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• Physics in carrom like game using cocos2d + Box2D

  - by Raj

  I am working on carrom like game using cocos2d + Box2D. I set world gravity(0,0), want gravity in z-axis. I set following values for coin and striker body: Coin body (circle with radius - 15/PTM_RATIO): density = 20.0f; friction = 0.4f; restitution = 0.6f; Striker body (circle with radius - 15/PTM_RATIO): density = 25.0f; friction = 0.6f; restitution = 0.3f; Output is not smooth. When I apply ApplyLinearImpulse(force,position) the coin movement looks like floating in the air - takes too much time to stop. What values for coin and striker make it look like real carrom?

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• Can't use the hardware scissor any more, should I use the stencil buffer or manually clip sprites?

  - by Alex Ames

  I wrote a simple UI system for my game. There is a clip flag on my widgets that you can use to tell a widget to clip any children that try to draw outside their parent's box (for scrollboxes for example). The clip flag uses glScissor, which is fed an axis aligned rectangle. I just added arbitrary rotation and transformations to my widgets, so I can rotate or scale them however I want. Unfortunately, this breaks the scissor that I was using as now my clip rectangle might not be axis aligned. There are two ways I can think of to fix this: either by using the stencil buffer to define the drawable area, or by having a wrapper function around my sprite drawing function that will adjust the vertices and texture coords of the sprites being drawn based on the clipper on the top of a clipper stack. Of course, there may also be other options I can't think of (something fancy with shaders possibly?). I'm not sure which way to go at the moment. Changing the implementation of my scissor functions to use the stencil buffer probably requires the smallest change, but I'm not sure how much overhead that has compared to the coordinate adjusting or if the performance difference is even worth considering.

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• First Minecraft mod not working: make a new sword

  - by yamikoWebs

  I am making my first mod and cannot see what is wrong with it. I am using MCP and Modloader. For my first mod I was going to make swords. I started with making a new EnumToolMaterials WOOD(0, 59, 2.0F, 0, 15), STONE(1, 131, 4.0F, 1, 5), IRON(2, 250, 6.0F, 2, 14), LAPIS(3, 750, 7.0F, 2, 14), OBSIDIAN(3, 1000, 7.5F, 3, 12), EMERALD(3, 1561, 8.0F, 3, 10),//diamond GREEN(3, 2000, 9.0F, 4, 10),//emerald GOLD(0, 200, 12.0F, 0, 22); then here is the mod class public class _Mod_Yamiko extends BaseMod{ /* mod itemts */ public static final Item swordLapis = (new ItemSword(600, EnumToolMaterial.LAPIS)).setItemName("swordLapis"); public static final Item swordObsidian = (new ItemSword(601, EnumToolMaterial.OBSIDIAN)).setItemName("swordObsidian"); public static final Item swordGreen = (new ItemSword(602, EnumToolMaterial.GREEN)).setItemName("swordGreen"); public void load(){ //set images swordLapis.iconIndex = ModLoader.addOverride("/gui/items.png","/gui/swordLapis.png"); ModLoader.addName(swordLapis, "Lapis Sword"); //craft ModLoader.addRecipe(new ItemStack(_Mod_Yamiko.swordLapis, 1), new Object[]{ " X ", " X ", " Y ", 'X', Block.dirt, 'Y', Item.stick }); } public String getVersion(){ return "0.1"; } } Then I made a 16×16 .png image. I am not sure where to save it so I recompiled and reobfuscated, took the mod files and put it in my local Minecraft install, added the image where it be should be. No problems when playing but I cannot make the new sword.

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• Normals vs Normal maps

  - by KaiserJohaan

  I am using Assimp asset importer (http://assimp.sourceforge.net/lib_html/index.html) to parse 3d models. So far, I've simply pulled out the normal vectors which are defined for each vertex in my meshes. Yet I have also found various tutorials on normal maps... As I understand it for normal maps, the normal vectors are stored in each texel of a normal map, and you pull these out of the normal texture in the shader. Why is there two ways to get the normals, which one is considered best-practice and why?

