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• Dynamic Components

  - by Alex

  I am attempting to design a component-based architecture that allows Components to be dynamically enabled and disabled, much like the system employed by Unity3D. For example, all Components are implicitly enabled by default; however, if one desires to halt execution of code for a particular Component, one can disable it. Naively, I want to have a boolean flag in Component (which is an abstract class), and somehow serialize all method calls into strings, so that some sort of ComponentManager can check if a given Component is enabled/disabled before processing a method call on it. However, this is a pretty bad solution. I feel like I should employ some variation of the state paradigm, but I have yet to make progress. Any help would be greatly appreciated,

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• Parsing glGetShaderInfoLog() to get error info. Is this reliable, or is there a better way?

  - by m4ttbush

  I want to get a list of errors and their line numbers so I can display the error information different to how it's formatted in the error string, and also show the line in error. It looks easy enough to just parse the result of glGetShaderInfoLog(), look for "ERROR:" then read the next number up to : and then the next, and then the error description up to the next newline. But the OpenGL docs say "Application developers should not expect different OpenGL implementations to produce identical information logs." Which makes me worry that my code may behave incorrectly on different systems. I don't need them to be identical, I just need them to follow the same format. So is there a better way to get a list of errors with line number separate, is it safe to assume that they'll always follow the "ERROR: 0:123:" format, or is there simply no reliable way to do this? Thanks!

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• Rotate Rigged and Animated Scene?

  - by Nick

  I have a rigged and animated mesh that I need to import into Unity. We several characters that all use the same script, and access their bones to do procedural animations as well. The problem is that the new model I was given is facing the wrong way. Instead of facing forward, the model is facing the right.. Is there any way to rotate the model with it's animations without screwing it up, so that it will import properly in unity facing forward? Because of the way it was done, selecting everything in the scene and just rotating it by 90 degrees ruins some of the animations, so I need a program that can fix this.

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• What are some ways of making manageable complex AI?

  - by Tetrad

  In the past I've used simple systems like finite state machines (FSMs) or hierarchical FSMs to control AI behavior. For any complex system, this pattern falls apart very quickly. I've heard about behavior trees and it seems like that's the next obvious step, but haven't seen a working implementation or really tried going down that route yet. Are there any other patterns to making manageable yet complex AI behaviors?

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• Enemies don't shoot. What is wrong? [closed]

