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• Restricted pathfinding Area

  - by SubZeron

  So i'm triying to create a little "XCOM : Enemy Unknown" like game ,and using the Aron Granberg's Pathfinding-Tool (free version) to handle the "click to move part. i want to add a little trap system where the hero get stuck inside an area, so he will have only the possibility to move inside this trapped area, so far everything is fine however when i click outside the trapped area, the hero try to reach the destination even though the wall will prevents him from reaching it. so my question is, is there any way to restrict the area where the pathfinding system work to the trapped area dynamically. and wich Graph Type is recommended to use in this situation or this kind of Games (Grid Graph/Navmesh Graph/Point Graph). Thank you. image link for explanation : https://dl.dropbox.com/u/77993668/exemple.jpg

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• How to display a projectile trajectory in c++? [on hold]

  - by sana

  I am trying to make a game of Gorillas in c++ whose specification is somewhat like....... is : "In this game both players should select their position on a level scaled ground. Scale of the ground should be from 0 to 20 divisions, each division corresponding to 10 meters. Each player will enter an angle and initial velocity (limits of both should be defined) and the player will hurl a stone with this velocity at given angle. Stone will make a projectile and if it hits the other player then shooting player wins. A random effect of air should also be incorporated. Air will support one player and resist other. Velocity of air should be generated randomly, within some limits, and subtracted or added in the horizontal velocity of the stone. An arrow of suitable length shall represent air direction and velocity. The player who hits first wins." How do I display the trajectory of the stone????

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• Draw "vision cone" / targetting element onto game world

  - by gkimsey

  I'm wanting to indicate various things using a "pie slice" sort of shape as below. Similar to vision cones in stealth game minimaps, or targetting indicators in RTS type games for frontal area attacks. Something generic enough to be used for both would be ideal. I need to be able to procedurally (and efficiently) change things like the slice width and length, color, transparency, position in the world, etc. For my particular situation, there's no concern with elevation, funky terrain, or really any third axis at all as far as this element is concerned. I have two first inclinations on how to accomplish this: 1) Manually generate the vertices for a main triangle, (possibly two, superimposed to get the border effect), a handful more to approximate the arc at the end, and roll it into a mesh. 2) Use some sort of 2D drawing library to create a circle and mask it off at the right angles, render to texture, and use that. For reference, I have some experience with Ogre3D, but I'm not attached to it as this is a mostly academic pursuit at the moment. Other technologies that might be better at accomplishing this are more than welcome. Finally, I'm kind of curious about how to do a "flashlight" or similar 3D effect that could produce the same result, but on all surfaces in the lit area.

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• XNA VertexBuffer.SetData performance suggestions

  - by CodeSpeaker

  I have a 3d world in a grid layout where each grid cell contains its separate vertex and index buffer for the mesh/terrain of that cell. When the player moves outside the boundaries of his cell, i dynamically load more cells in his walking direction based on his viewing distance. This triggers x number of vertex and indexbuffer initializations depending on how many cells that needs to be generated and causes the framerate to drop annoyingly during this time. The generation of terrain data is handled in a separate thread and runs smoothly. The vertex and index buffers are added during the update cycle of the game loop. I´ve tried batching the number of cells to be processed to avoid sending too much data at once into the buffers, which worked ok at a shorter viewing distance (about 9 cells to process), but not as well at greater distances with around 30 cells to process. Any idea how i can optimize this?