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• libgdx intersection problem between rectangle and circle

  - by Chris

  My collision detection in libgdx is somehow buggy. player.png is 20*80px and ball.png 25*25px. Code: @Override public void create() { // ... batch = new SpriteBatch(); playerTex = new Texture(Gdx.files.internal("data/player.png")); ballTex = new Texture(Gdx.files.internal("data/ball.png")); player = new Rectangle(); player.width = 20; player.height = 80; player.x = Gdx.graphics.getWidth() - player.width - 10; player.y = 300; ball = new Circle(); ball.x = Gdx.graphics.getWidth() / 2; ball.y = Gdx.graphics.getHeight() / 2; ball.radius = ballTex.getWidth() / 2; } @Override public void render() { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); camera.update(); // draw player, ball batch.setProjectionMatrix(camera.combined); batch.begin(); batch.draw(ballTex, ball.x, ball.y); batch.draw(playerTex, player.x, player.y); batch.end(); // update player position if(Gdx.input.isKeyPressed(Keys.DOWN)) player.y -= 250 * Gdx.graphics.getDeltaTime(); if(Gdx.input.isKeyPressed(Keys.UP)) player.y += 250 * Gdx.graphics.getDeltaTime(); if(Gdx.input.isKeyPressed(Keys.LEFT)) player.x -= 250 * Gdx.graphics.getDeltaTime(); if(Gdx.input.isKeyPressed(Keys.RIGHT)) player.x += 250 * Gdx.graphics.getDeltaTime(); // don't let the player leave the field if(player.y < 0) player.y = 0; if(player.y > 600 - 80) player.y = 600 - 80; // check collision if (Intersector.overlaps(ball, player)) Gdx.app.log("overlaps", "yes"); }

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• Pygame set_colorkey transparency issues

  - by Nathan Chowning

  I'm having a strange issue that I cannot seem to remedy. I am doing some prototyping with Pygame on a desktop running windows and a laptop running OS X. Both are running python v2.7.3 (installed via homebrew for the Macbook) and pygame v1.9.1. For transparency, I have been using set_colorkey with a transparency color of (255, 0, 255). Here is the applicable code: transColor = pygame.Color(255, 0, 255) image = pygame.image.load(playerPath + "idle.png").convert() image.set_colorkey(transColor) This works flawlessly on my windows machine. On my laptop, it does not work. It just shows the hideous magenta color. Here's the strange part. If I change the transColor to (0, 0, 0), all black pixels in my images are transparent. Has anyone run into this issue before?

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

  - by Miro

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

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• add collision detection to sprite?

  - by xBroak

  bassically im trying to add collision detection to the sprite below, using the following: self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") However it seems that when the collide is triggered it continuously prints 'collide' over and over when instead i want them to simply not be able to walk through the object, any help? def update(self, time_passed): """ Update the creep. time_passed: The time passed (in ms) since the previous update. """ if self.state == Creep.ALIVE: # Maybe it's time to change the direction ? # self._change_direction(time_passed) # Make the creep point in the correct direction. # Since our direction vector is in screen coordinates # (i.e. right bottom is 1, 1), and rotate() rotates # counter-clockwise, the angle must be inverted to # work correctly. # self.image = pygame.transform.rotate( self.base_image, -self.direction.angle) # Compute and apply the displacement to the position # vector. The displacement is a vector, having the angle # of self.direction (which is normalized to not affect # the magnitude of the displacement) # displacement = vec2d( self.direction.x * self.speed * time_passed, self.direction.y * self.speed * time_passed) self.pos += displacement # When the image is rotated, its size is changed. # We must take the size into account for detecting # collisions with the walls. # self.image_w, self.image_h = self.image.get_size() global bounds_rect bounds_rect = self.field.inflate( -self.image_w, -self.image_h) if self.pos.x < bounds_rect.left: self.pos.x = bounds_rect.left self.direction.x *= -1 elif self.pos.x > bounds_rect.right: self.pos.x = bounds_rect.right self.direction.x *= -1 elif self.pos.y < bounds_rect.top: self.pos.y = bounds_rect.top self.direction.y *= -1 elif self.pos.y > bounds_rect.bottom: self.pos.y = bounds_rect.bottom self.direction.y *= -1 self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") elif self.state == Creep.EXPLODING: if self.explode_animation.active: self.explode_animation.update(time_passed) else: self.state = Creep.DEAD self.kill() elif self.state == Creep.DEAD: pass #------------------ PRIVATE PARTS ------------------# # States the creep can be in. # # ALIVE: The creep is roaming around the screen # EXPLODING: # The creep is now exploding, just a moment before dying. # DEAD: The creep is dead and inactive # (ALIVE, EXPLODING, DEAD) = range(3) _counter = 0 def _change_direction(self, time_passed): """ Turn by 45 degrees in a random direction once per 0.4 to 0.5 seconds. """ self._counter += time_passed if self._counter > randint(400, 500): self.direction.rotate(45 * randint(-1, 1)) self._counter = 0 def _point_is_inside(self, point): """ Is the point (given as a vec2d) inside our creep's body? """ img_point = point - vec2d( int(self.pos.x - self.image_w / 2), int(self.pos.y - self.image_h / 2)) try: pix = self.image.get_at(img_point) return pix[3] > 0 except IndexError: return False def _decrease_health(self, n): """ Decrease my health by n (or to 0, if it's currently less than n) """ self.health = max(0, self.health - n) if self.health == 0: self._explode() def _explode(self): """ Starts the explosion animation that ends the Creep's life. """ self.state = Creep.EXPLODING pos = ( self.pos.x - self.explosion_images[0].get_width() / 2, self.pos.y - self.explosion_images[0].get_height() / 2) self.explode_animation = SimpleAnimation( self.screen, pos, self.explosion_images, 100, 300) global remainingCreeps remainingCreeps-=1 if remainingCreeps == 0: print("all dead")

