimpleNote for the web. These apps do an instant or incremental search in the files of a specific directory and make it easy/fast to narrow down the file you are looking for or create a new file. I use both but would rather live in one editor.(that being VIM) Is there some plug in that would do this?

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  • How to prioritize related game entity components?

    - by Paul Manta
    I want to make a game where you have to run over a bunch of zombies with your car. When moving around, the zombies have a few things to take into consideration: When there's no player around they might just roam about randomly. And even when some other component dictates a specific direction, they should wobble to the left and right randomly (like drunk people). This implies a small, random, deviation in their movement. They should avoid static obstacles. When they see they are headed towards a wall, they should reorient themselves. They should avoid the car. They should try to predict where the car will be based on its velocity and try to move out of the way. When they can, they should try to get near the player. All these types of decisions they have to do seem like they should be implemented in different components. But how should I manage them? How can I give different components different weights that reflect the importance of each decision (in a given situation)? I would need some other component that acts as a manager, but do you have any tips on how I should implement it? Or maybe there's a better solution?...

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  • Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

    - by Prog
    In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the entities (i.e. where the entities 'act': update their positions, invoke AI, etc) is in a different class, in the method updateEntities(List<Entity> entities). Also called from the gameloop, after the collision detection. When there's a collision between two entities, usually something needs to be done. For example, zero the velocity of both entities in the collision, or kill one of the entities. It would be easy to have this code in the CollisionDetector class. E.g. in psuedocode: for(Entity entityA in entities){ for(Entity entityB in entities){ if(collision(entityA, entityB)){ if(entityA instanceof Robot && entityB instanceof Robot){ entityA.setVelocity(0,0); entityB.setVelocity(0,0); } if(entityA instanceof Missile || entityB instanceof Missile){ entityA.die(); entityB.die(); } } } } However, I'm not sure if updating the state of entities in response to collision should be the job of CollisionDetector. Maybe it should be the job of EntityUpdater, which runs after the collision detection in the gameloop. Is it okay to have the code responding to collisions in the collision detection system? Or should the collision detection class only detect collisions, report them to some other class and have that class affect the state of the entities?

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  • CUDA 4.1 Update

    - by N0xus
    I'm currently working on porting a particle system to update on the GPU via the use of CUDA. With CUDA, I've already passed over the required data I need to the GPU and allocated and copied the date via the host. When I build the project, it all runs fine, but when I run it, the project says I need to allocate my h_position pointer. This pointer is my host pointer and is meant to hold the data. I know I need to pass in the current particle position to the required cudaMemcpy call and they are currently stored in a list with a for loop being created and interated for each particle calling the following line of code: m_particleList[i].positionY = m_particleList[i].positionY - (m_particleList[i].velocity * frameTime * 0.001f); My current host side cuda code looks like this: float* h_position; // Your host pointer. This holds the data (I assume it's already filled with the data.) float* d_position; // Your device pointer, we will allocate and fill this float* d_velocity; float* d_time; int threads_per_block = 128; // You should play with this value int blocks = m_maxParticles/threads_per_block + ( (m_maxParticles%threads_per_block)?1:0 ); const int N = 10; size_t size = N * sizeof(float); cudaMalloc( (void**)&d_position, m_maxParticles * sizeof(float) ); cudaMemcpy( d_position, h_position, m_maxParticles * sizeof(float), cudaMemcpyHostToDevice); Both of which were / can be found inside my UpdateParticle() method. I had originally thought it would be a simple case of changing the h_position variable in the cudaMemcpy to m_particleList[i] but then I get the following error: no suitable conversion function from "ParticleSystemClass::ParticleType" to "const void *" exists I've probably messed up somewhere, but could someone please help fix the issues I'm facing. Everything else seems to running fine, it's just when I try to run the program that certain things hit the fan.

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  • Disabling mouse acceleration in X.Org (Linux)

    - by aib
    This is the Linux version of my Disabling mouse acceleration in Mac OS X question. Hopefully I'll get an answer this time. I am tired of mouse acceleration and want to have a completely linear mouse response. This is easily achievable through any of the 5 or so methods (some subtly implied) on the X.Org wiki page on pointer acceleration. However, they also disable velocity scaling. I don't want a 1:1 mapping between device and screen coordinates. I want a 1:N mapping where N is a constant. Any ideas?