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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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• OpenGL : sluggish performance in extracting texture from GPU

  - by Cyan

  I'm currently working on an algorithm which creates a texture within a render buffer. The operations are pretty complex, but for the GPU this is a simple task, done very quickly. The problem is that, after creating the texture, i would like to save it. This requires to extract it from GPU memory. For this operation, i'm using glGetTexImage(). It works, but the performance is sluggish. No, i mean even slower than that. For example, an 8MB texture (uncompressed) requires 3 seconds (yes, seconds) to be extracted. That's mind puzzling. I'm almost wondering if my graphic card is connected by a serial link... Well, anyway, i've looked around, and found some people complaining about the same, but no working solution so far. The most promising advise was to "extract data in the native format of the GPU". Which i've tried and tried, but failed so far. Edit : by moving the call to glGetTexImage() in a different place, the speed has been a bit improved for the most dramatic samples : looking again at the 8MB texture, it knows requires 500ms, instead of 3sec. It's better, but still much too slow. Smaller texture sizes were not affected by the change (typical timing remained into the 60-80ms range). Using glFinish() didn't help either. Note that, if i call glFinish() (without glGetTexImage), i'm getting a fixed 16ms result, whatever the texture size or complexity. It really looks like the timing for a frame at 60fps. The timing is measured for the full rendering + saving sequence. The call to glGetTexImage() alone does not really matter. That being said, it is this call which changes the performance. And yes, of course, as stated at the beginning, the texture is "created into the GPU", hence the need to save it.

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• What is the purpose of the canonical view volume?

  - by breadjesus

  I'm currently learning OpenGL and haven't been able to find an answer to this question. After the projection matrix is applied to the view space, the view space is "normalized" so that all the points lie within the range [-1, 1]. This is generally referred to as the "canonical view volume" or "normalized device coordinates". While I've found plenty of resources telling me about how this happens, I haven't seen anything about why it happens. What is the purpose of this step?

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• Movement on the X an Z axis are combined?

  - by Magicaxis

  This is probably a stupid question, but I'm trying to simply move a 3D object up, down, left, and right (Not forward or backward). The Y axis works fine, but when I increment the object's X position, the object moves BOTH right and backwards! when I decrement X, left and forwards! setPosition(getPosition().X + 2/*times deltatime*/, getPosition().Y, getPosition().Z); I was astonished that XNA doesnt have its own setPosition function, so I made a parent class for all objects with a setPosition and Draw function. Setposition simply edits a variable "mPosition" and passes it to the common draw function: // Copy any parent transforms. Matrix[] transforms = new Matrix[block.Bones.Count]; block.CopyAbsoluteBoneTransformsTo(transforms); // Draw the model. A model can have multiple meshes, so loop. foreach (ModelMesh mesh in block.Meshes) { // This is where the mesh orientation is set, as well // as our camera and projection. foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(MathHelper.ToRadians(mOrientation.Y)) * Matrix.CreateTranslation(mPosition); effect.View = game1.getView(); effect.Projection = game1.getProjection(); } // Draw the mesh, using the effects set above. mesh.Draw(); } I tried to work it out by attempting to increment and decrement the Z axis, but nothing happens?! So using the X axis changes the objects x and z axis', but changing the Z does nothing. Great. So how do I seperate the X and Z axis movement?

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• how to decide face side of sprite

  - by user22135

  my first question here :] i am just starting game-dev with slick2D and marte engine and my question is when i move my sprite left and right i am doing walk animation but when the key is released how can i decide in which side the sprite face to set ? here's my Player.java http://pastebin.com/WjQ09Fij am i doing things right ? here's netbeans project without libs http://uppit.com/84vdufs35aas/SSheet.7z [< 45 KB] please help thanks in advance

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• pygame.Rect around circle

  - by geekkid

  I'm trying to make a pong game in pygame , but i can't figure out how to but a ball circle , which i can create with pygame.draw.circle into a pygame.Rect object so i can use the colliderect function and manipulate the ball's position. For example, with rectangles, i can do something like this : rect = pygame.Rect(255, 255, 100, 100) pygame.draw.rect(screen, yellow, rect) and then when i change the pygame.Rect object position , the drawing primitives position also changes. How can the same effect be achieved when i want to draw a circle, instead of a rectangle? Thank you.