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• Center directional light shadow to the cameras eye

  - by Caesar

  I'm currently drawing my directional light shadow using this view and projection: XMFLOAT3 dir((float)pitch, (float)yaw, (float)roll); XMFLOAT3 center(0.0f, 0.0f, 0.0f); XMVECTOR lightDir = XMLoadFloat3(&dir); XMVECTOR lightPos = radius * lightDir; XMVECTOR targetPos = XMLoadFloat3(&center); XMVECTOR up = XMVectorSet(0.0f, 1.0f, 0.0f, 0.0f); XMMATRIX V = XMMatrixLookAtLH(lightPos, targetPos, up); // This is the view // Transform bounding sphere to light space. XMFLOAT3 sphereCenterLS; XMStoreFloat3(&sphereCenterLS, XMVector3TransformCoord(targetPos, V)); // Ortho frustum in light space encloses scene. float l = sphereCenterLS.x - radius; float b = sphereCenterLS.y - radius; float n = sphereCenterLS.z - radius; float r = sphereCenterLS.x + radius; float t = sphereCenterLS.y + radius; float f = sphereCenterLS.z + radius; XMMATRIX P = XMMatrixOrthographicOffCenterLH(l, r, b, t, n, f); // This is the projection Which works prefect if the center of my scene is at 0.0, 0.0, 0.0. What I would like to do is move the center of the scene relative to the cameras position. How can I do that?

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• jerky walljump in unity rigidbody2d

  - by Lilz Votca Love

  hey there i know people have encountered issues with it before i looked upon the different solutions provided but i couldnt get any fix at all.im making a 2d game and am stuck with the walljump.i detect the wall wonderfully i also detect the jump and it works the player jumps off the wall when facing right with the use of rigidbody.addforce(new vector2(-1,2)*jumpforce) now when jumping on the oposite wall using the same vector with the sign in x axis changed to 1,the player jumps too but it goes more in the y axis than it should.Here is an image to show you the curves it(the player) follows. check the following url to see the behaviour https://scontent-b-mad.xx.fbcdn.net/hphotos-xpf1/t1.0-9/1470386_10152415957141154_156025539179003805_n.jpg voila the green one is happennig when player faces right and the other one happens when he is not here is the section of code if (wall) { if (wallJump) { if (facingRight) { rigidbody2D.velocity = Vector2.zero; flip (); rigidbody2D.AddForce (new Vector2 (-1f, 2f) * Jumpforce / 1.5f); Debug.Log ("saut mural gauche" + new Vector2 (-1f, 2f) * Jumpforce / 1.5f); } else { rigidbody2D.velocity = Vector2.zero; flip (); rigidbody2D.AddForce (new Vector2 (1f, 2f) * Jumpforce / 1.5f); Debug.Log ("saut mural droit--" + new Vector2 (Mathf.Sign (1f), 2f) * Jumpforce / 1.5f + "jump" + jump); } } } else { wallJump = false; } here the code is not optimized yet but i assure you it works so guys any help would be so awesome!! thanks

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• Help with "Cannot find ContentTypeReader BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral." needed

