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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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  • Flex Unit testing of library and mxml using FlexUnit

    - by user344722
    Hi, I have some software classes(library) to run commands on any mxml file. These classes(library) are wrapped in a SWC file. This SWC file is referenced by any sample mxml application (by adding as SWC file). My problem is that I want to test these software classes(library) against my sample mxml file using FlexUnit. That is, I should test methods run by software classes on the mxml file. How can I accomplish this? Thanks, Pradeep

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  • Is there a simpler way to create a borderless window with XNA 4.0?

    - by Cypher
    When looking into making my XNA game's window border-less, I found no properties or methods under Game.Window that would provide this, but I did find a window handle to the form. I was able to accomplish what I wanted by doing this: IntPtr hWnd = this.Window.Handle; var control = System.Windows.Forms.Control.FromHandle( hWnd ); var form = control.FindForm(); form.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None; I don't know why but this feels like a dirty hack. Is there a built-in way to do this in XNA that I'm missing?

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  • 2D game collision response: SAT & minimum displacement along a given axis?

    - by Archagon
    I'm trying to implement a collision system in a 2D game I'm making. The separating axis theorem (as described by metanet's collision tutorial) seems like an efficient and robust way of handling collision detection, but I don't quite like the collision response method they use. By blindly displacing along the axis of least overlap, the algorithm simply ignores the previous position of the moving object, which means that it doesn't collide with the stationary object so much as it enters it and then bounces out. Here's an example of a situation where this would matter: According to the SAT method described above, the rectangle would simply pop out of the triangle perpendicular to its hypotenuse: However, realistically, the rectangle should stop at the lower right corner of the triangle, as that would be the point of first collision if it were moving continuously along its displacement vector: Now, this might not actually matter during gameplay, but I'd love to know if there's a way of efficiently and generally attaining accurate displacements in this manner. I've been racking my brains over it for the past few days, and I don't want to give up yet! (Cross-posted from StackOverflow, hope that's not against the rules!)

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  • can't spot the error. Trying to increment

    - by Kevin Jensen Petersen
    I really can't spot the error, or the misspelling. This script should increase the variable currentTime with 1 every second, as long as i am holding the Space button down. This is Unity C#. using UnityEngine; using System.Collections; public class GameTimer : MonoBehaviour { //Timer private bool isTimeDone; public GUIText counter; public int currentTime; private bool starting; //Each message will be shown random each 20 seconds. public string[] messages; public GUIText msg; //To check if this is the end private bool end; void Update () { counter.guiText.text = currentTime.ToString(); if(Input.GetKey(KeyCode.Space)) { if(starting == false) { starting = true; } if(end == false) { if(isTimeDone) { StartCoroutine(timer()); } } else { msg.guiText.text = "You think you can do better? Press 'R' to Try again!"; if(Input.GetKeyDown(KeyCode.R)) { Application.LoadLevel(Application.loadedLevel); } } } if(!Input.GetKey(KeyCode.Space) & starting) { end = true; } } IEnumerator timer() { isTimeDone = false; yield return new WaitForSeconds(1); currentTime++; isTimeDone = true; } }

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  • 2D SAT Collision Detection not working when using certain polygons

    - by sFuller
    My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug?

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  • Efficient mapping layout in 2D side-scroller, and collisions between character and the world