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  • Day in the Life of Agile - The Forge Michigan November 27, 2012

    - by csmith18119
    Went to training at The Forge yesterday and did a Day in the life of Agile with Pillar.  It was pretty good. Check them out at: http://pillartechnology.com/ Abstract: A single-day agile project simulation that is engaging, educational, provocative, and fun. This simulation introduces concepts like time-boxed iterations, User Stories, collective estimation, commitment to a product owner for iteration scope, formal verification ritual at iteration conclusion, tracking velocity, and making results big and visible through charts. The exercise is designed to simulate not only how agile teams and practices work, but the inevitable challenges that arise as teams attempt to adopt such practices. One of the best parts of this training was getting some hands on experience with agile.  We used a program called Scratch to create an arcade video game.  Our team chose Frogger.  We had 3 iterations at 20 minutes each.  I think we did pretty good but in the panic of trying to get a bunch done in only 20 minutes made it interesting. To check out our project, I uploaded it to my CodePlex site Download Source Code (Under Scratch/Frogger) Cool class! I highly recommend if you get the opportunity.

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  • Hit Detection When rotating the camera

    - by SD1990
    This bug/feature has been plaguing me for a while and i want to know the best way to fix it. I'm testing simple hit detection with a wall, like: if (Forward button) if(Inv.w.z < -49 || Inv.w.z > 49) pos.z = 0.0f; else if(Inv.w.x < -49 || Inv.w.x > 49) pos.z = 0.0f; else pos.z = +1.0f; where Inv.w. is the camera positions. Now obviously when i now hit that certain point i can no longer move away from the wall or anywhere in fact. How can i change this code to allow for the camera to be turned away from the wall so therefore i should be allowed to move? for example, the player hits the wall and i cant move until i turn around or to the side? I know its something to do with velocity but im pretty new to this so please bare with me if this is easy.

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  • What could cause a sudden stop in Box2D?

    - by alexanderpine
    I'm using Box2d for a game, and I have a bug that's driving me nuts. I've simplified the situation down to a square player sliding back and forth frictionlessly on top of a floor composed of a series of square tiles, driven by the left and right keys (which apply a horizontal force). Works great, sliding back and forth across the whole floor. Except... Every once in a while, the player will suddenly stick at the edge of one of the tiles as if it is hitting a (nonexistent) wall. Further pushes in the same direction it was traveling will fail, but as soon as I push backwards once in the opposite direction, I can push forwards past the sticking point again. The sticking point seems to be random, except for being on the edge of a tile. Happens while going left or right. For debugging purposes, I keep the Positions/velocity values for the previous two update ticks and print them out when this stop occurs. As an example, here you see the player moving right, decelerating slightly; pos2 should be about 8.7, but it stops dead instead. tick0: pos= 8.4636 vel= 7.1875 tick1: pos= 8.5816 vel= 7.0833 tick2: pos= 8.5816 vel= 0.0000 So, as the player is 0.8 and the tiles 1.0 wide, the player is stopping just as it is about to cross onto the next tile (8.5816 + 0.8/2 = 8.9816). In fact, I get a collision message (which I ignore except noting that it happened). It only seems to happen at x.5816 (or -x.4184) while moving right, and x.4167 (or -x.5833) while moving left I said that it's like hitting a wall, but in fact, when it hits a wall, the numbers look more like: tick0: pos0= 12.4131 vel2= 8.4375 tick1: pos1= 12.5555 vel1= 8.5417 tick2: pos2= 12.5850 vel0= 0.0000 so it moves further right on the last tick, which puts it in contact with the wall. Anyone seen anything like this. Any suggestion on how I could be causing this behavior.

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  • Cocos2D: Change animation based on joystick direction

    - by Blade
    I'm trying to get my figure to look in the right directions, based on the input of the joystick. So if I tilt left it looks left and the left animation is used, if I used right, it looks right and right animation is used, if up, then up, down, down and so on. I just get animation for front and back. Also if I press up I see the back of the figure correctly, but it won't go back into the original state when I don't press up anymore. -(void)applyJoystick:(SneakyJoystick *)aJoystick forTimeDelta:(float) deltaTime { CGPoint scaledVelocity = ccpMult(aJoystick.velocity, 128.0f); CGPoint oldPosition = [self position]; CGPoint newPosition = ccp(oldPosition.x + scaledVelocity.x * deltaTime, oldPosition.y + scaledVelocity.y * deltaTime); [self setPosition:newPosition]; id action = nil; int extra = 50; if ((int) aJoystick.degrees > 180 - extra && aJoystick.degrees < 180 + extra) { action = [CCAnimate actionWithAnimation:walkingAnimLeft restoreOriginalFrame:NO]; } else if ((int) aJoystick.degrees > 360 - extra && aJoystick.degrees < 360 + extra) { action = [CCAnimate actionWithAnimation:walkingAnimRight restoreOriginalFrame:NO]; } else if ((int) aJoystick.degrees > 90 - extra && aJoystick.degrees < 90 + extra) { action = [CCAnimate actionWithAnimation:walkingAnimBack restoreOriginalFrame:NO]; } else if ((int) aJoystick.degrees > 270 - extra && aJoystick.degrees < 270 + extra) { action = [CCAnimate actionWithAnimation:walkingAnimFront restoreOriginalFrame:NO]; } if (action != nil) { [self runAction:action]; } } }

