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  • Rotation based on x coordinate and x velocity?

    - by Lewis
    -(void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration { float deceleration = 0.3f, sensitivity = 8.0f, maxVelocity = 150; // adjust velocity based on current accelerometer acceleration playerVelocity.x = playerVelocity.x * deceleration + acceleration.x * sensitivity; // we must limit the maximum velocity of the player sprite, in both directions (positive & negative values) playerVelocity.x = fmaxf(fminf(playerVelocity.x, maxVelocity), -maxVelocity); } Hi, I want to rotate my sprite based on the velocity and accelerometer input. My sprite can move along the X axis like so: <--------- sprite ----------- But it always faces forwards, if it is moving left I want it to point slightly to the left, the degree of how far it is pointing to be judged from the velocity. This should also work for the right. I tried using atan but as the y velocity and position is always the same the function returns 0, which doesn't rotate it at all. Any ideas? Regards, Lewis.

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  • Managing flash animations for a game

    - by LoveMeSomeCode
    Ok, I've been writing C# for a while, but I'm new to ActionScript, so this is a question about best practices. We're developing a simple match game, where the user selects tiles and tries to match various numbers - sort of like memory - and when the match is made we want a series of animations to take place, and when they're done, remove the tile and add a new one. So basically it's: User clicks the MC Animation 1 on the MC starts Animation 1 ends Remove the MC from the stage Add a new MC Start the animation on the new MC The problem I run into is that I don't want to make the same timeline motion tween on each and every tile, when the animation is all the same. It's just the picture in the tile that's different. The other method I've come up with is to just apply the tweens in code on the main stage. Then I attach an event handler for MOTION_FINISH, and in that handler I trigger the next animation and listen for that to finish etc. This works too, but not only do I have to do all the tweening in code, I have a seperate event handler for each stage of the animation. So is there a more structured way of chaining these animations together?

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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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  • 3d vertex translated onto 2d viewport

    - by Dan Leidal
    I have a spherical world defined by simple trigonometric functions to create triangles that are relatively similar in size and shape throughout. What I want to be able to do is use mouse input to target a range of vertices in the area around the mouse click in order to manipulate these vertices in real time. I read a post on this forum regarding translating 3d world coordinates into the 2d viewport.. it recommended that you should multiply the world vector coordinates by the viewport and then the projection, but they didn't include any code examples, and suffice to say i couldn't get any good results. Further information.. I am using a lookat method for the viewport. Does this cause a problem, and if so is there a solution? If this isn't the problem, does anyone have a simple code example illustrating translating one vertex in a 3d world into a 2d viewspace? I am using XNA.

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  • Making a game "resize-safe"

    - by CPP_Person
    It's one thing to get the graphics aligned perfectly, it's another to do this for every single resolution and not take too much time and/or make the code unreadable due to size. Games like Battlefield 3 and Minecraft seem to manage this. But what do they do to keep things from stretching or going off the screen? I don't know any algorithms to do this. I'd like some help on this topic. I've always programmed games that only handle a single resolution, so help would be appreciate.

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  • Why do meshes show up as bones in the Model class?

    - by Itamar Marom
    Right now I'm working on a 3D game and I've come across something very weird. When I created the model in Blender, I added an armature named "MyBone" to the stage and attached a cube ("MyCube") to it, so that when I move the armature, the cube moves with it. I exported this as an FBX and loaded it as a Model object. What I expected to see was: But what I got was this: I'm really confused. Why is the mesh I created showing up in the bone list? And what's Root Node? Here are the .blend and .fbx files: here or here. Thanks.

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  • Reasoner Conversion Problems:

    - by Annalyne
    I have this code right here in Java and I wanted to translate it in C++, but I had some problems going: this is the java code: import java.io.*; import java.util.*; public class ClueReasoner { private int numPlayers; private int playerNum; private int numCards; private SATSolver solver; private String caseFile = "cf"; private String[] players = {"sc", "mu", "wh", "gr", "pe", "pl"}; private String[] suspects = {"mu", "pl", "gr", "pe", "sc", "wh"}; private String[] weapons = {"kn", "ca", "re", "ro", "pi", "wr"}; private String[] rooms = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; private String[] cards; public ClueReasoner() { numPlayers = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; numCards = i; // Initialize solver solver = new SATSolver(); addInitialClauses(); } private int getPlayerNum(String player) { if (player.equals(caseFile)) return numPlayers; for (int i = 0; i < numPlayers; i++) if (player.equals(players[i])) return i; System.out.println("Illegal player: " + player); return -1; } private int getCardNum(String card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; System.out.println("Illegal card: " + card); return -1; } private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); } private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; } public void addInitialClauses() { // TO BE IMPLEMENTED AS AN EXERCISE // Each card is in at least one place (including case file). for (int c = 0; c < numCards; c++) { int[] clause = new int[numPlayers + 1]; for (int p = 0; p <= numPlayers; p++) clause[p] = getPairNum(p, c); solver.addClause(clause); } // If a card is one place, it cannot be in another place. // At least one card of each category is in the case file. // No two cards in each category can both be in the case file. } public void hand(String player, String[] cards) { playerNum = getPlayerNum(player); // TO BE IMPLEMENTED AS AN EXERCISE } public void suggest(String suggester, String card1, String card2, String card3, String refuter, String cardShown) { // TO BE IMPLEMENTED AS AN EXERCISE } public void accuse(String accuser, String card1, String card2, String card3, boolean isCorrect) { // TO BE IMPLEMENTED AS AN EXERCISE } public int query(String player, String card) { return solver.testLiteral(getPairNum(player, card)); } public String queryString(int returnCode) { if (returnCode == SATSolver.TRUE) return "Y"; else if (returnCode == SATSolver.FALSE) return "n"; else return "-"; } public void printNotepad() { PrintStream out = System.out; for (String player : players) out.print("\t" + player); out.println("\t" + caseFile); for (String card : cards) { out.print(card + "\t"); for (String player : players) out.print(queryString(query(player, card)) + "\t"); out.println(queryString(query(caseFile, card))); } } public static void main(String[] args) { ClueReasoner cr = new ClueReasoner(); String[] myCards = {"wh", "li", "st"}; cr.hand("sc", myCards); cr.suggest("sc", "sc", "ro", "lo", "mu", "sc"); cr.suggest("mu", "pe", "pi", "di", "pe", null); cr.suggest("wh", "mu", "re", "ba", "pe", null); cr.suggest("gr", "wh", "kn", "ba", "pl", null); cr.suggest("pe", "gr", "ca", "di", "wh", null); cr.suggest("pl", "wh", "wr", "st", "sc", "wh"); cr.suggest("sc", "pl", "ro", "co", "mu", "pl"); cr.suggest("mu", "pe", "ro", "ba", "wh", null); cr.suggest("wh", "mu", "ca", "st", "gr", null); cr.suggest("gr", "pe", "kn", "di", "pe", null); cr.suggest("pe", "mu", "pi", "di", "pl", null); cr.suggest("pl", "gr", "kn", "co", "wh", null); cr.suggest("sc", "pe", "kn", "lo", "mu", "lo"); cr.suggest("mu", "pe", "kn", "di", "wh", null); cr.suggest("wh", "pe", "wr", "ha", "gr", null); cr.suggest("gr", "wh", "pi", "co", "pl", null); cr.suggest("pe", "sc", "pi", "ha", "mu", null); cr.suggest("pl", "pe", "pi", "ba", null, null); cr.suggest("sc", "wh", "pi", "ha", "pe", "ha"); cr.suggest("wh", "pe", "pi", "ha", "pe", null); cr.suggest("pe", "pe", "pi", "ha", null, null); cr.suggest("sc", "gr", "pi", "st", "wh", "gr"); cr.suggest("mu", "pe", "pi", "ba", "pl", null); cr.suggest("wh", "pe", "pi", "st", "sc", "st"); cr.suggest("gr", "wh", "pi", "st", "sc", "wh"); cr.suggest("pe", "wh", "pi", "st", "sc", "wh"); cr.suggest("pl", "pe", "pi", "ki", "gr", null); cr.printNotepad(); cr.accuse("sc", "pe", "pi", "bi", true); } } how can I convert this? there are too many errors I get. for my C++ code (as a commentor asked for) #include <iostream> #include <cstdlib> #include <string> using namespace std; void Scene_Reasoner() { int numPlayer; int playerNum; int cardNum; string filecase = "Case: "; string players [] = {"sc", "mu", "wh", "gr", "pe", "pl"}; string suspects [] = {"mu", "pl", "gr", "pe", "sc", "wh"}; string weapons [] = {"kn", "ca", "re", "ro", "pi", "wr"}; string rooms[] = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; string cards [0]; }; void Scene_Reason_Base () { numPlayer = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; cardNum = i; }; private int getCardNum (string card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; cout << "Illegal card: " + card <<endl; return -1; }; private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); }; private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; }; int main () { return 0; }

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  • What is the benefit of triple buffering?