    - by Jack
    I haven't touched Visual Studio for a couple months now, but I was playing a game from the '90s toady and had an epiphany: I was looking for something what i didn't need, and I wasn't using what I knew correctly. One of those realizations was collision, so let me tell you a bit about my project that I was working on. The project's graphics looks like Mario or Dangerous Dave, etc., you get the idea - old-school pixels. So anyway I remember trying to think of something else than AABB for character form, but I couldn't think of anything. Perhaps I could get a suggestion for this? Another thing is the world - I don't want it to be just linear world, I want mountains, etc.. My idea is to use triangles, and no idea yet what to do if I want just part of the cube, say 3/4 or 2/4 or whatever. Hard-coding such things seems inefficient. P.S. I am not looking at the precision level offered by Box2D. Actually I remember trying to implement it at first, but I failed as my understanding of C++ wasn't advanced enough, as it'll be mentioned below. P.P.S. I am programming in C++, and I haven't done it for a couple months now. I have no means of testing it either, as my PC is broken down, and this one can barely run games from late '90s, not to speak about a compiler or a program with inefficient resource management... I am also not an expert (obviously), I don't even know if I can consider myself an average programmer. In short, I am simply curious about my thoughts and my past experience when programming the game. I may come back to it when my PC is fixed, I'm already filling a note about these things.

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  • In an Entity/Component system, can component data be implemented as a simple array of key-value pairs? [on hold]

    - by 010110110101
    I'm trying to wrap my head around how to organize components in an Entity Component Systems once everything in the current scene/level is loaded in memory. (I'm a hobbyist BTW) Some people seem to implement the Entity as an object that contains a list of of "Component" objects. Components contain data organized as an array of key-value pairs. Where the value is serialized "somehow". (pseudocode is loosely in C# for brevity) class Entity { Guid _id; List<Component> _components; } class Component { List<ComponentAttributeValue> _attributes; } class ComponentAttributeValue { string AttributeName; object AttributeValue; } Others describe Components as an in-memory "table". An entity acquires the component by having its key placed in a table. The attributes of the component-entity instance are like the columns in a table class Renderable_Component { List<RenderableComponentAttributeValue> _entities; } class RenderableComponentAttributeValue { Guid entityId; matrix4 transformation; // other stuff for rendering // everything is strongly typed } Others describe this actually as a table. (and such tables sound like an EAV database schema BTW) (and the value is serialized "somehow") Render_Component_Table ---------------- Entity Id Attribute Name Attribute Value and when brought into running code: class Entity { Guid _id; Dictionary<string, object> _attributes; } My specific question is: Given various components, (Renderable, Positionable, Explodeable, Hideable, etc) and given that each component has an attribute with a particular name, (TRANSLATION_MATRIX, PARTICLE_EMISSION_VELOCITY, CAN_HIDE, FAVORITE_COLOR, etc) should: an entity contain a list of components where each component, in turn, has their own array of named attributes with values serialized somehow or should components exist as in-memory tables of entity references and associated with each "row" there are "columns" representing the attribute with values that are specific to each entity instance and are strongly typed or all attributes be stored in an entity as a singular array of named attributes with values serialized somehow (could have name collisions) or something else???

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  • How do I implement collision detection with a sprite walking up a rocky-terrain hill?

    - by detectivecalcite
    I'm working in SDL and have bounding rectangles for collisions set up for each frame of the sprite's animation. However, I recently stumbled upon the issue of putting together collisions for characters walking up and down hills/slopes with irregularly curved or rocky terrain - what's a good way to do collisions for that type of situation? Per-pixel? Loading up the points of the incline and doing player-line collision checking? Should I use bounding rectangles in general or circle collision detection?

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  • How to limit click'n'drag movement to an area?

    - by Vexille
    I apologize for the somewhat generic title. I'm really don't have much clue about how to accomplish what I'm trying to do, which is making it harder even to research a possible solution. I'm trying to implement a path marker of sorts (maybe there's a most suitable name for it, but this is the best I could come up with). In front of the player there will be a path marker, which will determine how the player will move once he finishes planning his turn. The player may click and drag the marker to the position they choose, but the marker can only be moved within a defined working area (the gray bit). So I'm now stuck with two problems: First of all, how exactly should I define that workable area? I can imagine maybe two vectors that have the player as a starting point to form the workable angle, and maybe those two arcs could come from circles that have their center where the player is, but I definetly don't know how to put this all together. And secondly, after I've defined the area where the marker can be placed, how can I enforce that the marker should only stay within that area? For example, if the player clicks and drags the marker around, it may move freely within the working area, but must not leave the boundaries of the area. So for example, if the player starts dragging the marker upwards, it will move upwards until it hits he end of the working area (first diagram below), but if after that the player starts dragging sideways, the marker must follow the drag while still within the area (second diagram below). I hope this wasn't all too confusing. Thanks, guys.

