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• How to export Oracle statistics

  - by A_M

  Hi, I am writing some new SQL queries and want to check the query plans that the Oracle query optimiser would come up with in production. My development database doesn't have anything like the data volumes of the production database. How can I export database statistics from a production database and re-import them into a development database? I don't have access to the production database, so I can't simply generate explain plans on production without going through a third party hosting organisation. This is painful. So I want a local database which is in some way representative of production on which I can try out different things. Also, this is for a legacy application. I'd like to "improve" the schema, by adding appropriate indexes. constraints, etc. I need to do this in my development database first, before rolling out to test and production. If I add an index and re-generate statistics in development, then the statistics will be generated around the development data volumes, which makes it difficult to assess the impact my changes on production. Does anyone have any tips on how to deal with this? Or is it just a case of fixing unexpected behaviour once we've discovered it on production? I do have a staging database with production volumes, but again I have to go through a third party to run queries against this, which is painful. So I'm looking for ways to cut out the middle man as much as possible. All this is using Oracle 9i. Thanks.

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• Class Design - Space Simulator

  - by Peteyslatts

  I have pretty much taught myself everything I know about programming, so while I know how to teach myself (books, internet and reading API's), I'm finding that there hasn't been a whole lot in the way of good programming. So I have two questions: First the broad one: Does anyone have suggestions as to sources for learning about good programming habits and techniques? I'd prefer it if the resource wasn't a 5000 page tome. The more I can read it in installments the better. More specifically: I am finishing up learning the basics of XNA and I want to create a space simulator to test my knowledge. This isn't a full scale simulator, but just something that covers everything I learned. It's also going to be modular so I can build on it, after I get the basics down. One of the early features I want to implement is AI. And I want to take this into account as I'm designing my classes so I can minimize rewriting code. So my question: How should I design ship classes so that both the player and AI can use them? The only idea I have so far is: Create a ship class that contains stats, models, textures, collision data etc. The player and AI would then have the data for position, rotation, health, etc and would base their status off of the ship stats.

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• How do you get the total asset size (or total resource size) in an Android game?

  - by tom_mai78101

  In an Android Java project, there are two folders, asset and res. To me, I usually put some stuffs, like PNG files, sound files, etc. in either one of the two folder. When resources are increasingly becoming more and more in those folders, the time it takes to load them will increase. Therefore, a loading screen is a must in these situation. The total size is to be used in a loading screen, so that I can guess the average time it takes to load each resources, from 0 bytes to its individual resource file size. I only know that by adding all individual sizes in a respective order, I will then obtain the total asset or res folder size, simply by adding them up. So, when it comes to getting the total file size from either folder, how do you obtain their individual resource/object sizes, respectively? Thanks in advance.

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• How to snap a 2D Quad to the mouse cursor using OpenGL 3.0/WIN32?

  - by NoobScratcher

  I've been having issues trying to snap a 2D Quad to the mouse cursor position I'm able : 1.) To get values into posX, posY, posZ 2.) Translate with the values from those 3 variables But the quad positioning I'm not able to do correctly in such a way that the 2D Quad is near the mouse cursor using those values from those 3 variables eg."posX, posY, posZ" I need the mouse cursor in the center of the 2D Quad. I'm hoping someone can help me achieve this. I've tried searching around with no avail. Heres the function that is ment to do the snapping but instead creates weird flicker or shows nothing at all only the 3d models show up : void display() { glClearColor(0.0,0.0,0.0,1.0); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); for(std::vector<GLuint>::iterator I = cube.begin(); I != cube.end(); ++I) { glCallList(*I); } if(DrawArea == true) { glReadPixels(winX, winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ); cerr << winZ << endl; glGetDoublev(GL_MODELVIEW_MATRIX, modelview); glGetDoublev(GL_PROJECTION_MATRIX, projection); glGetIntegerv(GL_VIEWPORT, viewport); gluUnProject(winX, winY, winZ , modelview, projection, viewport, &posX, &posY, & posZ); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, DrawAreaSurface->w, DrawAreaSurface->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, DrawAreaSurface->pixels); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glTranslatef(posX , posY, posZ); glBegin(GL_QUADS); glTexCoord2f (0.0, 0.0); glVertex3f(0.5, 0.5, 0); glTexCoord2f (1.0, 0.0); glVertex3f(0, 0.5, 0); glTexCoord2f (1.0, 1.0); glVertex3f(0, 0, 0); glTexCoord2f (0.0, 1.0); glVertex3f(0.5, 0, 0); glEnd(); } SwapBuffers(hDC); } I'm using : OpenGL 3.0 WIN32 API C++ GLSL if you really want the full source here it is - http://pastebin.com/1Ncm9HNf , Its pretty messy.