  - by Bryan

  I want that every enemy shoots independently bullets. If an enemy’s bullet left the screen, the enemy can shoot a new bullet. Not earlier. But for the moment, the enemies don't shoot. Not a single bullet. I guess their is something wrong with my Enemy class, but I can't find a bug and I get no error message. What is wrong? public class Map { Texture2D myEnemy, myBullet ; Player Player; List<Enemy> enemieslist = new List<Enemy>(); List<Bullet> bulletslist = new List<Bullet>(); float fNextEnemy = 0.0f; float fEnemyFreq = 3.0f; int fMaxEnemy = 3 ; Vector2 Startposition = new Vector2(200, 200); GraphicsDeviceManager graphicsDevice; public Map(GraphicsDeviceManager device) { graphicsDevice = device; } public void Load(ContentManager content) { myEnemy = content.Load<Texture2D>("enemy"); myBullet = content.Load<Texture2D>("bullet"); Player = new Player(graphicsDevice); Player.Load(content); } public void Update(GameTime gameTime) { Player.Update(gameTime); float delta = (float)gameTime.ElapsedGameTime.TotalSeconds; for(int i = enemieslist.Count - 1; i >= 0; i--) { // Update Enemy Enemy enemy = enemieslist[i]; enemy.Update(gameTime, this.graphicsDevice, Player.playershape.Position, delta); // Try to remove an enemy if (enemy.Remove == true) { enemieslist.Remove(enemy); enemy.Remove = false; } } this.fNextEnemy += delta; //New enemy if (fMaxEnemy > 0) { if ((this.fNextEnemy >= fEnemyFreq) && (enemieslist.Count < 3)) { Vector2 enemyDirection = Vector2.Normalize(Player.playershape.Position - Startposition) * 100f; enemieslist.Add(new Enemy(Startposition, enemyDirection, Player.playershape.Position)); fMaxEnemy -= 1; fNextEnemy -= fEnemyFreq; } } } public void Draw(SpriteBatch batch) { Player.Draw(batch); foreach (Enemy enemies in enemieslist) { enemies.Draw(batch, myEnemy); } foreach (Bullet bullets in bulletslist) { bullets.Draw(batch, myBullet); } } } public class Enemy { List<Bullet> bulletslist = new List<Bullet>(); private float nextShot = 0; private float shotFrequency = 2.0f; Vector2 vPos; Vector2 vMove; Vector2 vPlayer; public bool Remove; public bool Shot; public Enemy(Vector2 Pos, Vector2 Move, Vector2 Player) { this.vPos = Pos; this.vMove = Move; this.vPlayer = Player; this.Remove = false; this.Shot = false; } public void Update(GameTime gameTime, GraphicsDeviceManager graphics, Vector2 PlayerPos, float delta) { nextShot += delta; for (int i = bulletslist.Count - 1; i >= 0; i--) { // Update Bullet Bullet bullets = bulletslist[i]; bullets.Update(gameTime, graphics, delta); // Try to remove a bullet... Collision, hit, or outside screen. if (bullets.Remove == true) { bulletslist.Remove(bullets); bullets.Remove = false; } } if (nextShot >= shotFrequency) { this.Shot = true; nextShot -= shotFrequency; } // Does the enemy shot? if ((Shot == true) && (bulletslist.Count < 1)) // New bullet { Vector2 bulletDirection = Vector2.Normalize(PlayerPos - this.vPos) * 200f; bulletslist.Add(new Bullet(this.vPos, bulletDirection, PlayerPos)); Shot = false; } if (!Remove) { this.vMove = Vector2.Normalize(PlayerPos - this.vPos) * 100f; this.vPos += this.vMove * delta; if (this.vPos.X > graphics.PreferredBackBufferWidth + 1) { this.Remove = true; } else if (this.vPos.X < -20) { this.Remove = true; } if (this.vPos.Y > graphics.PreferredBackBufferHeight + 1) { this.Remove = true; } else if (this.vPos.Y < -20) { this.Remove = true; } } } public void Draw(SpriteBatch batch, Texture2D myTexture) { if (!Remove) { batch.Draw(myTexture, this.vPos, Color.White); } } } public class Bullet { Vector2 vPos; Vector2 vMove; Vector2 vPlayer; public bool Remove; public Bullet(Vector2 Pos, Vector2 Move, Vector2 Player) { this.Remove = false; this.vPos = Pos; this.vMove = Move; this.vPlayer = Player; } public void Update(GameTime gameTime, GraphicsDeviceManager graphics, float delta) { if (!Remove) { this.vPos += this.vMove * delta; if (this.vPos.X > graphics.PreferredBackBufferWidth +1) { this.Remove = true; } else if (this.vPos.X < -20) { this.Remove = true; } if (this.vPos.Y > graphics.PreferredBackBufferHeight +1) { this.Remove = true; } else if (this.vPos.Y < -20) { this.Remove = true; } } } public void Draw(SpriteBatch spriteBatch, Texture2D myTexture) { if (!Remove) { spriteBatch.Draw(myTexture, this.vPos, Color.White); } } }

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• Sprite animation problem

  - by hustlerinc

  I have this sprite I have to animate. The sprite is 7 images total but animation is 10 frames (2 positions are repeated). The order I want to go through the frames is like this: 3 - 4 - 5 - 6 - 4 - 3 - 2 - 1 - 0 - 2. My problem is how can I skip 1 frame once I reach the end of each direction? The reason I want to skip is to save me from creating duplicate positions in the spritesheet. I'm doing this in Javascript.

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• How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

  - by Register Sole

  Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they would swing! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :) EDIT In response to Cholesky's comment about warm starting the solver and Baumgarte: Oh right, I forgot to mention! I do save the contact history and the impulse determined in this time step to be used as initial guess in the next time step. As for the Baumgarte, here's what actually happens in the code. Collision is detected when the bodies' closest distance is less than SKIN, meaning they are actually still separated. If at this moment, I used the PGS solver without Baumgarte, restitution of 0 alone would be able to stop the bodies, separated by a distance of ~SKIN, in mid-air! So this isn't right, I want to have the bodies touching each other. So I turn on the Baumgarte, where its role is actually to pull the bodies together! Weird I know, a scheme intended to push the body apart becomes useful for the reverse. Also, I found that if I increase the number of iteration to 100, stacks become much more stable, though the program becomes so slow. UPDATE Since the stack swings left and right, could it be something is wrong with my friction model? Current friction constraint: relative_tangential_velocity = 0