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  • RewriteMap syntax Regex

    - by ienabellamy
    in my .htaccess i've tons of directives, with same syntax: RewriteRule ^(.*)/PRODUCT_1.aspx http://www.site.com/product.php?id_product=2891 RewriteRule ^(.*)/PRODUCT_2.aspx http://www.site.com/product.php?id_product=2896 and everything works. Now, i created a RewriteMap in my because i need to increase velocity (20.000 redirect 301 in htaccess no good), so: RewriteEngine On RewriteMap redirects dbm=db:/var/www/html/presta152/prestashop/redirects.db RewriteCond ${redirects:$1} !="" RewriteRule ^(.*)$ ${redirects:$1} [redirect=permanent,last] and my redirects.db is created by redirects.txt, that contains: /PRODUCT_1.aspx http://www.site.com/product.php?id_product=2891 /PRODUCT_2.aspx http://www.site.com/product.php?id_product=2896 this works if i try to call for example: www.site.com/PRODUCT_1.aspx i'm redirected... but if i try to call www.site.com/everythingpossibileinside/PRODUCT_1.aspx the redirect doesn't work. So, in my .htaccess this rule: RewriteRule ^(.*)/PRODUCT_1.aspx http://www.site.com/product.php?id_product=2891 works, but in my RewriteMap no. I think i must change this directive: RewriteRule ^(.*)$ ${redirects:$1} [redirect=permanent,last] i tried, but unsuccessful. Thanks to all.

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  • Customer Highlight: NTT DOCOMO

    - by jeckels
    NTT DOCOMO is the largest mobile operator in Japan, and serves over 13 million smartphone customers. Due to their growing data processing and scalability needs, they turned to Oracle's Cloud Application Foundation products for an integral soultion. At Oracle OpenWorld 2012, we first showcased NTT DOCOMO as a customer who was utilizing Oracle Coherence to process mobile data at a rate of 700,000 events per second (and then using Hadoop for distributed processing of big data). Overall, this Led to a 50% cost reduction due to the ultra-high velocity traffic processing of their customers' events. Recently, on October 7th, 2013, Oracle and NTT DOCOMO were proud to again announce a partnership around another key component of Oracle CAF: WebLogic Server. WebLogic was recently deployed as the application platform of choice to run DOCOMO's mission-critical data system ALADIN, which connects nationwide shops and information centers. ALADIN, which also utilizes Oracle Database and Oracle Tuxedo, is based on Java Platform, Enterprise Edition (Java EE), which has allowed the company to operate smoothly while minimizing additional development and modification associated with the migration of application server products. We look forward to continuing to partner with NTT DOCOMO, and are proud that Oracle Cloud Application Foundation products are providing the mission-critical solutions - at scale - that DOCOMO requires. Want to learn more about how CAF products are working in the real world? Join us for a FREE Virtual Developer Day on November 5th from 9am-1pm Pacific Time!REGISTER NOW

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  • How do I have an arrow follow different height parabolas depending on how long the player holds down a key?

    - by Moondustt
    i'm trying to throw an arrow in my game, but i'm having a hard time trying to realize how to make a good parabola. What I need: The more you hold "enter" stronger the arrow goes. The arrow angle will be always the same, 45 degrees. This is what I have already have: private float velocityHeld = 1f; protected override void Update(GameTime gameTime) { private void GetKeyboardEvent() { if (Keyboard.GetState().IsKeyDown(Keys.Enter) && !released) { timeHeld += velocityHeld; holding = true; } else { if (holding) { released = true; holding = false; lastTimeHeld = timeHeld; } } } if (released && timeHeld > 0) { float alpha = MathHelper.ToRadians(45f); double vy = timeHeld * Math.Sin(alpha); double vx = timeHeld * Math.Cos(alpha); ShadowPosition.Y -= (int)vy; ShadowPosition.X += (int)vx; timeHeld -= velocityHeld; } else { released = false; } } My question is, what do I need to do to make the arrow to go bottom as it loses velocity (timeHeld) to make a perfect parabola?