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• how to prevent showing outside of world game in cocos2dx

  - by HRZ

  Im trying to make a tower defence game and it can zoom in/out and scrolling over my world map.How to scroll over the game and how to restrict it to don't show outside of my map. At below I scroll over the map by using CCCamera but i don't know how i can restrict it. CCPoint tap = touch->getLocation(); CCPoint prev_tap = touch->getPreviousLocation(); CCPoint sub_point = tap - prev_tap; float xNewPos, yNewPos; float xEyePos, yEyePos, zEyePos; float cameraPosX, cameraPosY, cameraPosZ; // First we get the current camera position. GameLayer->getCamera()->getCenterXYZ(&cameraPosX, &cameraPosY, &cameraPosZ); GameLayer->getCamera()->getEyeXYZ(&xEyePos, &yEyePos, &zEyePos); // Calculate the new position xNewPos = cameraPosX - sub_point.x; yNewPos = cameraPosY - sub_point.y; GameLayer->getCamera()->setCenterXYZ(xNewPos, yNewPos, cameraPosZ); GameLayer->getCamera()->setEyeXYZ(xNewPos, yNewPos, zEyePos); And for zooming i used such code: GameLayer->setScale(this->getScale() + 0.002); //zooming in

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• What techniques can I use to render very large numbers of objects more efficiently in OpenGL?

  - by Luke

  You can think of my application as drawing a very large ball-and-stick diagram (or graph). At times, this graph can get very large, where the number of elements even outnumbers the pixels on the screen. Currently I am simply passing all of my textures (as GL_POINTS) and lines to the graphics card using VBO's. When the number of elements outnumbers the number of pixels, is this the most efficient way to do this? Or should I do some calculations on the CPU side before handing everything over to the GPU? If it matters, I do use GL_DEPTH_TEST and GL_ALPHA_TEST. I do some alpha blending, but probably not enough to make a huge performance difference. My scene can be static at times, but the user has control over a typical arc-ball camera and can pan, rotate, or zoom. It is during these operations that performance degradation is noticeable.

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• Detect click on Triangle and Circle buttons

  - by chr1s89

  How can i detect clicks on a texture (will be a button in my game) that has a form of a triangle or circle. I know only the rectangle solution where u can use the positions + the width/height but this dont work for that because clicks will be detected at the transparent pixels. I heard of pixel-perfect collision is it the right way for this? It would be great if someone can give me a example for such a solution or other.

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• Vector reflect problem

  - by xdevel2000

  I'm testing some vector reflection and I want to check what happens when a ball collides with a paddle. So if I have: Vector2 velocity = new Vector2(-5, 2); position_ball += velocity; if (position_ball.X < 10) { Vector2 v = new Vector2(1,0); // or Vector2.UnitX velocity = Vector2.Reflect(velocity, v); } then, correctly, velocity is (5,2) after Reflect, but if I do: if (position_ball.X < 10) { Vector2 v = new Vector2(1,1); velocity = Vector2.Reflect(velocity, v); } then velocity is (1,8) and not (5, -2) that is the solution of reflection equation R = V - 2 * (V . N) Why is that?

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• Checking collision of bullets and Asteroids

  - by Moaz ELdeen

  I'm trying to detect collision between two list of bullets and asteroids. The code works fine, but when the bullet intersects with an asteroid, and that bullet passes through another asteroid, the code gives an assertion, and it says about it can't increment the iterator. I'm sure there is a small bug in that code, but I can't find it. for (list<Bullet>::iterator itr_bullet = ship.m_Bullets.begin(); itr_bullet!=ship.m_Bullets.end();) { for (list<Asteroid>::iterator itr_astroid = asteroids.begin(); itr_astroid!=asteroids.end(); itr_astroid++) { if(checkCollision(itr_bullet->getCenter(),itr_astroid->getCenter(), itr_bullet->getRadius(), itr_astroid->getRadius())) { itr_astroid = asteroids.erase(itr_astroid); } } itr_bullet++; }

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• How should game objects be aware of each other?

