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  • Texture not drawing on cubes

    - by Christian Frantz
    I can draw the cubes fine but they are just solid black besides the occasional lighting that goes on. The basic effect is being set for each cube also. public void Draw(BasicEffect effect) { foreach (EffectPass pass in effect.CurrentTechnique.Passes) { pass.Apply(); device.SetVertexBuffer(vertexBuffer); device.Indices = indexBuffer; device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, 8, 0, 12); } } The cubes draw method. TextureEnabled is set to true in my main draw method. My texture is also loading fine. public Cube(GraphicsDevice graphicsDevice, Vector3 Position, Texture2D Texture) { device = graphicsDevice; texture = Texture; cubePosition = Position; effect = new BasicEffect(device); } The constructor seems fine too. Could this be caused by the Vector2's of my VertexPositionNormalTexture? Even if they were out of order something should still be drawn other than a black cube

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  • Why is C++ used for game engines? How about its future in game engines?

    - by kasperov
    C++, as I have seen, is being heavily used in 3d video game engines.... Is it because of the performance issues, legecy code or libraries such as DriverX? If performance, libraries and code infrastructure are the reasons, dosen't that make C++ indispensible, at least for game engines? (ie, we have no other option even in the very distant future). I asked this because, I have the right to know the upcomming future trends in game engines.

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  • Most efficient 3d depth sorting for isometric 3d in AS3?

    - by AttackingHobo
    I am not using the built in 3d MovieClips, and I am storing the 3d location my way. I have read a few different articles on sorting depths, but most of them seem in efficient. I had a really efficient way to do it in AS2, but it was really hacky, and I am guessing there are more efficient ways that do not rely on possibly unreliable hacks. What is the most efficient way to sort display depths using AS3 with Z depths I already have?

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  • Are there any alternative JS ports of Box2D?

    - by Petteri Hietavirta
    I have been thinking about creating a top down 2D car game for HTML5. For my first game I wrote the physics and collisions my self but for this one I would like to use some ready made library. I found out Box2D and its JS port. http://box2d-js.sourceforge.net It seems to be quite old port, made in 2008. Is it lacking many features of current Box2D or does it have major issues with it? And are there any alternatives for it?

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  • Dynamic Jump spot

    - by Pasquale Sada
    I have an initial velocity V(Vx,Vy,VZ) and a spot where he stands still at S(Sx,Sy,Sz). What I'm trying to achieve is a jump on a spot E(Ex,Ey,Ez) where you have clicked on(only lower or higher spot, because I've in place a simple steering behavior for even terrains). There are no obstacle around. I've implemented a formula that can make him jump in a precise way on a spot but you need to declare an angle: the problem arise when the selected spot is straight above your head. It' pretty lame that the char hang there and can reach a thing that is 1cm above is head. I'll share the code I'm using: Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 *a)); return vel * dir.normalized;

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  • How do I make A* check all diagonal and orthogonal directions?