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  • Qwt plot not working , simple plot curve not appeat

    - by user1629213
    I followed the example of simple plot in qwt examples to plot a curve. The axis and the graph appear in the Qt main window user interface but the curve not. I assigned values to fit the curve but the curve not appear. Any suggestions and help how to solve the problem? Here is my code MainWindow::MainWindow( int argc, char** argv, QWidget *parent ) : QMainWindow( parent ) , qnode( argc,argv ) { ui.setupUi( this ); // Calling this incidentally connects all ui's triggers to on_...() callbacks in this class. QObject::connect( ui.actionAbout_Qt, SIGNAL( triggered( bool )), qApp, SLOT( aboutQt( ))); // qApp is a global variable for the application ReadSettings( ); setWindowIcon( QIcon( ":/images/icon.png" )); ui.tab_manager->setCurrentIndex( 0 ); // ensure the first tab is showing - qt-designer should have this already hardwired, but often loses it (settings?). QObject::connect( &qnode, SIGNAL( rosShutdown( )), this, SLOT( close( ))); /********************* ** Logging **********************/ ui.view_logging->setModel( qnode.loggingModel( )); QObject::connect( &qnode, SIGNAL( loggingUpdated( )), this, SLOT( updateLoggingView( ))); QObject::connect( &qnode, SIGNAL( graphReceived( )), this, SLOT( onGraphReceived( ))); QObject::connect( &qnode, SIGNAL( parameterReceived( )), this, SLOT( onParameterReceived( ))); /********************* ** Auto Start **********************/ if ( ui.checkbox_remember_settings->isChecked( )) { on_button_connect_clicked( true ); } ui.parameters->setAttribute( Qt::WA_NoMousePropagation ); ui.parameters->setAttribute( Qt::WA_OpaquePaintEvent ); ui.plotgraph->setAttribute( Qt::WA_NoMousePropagation ); ui.plotgraph->setAttribute( Qt::WA_OpaquePaintEvent ); p_plot = new QwtPlot(ui.plotgraph); p_plot->setTitle( "Plot LinVel" ); p_plot->setCanvasBackground( Qt::white ); // Axis p_plot->setAxisTitle( QwtPlot::xBottom, "Time(sec)" ); p_plot->setAxisTitle( QwtPlot::yLeft, "Linear Velocity (m/sec)" ); p_plot->setAxisScale( QwtPlot::yLeft, 0.0, 10.0 ); p_plot->setAxisScale( QwtPlot::xBottom, 0.0, 50.0 ); p_plot->insertLegend( new QwtLegend() ); //samplingThread.start(); QwtPlotGrid *grid = new QwtPlotGrid(); grid->attach( p_plot ); curve = new QwtPlotCurve(); curve->setTitle( "Linear velocity" ); // Set curve styles curve->setPen( Qt::blue, 4 ), curve->setRenderHint( QwtPlotItem::RenderAntialiased, true ); QwtSymbol *symbol = new QwtSymbol( QwtSymbol::Ellipse, QBrush( Qt::yellow), QPen( Qt::red, 2 ), QSize( 8, 8 ) ); curve->setSymbol( symbol); // Assign values to the curve //curve->setSamples(ui.plotgraph.get_linv_g());//yaw_g,trav_g,wall_g; curve->attach( p_plot ); p_plot->resize( 600, 400 ); p_plot->show(); void MainWindow::onGraphReceived( ) { { QMutexLocker locker( &qnode.m_mutex ); } } void MainWindow::onParameterReceived( ) { { QMutexLocker locker( &qnode.m_mutex ); std::vector<double> p_ = qnode.get_parameters(); std::cout << p_[0]<<" "<<p_[1]<<" "<<p_[2]<<" "<<p_[3]<<" "<<p_[4] << std::endl; } } Any help?

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  • Calculus? Need help solving for a time-dependent variable given some other variables.