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• Undeclared Scope in Rock Paper Scissors Simple Game

  - by Rianelle

  #include <iostream> #include <string> #include <cstdlib> #include <ctime> using namespace std; bool win; int winnings; int draws; int loses; string comChoice; string playerChoice; void winGame () { cout << "You won! Play again?" <<endl; cout << "Type y/n" <<endl; char x; cin >> x; if (x == 'y') { beginGame(); } else if ('n'){ cout << "Game Stopped." <<endl; cout << "Number of Draws: " <<draws << endl; cout << "Number of Loses: " <<loses << endl; cout << "Number of Wins: " << winnings << endl; win = true; } } void drawGame (){ ++draws; cout << "Draw! Try again" << endl; return; } void lose () { cout << "You lose! Try again?" <<endl; cout << "Type y/n" <<endl; char feedback; cin >> feedback; if (feedback == 'y') { beginGame(); } else if ('n'){ cout << "Game Stopped." <<endl; cout << "Number of Draws: " <<draws << endl; cout << "Number of Loses: " <<loses << endl; cout << "Number of Wins: " << winnings << endl; } } void beginGame() { cout << "Welcome to the Rock, Paper and Scissors Game!" <<endl; cout << "Let's begin. Type <rock, paper, scissors> for your choice!" <<endl; cin >> playerChoice; srand(time(0)); int randomizer = 1+(rand()%3); if (randomizer == 1) comChoice = "rock"; if (randomizer == 2) comChoice = "paper"; if (randomizer == 3) comChoice = "scissors"; do { if (playerChoice == comChoice) { drawGame(); } if (playerChoice == "rock" && comChoice == "paper") ++loses; lose(); if (playerChoice == "rock" && comChoice == "scissors") ++winnings; winGame(); if (playerChoice == "paper" && comChoice == "rock") ++winnings; winGame(); if (playerChoice == "paper" && comChoice == "scissors") ++loses; lose(); if (playerChoice == "scissors" && comChoice == "rock") ++loses; lose(); if (playerChoice == "scissors" && comChoice == "paper") ++winnings; winGame(); }while (win != true); } int main () { beginGame(); return 0; }

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• Using two joysticks in Cocos2D

  - by Blade

  Here is what I am trying to do: With the left joystick the player can steer the figure and with the right joystick it can attack. Problem is that the left joystick seems to get all the input, the right one does not even register anything. I enabled multipletouch after the eagleView and gone thoroughly over the code. But I seem to miss something. I initiliaze both sticks and it shows me both of them in game, but like I said, only the left one works. I initialize them both. From the h. file: SneakyJoystick *joystick; SneakyJoystick *joystickRight; And in m.file I synthesize, deallocate and initialize them. In order to use one for controlling and the other for attacking I put this: -(void)updateStateWithDeltaTime:(ccTime)deltaTime andListOfGameObjects:(CCArray*)listOfGameObjects { if ((self.characterState == kStateIdle) || (self.characterState == kStateWalkingBack) || (self.characterState == kStateWalkingLeft) || (self.characterState == kStateWalkingRight)|| (self.characterState == kStateWalkingFront) || (self.characterState == kStateAttackingFront) || (self.characterState == kStateAttackingBack)|| (self.characterState == kStateAttackingRight)|| (self.characterState == kStateAttackingLeft)) { if (joystick.degrees > 60 && joystick.degrees < 120) { if (self.characterState != kStateWalkingBack) [self changeState:kStateWalkingBack]; }else if (joystick.degrees > 1 && joystick.degrees < 59) { if (self.characterState != kStateWalkingRight) [self changeState:kStateWalkingRight]; } else if (joystick.degrees > 211 && joystick.degrees < 300) { if (self.characterState != kStateWalkingFront) [self changeState:kStateWalkingFront]; } else if (joystick.degrees > 301 && joystick.degrees < 360){ if (self.characterState != kStateWalkingRight) [self changeState:kStateWalkingRight]; } else if (joystick.degrees > 121 && joystick.degrees < 210) { if (self.characterState != kStateWalkingLeft) [self changeState:kStateWalkingLeft]; } if (joystickRight.degrees > 60 && joystickRight.degrees < 120) { if (self.characterState != kStateAttackingBack) [self changeState:kStateAttackingBack]; }else if (joystickRight.degrees > 1 && joystickRight.degrees < 59) { if (self.characterState != kStateAttackingRight) [self changeState:kStateAttackingRight]; } else if (joystickRight.degrees > 211 && joystickRight.degrees < 300) { if (self.characterState != kStateAttackingFront) [self changeState:kStateAttackingFront]; } else if (joystickRight.degrees > 301 && joystickRight.degrees < 360){ if (self.characterState != kStateAttackingRight) [self changeState:kStateAttackingRight]; } else if (joystickRight.degrees > 121 && joystickRight.degrees < 210) { if (self.characterState != kStateAttackingLeft) [self changeState:kStateAttackingLeft]; } [self applyJoystick:joystick forTimeDelta:deltaTime]; [self applyJoystick:joystickRight forTimeDelta:deltaTime]; } Maybe it has something to do with putting them both to time delta? I tried working around it, but it did not work. So I am thankful for any input you guys can give me :)