    - by Munezane
    I'm making a turn-based tactical game and I'm trying to implement the A* algorithm. I've been following a tutorial and got to this point, but my characters can't move diagonally up and left. Can anyone help me with this? The return x and y are int pointers which the characters are using to move towards the target. void level::aStar(int startx, int starty, int targetx, int targety, int* returnx, int* returny) { aStarGridSquare* currentSquare = new aStarGridSquare(); aStarGridSquare* startSquare = new aStarGridSquare(); aStarGridSquare* targetSquare = new aStarGridSquare(); aStarGridSquare* adjacentSquare = new aStarGridSquare(); aStarOpenList.clear(); for(unsigned int i=0; i<aStarGridSquareList.size(); i++) { aStarGridSquareList[i]->open=false; aStarGridSquareList[i]->closed=false; } startSquare=getaStarGridSquare(startx, starty); targetSquare=getaStarGridSquare(targetx, targety); if(startSquare==targetSquare) { *returnx=startx; *returny=starty; return; } startSquare->CostFromStart=0; startSquare->CostToTraverse=0; startSquare->parent = NULL; currentSquare=startSquare; aStarOpenList.push_back(currentSquare); while(currentSquare!=targetSquare && aStarOpenList.size()>0) { //unsigned int totalCostEstimate=aStarOpenList[0]->TotalCostEstimate; //currentSquare=aStarOpenList[0]; for(unsigned int i=0; i<aStarOpenList.size(); i++) { if(aStarOpenList.size()>1) { for(unsigned int j=1; j<aStarOpenList.size()-1; j++) { if(aStarOpenList[i]->TotalCostEstimate<aStarOpenList[j]->TotalCostEstimate) { currentSquare=aStarOpenList[i]; } else { currentSquare=aStarOpenList[j]; } } } else { currentSquare = aStarOpenList[i]; } } currentSquare->closed=true; currentSquare->open=false; for(unsigned int i=0; i<aStarOpenList.size(); i++) { if(aStarOpenList[i]==currentSquare) { aStarOpenList.erase(aStarOpenList.begin()+i); } } for(unsigned int i = currentSquare->blocky - 32; i <= currentSquare->blocky + 32; i+=32) { for(unsigned int j = currentSquare->blockx - 32; j<= currentSquare->blockx + 32; j+=32) { adjacentSquare=getaStarGridSquare(j/32, i/32); if(adjacentSquare!=NULL) { if(adjacentSquare->blocked==false && adjacentSquare->closed==false) { if(adjacentSquare->open==false) { adjacentSquare->parent=currentSquare; if(currentSquare->parent!=NULL) { currentSquare->CostFromStart = currentSquare->parent->CostFromStart + currentSquare->CostToTraverse + startSquare->CostFromStart; } else { currentSquare->CostFromStart=0; } adjacentSquare->CostFromStart =currentSquare->CostFromStart + adjacentSquare->CostToTraverse;// adjacentSquare->parent->CostFromStart + adjacentSquare->CostToTraverse; //currentSquare->CostToEndEstimate = abs(currentSquare->blockx - targetSquare->blockx) + abs(currentSquare->blocky - targetSquare->blocky); //currentSquare->TotalCostEstimate = currentSquare->CostFromStart + currentSquare->CostToEndEstimate; adjacentSquare->open = true; adjacentSquare->CostToEndEstimate=abs(adjacentSquare->blockx- targetSquare->blockx) + abs(adjacentSquare->blocky-targetSquare->blocky); adjacentSquare->TotalCostEstimate = adjacentSquare->CostFromStart+adjacentSquare->CostToEndEstimate; //adjacentSquare->open=true;*/ aStarOpenList.push_back(adjacentSquare); } else { if(adjacentSquare->parent->CostFromStart > currentSquare->CostFromStart) { adjacentSquare->parent=currentSquare; if(currentSquare->parent!=NULL) { currentSquare->CostFromStart = currentSquare->parent->CostFromStart + currentSquare->CostToTraverse + startSquare->CostFromStart; } else { currentSquare->CostFromStart=0; } adjacentSquare->CostFromStart =currentSquare->CostFromStart + adjacentSquare->CostToTraverse;// adjacentSquare->parent->CostFromStart + adjacentSquare->CostToTraverse; //currentSquare->CostToEndEstimate = abs(currentSquare->blockx - targetSquare->blockx) + abs(currentSquare->blocky - targetSquare->blocky); //currentSquare->TotalCostEstimate = currentSquare->CostFromStart + currentSquare->CostToEndEstimate; adjacentSquare->CostFromStart = adjacentSquare->parent->CostFromStart + adjacentSquare->CostToTraverse; adjacentSquare->CostToEndEstimate=abs(adjacentSquare->blockx - targetSquare->blockx) + abs(adjacentSquare->blocky - targetSquare->blocky); adjacentSquare->TotalCostEstimate = adjacentSquare->CostFromStart+adjacentSquare->CostToEndEstimate; } } } } } } } if(aStarOpenList.size()==0)//if empty { *returnx =startx; *returny =starty; return; } else { for(unsigned int i=0; i< aStarOpenList.size(); i++) { if(currentSquare->parent==NULL) { //int tempX = targetSquare->blockx; //int tempY = targetSquare->blocky; *returnx=targetSquare->blockx; *returny=targetSquare->blocky; break; } else { currentSquare=currentSquare->parent; } } } }

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  • Can DrawIndexedPrimitives() be used for drawing a loaded model mesh-wise?

    - by Afzal
    I am using DrawIndexedPrimitives() for drawing a loaded 3D model by drawing each mesh part, but this process makes my application very slow. This is perhaps because of a very large number of vertex/index buffer data created in video memory. That is why I am looking for a way to use the same method for each model mesh instead. The problem is that I don't know how I will set the textures of that mesh. Can anyone offer me some guidance?