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  • Do Apple and Google ask for a share if custom payment is done in a free app?

    - by user1590354
    I have a multiplatform game (web/iOS/Android) in the making. In the free version the core game is still fully playable but people who choose to pay will get more social features (and no ads, of course). I was thinking that rather than having a free and a paid version for all the platforms I may release the apps just for free and if the users want more, they have to register and pay a one-time fee (through a payment gateway or PayPal). The extra content would then be available in all the clients they have access to. Theoretically, this means a better value for the players and less maintenance and headache for me (obviously I have to handle all the payment troubles myself). Does it fit into the business model of Apple/Google? Or will they still claim their share of the registration fee?

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  • Resultant Vector Algorithm for 2D Collisions

    - by John
    I am making a Pong based game where a puck hits a paddle and bounces off. Both the puck and the paddles are Circles. I came up with an algorithm to calculate the resultant vector of the puck once it meets a paddle. The game seems to function correctly but I'm not entirely sure my algorithm is correct. Here are my variables for the algorithm: Given: velocity = the magnitude of the initial velocity of the puck before the collision x = the x coordinate of the puck y = the y coordinate of the puck moveX = the horizontal speed of the puck moveY = the vertical speed of the puck otherX = the x coordinate of the paddle otherY = the y coordinate of the paddle piece.horizontalMomentum = the horizontal speed of the paddle before it hits the puck piece.verticalMomentum = the vertical speed of the paddle before it hits the puck slope = the direction, in radians, of the puck's velocity distX = the horizontal distance between the center of the puck and the center of the paddle distY = the vertical distance between the center of the puck and the center of the paddle Algorithm solves for: impactAngle = the angle, in radians, of the angle of impact. newSpeedX = the speed of the resultant vector in the X direction newSpeedY = the speed of the resultant vector in the Y direction Here is the code for my algorithm: int otherX = piece.x; int otherY = piece.y; double velocity = Math.sqrt((moveX * moveX) + (moveY * moveY)); double slope = Math.atan(moveX / moveY); int distX = x - otherX; int distY = y - otherY; double impactAngle = Math.atan(distX / distY); double newAngle = impactAngle + slope; int newSpeedX = (int)(velocity * Math.sin(newAngle)) + piece.horizontalMomentum; int newSpeedY = (int)(velocity * Math.cos(newAngle)) + piece.verticalMomentum; for those who are not program savvy here is it simplified: velocity = v(moveX² + moveY²) slope = arctan(moveX / moveY) distX = x - otherX distY = y - otherY impactAngle = arctan(distX / distY) newAngle = impactAngle + slope newSpeedX = velocity * sin(newAngle) + piece.horizontalMomentum newSpeedY = velocity * cos(newAngle) + piece.verticalMomentum My Question: Is this algorithm correct? Is there an easier/simpler way to do what I'm trying to do?

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  • Embed Unity3D and load multiple games from a single app

    - by Rafael Steil
    Is is possible to export an entire unity3d project/game as an AssetBundle and load it on iOS/Android/Windows on an app that doesn't know anything about such game beforehand? What I have in mind is something like the web plugin does - it loads a series of .unity3d files over http, and render inline in the browser window. Is it even possible to do something closer for iOS/Android? I have read a lot of docs so far, but still can't be sure: http://floored.com/blog/2013/integrating-unity3d-within-ios-native-application.html http://docs.unity3d.com/Manual/LoadingResourcesatRuntime.html http://docs.unity3d.com/Manual/AssetBundlesIntro.html The code from the post at http://forum.unity3d.com/threads/112703-Override-Unity-Data-folder-path?p=749108&viewfull=1#post749108 works for Android, but how about iOS and other platforms?