  - by Jefffrey

  I find it hard to find a way to organize game objects so that they are polymorphic but at the same time not polymorphic. Here's an example: assuming that we want all our objects to update() and draw(). In order to do that we need to define a base class GameObject which have those two virtual pure methods and let polymorphism kicks in: class World { private: std::vector<GameObject*> objects; public: // ... update() { for (auto& o : objects) o->update(); for (auto& o : objects) o->draw(window); } }; The update method is supposed to take care of whatever state the specific class object needs to update. The fact is that each objects needs to know about the world around them. For example: A mine needs to know if someone is colliding with it A soldier should know if another team's soldier is in proximity A zombie should know where the closest brain, within a radius, is For passive interactions (like the first one) I was thinking that the collision detection could delegate what to do in specific cases of collisions to the object itself with a on_collide(GameObject*). Most of the the other informations (like the other two examples) could just be queried by the game world passed to the update method. Now the world does not distinguish objects based on their type (it stores all object in a single polymorphic container), so what in fact it will return with an ideal world.entities_in(center, radius) is a container of GameObject*. But of course the soldier does not want to attack other soldiers from his team and a zombie doesn't case about other zombies. So we need to distinguish the behavior. A solution could be the following: void TeamASoldier::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<TeamBSoldier*>(e)) // shoot towards enemy } void Zombie::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<Human*>(e)) // go and eat brain } but of course the number of dynamic_cast<> per frame could be horribly high, and we all know how slow dynamic_cast can be. The same problem also applies to the on_collide(GameObject*) delegate that we discussed earlier. So what it the ideal way to organize the code so that objects can be aware of other objects and be able to ignore them or take actions based on their type?

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• Sprite batching in OpenGL

  - by Roy T.

  I've got a JAVA based game with an OpenGL rendering front that is drawing a large amount of sprites every frame (during testing it peaked at 700). Now this game is completely unoptimized. There is no spatial partitioning (so a sprite is drawn even if it isn't on screen) and every sprite is drawn separately like this: graphics.glPushMatrix(); { graphics.glTranslated(x, y, 0.0); graphics.glRotated(degrees, 0, 0, 1); graphics.glBegin(GL2.GL_QUADS); graphics.glTexCoord2f (1.0f, 0.0f); graphics.glVertex2d(half_size , half_size); // upper right // same for upper left, lower left, lower right graphics.glEnd(); } graphics.glPopMatrix(); Currently the game is running at +-25FPS and is CPU bound. I would like to improve performance by adding spatial partitioning (which I know how to do) and sprite batching. Not drawing sprites that aren't on screen will help a lot, however since players can zoom out it won't help enough, hence the need for batching. However sprite batching in OpenGL is a bit of mystery to me. I usually work with XNA where a few classes to do this are built in. But in OpenGL I don't know what to do. As for further optimization, the game I'm working on as a few interesting characteristics. A lot of sprites have the same texture and all the sprites are square. Maybe these characteristics will help determine an efficient batching technique?

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• Multi-threaded JOGL Problem