    - by user782220
    I read everything written in a previous question. From what I understand in double buffering the program must wait until the finished drawing is copied or swapped before starting the next drawing. In triple buffering the program has two back buffers and can immediately start drawing in the one that is not involved in such copying. But with triple buffering if you're in a situation where you can take advantage of the third buffer doesn't that suggest that you are drawing frames faster than the monitor can refresh. So then you don't actually get a higher frame rate. So what is the benefit of triple buffering then?

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  • Using XNA for a 2D isometric game, but wanna move on

    - by Daniel Ribeiro
    I've been building a 2D isometric game (with learning purposes) in C# using XNA. I found it's really easy to manage sprite sheets loading, collision, basic physics and such with the XNA api. The thing is, I want to move on. My real goal is to learn C++ and develop a game using that language. What engine/library would you guys recommend for me to keep going on that same 2D isometric game direction using pretty much sprite sheets for the graphical part of the game?

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  • Algorithm to find average position

    - by Simran kaur
    In the given diagram, I have the extreme left and right points, that is -2 and 4 in this case. So, obviously, I can calculate the width which is 6 in this case. What we know: The number of partitions:3 in this case The partition number at at any point i.e which one is 1st,second or third partition (numbered starting from left) What I want: The position of the purple line drawn which is positio of average of a particular partition So, basically I just want a generalized formula to calculate position of the average at any point.

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  • Group arrival steering

    - by ltjax
    I've got group movement implemented pretty much like this: http://www.red3d.com/cwr/steer/CrowdPath.html Basically, that's combining path following and separation. It works nicely as long as units are in transit, but arrival does not work very well at all. Right now, units just cease to use the path following component once the "exit" the path, i.e. when their closest point on the path is on or past the end. This leads to those units bumping into each other and also overshooting the point the player clicked. Ideally, I'd have the units arrive scattered around the finish point (and reasonable close to each other), not all clumped up past the finish line. I'd imagine that some kind of arrival steering might work here, but based on other units and a "fuzzy" classification of the end of the path. Is there any proven way to do this?

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  • How to bind std::map to Lua with LuaBind

    - by MahanGM
    Is this possible in lua to achieve? player.scripts["movement"].properties["stat"] = "stand" print (player.scripts["movement"].properties["stat"]) I've done getter method in c++ with this approach: luabind::object FakeScript::getProp() { luabind::object obj = luabind::newtable(L); for(auto i = this->properties.begin(); i != this->properties.end(); i++) { obj[i->first] = i->second; } return obj; } But I'm stuck with setter. The first line in lua code which I'm trying to set value "stand" for key "stat" is not going to work and it keep redirecting me to the getter method. Setter method only works when I drop ["stat"] from properties. I can do something like this for setter in my script: player.scripts["movement"].properties = {stat = "stand"} But this isn't what I want because I have to go through my real keys in c++ to determine which key is placed in setter argument table value. This is my map in class: std::map<std::string, std::string> properties;

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  • Structure gameobjects and call events

    - by waco001
    I'm working on a 2D tile based game in which the player interacts with other game objects (chests, AI, Doors, Houses etc...). The entire map will be stored in a file which I can read. When loading the tilemap, it will find any tile with the ID that represents a gameobject and store it in a hashmap (right data structure I think?). private static HashMap<Integer, Class<GameObject>> gameObjects = new HashMap<Integer, Class<GameObject>>(); How exactly would I go about calling, and checking for events? I figure that I would just call the update, render and input methods of each gameobject using the hashmap. Should I got towards a Minecraft/Bukkit approach (sorry only example I can think of), where the user registers an event, and it gets called whenever that event happens, and where should I go as in resources to learn about that type of programming, (Java, LWJGL). Or should I just loop through the entire hashmap looking for an event that fits? Thanks waco