  - by rFactor

  Hi, I have this irritating problem in XNA that I have spent my Saturday with: Cannot find ContentTypeReader BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral. It throws me that when I do (within the game assembly's Renderer.cs class): this.terrain = this.game.Content.Load<Model>("heightmap"); There is a heightmap.bmp and I don't think there's anything wrong with it, because I used it in a previous version which I switched to this new better system. So, I have a GeneratedGeometryPipeline assembly that has these classes: HeightMapInfoContent, HeightMapInfoWriter, TerrainProcessor. The GeneratedGeometryPipeline assembly does not reference any other assemblies under the solution. Then I have the game assembly that neither references any other solution assemblies and has these classes: HeightMapInfo, HeightMapInfoReader. All game assembly classes are under namespace BB and the GeneratedGeometryPipeline classes are under the namespace GeneratedGeometryPipeline. I do not understand why it does not find it. Here's some code from the GeneratedGeometryPipeline.HeightMapInfoWriter: /// <summary> /// A TypeWriter for HeightMapInfo, which tells the content pipeline how to save the /// data in HeightMapInfo. This class should match HeightMapInfoReader: whatever the /// writer writes, the reader should read. /// </summary> [ContentTypeWriter] public class HeightMapInfoWriter : ContentTypeWriter<HeightMapInfoContent> { protected override void Write(ContentWriter output, HeightMapInfoContent value) { output.Write(value.TerrainScale); output.Write(value.Height.GetLength(0)); output.Write(value.Height.GetLength(1)); foreach (float height in value.Height) { output.Write(height); } foreach (Vector3 normal in value.Normals) { output.Write(normal); } } /// <summary> /// Tells the content pipeline what CLR type the /// data will be loaded into at runtime. /// </summary> public override string GetRuntimeType(TargetPlatform targetPlatform) { return "BB.HeightMapInfo, BB, Version=1.0.0.0, Culture=neutral"; } /// <summary> /// Tells the content pipeline what worker type /// will be used to load the data. /// </summary> public override string GetRuntimeReader(TargetPlatform targetPlatform) { return "BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral"; } } Can someone help me out?

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• Secure login for a game that is open source

  - by David Park

  I am making a game which i will be open sourcing. Its a simple arcade like game but requires a network connection because it is meant to be played with other people. The thing i am worrying about is how would i be sure that the client is the one that i put out for the end user to play with? Kind of a like of sv_pure for Team Fortress 2. I was thinking of different ways to combat this such as the server requesting the client's version or even it's md5 hash but people with simple java knowledge could just force a method to always return what the server wants.

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• Android-Libgdx-ProGuard: Usefulness without DexGuard? [on hold]

  - by Rico Pablo Mince

  So I'm developing a game for Android - using LibGDX - and noticed that the Android SDK (HDK, MDK, WhatTheHellEvarDK) has ProGuard built-in. Browsing the ProGuard page is like searching Google: you get that the idea is to sell some product (in this case, it's DexGuard). That leaves me wondering what features are left out of ProGuard that a game developer targeting Android should worry about. For instance, the ProGuard FAQs answer the question: "Does ProGuard encrypt string constants?" by saying: "No. String encryption in program code has to be perfectly reversible by definition, so it only improves the obfuscation level. It increases the footprint of the code. However, by popular demand, ProGuard's closed-source sibling for Android, DexGuard, does provide string encryption, along with more protection techniques against static and dynamic analysis." Alright. OK. But isn't "...improves the obfuscation level" EXACTLY what ProGuard is supposed to do? Are there better options that can be implemented at build-time in Eclipse using the Gradle options and Libgdx? In particular, the assets folder and res-specific folders will need some protection. The code itself doesn't cure cancer, but I'd prefer if nobody could copy/paste it with different game art and call it "IhAxEdUrGamE"....

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• How to fetch only the sprites in the player's range of motion for collision testing? (2D, axis aligned sprites)

  - by Twodordan

  I am working on a 2D sprite game for educational purposes. (In case you want to know, it uses WebGl and Javascript) I've implemented movement using the Euler method (and delta time) to keep things simple. Now I'm trying to tackle collisions. The way I wrote things, my game only has rectangular sprites (axis aligned, never rotated) of various/variable sizes. So I need to figure out what I hit and which side of the target sprite I hit (and I'm probably going to use these intersection tests). The old fashioned method seems to be to use tile based grids, to target only a few tiles at a time, but that sounds silly and impractical for my game. (Splitting the whole level into blocks, having each sprite's bounding box fit multiple blocks I might abide. But if the sprites change size and move around, you have to keep changing which tiles they belong to, every frame, it doesn't sound right.) In Flash you can test collision under one point, but it's not efficient to iterate through all the elements on stage each frame. (hence why people use the tile method). Bottom line is, I'm trying to figure out how to test only the elements within the player's range of motion. (I know how to get the range of motion, I have a good idea of how to write a collisionCheck(playerSprite, targetSprite) function. But how do I know which sprites are currently in the player's vicinity to fetch only them?) Please discuss. Cheers!