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• Making a Living Developing Games

  - by cable729

  I'm in my last year of high school, and I've been looking at colleges. I'm taking a C++ class at a local community college and I don't feel that it's worth it. I could have learned everything in that class in a week. This had me thinking, would a CS degree even be worth it? How much can it teach me if I can learn everything on my own? Even if I do need to learn more advanced subjects, many colleges put their material online AND I can buy a book. Will companies hire me if I don't have a CS degree? If I have a portfolio will I stand a chance? What kind of things are needed in the portfolio? I want to live doing what I love - programming. So I will do it. I'm just not sure that a CS degree will do anything to me. In addition, if there is a benefit to getting a CS degree, what places are the best?

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• How to do proper Alpha in XNA?

  - by Soshimo

  Okay, I've read several articles, tutorials, and questions regarding this. Most point to the same technique which doesn't solve my problem. I need the ability to create semi-transparent sprites (texture2D's really) and have them overlay another sprite. I can achieve that somewhat with the code samples I've found but I'm not satisfied with the results and I know there is a way to do this. In mobile programming (BREW) we did it old school and actually checked each pixel for transparency before rendering. In this case it seems to render the sprite below it blended with the alpha above it. This may be an artifact of how I'm rendering the texture but, as I said before, all examples point to this one technique. Before I go any further I'll go ahead and paste my example code. public void Draw(SpriteBatch batch, Camera camera, float alpha) { int tileMapWidth = Width; int tileMapHeight = Height; batch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, null, camera.TransformMatrix); for (int x = 0; x < tileMapWidth; x++) { for (int y = 0; y < tileMapHeight; y++) { int tileIndex = _map[y, x]; if (tileIndex != -1) { Texture2D texture = _tileTextures[tileIndex]; batch.Draw( texture, new Rectangle( (x * Engine.TileWidth), (y * Engine.TileHeight), Engine.TileWidth, Engine.TileHeight), new Color(new Vector4(1f, 1f, 1f, alpha ))); } } } batch.End(); } As you can see, in this code I'm using the overloaded SpriteBatch.Begin method which takes, among other things, a blend state. I'm almost positive that's my problem. I don't want to BLEND the sprites, I want them to be transparent when alpha is 0. In this example I can set alpha to 0 but it still renders both tiles, with the lower z ordered sprite showing through, discolored because of the blending. This is not a desired effect, I want the higher z-ordered sprite to fade out and not effect the color beneath it in such a manner. I might be way off here as I'm fairly new to XNA development so feel free to steer me in the correct direction in the event I'm going down the wrong rabbit hole. TIA

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• What is causing this behavior with the movement of Pong Ball in 2D? [closed]

  - by thegermanpole

  //edit after running it through the debugger it turned out i had the display function set to x,x...TIL how to use a debugger I've been trying to teach myself C++ SDL with the lazyfoo tutorial and seem to have run into a roadblock. The code below is the movement function of my Dot class, which controls the ball. The ball seems to ignore yvel and moves with xvel to the bottom right. The code should be pretty readable, the rest of the relevant facts are: All variables are names Constants are in caps dotrad is the radius of my dot yvel and xvel are set to 5 in the constructor The dot is created at x and y equal to 100 When I comment out the x movement block it doesn't move, but if i comment out the y movement block, it keeps on going down to the right. void Dot::move() { if(((y+yvel+dotrad) <= SCREEN_HEIGHT) && (0 <= (y-dotrad+yvel))) { y+=yvel; } else { yvel = -1*yvel; } if(((x+xvel+dotrad) <= SCREEN_WIDTH) && (0 <= (x-dotrad+xvel))) { x +=xvel; } else { xvel = -1*xvel; } }

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• Should I drawing directly on CCLayer or CCSprite?

  - by einverne

  Now I am a little confused in my cocos2d-x cpp project. I want to draw lines with user's finger touch. Following the screenshot of a CCScene: In the screen, there are two squares. I want show an animation in the first square and let the second one draw lines with user touch. Now these two squares are CCSprite. And I can draw dots in the second one on the CCLayer. But I am little confused that I should draw lines on the Sprite or on the Layer. Or are there other ways to organize the code?