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  • Joystick example problem for android 2D

    - by iQue
    I've searched all over the web for an answer to this, and there are simular topics but nothing works for me, and I have no Idea why. I just want to move my sprite using a joystick, since I'm useless at math when it comes to angles etc I used an example, Ill post the code here: public float initx = 50; //og 425; public float inity = 300; //og 267; public Point _touchingPoint = new Point(50, 300); //og(425, 267); public Point _pointerPosition = new Point(100, 170); private Boolean _dragging = false; private MotionEvent lastEvent; @Override public boolean onTouchEvent(MotionEvent event) { if (event == null && lastEvent == null) { return _dragging; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } // drag drop if (event.getAction() == MotionEvent.ACTION_DOWN) { _dragging = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { _dragging = false; } if (_dragging) { // get the pos _touchingPoint.x = (int) event.getX(); _touchingPoint.y = (int) event.getY(); // bound to a box if (_touchingPoint.x < 25) { _touchingPoint.x = 25; //og 400 } if (_touchingPoint.x > 75) { _touchingPoint.x = 75; //og 450 } if (_touchingPoint.y < 275) { _touchingPoint.y = 275; //og 240 } if (_touchingPoint.y > 325) { _touchingPoint.y = 325; //og 290 } // get the angle double angle = Math.atan2(_touchingPoint.y - inity, _touchingPoint.x - initx) / (Math.PI / 180); // Move the beetle in proportion to how far // the joystick is dragged from its center _pointerPosition.y += Math.sin(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); _pointerPosition.x += Math.cos(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); // stop the sprite from goin thru if (_pointerPosition.x + happy.getWidth() >= getWidth()) { _pointerPosition.x = getWidth() - happy.getWidth(); } if (_pointerPosition.x < 0) { _pointerPosition.x = 0; } if (_pointerPosition.y + happy.getHeight() >= getHeight()) { _pointerPosition.y = getHeight() - happy.getHeight(); } if (_pointerPosition.y < 0) { _pointerPosition.y = 0; } } public void render(Canvas canvas) { canvas.drawColor(Color.BLUE); canvas.drawBitmap(joystick.get_joystickBg(), initx-45, inity-45, null); canvas.drawBitmap(happy, _pointerPosition.x, _pointerPosition.y, null); canvas.drawBitmap(joystick.get_joystick(), _touchingPoint.x - 26, _touchingPoint.y - 26, null); } public void update() { this.onTouchEvent(null); } og= original position. as you can see Im trying to move the joystick, but when I do it stops working correctly, I mean it still works like a joystick but the sprite dosnt move accordingly, if I for example push the joystick down, the sprite moves up, and if I push it up it moves left. can anyone PLEASE help me, I've been stuck here for sooo long and its really frustrating.

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  • Android Touch Event Collision Detection