    - by user451527
    Long story short, I'm making a platform game. I'm not old enough to have taken Calculus yet, so I know not of derivatives or integrals, but I know of them. The desired behavior is for my character to automagically jump when there is a block to either side of him that is above the one he's standing on; for instance, stairs. This way the player can just hold left / right to climb stairs, instead of having to spam the jump key too. The issue is with the way I've implemented jumping; I've decided to go mario-style, and allow the player to hold 'jump' longer to jump higher. To do so, I have a 'jump' variable which is added to the player's Y velocity. The jump variable increases to a set value when the 'jump' key is pressed, and decreases very quickly once the 'jump' key is released, but decreases less quickly so long as you hold the 'jump' key down, thus providing continuous acceleration up as long as you hold 'jump.' This also makes for a nice, flowing jump, rather than a visually jarring, abrupt acceleration. So, in order to account for variable stair height, I want to be able to calculate exactly what value the 'jump' variable should get in order to jump exactly to the height of the stair; preferably no more, no less, though slightly more is permissible. This way the character can jump up steep or shallow flights of stairs without it looking weird or being slow. There are essentially 5 variables in play: h -the height the character needs to jump to reach the stair top<br> j -the jump acceleration variable<br> v -the vertical velocity of the character<br> p -the vertical position of the character<br> d -initial vertical position of the player minus final position<br> Each timestep:<br> j -= 1.5; //the jump variable's deceleration<br> v -= j; //the jump value's influence on vertical speed<br> v *= 0.95; //friction on the vertical speed<br> v += 1; //gravity<br> p += v; //add the vertical speed to the vertical position<br> v-initial is known to be zero<br> v-final is known to be zero<br> p-initial is known<br> p-final is known<br> d is known to be p-initial minus p-final<br> j-final is known to be zero<br> j-initial is unknown<br> Given all of these facts, how can I make an equation that will solve for j? tl;dr How do I Calculus? Much thanks to anyone who's made it this far and decides to plow through this problem.

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  • A rocket following the tracks height. Not Homing Missile.

    - by confusedEj
    What I am trying to create is a rocket that will hug the track in a straight direction. ie) The rocket travels in a straight direction and can orientate based on its local x axis. This is so it can go up/down ramps and never hit the ground. Currently I am using PhysX opengl and C++. This is the method I'm trying right now: 1. Ray cast from ahead of the missile (ray casting downwards) 2. If the ray cast is less then the expected ray cast length, then I have to orientate up. 3. If the ray cast is more then the expected ray cast length, then I have to orientate down. Now the problem, I am having is that my missile is orientating at an arbitary angle (I'm giving it 1 degrees.) Though I think this is a bad approach because the amount of frames in the game is not as much as I would think there would be. So the rocket would run into a ramp. My main question is: is there a better way of approaching this and how? NxVec3 frontRayLoc = m_rocketConfig->getValueForKey<NxVec3>("r_frontRayCastLocation"); float threshhold = m_rocketConfig->getValueForKey<float>("r_angleThreshhold"); float predRayCastHeight = m_rocketConfig->getValueForKey<float>("r_predRayCastHeight"); NxVec3 rayGlobalPos_1 = m_actor->getGlobalPosition() + m_actor->getGlobalOrientation() * frontRayLoc; NxVec3 dir = m_actor->getGlobalOrientation() * NxVec3(0,-1.0,0); NxReal dist1 = castRay(rayGlobalPos_1, dir); // Get the percentage difference float actualFrontHeight = abs(1 - (dist1/predRayCastHeight)); // See if the percentage difference is greater then threshold // Also check if we are being shot off track if ((actualFrontHeight > threshhold) && (dist1 != m_rayMaxDist)){ // Dip Down if (dist1 > predRayCastHeight){ printf("DOWN - Distance 1: %f\n", dist1); // Get axis of rotation NxVec3 newAxis = m_actor->getGlobalOrientation() * NxVec3(1.0,0,0.0); // Rotate based on that axis m_orientateAngle = -1.0 * m_orientateAngle; // For rotating clockwise NxQuat newOrientation(m_orientateAngle, newAxis); NxMat33 orientation(newOrientation); m_orientation = m_orientation * orientation; // Orientate the linear velocity to keep speed of rocket and direct away from road NxVec3 linVel = m_actor->getLinearVelocity(); m_actor->setLinearVelocity(m_orientation * linVel); } // Go Up else if (dist1 < predRayCastHeight){ printf("UP - Distance 1: %f\n", dist1); // Get axis of rotation NxVec3 newAxis = m_actor->getGlobalOrientation() * NxVec3(1.0,0,0.0); // Rotate around axis NxQuat newOrientation(m_orientateAngle, newAxis); m_actor->setGlobalOrientationQuat(newOrientation); NxMat33 orientation(newOrientation); m_orientation = m_orientation * orientation; // Orientate the linear velocity to keep speed of rocket and direct away from road NxVec3 linVel = m_actor->getLinearVelocity(); m_actor->setLinearVelocity(m_orientation*linVel); } m_actor->setGlobalOrientation(m_orientation); } Thanks for the support :)

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  • Can't get my object to point at the mouse.