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• Cannot find the Cocos2d templates

  - by PeterK

  I am about to upgrade to the last version of Cocos2d and would like to uninstall my current Cocos2d templates before installing the new one but cannot find the templates to delete. I have looked at a number of web comments on this such as Uninstall Cocos2D ans another uninstall example but to no avail. However, I still see Cocos2d in my Xcode (4.5) framework. I have been searching my directories but cannot find it. Is there anyone out there who can give me a hint where to find it so i can delete in?

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• What is the minimum of shader I need to use to run basic calculation on GPU?

  - by Jinxi

  I read, that the Hull Shader, Domain Shader, Geometry Shader and Pixel Shader can be used optional. So, is the Vertex Shader optional too? If no: What does a basic Vertex Shader look like? Just like a simple pass through? Is the Vertex Shader necessary to tell what kind of datastructure (Van Stripes or Meshes) are used? What can I do, with just the vertex shader? Are the fixed functions working without any help of programming a programmable stage?

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• How to calculate new velocities between resting objects (AABB) after accelerations?

  - by Tiedye

  lately I have been trying to create a 2D platformer engine in C++ with Direct2D. The problem I am currently having is getting objects that are resting against each other to interact correctly after accelerations like gravity have been applied to them. Right now I can detect collisions and respond to them correctly (I think) and when objects collide they remember what other objects they're resting against so objects can be pushed by other objects (note that there is no bounce in any collisions so when objects collide they are guaranteed to become resting until something else happens). Every time the simulation advances, the acceleration for objects is applied to their velocities (for example vx += ax * t, where t is time elapsed since last advancement). After these accelerations are applied, I want to check if any objects that are resting against each other are moving at different speeds than their counterparts (as different objects can have different accelerations) and depending on that difference either unlink the two objects so they are no longer resting, or even out their velocities so they are moving at the same speed once again. I am having trouble creating an algorithm that can do this across many resting objects. Here's a diagram to help explain my problem

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• Keep Getting Syntax Error C2199?

  - by DARK3ZOOZ

  Here's my problem I'm trying to define something, but keep getting a syntax error Code: #define R_RegisterShader 0x50C8A0 int (*trap_R_RegisterShader)( const char *name, int Arg_1 ) = (int (_cdecl *)(const char *, int ))R_RegisterShader; ^^^^^^^ This last part is where I keep getting the error if you need more lines of codes, just let me know. thanks http://gyazo.com/1a47ebc12cfbd6ea72feb72c686ae84d screenshot of error

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• Is my implementation of A* wrong?

  - by Bloodyaugust

  I've implemented the A* algorithm in my program. However, it would seem to be functioning incorrectly at times. Below is a screenshot of one such time. The obviously shorter line is to go immediately right at the second to last row. Instead, they move down, around the tower, and continue to their destination (bottom right from top left). Below is my actual code implementation: nodeMap.prototype.findPath = function(p1, p2) { var openList = []; var closedList = []; var nodes = this.nodes; for (var i = 0; i < nodes.length; i++) { //reset heuristics and parents for nodes var curNode = nodes[i]; curNode.f = 0; curNode.g = 0; curNode.h = 0; curNode.parent = null; if (curNode.pathable === false) { closedList.push(curNode); } } openList.push(this.getNode(p1)); while(openList.length > 0) { // Grab the lowest f(x) to process next var lowInd = 0; for(i=0; i<openList.length; i++) { if(openList[i].f < openList[lowInd].f) { lowInd = i; } } var currentNode = openList[lowInd]; if (currentNode === this.getNode(p2)) { var curr = currentNode; var ret = []; while(curr.parent) { ret.push(curr); curr = curr.parent; } return ret.reverse(); } closedList.push(currentNode); for (i = 0; i < openList.length; i++) { //remove currentNode from openList if (openList[i] === currentNode) { openList.splice(i, 1); break; } } for (i = 0; i < currentNode.neighbors.length; i++) { if(closedList.indexOf(currentNode.neighbors[i]) !== -1 ) { continue; } if (currentNode.neighbors[i].isPathable === false) { closedList.push(currentNode.neighbors[i]); continue; } var gScore = currentNode.g + 1; // 1 is the distance from a node to it's neighbor var gScoreIsBest = false; if (openList.indexOf(currentNode.neighbors[i]) === -1) { //save g, h, and f then save the current parent gScoreIsBest = true; currentNode.neighbors[i].h = currentNode.neighbors[i].heuristic(this.getNode(p2)); openList.push(currentNode.neighbors[i]); } else if (gScore < currentNode.neighbors[i].g) { //current g better than previous g gScoreIsBest = true; } if (gScoreIsBest) { currentNode.neighbors[i].parent = currentNode; currentNode.neighbors[i].g = gScore; currentNode.neighbors[i].f = currentNode.neighbors[i].g + currentNode.neighbors[i].h; } } } return false; } Towers block pathability. Is there perhaps something I am missing here, or does A* not always find the shortest path in a situation such as this? Thanks in advance for any help.