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  • Lighting get darker when texture is aplied

    - by noah
    Im using OpenGL ES 1.1 for iPhone. I'm attempting to implement a skybox in my 3d world and started out by following one of Jeff Lamarches tutorials on creating textures. Heres the tutorial: iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-part-6_25.html Ive successfully added the image to my 3d world but am not sure why the lighting on the other shapes has changed so much. I want the shapes to be the original color and have the image in the background. Before: https://www.dropbox.com/s/ojmb8793vj514h0/Screen%20Shot%202012-10-01%20at%205.34.44%20PM.png After: https://www.dropbox.com/s/8v6yvur8amgudia/Screen%20Shot%202012-10-01%20at%205.35.31%20PM.png Heres the init OpenGL: - (void)initOpenGLES1 { glShadeModel(GL_SMOOTH); // Enable lighting glEnable(GL_LIGHTING); // Turn the first light on glEnable(GL_LIGHT0); const GLfloat lightAmbient[] = {0.2, 0.2, 0.2, 1.0}; const GLfloat lightDiffuse[] = {0.8, 0.8, 0.8, 1.0}; const GLfloat matAmbient[] = {0.3, 0.3, 0.3, 0.5}; const GLfloat matDiffuse[] = {1.0, 1.0, 1.0, 1.0}; const GLfloat matSpecular[] = {1.0, 1.0, 1.0, 1.0}; const GLfloat lightPosition[] = {0.0, 0.0, 1.0, 0.0}; const GLfloat lightShininess = 100.0; //Configure OpenGL lighting glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, matAmbient); glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, matDiffuse); glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, matSpecular); glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, lightShininess); glLightfv(GL_LIGHT0, GL_AMBIENT, lightAmbient); glLightfv(GL_LIGHT0, GL_DIFFUSE, lightDiffuse); glLightfv(GL_LIGHT0, GL_POSITION, lightPosition); // Define a cutoff angle glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 40.0); // Set the clear color glClearColor(0, 0, 0, 1.0f); // Projection Matrix config glMatrixMode(GL_PROJECTION); glLoadIdentity(); CGSize layerSize = self.view.layer.frame.size; // Swapped height and width for landscape mode gluPerspective(45.0f, (GLfloat)layerSize.height / (GLfloat)layerSize.width, 0.1f, 750.0f); [self initSkyBox]; // Modelview Matrix config glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // This next line is not really needed as it is the default for OpenGL ES glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glDisable(GL_BLEND); // Enable depth testing glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LESS); glDepthMask(GL_TRUE); } Heres the drawSkybox that gets called in the drawFrame method: -(void)drawSkyBox { glDisable(GL_LIGHTING); glDisable(GL_DEPTH_TEST); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_NORMAL_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); static const SSVertex3D vertices[] = { {-1.0, 1.0, -0.0}, { 1.0, 1.0, -0.0}, {-1.0, -1.0, -0.0}, { 1.0, -1.0, -0.0} }; static const SSVertex3D normals[] = { {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0} }; static const GLfloat texCoords[] = { 0.0, 0.5, 0.5, 0.5, 0.0, 0.0, 0.5, 0.0 }; glLoadIdentity(); glTranslatef(0.0, 0.0, -3.0); glBindTexture(GL_TEXTURE_2D, texture[0]); glVertexPointer(3, GL_FLOAT, 0, vertices); glNormalPointer(GL_FLOAT, 0, normals); glTexCoordPointer(2, GL_FLOAT, 0, texCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glEnable(GL_LIGHTING); glEnable(GL_DEPTH_TEST); } Heres the init Skybox: -(void)initSkyBox { // Turn necessary features on glEnable(GL_TEXTURE_2D); glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_SRC_COLOR); // Bind the number of textures we need, in this case one. glGenTextures(1, &texture[0]); // create a texture obj, give unique ID glBindTexture(GL_TEXTURE_2D, texture[0]); // load our new texture name into the current texture glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); NSString *path = [[NSBundle mainBundle] pathForResource:@"space" ofType:@"jpg"]; NSData *texData = [[NSData alloc] initWithContentsOfFile:path]; UIImage *image = [[UIImage alloc] initWithData:texData]; GLuint width = CGImageGetWidth(image.CGImage); GLuint height = CGImageGetHeight(image.CGImage); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); void *imageData = malloc( height * width * 4 ); // times 4 because will write one byte for rgb and alpha CGContextRef cgContext = CGBitmapContextCreate( imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big ); // Flip the Y-axis CGContextTranslateCTM (cgContext, 0, height); CGContextScaleCTM (cgContext, 1.0, -1.0); CGColorSpaceRelease( colorSpace ); CGContextClearRect( cgContext, CGRectMake( 0, 0, width, height ) ); CGContextDrawImage( cgContext, CGRectMake( 0, 0, width, height ), image.CGImage ); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData); CGContextRelease(cgContext); free(imageData); [image release]; [texData release]; } Any help is greatly appreciated.