    - by chrissb
    I'm relatively new to both Java and Android, so hopefully the problem I'm having is stemming from something pretty minor that I've overlooked. I've got a (very early stage) game that I've started working on, for Android using Java. At this stage, when the user touches the screen, if they touched a point at which there is an enemy, the enemies health is decreased and they become immobile (for the current implementation at least). The issue that I'm having is that the touch detection doesn't always seem to work. I've got a testing sprite set up that goes to the eventX and eventY coordinates of the touch down event, and it always seems to collide with the enemy object. Yet, the enemy doesn't always register as being hit, and sometimes a hit is registered when the sprite indicates the touch coordinates were outside of the enemies bounding box. I realise that this probably doesn't mean much without any code, so here's what I've got so far. Be gentle, as this is literally my first attempt at something more than basic movement etc. First off, the MainGamePanel class registers the touch event, and informs the levelmanager class (which is what I set up to monitor/handle enemies) public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN){ levelManager.handleActionDown((int)event.getX(), (int)event.getY()); targetX=event.getX(); targetY=event.getY(); } if (event.getAction() == MotionEvent.ACTION_MOVE) { //the gestures } if (event.getAction() == MotionEvent.ACTION_UP) { //touch was released } return true; } From there, in the levelmanager class the touch event is passed on to all of the enemies within a list array: public static void handleActionDown(int eventX,int eventY){ hit=false; for (enemy1 en : enemy1array){ en.handleActionDown(eventX, eventY); } } The rest of the collision code is handled within the enemies handleActionDown function: public void handleActionDown(int eventX, int eventY) { if(eventX>this.x-enemy1bitmap.getWidth() && eventX<this.x+enemy1bitmap.getWidth() && eventY>this.y-enemy1bitmap.getHeight() && eventY<this.x+enemy1bitmap.getHeight()){ takeDamage(1); levelmanager.setHit(); } } I should probably be using getWidth()/2 and getHeight()/2 for it to be more accurate, but I expanded the area to test this - although I've noticed no improvement. At this stage, the games detection over whether or not the enemy is hit is spotty at best. Generally it takes two or three attempts before a collision is successfully registered, even though the sprite that is being used for testing and set to the eventX and eventY coordinates always indicates that the collision should have worked. Hopefully someone can steer me in the right direction here, and if more information is needed, ask away! Cheers, -Chris

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  • Doubling the DPI with a shader?

    - by Mathias Lykkegaard Lorenzen
    I'm developing a game where the map is generated with Perlin Noise, but on the CPU. I am generating some perlin noise onto a texture with a small size, and then I stretch it out to the whole screen to simulate a map. The reason for the CPU generating the noise is that I want it to look the same on all devices. Now, here's the end-result. Please ignore the bullets and the explosion on the picture. What matters is the background (the black/gray pixels) and the ground (the brown-ish pixels). They are rendered to the same texture through perlin noise. However, this doesn't look very pretty. So I was wondering if it would be possible to double the amount of pixels using a shader, and rounding edges at the same time? In other words, improve the DPI. I'm using SharpDX with DirectX 11, through its toolkit feature. But any help that'll lead me in the right direction (for instance through HLSL) would be a great help. Thanks in advance.

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  • How to transform gameObjects in array?

    - by user1764781
    I have an array of available gameObjects in the scene. An array of GO should be transformed according to received floats through UDP connection. I know it is simple, but can't figure it out how to accomplish the transformation an array of GO according to received unique floats for each GO, any help will be appreciated. Here is a transformation floats, it might be helpful I guess: x =ReadSingleBigEndian(data, signalOffset); signalOffset+=4; y= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; z= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; alpha= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; theta= ReadSingleBigEndian(data,signalOffset); signalOffset+=4; phi= ReadSingleBigEndian(data,signalOffset); signalOffset+=4;

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  • Draw depth works on WP7 emulator but not device

    - by Luke
    I am making a game on a WP7 device using C# and XNA. I have a system where I always want the object the user is touching to be brought to the top, so every time it is touched I add float.Epsilon to its draw depth (I have it set so that 0 is the back and 1 is the front). On the Emulator that all works fine, but when I run it on my device the draw depths seem to be completely random. I am hoping that anybody knows a way to fix this. I have tried doing a Clean & Rebuild and uninstalling from the device but that is no luck. My call to spritebatch.Begin is: spriteBatch.Begin(SpriteSortMode.FrontToBack, BlendState.AlphaBlend); and to draw I use spriteBatch.Draw(Texture, new Rectangle((int)X, (int)Y, (int)Width, (int)Height), null, Color.White, 0, Vector2.Zero, SpriteEffects.None, mDrawDepth); Where mDrawDepth is a float value of the draw depth (likely to be a very small number; a small multiple of float.Epsilon. Any help much appreciated, thanks!