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• Calculating a child object's Position, Rotation and Scale values?

  - by Sergio Plascencia

  I am making my own game editor, but have encountered the following problem: I have two objects, A and B. A's initial values: Position: (3,3,3), Rotation: (45,10,0), Scale(1,2,2.5) B's initial values: Position: (1,1,1), Rotation: (10,34,18), Scale(1.5,2,1) If I now make B a child of A, I need to re-calculate the B's Position, Rotation and Scale relative to A such that it maintains its current position, rotation and scale in world coordinates. So B's position would now be (-2, -2, -2) since now A is its center and (-2, -2, -2) will keep B in the same position. I think I got the Position and scale figured out, but not rotation. So I opened Unity and ran the same example and I noticed that when making a child object, the child object did not move at all. but had its Position, Rotation and Scale values changed relative to the parent. For example: Unity (Parent Object "A"): Position: (0,0,0) Rotation: (45,10,0) Scale: (1,1,1) Unity (Child Object "B"): Position: (0,0,0) Rotation: (0,0,0) Scale: (1,1,1) When B becomes a child of A, it's rotation values become: X: -44.13605 Y: -14.00195 Z: 9.851074 If I plug the same rotation values into the B object in my editor, the object does not move at all. How did Unity arrive at those rotation values for the child? What are the calculations? If you can put all the equations for the Position, Rotation or Scale then I can double check I am doing it correctly but the Rotation is what I really need.

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• Make Interactive Story more Variable [on hold]

  - by Guest0343

  I'm creating an interactive story that allows users to make choices based on a story. However, it doesn't give users room to do much creatively on their own. They are bound by the script at the moment. I'm wondering if anyone can suggest any element I can add that might give users some personalization. I was thinking about maybe character editing, but that doesn't add too much. I also thought about a stats system where they can have certain attributes and stats they might earn, but I'm not sure how they might use those stats. Anything is helpful!

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• Architecture a for a central renderer rather than self-rendering

  - by The Communist Duck

  For the architectural side of rendering, there's two main ways: having each object render itself, and having a single renderer which renders everything. I'm currently aiming for the second idea, for the following reasons: The list can be sorted to only use shaders once. Else each object would have to bind the shader, because it's not sure if it's active. The objects could be sorted and grouped. Easier to swap APIs. With a few macro lines, it can be easy to swap between a DirectX renderer and an OpenGL renderer (not a reason for my project, but still a good point) Easier to manage rendering code Of course, if anyone has strong recommendations for the first method, I will listen to them. But I was wondering how make this work. First idea The renderer has a list of pointers to the renderable components of each entity, which register themselves on RenderCompoent creation. However, I'm worrying that this may end up as a lot of extra pointer weight. But I can sort the list of pointers every so often. Second idea The entire list of entities is passed to the renderer each render call. The renderer then sorts the list (each call, or maybe once?) and gets what it wants. That's a lot of passing and/or sorting, however. Other ideas ??? PROFIT Anyone got ideas? Thank you.