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• Rotate 2d sprite towards pointer

  - by Phil

  I'm using Crafty.js and am trying to point a sprite towards the mouse pointer. I have a function for getting the degree between two points and I'm pretty sure it works mathematically (I have it under unit tests). At least it responds that the degree between { 0,0} and {1,1} is 45, which seems right. However, when I set the sprite rotation to the returned degree, it's just wrong all the time. If I manually set it to 90, 45, etc, it gets the right direction.. I have a jsfiddle that shows what I've done so far. Any ideas?

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• How do I swap two objects in a GC language without triggering GC?

  - by TenFour04

  I have two array lists. that I want to swap each frame. My question is, does the variable 'temp' need to be a member variable to avoid triggering GC, assuming this method is called on dozens of objects each frame? I'm not creating a new object, just a new reference to an object. public void LateUpdate(){ ArrayList<int> temp = previousFrameCollisions; previousFrameCollisions = currentFrameCollisions; currentFrameCollisions = temp; currentFrameCollisions.clear(); } I've been told there's no reason to make a primitive into a member variable just to avoid GC, so my best guess is that this also applies to object references.

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• Following a set of points?

  - by user1010005

  Lets assume that i have a set of path that an entity should follow : const int Paths = 2 Vector2D<float> Path[Paths] = { Vector2D(100,0),Vector2D(100,50) }; Now i define my entity's position in a 2D vector as follows : Vector2D<float> FollowerPosition(0,0); And now i would like to move the "follower" to the path at index 1 : int PathPosition = 0; //Start with path 1 Currently i do this : Vector2D<float>& Target = Path[PathPosition]; bool Changed = false; if (FollowerPosition.X < Target.X) FollowerPosition.X += Vel,Changed = true; if (FollowerPosition.X > Target.X) FollowerPosition.X -= Vel,Changed = true; if (FollowerPosition.Y < Target.Y) FollowerPosition.Y += Vel;,Changed = true; if (FollowerPosition.Y > Target.Y) FollowerPosition.Y -= Vel,Changed = true; if (!Changed) { PathPosition = PathPosition + 1; if (PathPosition > Paths) PathPosition = 0; } Which works except for one little detail : The movement is not smooth!! ...So i would like to ask if anyone sees anything wrong with my code. Thanks and sorry for my english.

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• Position sprite at center of screen

  - by Wellie

  I am trying to get a sprite to position itself at the center of the screen but nothing seems to be working for me. I'm trying Viewport viewport = graphics.GraphicsDevice.Viewport; logoPosition = new Vector2((viewport.Width - towerImage.Width) / 2, (viewport.Height - towerImage.Height) / 2); and spriteBatch.Draw(towerImage, centre, null, Color.White, 0, baseOrigin, 1.0f, SpriteEffects.None, 0); This is my first time using XNA and I don't really have a clue what I'm doing.

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• Pathfinding in Warcraft 1

  - by Valmond

  Dijkstra and A* are all nice and popular but what kind of algorithm was used in Warcraft 1 for pathfinding? I remember that the enemy could get trapped in bowl-like caverns which means there were (most probably) no full-path calculations from "start to end". If I recall correctly, the algorithm could be something like this: A) Move towards enemy until success or hitting a wall B) If blocked by a wall, follow the wall until you can move towards the enemy without being blocked and then do A) But I'd like to know, if someone knows :-)