    - by melignus
    I'm using a combination of SDL and OpenGL in a sort of crash course project to teach myself how this all works. I'm really only interested in OpenGL as a way to use acceleration in 2D games so I just need this to work in a 2D plane. I have been having a lot of problems today with my current issue, I would like an object to point towards the mouse while the mouse button is clicked and then of course stay pointing in that direction after the mouse is lifted. void Square::handle_input() { //If a key was pressed if( event.type == SDL_KEYDOWN ) { //Adjust the velocity switch( event.key.keysym.sym ) { case SDLK_UP: upUp = false; yVel = -1; break; case SDLK_DOWN: downUp = false; yVel = 1; break; case SDLK_LEFT: leftUp = false; xVel = -1; break; case SDLK_RIGHT: rightUp = false; xVel = 1; break; case SDLK_w: wUp = false; sAng = 1; break; case SDLK_s: sUp = false; sAng = -1; break; } } //If a key was released else if( event.type == SDL_KEYUP ) { //Adjust the velocity switch( event.key.keysym.sym ) { case SDLK_UP: upUp = true; yVel = 0; break; case SDLK_DOWN: downUp = true; yVel = 0; break; case SDLK_LEFT: leftUp = true; xVel = 0; break; case SDLK_RIGHT: rightUp = true; xVel = 0; break; case SDLK_w: wUp = true; sAng = 0; break; case SDLK_s: sUp = true; sAng = 0; break; } } //If a mouse button was pressed if( event.type == SDL_MOUSEBUTTONDOWN ) { switch ( event.type ) { case SDL_MOUSEBUTTONDOWN: mouseUp = false; mousex == event.button.x; mousey == event.button.y; break; case SDL_MOUSEBUTTONUP: mouseUp = true; break; } } } And then this is called at the end of my Object::Move call which also handles x and y translation if (!mouseUp) { xVect = mousex - x; yVect = mousey - y; radAng = atan2 ( mousey - y, mousex - x ); sAng = radAng * 180 / 3.1415926l; } Right now when I click the object turns and faces down to the bottom left but then no longer changes direction. I'd really appreciate any help I could get here. I'm guessing there might be an issue here with state versus polled events but from all the tutorials that I've been through I was pretty sure I had fixed that. I've just hit a wall and I need some advice!

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  • Changes to data inside class not being shown when accessed from outside class.

    - by Hypatia
    I have two classes, Car and Person. Car has as one of its members an instance of Person, driver. I want to move a car, while keeping track of its location, and also move the driver inside the car and get its location. However, while this works from inside the class (I have printed out the values as they are calculated), when I try to access the data from main, there's nothing there. I.e. the array position[] ends up empty. I am wondering if there is something wrong with the way I have set up the classes -- could it be a problem of the scope of the object? I have tried simplifying the code so that I only give what is necessary. Hopefully that covers everything that you would need to see. The constructer Car() fills the offset array of driver with nonzero values. class Car{ public: Container(float=0,float=0,float=0); ~Container(); void move(float); void getPosition(float[]); void getDriverPosition(float[]); private: float position[3]; Person driver; float heading; float velocity; }; class Person{ public: Person(float=0,float=0,float=0); ~Person(); void setOffset(float=0,float=0,float=0); void setPosition(float=0,float=0,float=0); void getOffset(float[]); void getPosition(float[]); private: float position[3]; float offset[3]; }; Some of the functions: void Car::move(float time){ float distance = velocity*time; location[0] += distance*cos(PI/2 - heading); location[1] += distance*sin(PI/2 - heading); float driverLocation [3]; float offset[3]; driver->getOffset(offset); for (int i = 0; i < 3; i++){ driverLocation[i] = offset[i] + location[i]; } } void Car::getDriverPosition(float p[]){ driver.getPosition(p); } void Person::getPosition(float p[]){ for (int i = 0; i < 3; i++){ p[i] = position[i]; } } void Person::getOffset(float o[]){ for (int i = 0; i < 3; i++){ o[i] = offset[i]; } } In Main: Car * car = new Car(); car->move(); float p[3]; car->getDriverPosition(p); When I print driverLocation[] inside the move() function, I have actual nonzero values. When I print p[] inside main, all I get are zeros.

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