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• Help understand GLSL directional light on iOS (left handed coord system)

  - by Robse

  I now have changed from GLKBaseEffect to a own shader implementation. I have a shader management, which compiles and applies a shader to the right time and does some shader setup like lights. Please have a look at my vertex shader code. Now, light direction should be provided in eye space, but I think there is something I don't get right. After I setup my view with camera I save a lightMatrix to transform the light from global space to eye space. My modelview and projection setup: - (void)setupViewWithWidth:(int)width height:(int)height camera:(N3DCamera *)aCamera { aCamera.aspect = (float)width / (float)height; float aspect = aCamera.aspect; float far = aCamera.far; float near = aCamera.near; float vFOV = aCamera.fieldOfView; float top = near * tanf(M_PI * vFOV / 360.0f); float bottom = -top; float right = aspect * top; float left = -right; // projection GLKMatrixStackLoadMatrix4(projectionStack, GLKMatrix4MakeFrustum(left, right, bottom, top, near, far)); // identity modelview GLKMatrixStackLoadMatrix4(modelviewStack, GLKMatrix4Identity); // switch to left handed coord system (forward = z+) GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeScale(1, 1, -1)); // transform camera GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeWithMatrix3(GLKMatrix3Transpose(aCamera.orientation))); GLKMatrixStackTranslate(modelviewStack, -aCamera.position.x, -aCamera.position.y, -aCamera.position.z); } - (GLKMatrix4)modelviewMatrix { return GLKMatrixStackGetMatrix4(modelviewStack); } - (GLKMatrix4)projectionMatrix { return GLKMatrixStackGetMatrix4(projectionStack); } - (GLKMatrix4)modelviewProjectionMatrix { return GLKMatrix4Multiply([self projectionMatrix], [self modelviewMatrix]); } - (GLKMatrix3)normalMatrix { return GLKMatrix3InvertAndTranspose(GLKMatrix4GetMatrix3([self modelviewProjectionMatrix]), NULL); } After that, I save the lightMatrix like this: [self.renderer setupViewWithWidth:view.drawableWidth height:view.drawableHeight camera:self.camera]; self.lightMatrix = [self.renderer modelviewProjectionMatrix]; And just before I render a 3d entity of the scene graph, I setup the light config for its shader with the lightMatrix like this: - (N3DLight)transformedLight:(N3DLight)light transformation:(GLKMatrix4)matrix { N3DLight transformedLight = N3DLightMakeDisabled(); if (N3DLightIsDirectional(light)) { GLKVector3 direction = GLKVector3MakeWithArray(GLKMatrix4MultiplyVector4(matrix, light.position).v); direction = GLKVector3Negate(direction); // HACK -> TODO: get lightMatrix right! transformedLight = N3DLightMakeDirectional(direction, light.diffuse, light.specular); } else { ... } return transformedLight; } You see the line, where I negate the direction!? I can't explain why I need to do that, but if I do, the lights are correct as far as I can tell. Please help me, to get rid of the hack. I'am scared that this has something to do, with my switch to left handed coord system. My vertex shader looks like this: attribute highp vec4 inPosition; attribute lowp vec4 inNormal; ... uniform highp mat4 MVP; uniform highp mat4 MV; uniform lowp mat3 N; uniform lowp vec4 constantColor; uniform lowp vec4 ambient; uniform lowp vec4 light0Position; uniform lowp vec4 light0Diffuse; uniform lowp vec4 light0Specular; varying lowp vec4 vColor; varying lowp vec3 vTexCoord0; vec4 calcDirectional(vec3 dir, vec4 diffuse, vec4 specular, vec3 normal) { float NdotL = max(dot(normal, dir), 0.0); return NdotL * diffuse; } ... vec4 calcLight(vec4 pos, vec4 diffuse, vec4 specular, vec3 normal) { if (pos.w == 0.0) { // Directional Light return calcDirectional(normalize(pos.xyz), diffuse, specular, normal); } else { ... } } void main(void) { // position highp vec4 position = MVP * inPosition; gl_Position = position; // normal lowp vec3 normal = inNormal.xyz / inNormal.w; normal = N * normal; normal = normalize(normal); // colors vColor = constantColor * ambient; // add lights vColor += calcLight(light0Position, light0Diffuse, light0Specular, normal); ... }

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• Any technical references for game-oriented icons and symbols?