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• running GL ES 2.0 code under Linux ( no Android no iOS )

  - by user827992

  I need to code OpenGL ES 2.0 bits and i would like to do this and run the programs on my desktop for practical reasons. Now, i already have tried the official GLES SDK from ATI for my videocard but it not even runs the examples that comes with the SDK itself, i'm not looking for performance here, even a software based rendering pipeline could be enough, i just need full support for GLES 2.0 and GLSL to code and run GL stuff. There is a reliable solution for this under Ubuntu Linux ?

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• How to change speed without changing path travelled?

  - by Ben Williams

  I have a ball which is being thrown from one side of a 2D space to the other. The formula I am using for calculating the ball's position at any one point in time is: x = x0 + vx0*t y = y0 + vy0*t - 0.5*g*t*t where g is gravity, t is time, x0 is the initial x position, vx0 is the initial x velocity. What I would like to do is change the speed of this ball, without changing how far it travels. Let's say the ball starts in the lower left corner, moves upwards and rightwards in an arc, and finishes in the lower right corner, and this takes 5s. What I would like to be able to do is change this so it takes 10s or 20s, but the ball still follows the same curve and finishes in the same position. How can I achieve this? All I can think of is manipulating t but I don't think that's a good idea. I'm sure it's something simple, but my maths is pretty shaky.

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• Moving my sprite in XNA using classes

  - by Tom

  Hey, im a newbie at this programming lark and its really frustrating me. I'm trying to move a snake in all directions while using classes. Ive created a vector2 for speed and ive attempted creating a method which moves the snake within the snake class. Now I'm confused and not sure what to do next. Appreciate any help. Thanks :D This is what i've done in terms of the method... public Vector2 direction() { Vector2 inputDirection = Vector2.Zero; if (Keyboard.GetState().IsKeyDown(Keys.Left)) inputDirection.X -= -1; if (Keyboard.GetState().IsKeyDown(Keys.Right)) inputDirection.X += 1; if (Keyboard.GetState().IsKeyDown(Keys.Up)) inputDirection.Y -= -1; if (Keyboard.GetState().IsKeyDown(Keys.Down)) inputDirection.Y += 1; return inputDirection * snakeSpeed; } Appreciate any help. Thanks :D EDIT: Well let me make everything clear. Im making a small basic game for an assignment. The game is similar to the old snake game on the old Nokia phones. I've created a snake class (even though I'm not sure whether this is needed because im only going to be having one moving sprite within the game). After I written the code above (in the snake class), the game ran with no errors but I couldn't actually move the image :( EDIT2: Thanks so much for everyones responses!!

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• Scale a game object to Bounds

  - by Spikeh

  I'm trying to scale a lot of dynamically created game objects in Unity3D to the bounds of a sphere collider, based on the size of their current mesh. Each object has a different scale and mesh size. Some are bigger than the AABB of the collider, and some are smaller. Here's the script I've written so far: private void ScaleToCollider(GameObject objectToScale, SphereCollider sphere) { var currentScale = objectToScale.transform.localScale; var currentSize = objectToScale.GetMeshHierarchyBounds().size; var targetSize = (sphere.radius * 2); var newScale = new Vector3 { x = targetSize * currentScale.x / currentSize.x, y = targetSize * currentScale.y / currentSize.y, z = targetSize * currentScale.z / currentSize.z }; Debug.Log("{0} Current scale: {1}, targetSize: {2}, currentSize: {3}, newScale: {4}, currentScale.x: {5}, currentSize.x: {6}", objectToScale.name, currentScale, targetSize, currentSize, newScale, currentScale.x, currentSize.x); //DoorDevice_meshBase Current scale: (0.1, 4.0, 3.0), targetSize: 5, currentSize: (2.9, 4.0, 1.1), newScale: (0.2, 5.0, 13.4), currentScale.x: 0.125, currentSize.x: 2.869114 //RedControlPanelForAirlock_meshBase Current scale: (1.0, 1.0, 1.0), targetSize: 5, currentSize: (0.0, 0.3, 0.2), newScale: (147.1, 16.7, 25.0), currentScale.x: 1, currentSize.x: 0.03400017 objectToScale.transform.localScale = newScale; } And the supporting extension method: public static Bounds GetMeshHierarchyBounds(this GameObject go) { var bounds = new Bounds(); // Not used, but a struct needs to be instantiated if (go.renderer != null) { bounds = go.renderer.bounds; // Make sure the parent is included Debug.Log("Found parent bounds: " + bounds); //bounds.Encapsulate(go.renderer.bounds); } foreach (var c in go.GetComponentsInChildren<MeshRenderer>()) { Debug.Log("Found {0} bounds are {1}", c.name, c.bounds); if (bounds.size == Vector3.zero) { bounds = c.bounds; } else { bounds.Encapsulate(c.bounds); } } return bounds; } After the re-scale, there doesn't seem to be any consistency to the results - some objects with completely uniform scales (x,y,z) seem to resize correctly, but others don't :| Its one of those things I've been trying to fix for so long I've lost all grasp on any of the logic :| Any help would be appreciated!