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  • What is wrong with my specular phong shading

    - by Thijser
    I'm sorry if this should be placed on stackoverflow instead however seeing as this is graphics related I was hoping you guys could help me: I'm attempting to write a phong shader and currently working on the specular. I came acros the following formula: base*pow(dot(V,R),shininess) and attempted to implement it (V is the posion of the viewer and R the reflective vector). This gave the following result and code: Vec3Df phongSpecular(const Vec3Df & vertexPos, Vec3Df & normal, const Vec3Df & lightPos, const Vec3Df & cameraPos, unsigned int index) { Vec3Df relativeLightPos=(lightPos-vertexPos); relativeLightPos.normalize(); Vec3Df relativeCameraPos= (cameraPos-vertexPos); relativeCameraPos.normalize(); int DotOfNormalAndLight = Vec3Df::dotProduct(normal,relativeLightPos); Vec3Df reflective =(relativeLightPos-(2*DotOfNormalAndLight*normal))*-1; reflective.normalize(); float phongyness= Vec3Df::dotProduct(reflective,relativeCameraPos); if (phongyness<0){ phongyness=0; } float shininess= Shininess[index]; float speculair = powf(phongyness,shininess); return Ks[index]*speculair; } I'm looking for something more like this:

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  • Solving 2D Collision Detection Issues with Relative Velocities

    - by Jengerer
    Imagine you have a situation where two objects are moving parallel to one-another and are both within range to collide with a static wall, like this: A common method used in dynamic collision detection is to loop through all objects in arbitrary order, solve for pair-wise collision detection using relative velocities, and then move the object to the nearest collision, if any. However, in this case, if the red object is checked first against the blue one, it would see that the relative velocity to the blue object is -20 m/s (and would thereby not collide this time frame). Then it would see that the red object would collide with the static wall, and the solution would be: And the red object passes through the blue one. So it appears to be a matter of choosing the right order in which you check collisions; but how can you determine which order is correct? How can this passing through of objects be avoided? Is ignoring relative velocity and considering every object as static during pair-wise checks a better idea for this reason?

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  • Making a Background Scrolling in Stacking Game

    - by David Dimalanta
    Hmmm...Is it a good idea to use a LibGDX parallax background for making a stacking game (i.e. PAPA STACKer Lite)? For example, I'm starting to use the blocks to drag-n-drop it. Next, when the next piece reaches the top of the screen, it automatically scrolls to the next one where the available space left. Aside from that, is it also involved with the camera code (Orthographic Camera) that the screen size appeared like 720x1280 but actually it's 1440x2560 for example? And another thing, does the background scrolling have the option to scroll from start to finish and infinite?

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  • Simulating smooth movement along a line after calculating a collision containing a restitution of zero in 2D