  - by willc2

  To make localizing easier, I'm using icons to show in-game information like achievements and bonuses. Coming up with good designs isn't easy, especially when it has to be integrated into the rest of the game's art style. Can I do better than looking at some random selection of existing games? Are there any reference books or sites that cover game graphics specifically? I'm looking for more theory and best-practices rather than pre-made graphics.

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• Enemy Spawning method in a Top-Down Shooter

  - by Chris Waters

  I'm working on a top-down shooter akin to DoDonPachi, Ikaruga, etc. The camera movement through the world is handled automatically with the player able to move inside of the camera's visible region. Along the way, enemies are scripted to spawn at particular points along the path. While this sounds straightforward, I could see two ways to define these points: Camera's position: 'trigger' spawning as the camera passes by the points Time along path: "30 seconds in, spawn 2 enemies" In both cases, the camera-relative positions would be defined as well as the behavior of the enemy. The way I see it, the way you define these points will directly affect how the 'level editor', or what have you, will work. Would there be any benefits of one approach over the other?

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• Frame Independent Movement

  - by ShrimpCrackers

  I've read two other threads here on movement: Time based movement Vs Frame rate based movement?, and Fixed time step vs Variable time step but I think I'm lacking a basic understanding of frame independent movement because I don't understand what either of those threads are talking about. I'm following along with lazyfoo's SDL tutorials and came upon the frame independent lesson. http://lazyfoo.net/SDL_tutorials/lesson32/index.php I'm not sure what the movement part of the code is trying to say but I think it's this (please correct me if I'm wrong): In order to have frame independent movement, we need to find out how far an object (ex. sprite) moves within a certain time frame, for example 1 second. If the dot moves at 200 pixels per second, then I need to calculate how much it moves within that second by multiplying 200 pps by 1/1000 of a second. Is that right? The lesson says: "velocity in pixels per second * time since last frame in seconds. So if the program runs at 200 frames per second: 200 pps * 1/200 seconds = 1 pixel" But...I thought we were multiplying 200 pps by 1/1000th of a second. What is this business with frames per second? I'd appreciate if someone could give me a little bit more detailed explanation as to how frame independent movement works. Thank you.

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• How to attach two XNA models together?

  - by jeangil

  I go back on unsolved question I asked about attaching two models together, could you give me some help on this ? For example, If I want to attach together Model1 (= Main model) & Model2 ? I have to get the transformation matrix of Model1 and after get the Bone index on Model1 where I want to attach Model2 and then apply some transformation to attach Model2 to Model1 I wrote some code below about this, but It does not work at all !! (6th line of my code seems to be wrong !?) Model1TransfoMatrix=New Matrix[Model1.Bones.Count]; Index=Model1.bone[x].Index; foreach (ModelMesh mesh in Model2.Meshes) { foreach(BasicEffect effect in mesh.effects) { matrix model2Transform = Matrix.CreateScale(0.1.0f)*Matrix.CreateFromYawPitchRoll(x,y,z); effect.World= model2Transform *Model1TransfoMatrix[Index]; effect.view = camera.View; effect.Projection= camera.Projection; } mesh.draw(); }

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• The purpose of using invert and transpose

  - by user699215

  In openGl ES and the World of 3D - why use the invers matrix? The thing is that I dont have any intuition to, why it is used, therefore please correct me: As fare as I understand, it is used in shaders - and can help you to figure out the opposite direction of the normals? Invers in ordinary numbers is like; The product of a number and its multiplicative inverse is 1. Observe that 3/5 * 5/3 = 1. In a matrix this will give you the Identity Matrix, which is the base coordinate system or the orion of the World space - right. But the invers is - some other coordinate system? You can use the transpose(Row-major order to Column-major order) of a square matrix to find the inverted matrix, as calculating the invers is process heavy - and the transpose is giving you the inverted matrix as a bi product? Again, I am looking for getting some intuition of this - and therefore be able to use it as intended. Thank you for any reply that will guide me in the right direction. Regards

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• Resolving a collision between point and moving line

  - by Conundrumer

  I am designing a 2d physics engine that uses Verlet integration for moving points (velocities mentioned below can be derived), constraints to represent moving line segments, and continuous collision detection to resolve collisions between moving points and static lines, and collisions between moving/static points and moving lines. I already know how to calculate the Time of Impact for both types of collision events, and how to resolve moving point static line collisions. However, I can't figure out how to resolve moving/static point moving line collisions. Here are the initial conditions in a point and moving line collision event. We have a line segment joined by two points, A and B. At this instant, point P is touching/colliding with line AB. These points have unit mass and some might have an initial velocity, unless point P is static. The line is massless and has no explicit rotational component, since points A and B could freely move around, extending or contracting the line as a result (which will be fixed later by the constraint solver). Collision is inelastic. What are the final velocities of the points after collision?