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• How does an Engine like Source process entities?

  - by Júlio Souza

  [background information] On the Source engine (and it's antecessor, goldsrc, quake's) the game objects are divided on two types, world and entities. The world is the map geometry and the entities are players, particles, sounds, scores, etc (for the Source Engine). Every entity has a think function, which do all the logic for that entity. So, if everything that needs to be processed comes from a base class with the think function, the game engine could store everything on a list and, on every frame, loop through it and call that function. On a first look, this idea is reasonable, but it can take too much resources, if the game has a lot of entities.. [end of background information] So, how does a engine like Source take care (process, update, draw, etc) of the game objects?

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• Extra fire simulation on iPad device

  - by Nezam

  I have with me an iOS app for iPad which creates a few fire simulations over a png.Well,its working well exactly how we wanted it but when we are testing it on a device,we get an extra fire simulation.Heres the screen: iPad Simulator: This is how it should display (iPad Simulation) iPad Device: This is how its displaying (iPad Device) M ready to share whichever portion of my code which gets me to my solution once someone gets hit here.Thanks in advance

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• how to do partial updates in OpenGL?

  - by Will

  It is general wisdom that you redraw the entire viewport on each frame. I would like to use partial updates; what are the various ways can do that, and what are their pros, cons and relative performance? (Using textures, FBOs, the accumulator buffer, any kind of scissors that can affect swapbuffers etc?) A scenario: a scene with a fair few thousand visible trees; although the textures are mipmapped and they are drawn via VBOs roughly front-to-back with so on, its still a lot of polys. Would streaming a single screen-sized texture be better than throwing them at the screen every frame? You'd have to redraw and recapture them only on camera movement or as often as your wind model updates or whatever, which need not be every frame.

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• Best way to store a large amount of game objects and update the ones onscreen

  - by user3002473

  Good afternoon guys! I'm a young beginner game developer working on my first large scale game project and I've run into a situation where I'm not quite sure what the best solution may be (if there is a lone solution). The question may be vague (if anyone can think of a better title after having read the question, please edit it) or broad but I'm not quite sure what to do and I thought it would help just to discuss the problem with people more educated in the field. Before we get started, here are some of the questions I've looked at for help in the past: Best way to keep track of game objects Elegant way to simulate large amounts of entities within a game world What is the most efficient container to store dynamic game objects in? I've also read articles about different data structures commonly used in games to store game objects such as this one about slot maps, but none of them are really what I'm looking for. Also, if it helps at all I'm using Python 3 to design the game. It has to be Python 3, if I could I would use C++ or Unityscript or something else, but I'm restricted to having to use Python 3. My game will be a form of side scroller shooter game. In said game the player will traverse large rooms with large amounts of enemies and other game objects to update (think some of the larger areas in Cave Story or Iji). The player obviously can't see the entire room all at once, so there is a viewport that follows the player around and renders only a selection of the room and the game objects that it contains. This is not a foreign concept. The part that's getting me confused has to do with how certain game objects are updated. Some of them are to be updated constantly, regardless of whether or not they can be seen. Other objects however are only to be updated when they are onscreen (for example, an enemy would only be updated to react to the player when it is onscreen or when it is in a certain range of the screen). Another problem is that game objects have to be easily referable by other game objects; something that happens in the player's update() method may affect another object in the world. Collision detection in games is always a serious problem. I need a way of containing the game objects such that it minimizes the number of cases when testing for collisions against one another. The final problem is that of creating and destroying game objects. I think this problem is pretty self explanatory. To store the game objects then I've considered a number of different methods. The original method I had was to simply store all the objects in a hash table by an id. This method was simple, and decently fast as it allows all the objects to be looked up in O(1) complexity, and also allows them to be deleted fairly easily. Hash collisions would not be a major problem; I wasn't originally planning on using computer generated ids to store the game objects I was going to rely on them all using ids given to them by the game designer (such names would be strings like 'Player' or 'EnemyWeapon4'), and even if I did use computer generated ids, if I used a decent hashing algorithm then the chances of collisions would be around 1 in 4 billion. The problem with using a hash table however is that it is inefficient in checking to see what objects are in range of the viewport. Considering the fact that certain game objects move (as well as the viewport itself), the only solution I could think of in order to only update objects that are in the viewport would be to iterate through every object in the hash table and check if it is in the viewport or not, updating only the ones that are in the valid area. This would be incredibly slow in scenarios where the amount of game objects exceeds 500, or even 200. The second solution was to store everything in a 2-d list. The world is partitioned up into cells (a tilemap essentially), where each cell or tile is the same size and is square. Each cell would contain a list of the game objects that are currently occupying it (each game object would be inserted into a cell depending on the center of the object's collision mask). A 2-d list would allow me to take the top-left and bottom-right corners of the viewport and easily grab a rectangular area of the grid containing only the cells containing entities that are in valid range to be updated. This method also solves the problem of collision detection; when I take an entity I can find the cell that it is currently in, then check only against entities in it's cell and the 8 cells around it. One problem with this system however is that it prohibits easy lookup of game objects. One solution I had would be to simultaneously keep a hash table that would contain all the positions of the objects in the 2-d list indexed by the id of said object. The major problem with a 2-d list is that it would need to be rebuilt every single game frame (along with the hash table of object positions), which may be a serious detriment to game speed. Both systems have ups and downs and seem to solve some of each other's problems, however using them both together doesn't seem like the best solution either. If anyone has any thoughts, ideas, suggestions, comments, opinions or solutions on new data structures or better implementations of the existing data structures I have in mind, please post, any and all criticism and help is welcome. Thanks in advance! EDIT: Please don't close the question because it has a bad title, I'm just bad with names!