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  • Looking for literature about graphics pipeline optimization

    - by zacharmarz
    I am looking for some books, articles or tutorials about graphics architecture and graphics pipeline optimizations. It shouldn't be too old (2008 or newer) - the newer, the better. I have found something in [Optimising the Graphics Pipeline, NVIDIA, Koji Ashida] - too old, [Real-time rendering, Akenine Moller], [OpenGL Bindless Extensions, NVIDIA, Jeff Bolz], [Efficient multifragment effects on graphics processing units, Louis Frederic Bavoil] and some internet discussions. But there is not too much information and I want to read more. It should contain something about application, driver, memory and shader units communication and data transfers. About vertices and attributes. Also pre and post T&L cache (if they still exist in nowadays architectures) etc. I don't need anything about textures, frame buffers and rasterization. It can also be about OpenGL (not about DirecX) and optimizing extensions (not old extensions like VBOs, but newer like vertex_buffer_unified_memory).

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  • (Quaternion based) Trouble moving foward based on model rotation

    - by ChocoMan
    Using quaternions, I'm having trouble moving my model in its facing direction. Currently the model moves can move in all cardinal directions with no problems. The problem comes when I rotate the move as it still travelling in the direction of world space. Meaning, if I'm moving forward, backward or any other direction while rotating the model, the model acts like its a figure skater spinning while traveling in the same direction. How do I update the direction of travel proper with the facing direction of the model? Rotates model on Y-axis: Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromYawPitchRoll(yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Moves model forward: // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { SpeedX = (float)(Math.Sin(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; SpeedZ = (float)(Math.Cos(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; // Update model position ModelLoad._modelPos += Vector3.Forward * SpeedZ; ModelLoad._modelPos += Vector3.Left * SpeedX; }

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  • What's a good way to programmatically manage a cloneable entity?

    - by bobobobo
    Say you have missiles or rockets that a player can fire. What's a good way to programmatically manage the cloning of a base rocket, for example? I can think of 2 ways to do it: Player has a currently selected weapon (which is an int) When player shoots, the selectedWeapon member is looked at, and the correct instance of rocket is created (with some base parameters) Or Player has a currently selected weapon (which is a pointer, to a "base instance" of the rocket object) When player shoots, the base instance rocket is cloned, transformed, and shot into the game world

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  • Why is GL_TEXTURE_MAX_ANISOTROPY_EXT undefined?

    - by Haydn
    So I'm writing my texture class in my opengl game, I get to the part where I would normally set GL_TEXTURE_MAX_ANISOTROPY_EXT, and I'm shocked to discover that it's undefined! This exact same extensions worked perfectly in a different application, so I know it's not a typo or something. It's worth noting that I'm getting my extensions using glcorearb.h, instead of glext.h, because I have no intention of supporting the compatibility profile. Could this be my problem, and if so, how do I work around it?

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  • Read only array, deep copy or retrieve copies one by one? (Performance and Memory)

    - by Arthur Wulf White
    In a garbage collection based system, what is the most effective way to handle a read only array if such a structure does not exist natively in the language. Is it better to return a copy of an array or allow other classes to retrieve copies of the objects stored in the array one by one? @JustinSkiles: It is not very broad. It is performance related and can actually be answered specifically for two general cases. You only need very few items: in this situation it's more effective to retrieve copies of the objects one by one. You wish to iterate over 30% or more objects. In this cases it is superior to retrieve all the array at once. This saves on functions calls. Function calls are very expansive when compared to reading directly from an array. A good specific answer could include performance, reading from an array and reading indirectly through a function. It is a simple performance related question.