    - by Casey
    [for tl;dr see after listing] //...Code to determine shapes types involved in collision here... //...Rectangle-Line collision detected. if(_rbTest->GetCollisionShape()->Intersects(*_ground->GetCollisionShape())) { //Convert incoming shape to a line. a2de::Line l(*dynamic_cast<a2de::Line*>(_ground->GetCollisionShape())); //Get line's normal. a2de::Vector2D normal_vector(l.GetSlope().GetY(), -l.GetSlope().GetX()); a2de::Vector2D::Normalize(normal_vector); //Accumulate forces involved. a2de::Vector2D intermediate_forces; a2de::Vector2D normal_force = normal_vector * _rbTest->GetMass() * _world->GetGravityHandler()->GetGravityValue(); intermediate_forces += normal_force; //Calculate final velocity: See [1] double Ma = _rbTest->GetMass(); a2de::Vector2D Ua = _rbTest->GetVelocity(); double Mb = _ground->GetMass(); a2de::Vector2D Ub = _ground->GetVelocity(); double mCr = Mb * _ground->GetRestitution(); a2de::Vector2D collision_velocity( ((Ma * Ua) + (Mb * Ub) + ((mCr * Ub) - (mCr * Ua))) / (Ma + Mb)); //Calculate reflection vector: See [2] a2de::Vector2D reflect_velocity( -collision_velocity + 2 * (a2de::Vector2D::DotProduct(collision_velocity, normal_vector)) * normal_vector ); //Affect velocity to account for restitution of colliding bodies. reflect_velocity *= (_ground->GetRestitution() * _rbTest->GetRestitution()); _rbTest->SetVelocity(reflect_velocity); //THE ULTIMATE ISSUE STEMS FROM THE FOLLOWING LINE: //Move object away from collision one pixel to prevent constant collision. _rbTest->SetPosition(_rbTest->GetPosition() + normal_vector); _rbTest->ApplyImpulse(intermediate_forces); } Sources: (1) Wikipedia: Coefficient of Restitution: Speeds after impact (2) Wikipedia: Specular Reflection: Direction of reflection First, I have a system in place to account for friction (that is, a coefficient of friction) but is not used right now (in addition, it is zero, which should not affect the math anyway). I'll deal with that after I get this working. Anyway, when the restitution of either object involved in the collision is zero the object stops as required, but if movement along the same direction (again, irrespective of the friction value that isn't used) as the line is attempted the object moves as if slogging through knee deep snow. If I remove the line of code in question and the object is not push away one pixel the object barely moves at all. All because the object collides, is stopped, is pushed up, collides, is stopped...etc. OR collides, is stopped, collides, is stopped, etc... TL;DR How do I only account for a collision ONCE for restitution purposes (BONUS: but CONTINUALLY for frictional purposes, to be implemented later)

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  • How AlphaBlend Blendstate works in XNA when accumulighting light into a RenderTarget?

    - by cubrman
    I am using a Deferred Rendering engine from Catalin Zima's tutorial: His lighting shader returns the color of the light in the rgb channels and the specular component in the alpha channel. Here is how light gets accumulated: Game.GraphicsDevice.SetRenderTarget(LightRT); Game.GraphicsDevice.Clear(Color.Transparent); Game.GraphicsDevice.BlendState = BlendState.AlphaBlend; // Continuously draw 3d spheres with lighting pixel shader. ... Game.GraphicsDevice.BlendState = BlendState.Opaque; MSDN states that AlphaBlend field of the BlendState class uses the next formula for alphablending: (source × Blend.SourceAlpha) + (destination × Blend.InvSourceAlpha), where "source" is the color of the pixel returned by the shader and "destination" is the color of the pixel in the rendertarget. My question is why do my colors are accumulated correctly in the Light rendertarget even when the new pixels' alphas equal zero? As a quick sanity check I ran the following code in the light's pixel shader: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); if (light4.a == 0) light4 = 0; return light4; This prevents lighting from getting accumulated and, subsequently, drawn on the screen. But when I do the following: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); return light4; The light is accumulated and drawn exactly where it needs to be. What am I missing? According to the formula above: (source x 0) + (destination x 1) should equal destination, so the "LightRT" rendertarget must not change when I draw light spheres into it! It feels like the GPU is using the Additive blend instead: (source × Blend.One) + (destination × Blend.One)

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  • Capitalizing on JavaScript's prototypal inheritance

    - by keithjgrant
    JavaScript has a class-free object system in which objects inherit properties directly from other objects. This is really powerful, but it is unfamiliar to classically trained programmers. If you attempt to apply classical design patterns directly to JavaScript, you will be frustrated. But if you learn to work with JavaScript's prototypal nature, your efforts will be rewarded. ... It is Lisp in C's clothing. -Douglas Crockford What does this mean for a game developer working with canvas and HTML5? I've been looking over this question on useful design patterns in gaming, but prototypal inheritance is very different than classical inheritance, and there are surely differences in the best way to apply some of these common patterns. For example, classical inheritance allows us to create a moveableEntity class, and extend that with any classes that move in our game world (player, monster, bullet, etc.). Sure, you can strongarm JavaScript to work that way, but in doing so, you are kind of fighting against its nature. Is there a better approach to this sort of problem when we have prototypal inheritance at our fingertips?