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• How to implement smooth flocking

  - by Craig

  I'm working on a simple survival game, avoid the big guy and chase the the small guys to stay alive for as long as possible. I have taken the chase and evade example from MSDN create and drawn 20 mice on the screen. I want the small guys to flock when they arent evading. They are doing this, but it isnt as smooth as I would like it to be. How do i make the movement smoother? Its very jittery.# Below is what I have going at the moment, flocking code is within the IF statement, when it isnt set to evading. Any help would be greatly appreciated! :) namespace ChaseAndEvade { class MouseSprite { public enum MouseAiState { // evading the cat Evading, // the mouse can't see the "cat", and it's wandering around. Wander } // how fast can the mouse move? public float MaxMouseSpeed = 4.5f; // and how fast can it turn? public float MouseTurnSpeed = 0.20f; // MouseEvadeDistance controls the distance at which the mouse will flee from // cat. If the mouse is further than "MouseEvadeDistance" pixels away, he will // consider himself safe. public float MouseEvadeDistance = 100.0f; // this constant is similar to TankHysteresis. The value is larger than the // tank's hysteresis value because the mouse is faster than the tank: with a // higher velocity, small fluctuations are much more visible. public float MouseHysteresis = 60.0f; public Texture2D mouseTexture; public Vector2 mouseTextureCenter; public Vector2 mousePosition; public MouseAiState mouseState = MouseAiState.Wander; public float mouseOrientation; public Vector2 mouseWanderDirection; int separationImpact = 4; int cohesionImpact = 6; int alignmentImpact = 2; int sensorDistance = 50; public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; // first, calculate how far away the mouse is from the cat, and use that // information to decide how to behave. If they are too close, the mouse // will switch to "active" mode - fleeing. if they are far apart, the mouse // will switch to "idle" mode, where it roams around the screen. // we use a hysteresis constant in the decision making process, as described // in the accompanying doc file. float distanceFromCat = Vector2.Distance(mousePosition, catPosition); // the cat is a safe distance away, so the mouse should idle: if (distanceFromCat > MouseEvadeDistance + MouseHysteresis) { mouseState = MouseAiState.Wander; } // the cat is too close; the mouse should run: else if (distanceFromCat < MouseEvadeDistance - MouseHysteresis) { mouseState = MouseAiState.Evading; } // if neither of those if blocks hit, we are in the "hysteresis" range, // and the mouse will continue doing whatever it is doing now. // the mouse will move at a different speed depending on what state it // is in. when idle it won't move at full speed, but when actively evading // it will move as fast as it can. this variable is used to track which // speed the mouse should be moving. float currentMouseSpeed; // the second step of the Update is to change the mouse's orientation based // on its current state. if (mouseState == MouseAiState.Evading) { // If the mouse is "active," it is trying to evade the cat. The evasion // behavior is accomplished by using the TurnToFace function to turn // towards a point on a straight line facing away from the cat. In other // words, if the cat is point A, and the mouse is point B, the "seek // point" is C. // C // B // A Vector2 seekPosition = 2 * mousePosition - catPosition; // Use the TurnToFace function, which we introduced in the AI Series 1: // Aiming sample, to turn the mouse towards the seekPosition. Now when // the mouse moves forward, it'll be trying to move in a straight line // away from the cat. mouseOrientation = ChaseAndEvadeGame.TurnToFace(mousePosition, seekPosition, mouseOrientation, MouseTurnSpeed); // set currentMouseSpeed to MaxMouseSpeed - the mouse should run as fast // as it can. currentMouseSpeed = MaxMouseSpeed; } else { // if the mouse isn't trying to evade the cat, it should just meander // around the screen. we'll use the Wander function, which the mouse and // tank share, to accomplish this. mouseWanderDirection and // mouseOrientation are passed by ref so that the wander function can // modify them. for more information on ref parameters, see // http://msdn2.microsoft.com/en-us/library/14akc2c7(VS.80).aspx ChaseAndEvadeGame.Wander(mousePosition, ref mouseWanderDirection, ref mouseOrientation, MouseTurnSpeed); // if the mouse is wandering, it should only move at 25% of its maximum // speed. currentMouseSpeed = .25f * MaxMouseSpeed; Vector2 separate = Vector2.Zero; Vector2 moveCloser = Vector2.Zero; Vector2 moveAligned = Vector2.Zero; // What the AI does when it sees other AIs for (int j = 0; j < enemies; j++) { if (index != j) { // Calculate a vector towards another AI Vector2 separation = mice[index].mousePosition - mice[j].mousePosition; // Only react if other AI is within a certain distance if ((separation.Length() < this.sensorDistance) & (separation.Length()> 0) ) { moveAligned += mice[j].mouseWanderDirection; float distance = Math.Abs(separation.Length()); if (distance == 0) distance = 1; moveCloser += mice[j].mousePosition; separation.Normalize(); separate += separation / distance; } } } if (moveAligned.LengthSquared() != 0) { moveAligned.Normalize(); } if (moveCloser.LengthSquared() != 0) { moveCloser.Normalize(); } moveCloser /= enemies; mice[index].mousePosition += (separate * separationImpact) + (moveCloser * cohesionImpact) + (moveAligned * alignmentImpact); } // The final step is to move the mouse forward based on its current // orientation. First, we construct a "heading" vector from the orientation // angle. To do this, we'll use Cosine and Sine to tell us the x and y // components of the heading vector. See the accompanying doc for more // information. Vector2 heading = new Vector2( (float)Math.Cos(mouseOrientation), (float)Math.Sin(mouseOrientation)); // by multiplying the heading and speed, we can get a velocity vector. the // velocity vector is then added to the mouse's current position, moving him // forward. mousePosition += heading * currentMouseSpeed; } } }