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  • Largest sphere inside a frustum

    - by Will
    How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. We can unproject all eight corners of the frusum, and the centres of the near and far ends. So we know point 1, 3 and 4. We also know that point 2 is the same distance from 3 as 4 is from 3. So then we can compute the nearest point on the line 1 to 4 to point 2 in order to get the centre? But the actual math and code escapes me. I want to draw models (which are approximately spherical and which I have a miniball bounding sphere for) as large as possible. Update: I've tried to implement the incircle-on-two-planes approach as suggested by bobobobo and Nathan Reed : function getFrustumsInsphere(viewport,invMvpMatrix) { var midX = viewport[0]+viewport[2]/2, midY = viewport[1]+viewport[3]/2, centre = unproject(midX,midY,null,null,viewport,invMvpMatrix), incircle = function(a,b) { var c = ray_ray_closest_point_3(a,b); a = a[1]; // far clip plane b = b[1]; // far clip plane c = c[1]; // camera var A = vec3_length(vec3_sub(b,c)), B = vec3_length(vec3_sub(a,c)), C = vec3_length(vec3_sub(a,b)), P = 1/(A+B+C), x = ((A*a[0])+(B*a[1])+(C*a[2]))*P, y = ((A*b[0])+(B*b[1])+(C*b[2]))*P, z = ((A*c[0])+(B*c[1])+(C*c[2]))*P; c = [x,y,z]; // now the centre of the incircle c.push(vec3_length(vec3_sub(centre[1],c))); // add its radius return c; }, left = unproject(viewport[0],midY,null,null,viewport,invMvpMatrix), right = unproject(viewport[2],midY,null,null,viewport,invMvpMatrix), horiz = incircle(left,right), top = unproject(midX,viewport[1],null,null,viewport,invMvpMatrix), bottom = unproject(midX,viewport[3],null,null,viewport,invMvpMatrix), vert = incircle(top,bottom); return horiz[3]<vert[3]? horiz: vert; } I admit I'm winging it; I'm trying to adapt 2D code by extending it into 3 dimensions. It doesn't compute the insphere correctly; the centre-point of the sphere seems to be on the line between the camera and the top-left each time, and its too big (or too close). Is there any obvious mistakes in my code? Does the approach, if fixed, work?

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  • Determining explosion radius damage - Circle to Rectangle 2D

    - by Paul Renton
    One of the Cocos2D games I am working on has circular explosion effects. These explosion effects need to deal a percentage of their set maximum damage to all game characters (represented by rectangular bounding boxes as the objects in question are tanks) within the explosion radius. So this boils down to circle to rectangle collision and how far away the circle's radius is from the closest rectangle edge. I took a stab at figuring this out last night, but I believe there may be a better way. In particular, I don't know the best way to determine what percentage of damage to apply based on the distance calculated. Note : All tank objects have an anchor point of (0,0) so position is according to bottom left corner of bounding box. Explosion point is the center point of the circular explosion. TankObject * tank = (TankObject*) gameSprite; float distanceFromExplosionCenter; // IMPORTANT :: All GameCharacter have an assumed (0,0) anchor if (explosionPoint.x < tank.position.x) { // Explosion to WEST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, tank.position); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = tank.position.x - explosionPoint.x; } // end if } else if (explosionPoint.x > (tank.position.x + tank.contentSize.width)) { // Explosion to EAST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y)); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = explosionPoint.x - (tank.position.x + tank.contentSize.width); } // end if } else { // Tank is either north or south and is inbetween left and right corner of rect if (explosionPoint.y < tank.position.y) { // Explosion is South distanceFromExplosionCenter = tank.position.y - explosionPoint.y; } else { // Explosion is North distanceFromExplosionCenter = explosionPoint.y - (tank.position.y + tank.contentSize.height); } // end if } // end outer if if (distanceFromExplosionCenter < explosionRadius) { /* Collision :: Smaller distance larger the damage */ int damageToApply; if (self.directHit) { damageToApply = self.explosionMaxDamage + self.directHitBonusDamage; [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explsoion-> DIRECT HIT with total damage %d", damageToApply); } else { // TODO adjust this... turning out negative for some reason... damageToApply = (1 - (distanceFromExplosionCenter/explosionRadius) * explosionMaxDamage); [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explosion-> Non direct hit collision with tank"); CCLOG(@"Damage to apply is %d", damageToApply); } // end if } else { CCLOG(@"Explosion-> Explosion distance is larger than explosion radius"); } // end if } // end if Questions: 1) Can this circle to rect collision algorithm be done better? Do I have too many checks? 2) How to calculate the percentage based damage? My current method generates negative numbers occasionally and I don't understand why (Maybe I need more sleep!). But, in my if statement, I ask if distance < explosion radius. When control goes through, distance/radius must be < 1 right? So 1 - that intermediate calculation should not be negative. Appreciate any help/advice!