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• Implementing `fling` logic without pan gesture recognizers

  - by KDiTraglia

  So I am trying to port over a simple game that I originally wrote to iphone into cocos2d-x. I've hit a minor bump however in implementing simple 'fling' logic I had in the iphone version that is difficult to port over to the c++. In iOS I could get the velocity of a pan gesture very easily: CGPoint velocity = [recognizer velocityInView:recognizer.view]; However now I basically only know where the touch began, where the touch ended, and all the touches that are logged in between. For now I logged all the pts onto a stack then pulled the last point and the 6th to last point (seemed to work the best), find the difference between those pts multiply by a constant and use that as the velocity. It works relatively well, but I'm wondering if anyone else has any better algorithms, when given a bunch of touch pts, to figure out a new speed upon releasing an object that feels natural (Note speed in my game is just a constant x and y, there's no drag or spin or anything tricky like that). Bonus points if anyone has figured out how to get pan gestures into the newest version (3.0 alpha) of cocos2d-x without losing ability to build cross platform.

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• Central renderer for a given scene

  - by Loggie

  When creating a central rendering system for all game objects in a given scene I am trying to work out the best way to go about passing the scene to the render system to be rendered. If I have a scene managed by an arbitrary structure, i.e., an octree, bsp trees, quad-tree, kd tree, etc. What is the best way to pass this to the render system? The obvious problem is that if simply given the root node of the structure, the render system would require an intrinsic knowledge of the structure in order to traverse the structure. My solution to this is to clip all objects outside the frustum in the scene manager and then create a list of the objects which are left and pass this simple list to the render system, be it an array, a vector, a linked list, etc. (This would be a structure required by the render system as a means to know which objects should be rendered). The list would of course attempt to minimise OpenGL state changes by grouping objects that require the same rendering operations to be performed on them. I have been thinking a lot about this and started searching various terms on here and followed any additional information/links but I have not really found a definitive answer. The case may be that there is no definitive answer but I would appreciate some advice and tips. My question is, is this a reasonable solution to the problem? Are there any improvements that I could make? Are there any caveats I should know about? Side question: Am I right in assuming that octrees, bsp trees, etc are all forms of BVH?

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• How to avoid game objects accidentally deleting themselves in C++

  - by Tom Dalling

  Let's say my game has a monster that can kamikaze explode on the player. Let's pick a name for this monster at random: a Creeper. So, the Creeper class has a method that looks something like this: void Creeper::kamikaze() { EventSystem::postEvent(ENTITY_DEATH, this); Explosion* e = new Explosion; e->setLocation(this->location()); this->world->addEntity(e); } The events are not queued, they get dispatched immediately. This causes the Creeper object to get deleted somewhere inside the call to postEvent. Something like this: void World::handleEvent(int type, void* context) { if(type == ENTITY_DEATH){ Entity* ent = dynamic_cast<Entity*>(context); removeEntity(ent); delete ent; } } Because the Creeper object gets deleted while the kamikaze method is still running, it will crash when it tries to access this->location(). One solution is to queue the events into a buffer and dispatch them later. Is that the common solution in C++ games? It feels like a bit of a hack, but that might just be because of my experience with other languages with different memory management practices. In C++, is there a better general solution to this problem where an object accidentally deletes itself from inside one of its methods?

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• How to implment the database for event conditions and item bonuses for a browser based game

  - by Saifis

  I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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• Continuous Collision Detection Techniques

  - by Griffin

  I know there are quite a few continuous collision detection algorithms out there , but I can't find a list or summary of different 2D techniques; only tutorials on specific algorithms. What techniques are out there for calculating when different 2D bodies will collide and what are the advantages / disadvantages of each? I say techniques and not algorithms because I have not yet decided on how I will store different polygons which might be concave or even have holes. I plan to make a decision on this based on what the algorithm requires (for instance if an algorithm breaks down a polygon into triangles or convex shapes I will simply store the polygon data in this form).