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• The best way to structure/design game code

  - by Edward

  My question is quite broad and related to the 2D game code design/architecture/structure. Usually the main game consists of the main loop where you update & render your world states. However, it's recommended for many purposes to separate rendering from the game-logic and so on. I am kinda confused about the whole situation. Many game engines/libs/sdks don't follow separation schema. They propagate a way where you define some scenes/stages and they contain some objects and the scene/stage controls the user input and so on. For example, in cocos2d(-x) and libgdx (stage2d) the games are usually done the way that the update logic happens at the same time/place as rendering. Also, the propagated way is to have a structure where an object knows how to draw itself - which is not a separation of updating & rendering. The same with Flash based games, they are usually done the way when an object (class) contains a swf or a texture and some data and holds some update logic itself, or updated from main Scene. And again this object already knows how to draw itself via "addChild". Also, some people recommend to use MVC pattern, which will require to completely obey the structure of those engines/libs/sdks. Maybe I am overthinking everything, but I am totally confused. I would be grateful if somebody could point me to a correct direction with the game code structures. What is your way of doing things in libgdx/cocos2d/flash?

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• When should a bullet texture be loaded in XNA?

  - by Bill

  I'm making a SpaceWar!-esque game using XNA. I want to limit my ships to 5 active bullets at any time. I have a Bullet DrawableGameComponent and a Ship DrawableGameComponent. My Ship has an array of 5 Bullet. What is the best way to manage the Bullet textures? Specifically, when should I be calling LoadTexture? Right now, my solution is to populate the Bullet array in the Ship's constructor, with LoadTexture being called in the Bullet constructor. The Bullet objects will be disabled/not visible except when they are active. Does the texture really need to be loaded once for each individual instance of the bullet object? This seems like a very processor-intensive operation. Note: This is a small-scale project, so I'm OK with not implementing a huge texture-management framework since there won't be more than half a dozen or so in the entire game. I'd still like to hear about scalable solutions for future applications, though.

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