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  • Shadow mapping: what is the light looking at?

    - by PgrAm
    I'm all set to set up shadow mapping in my 3d engine but there is one thing I am struggling to understand. The scene needs to be rendered from the light's point of view so I simply first move my camera to the light's position but then I need to find out which direction the light is looking. Since its a point light its not shining in any particular direction. How do I figure out what the orientation for the light point of view is?

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  • Xna model parts are overlying others

    - by Federico Chiaravalli
    I am trying to import in XNA an .fbx model exported with blender. Here is my drawing code public void Draw() { Matrix[] modelTransforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo(modelTransforms); foreach (ModelMesh mesh in Model.Meshes) { foreach (BasicEffect be in mesh.Effects) { be.EnableDefaultLighting(); be.World = modelTransforms[mesh.ParentBone.Index] * GameCamera.World * Translation; be.View = GameCamera.View; be.Projection = GameCamera.Projection; } mesh.Draw(); } } The problem is that when I start the game some model parts are overlying others instead of being behind. I've tried to download other models from internet but they have the same problem.

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  • Calculating collision force with AfterCollision/NormalImpulse is unreliable when IgnoreCCD = false?

    - by Michael
    I'm using Farseer Physics Engine 3.3.1 in a very simple XNA 4 test game. (Note: I'm also tagging this Box2D, because Farseer is a direct port of Box2D and I will happily accept Box2D answers that solve this problem.) In this game, I'm creating two bodies. The first body is created using BodyFactory.CreateCircle and BodyType.Dynamic. This body can be moved around using the keyboard (which sets Body.LinearVelocity). The second body is created using BodyFactory.CreateRectangle and BodyType.Static. This body is static and never moves. Then I'm using this code to calculate the force of collision when the two bodies collide: staticBody.FixtureList[0].AfterCollision += new AfterCollisionEventHandler(AfterCollision); protected void AfterCollision(Fixture fixtureA, Fixture fixtureB, Contact contact) { float maxImpulse = 0f; for (int i = 0; i < contact.Manifold.PointCount; i++) maxImpulse = Math.Max(maxImpulse, contact.Manifold.Points[i].NormalImpulse); // maxImpulse should contain the force of the collision } This code works great if both of these bodies are set to IgnoreCCD=true. I can calculate the force of collision between them 100% reliably. Perfect. But here's the problem: If I set the bodies to IgnoreCCD=false, that code becomes wildly unpredictable. AfterCollision is called reliably, but for some reason the NormalImpulse is 0 about 75% of the time, so only about one in four collisions is registered. Worse still, the NormalImpulse seems to be zero for completely random reasons. The dynamic body can collide with the static body 10 times in a row in virtually exactly the same way, and only 2 or 3 of the hits will register with a NormalImpulse greater than zero. Setting IgnoreCCD=true on both bodies instantly solves the problem, but then I lose continuous physics detection. Why is this happening and how can I fix it? Here's a link to a simple XNA 4 solution that demonstrates this problem in action: http://www.mediafire.com/?a1w242q9sna54j4

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  • Exporting XNA class library as a DLL file

    - by Will Bagley
    I have downloaded an open source project that I intend to use with my current game. The download came with all the class files from the original project as well as a pre-compiled DLL file representing the project. I was able to easily link this DLL with my current project and get it working just fine, no problems there. The problem I now have is that I want to make a couple of changes to the original libraries (extend its functionality a bit to better suit my needs) and re-export the class library as a DLL again, but I have no clue how to do this. Is there some simple way in VS where I can just take the class library and export/compile it as a DLL file again or is there more to it than that? This seems like something that should be pretty simple but my efforts to find an answer have so far come up with nothing. Thanks in advance.

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