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  • GameplayScreen does not contain a definition for GraphicsDevice

    - by Dave Voyles
    Long story short: I'm trying to intergrate my game with Microsoft's Game State Management. In doing so I've run into some errors, and the latest one is in the title. I'm not able to display my HUD for the reasons listed above. Previously, I had much of my code in my Game.cs class, but the GSM has a bit of it in Game1, and most of what you have drawn for the main screen in your GameplayScreen class, and that is what is causing confusion on my part. I've created an instance of the GameplayScreen class to be used in the HUD class (as you can see below). Before integrating with the GSM however, I created an instance of my Game class, and all worked fine. It seems that I need to define my graphics device somewhere, but I am not sure of where exactly. I've left some code below to help you understand. public class GameStateManagementGame : Microsoft.Xna.Framework.Game { #region Fields GraphicsDeviceManager graphics; ScreenManager screenManager; // Creates a new intance, which is used in the HUD class public static Game Instance; // By preloading any assets used by UI rendering, we avoid framerate glitches // when they suddenly need to be loaded in the middle of a menu transition. static readonly string[] preloadAssets = { "gradient", }; #endregion #region Initialization /// <summary> /// The main game constructor. /// </summary> public GameStateManagementGame() { Content.RootDirectory = "Content"; graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = 1280; graphics.PreferredBackBufferHeight = 720; graphics.IsFullScreen = false; graphics.ApplyChanges(); // Create the screen manager component. screenManager = new ScreenManager(this); Components.Add(screenManager); // Activate the first screens. screenManager.AddScreen(new BackgroundScreen(), null); //screenManager.AddScreen(new MainMenuScreen(), null); screenManager.AddScreen(new PressStartScreen(), null); } namespace Pong { public class HUD { public void Update(GameTime gameTime) { // Used in the Draw method titleSafeRectangle = new Rectangle (GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.X, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Y, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Width, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Height); } } } class GameplayScreen : GameScreen { #region Fields ContentManager content; public static GameStates gamestate; private GraphicsDeviceManager graphics; public int screenWidth; public int screenHeight; private Texture2D backgroundTexture; private SpriteBatch spriteBatch; private Menu menu; private SpriteFont arial; private HUD hud; Animation player; // Creates a new intance, which is used in the HUD class public static GameplayScreen Instance; public GameplayScreen() { TransitionOnTime = TimeSpan.FromSeconds(1.5); TransitionOffTime = TimeSpan.FromSeconds(0.5); } protected void Initialize() { lastScored = false; menu = new Menu(); resetTimer = 0; resetTimerInUse = true; ball = new Ball(content, new Vector2(screenWidth, screenHeight)); SetUpMulti(); input = new Input(); hud = new HUD(); // Places the powerup animation inside of the surrounding box // Needs to be cleaned up, instead of using hard pixel values player = new Animation(content.Load<Texture2D>(@"gfx/powerupSpriteSheet"), new Vector2(103, 44), 64, 64, 4, 5); // Used by for the Powerups random = new Random(); vec = new Vector2(100, 50); vec2 = new Vector2(100, 100); promptVec = new Vector2(50, 25); timer = 10000.0f; // Starting value for the cooldown for the powerup timer timerVector = new Vector2(10, 10); //JEP - one time creation of powerup objects playerOnePowerup = new Powerup(); playerOnePowerup.Activated += PowerupActivated; playerOnePowerup.Deactivated += PowerupDeactivated; playerTwoPowerup = new Powerup(); playerTwoPowerup.Activated += PowerupActivated; playerTwoPowerup.Deactivated += PowerupDeactivated; //JEP - moved from events since these only need set once activatedVec = new Vector2(100, 125); deactivatedVec = new Vector2(100, 150); powerupReady = false; }

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