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• 16-bit PNGs in Slick2D

  - by Neglected

  I'm working on a project and I'm using some 3rd party sprites just to get it off the ground; recently I've come into a hitch. Slick2D doesn't seem to want to load my images. That is, it will warn me that images are the wrong bit-depth. All the images are in 16-bit PNG form (PNG is required for transparency). Is there any way I can disable the warning (being the bad guy programmer (the console print for each individual load REALLY SLOWS DOWN the image)) or is there another solution? I was thinking about converting all images (using imagemagick) to .gif (with an alpha channel). Would there be any loss in quality between formats? EDIT: I tried using imagemagick but some of the sprites use pure black so I can't do that without wrecking the image. EDIT2: using "identify" on any of the images show them as being 8-bit.. but Slick2D won't load them. What the hell? D: EDIT3: Issue solved (ish). If you are googling this then just disable the java png loader from slick by sticking this somewhere in your code (like the main method): System.setProperty("org.newdawn.slick.pngloader", "false");

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• LibGDX onTouch() method kill on touch

  - by johnny-b

  How can I add this on my application. i want to use the onTouch() method from the implementation of the InputProcessor to kill the enemies on screen. how do i do that? do i have to do anything to the enemy class? please help Thank you M @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { return false; } here is my enemy class public class Bullet extends Sprite { private Vector2 velocity; private float lifetime; public Bullet(float x, float y) { velocity = new Vector2(0, 0); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); velocity.x += dx * delta; velocity.y += dy * delta; } } i am rendering all graphics in a GameRender class and a gameworld class if you need more info please let me know Thank you

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• Physics Engine [Collision Response, 2-dimensional] experts, help!! My stack is unstable!

  - by Register Sole

  Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they hardly stand still! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have: I would try adding a damping term (proportional to velocity) to the Baumgarte. Is this a good idea in general? If not I would not want to waste my time trying to tune the parameter hoping it magically works. Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :)

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• How do I make camera move at same speed when rotating and moving forward

  - by dez

  I made a camera in DX9. To move forward I press the Up arrow. To rotate on the Y axis I use the mouse. When I perform these movements on their own the camera moves at the speed I want. However, if I hold down Up and move the mouse at the same time then the camera moves a lot faster than it should. I want it to move at the same speed as it does when only the Up arrow is pressed. I think I need to normalize something somewhere but not sure what and not sure where. Have tried various combinations without success so if anyone can point me in the right direction that would be great. Thanks. I've post code below. #define KEY_DOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0) LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ) { if( KEY_DOWN(VK_UP)) MovePlayer(D3DXVECTOR3(0, 0, -1.0f)); if( KEY_DOWN(VK_DOWN)) MovePlayer(D3DXVECTOR3(0, 0, 1.0f)); switch( msg ) { case WM_MOUSEMOVE: ProcessMouseInput(); } } void MovePlayer( D3DXVECTOR3 in_vec ) { D3DXMATRIX CameraRot; D3DXMatrixRotationY(&CameraRot,D3DXToRadian(AngleY)); D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&in_vec,&CameraRot); CameraPos += (m_timeElapsed * CameraRotTarget); } void ProcessMouseInput() { GetCursorPos( &CurrentMouseState ); if ((CurrentMouseState.x != GameMouseState.x) || (CurrentMouseState.y != GameMouseState.y)) { int dx = CurrentMouseState.x - GameMouseState.x; int dy = CurrentMouseState.y - GameMouseState.y; AngleY+=m_timeElapsed*dx*7.0f; } GameMouseState = CurrentMouseState; // Set back to window center in Render function } VOID UpdateCamera() { D3DXVECTOR3 CameraOrigTarget(0, 0, -1); D3DXVECTOR3 CameraOrigUp(0, 1, 0); D3DXMATRIX CameraRot; D3DXMATRIX CameraRotX; D3DXMatrixRotationX(&CameraRotX,D3DXToRadian(AngleX)); D3DXMATRIX CameraRotY; D3DXMatrixRotationY(&CameraRotY,D3DXToRadian(AngleY)); CameraRot = CameraRotX * CameraRotY; D3DXVECTOR3 CameraRotTarget; D3DXVec3TransformNormal(&CameraRotTarget,&CameraOrigTarget,&CameraRot); D3DXVECTOR3 CameraTarget; CameraTarget = CameraPos + CameraRotTarget; D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f ); D3DXMatrixLookAtLH( &matView, &CameraPos, &CameraTarget, &vUpVec ); g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView ); D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI / 4, 1.0f, 1.0f, 100.0f ); g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj ); }

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