  - by moeabdol

  I'm writing a simple OpenGL application in Java that implements the Monte Carlo method for estimating the value of PI. The method is pretty easy. Simply, you draw a circle inside a unit square and then plot random points over the scene. Now, for each point that is inside the circle you increment the counter for in points. After determining for all the random points wither they are inside the circle or not you divide the number of in points over the total number of points you have plotted all multiplied by 4 to get an estimation of PI. It goes something like this PI = (inPoints / totalPoints) * 4. This is because mathematically the ratio of a circle's area to a square's area is PI/4, so when we multiply it by 4 we get PI. My problem doesn't lie in the algorithm itself; however, I'm having problems trying to plot the points as they are being generated instead of just plotting everything at once when the program finishes executing. I want to give the application a sense of real-time display where the user would see the points as they are being plotted. I'm a beginner at OpenGL and I'm pretty sure there is a multi-threading feature built into it. Non the less, I tried to manually create my own thread. Each worker thread plots one point at a time. Following is the psudo-code: /* this part of the code exists in display() method in MyCanvas.java which extends GLCanvas and implements GLEventListener */ // main loop for(int i = 0; i < number_of_points; i++){ RandomGenerator random = new RandomGenerator(); float x = random.nextFloat(); float y = random.nextFloat(); Thread pointThread = new Thread(new PointThread(x, y)); } gl.glFlush(); /* this part of the code exists in run() method in PointThread.java which implements Runnable */ void run(){ try{ gl.glPushMatrix(); gl.glBegin(GL2.GL_POINTS); if(pointIsIn) gl.glColor3f(1.0f, 0.0f, 0.0f); // red point else gl.glColor3f(0.0f, 0.0f, 1.0f); // blue point gl.glVertex3f(x, y, 0.0f); // coordinates gl.glEnd(); gl.glPopMatrix(); }catch(Exception e){ } } I'm not sure if my approach to solving this issue is correct. I hope you guys can help me out. Thanks.

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• glTexImage2D not loading my data

  - by Clyde

  Can anyone suggest why this code doesn't work? When I draw using this texture all I get is black. If I use GLUtils.texImage2D() to load a png file, it works correctly. ByteBuffer bb = ByteBuffer.allocateDirect(128*128*4).order(ByteOrder.nativeOrder()); bb.position(0); for(int row = 0; row != 128; row++) { for(int i = 0 ; i != 128 ; i++) { bb.put((byte)0x80); bb.put((byte)0xFF); bb.put((byte)0xFF); bb.put((byte)i); } } int[] handle = new int[1]; GLES20.glEnable(GLES20.GL_TEXTURE_2D); GLES20.glGenTextures(1, handle, 0); DrawAdapter.checkGlError("Gen textures"); GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, handle[0]); DrawAdapter.checkGlError("Bind textures"); bb.position(0); GLES20.glTexImage2D(GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA, 128, 128, 0, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, bb); DrawAdapter.checkGlError("glTexImage2D"); return handle[0];

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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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• How to create a scripted sequence

  - by igrad

  Like countless other video games, I'd like to have scripted sequences in my game. Character 1 says something, the player replies, then a rock falls, that sorta stuff. I could find a way to do it, but I would like to use a common method, assuming there is one. My current thought is to have a separate file for each level of the game that contains all the possible scripted actions for that level. When the corresponding trigger is activated, the function is called. I think early Call of Duty games (up to CoD4) used something similar, but I'm not entirely sure.

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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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• Inventory Item Exist checker

  - by Annalyne

  I have a question regarding declaring my inventory. I made it a string named inventory, with a constant number as its max value. The thing is, I want the user to use an item if he / she gains an item. The problem is, I do not know what syntax should I use to determine if the user has an item and use that item. Here's my code I just started: so declaring the inventory: const int MAX_ITEMS = 15; string game_inventory [MAX_ITEMS]; int itemnum = 0; I have some items like potion, antidote, gems and others. I use the: game_inventory[itemnum++] = "Potion" to place items in my inventory. If I want to use the potion, IF I HAVE one, how can i make a function to check whether I have a potion or anything and use it?

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• Particles are not moving correctly [closed]

  - by cr33p

  I want to make a particle explosion, after something gets destroyed, but somehow only one line of mixed colors show up on the screen. Here's the header: http://pastebin.com/JW5bPLj2 Here's the source: http://pastebin.com/KHmFqytD I don't get what's wrong, as it's nearly the same as in "Programming Linux Games" Can somebody help me fix that? PS: "Uint32 delta" is needed to update the pixels based on time. PSS: Maybe I should add that it's programmed in C and includes SDL. EDIT: Found the problem. It was the "drawParticles" function. The problem was, that I passed a double to "offset" (as particles[i].x, etc are all doubles). So I ended up with values like ~MAX_INT because I didn't cast the doubles properly to ints.

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