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• How do I design a game framework for fast reaction to user input?

  - by Miro

  I've played some games at cca 30 fps and some of them had low reaction time - cca 0.1sec. I hadn't knew why. Now when I'm designing my framework for crossplatform game, I know why. Probably they've been preparing new frame during rendering the previous. RENDER 1 | RENDER 2 | RENDER 3 | RENDER 4 PREPARE 2 | PREPARE 3 | PREPARE 4 | PREPARE 5 I see first frame when second frame is being rendered and third frame being prepared. If I react in that time to 1st frame it will result in forth frame. So it takes 3/FPS seconds to appear results. In 30 fps it would be 100ms, what is quite bad. So i'm wondering what should I design my framework to response to user interaction quickly?

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• Two graphical entities, smooth blending between them (e.g. asphalt and grass)

  - by Gabriel Conrad

  Supposedly in a scenario there are, among other things, a tarmac strip and a meadow. The tarmac has an asphalt texture and its model is a triangle strip long that might bifurcate at some point into other tinier strips, and suppose that the meadow is covered with grass. What can be done to make the two graphical entities seem less cut out from a photo and just pasted one on top of the other at the edges? To better understand the problem, picture a strip of asphalt and a plane covered with grass. The grass texture should also "enter" the tarmac strip a little bit at the edges (i.e. feathering effect). My ideas involve two approaches: put two textures on the tarmac entity, but that involves a serious restriction in how the strip is modeled and its texture coordinates are mapped or try and apply a post-processing filter that mimics a bloom effect where "grass" is used instead of light. This could be a terrible failure to achieve correct results. So, is there a better or at least a more obvious way that's widely used in the game dev industry?

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• 2D scene graph not transforming relative to parent

  - by Dr.Denis McCracleJizz

  I am currently in the process of coding my own 2D Scene graph, which is basically a port of flash's render engine. The problem I have right now is my rendering doesn't seem to be working properly. This code creates the localTransform property for each DisplayObject. Matrix m_transform = Matrix.CreateRotationZ(rotation) * Matrix.CreateScale(scaleX, scaleY, 1) * Matrix.CreateTranslation(new Vector3(x, y, z)); This is my render code. float dRotation; Vector2 dPosition, dScale; Matrix transform; transform = this.localTransform; if (parent != null) transform = localTransform * parent.localTransform; DecomposeMatrix(ref transform, out dPosition, out dRotation, out dScale); spriteBatch.Draw(this.texture, dPosition, null, Color.White, dRotation, new Vector2(originX, originY), dScale, SpriteEffects.None, 0.0f); Here is the result when I try to add the Stage then to the stage a First DisplayObjectContainer and then a second one. It may look fine but the problem lies in the fact that I add a first DisplayObjectContainer at (400,400) and the second one within it (that's the smallest one) at position (0,0). So he should be right over its parent but he gets render within the parent at the same position the parent has (400, 400) for some reason. It's just as if I double the parent's localMatrix and then render the second cat there. This is the code i use to loop through every childs. base.Draw(spriteBatch); foreach (DisplayObject childs in _childs) { childs.Draw(spriteBatch); }

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• Which Graphics/Geometry abstraction to choose?

  - by Robz

  I've been thinking about the design for a browser app on the HTML5 canvas that simulates a 2D robot zooming around, sensing the world around it. I decided to do this from scratch just for fun. I need shapes, like polygons, circles, and lines in order to model the robot and the world it lives in. These shapes need to be drawn with different appearance attributes, like border/fill style/width/color. I also need to have geometry functions to detect intersections and containment for the robot's sensors and so that the robot doesn't go inside stuff. One idea for functions is to have two totally separate libraries, one to implement graphics (like drawShape(context, shape)) and one for geometry operations (like shapeIntersectsShape(shape1, shape2)). Or, in a more object-oriented approach, the shape objects themselves could implement methods to do their own graphics (shape.draw(context)) and geometry operations (shape1.intersects(shape2)). Then there is the data itself: whether the data to draw a shape and the data to do geometric operations on that shape should be encapsulated within the same object, or be separate structures (where one would contain the other, or both be contained inside another structure). How do existing applications that do graphics/geometry stuff deal with this? Is there one model that is best, or is each good for certain applications? Should the fact that I'm using Javascript instead of a more classical language change how I approach the design?

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