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  • How to keep track of previous scenes and return to them in libgdx

    - by MxyL
    I have three scenes: SceneTitle, SceneMenu, SceneLoad. (The difference between the title scene and the menu scene is that the title scene is what you see when you first turn on the game, and the menu scene is what you can access during the game. During the game, meaning, after you've hit "play!" in the title scene.) I provide the ability to save progress and consequently load a particular game. An issue that I've run into is being able to easily keep track of the previous scene. For example, if you enter the load scene and then decide to change your mind, the game needs to go back to where you were before; this isn't something that can be hardcoded. Now, an easy solution off the top of my head is to simply maintain a scene stack, which basically keeps track of history for me. A simple transaction would be as follows I'm currently in the menu scene, so the top of the stack is SceneMenu I go to the load scene, so the game pushes SceneLoad onto the stack. When I return from the load scene, the game pops SceneLoad off the stack and initializes the scene that's currently at the top, which is SceneMenu I'm coding in Java, so I can't simply pass around Classes as if they were objects, so I've decided implemented as enum for eac scene and put that on the stack and then have my scene managing class go through a list of if conditions to return the appropriate instance of the class. How can I implement my scene stack without having to do too much work maintaining it?

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  • Very basic OpenGL ES 2 error

    - by user16547
    This is an incredibly simple shader, yet I'm having a lot of trouble understanding what's wrong with it. I'm trying to send a float to my fragment shader. Its purpose is to adjust the alpha of the fragment colour. Here is my fragment shader: precision mediump float; uniform sampler2D u_Texture; uniform float u_Alpha; varying vec2 v_TexCoordinate; void main() { gl_FragColor = texture2D(u_Texture, v_TexCoordinate); gl_FragColor.a *= u_Alpha; } and below is my rendering method. I get a 1282 (invalid operation) on the GLES20.glUniform1f(u_Alpha, alpha); line. alpha is 1 (but I tried other values as well) and transparent is true: public void render() { GLES20.glUseProgram(mProgram); if(transparent) { GLES20.glEnable(GLES20.GL_BLEND); GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA); GLES20.glUniform1f(u_Alpha, alpha); } Matrix.setIdentityM(mModelMatrix, 0); Matrix.rotateM(mModelMatrix, 0, angle, 0, 0, 1); Matrix.translateM(mModelMatrix, 0, x, y, z); Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0); GLES20.glUniformMatrix4fv(u_MVPMatrix, 1, false, mMVPMatrix, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[0]); GLES20.glVertexAttribPointer(a_Position, 3, GLES20.GL_FLOAT, false, 12, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[1]); GLES20.glVertexAttribPointer(a_TexCoordinate, 2, GLES20.GL_FLOAT, false, 8, 0); //snowTexture start GLES20.glActiveTexture(GLES20.GL_TEXTURE0); GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]); GLES20.glUniform1i(u_Texture, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, ibo[0]); GLES20.glDrawElements(GLES20.GL_TRIANGLE_STRIP, indices.capacity(), GLES20.GL_UNSIGNED_BYTE, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, 0); if(transparent) { GLES20.glDisable(GLES20.GL_BLEND); } GLES20.glUseProgram(0); }

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  • Efficient way of detecting a touched object in a game?

    - by Pin
    Imagine a Sims-like 2D game for a touch based mobile phone where one can interact with virtually any object in the scene. How can I efficiently detect which object is being touched by the player? In my short experience, looping through all the visible objects in the scene and checking if they're touched has so far done the job, but when there may be many many moving objects in the screen that sounds kind of inefficient isn't it? Keeping the visible moving objects list can consume time in itself as one may have to loop through all of them each frame. Other solutions I've thought are: Spatial hashing. Divide the screen as a grid and place the visible objects in the corresponding bucket. Detection of the clicked object is fast but there's additional overhead for placing the objects in the correct bucket each frame. Maintaining a quad-tree. Moving objects have to be rearranged all the time, the previous solution looks better. What is usually done in this case?

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  • Implement Fast Inverse Square Root in Javascript?

    - by BBz
    The Fast Inverse Square Root from Quake III seems to use a floating-point trick. As I understand, floating-point representation can have some different implementations. So is it possible to implement the Fast Inverse Square Root in Javascript? Would it return the same result? float Q_rsqrt(float number) { long i; float x2, y; const float threehalfs = 1.5F; x2 = number * 0.5F; y = number; i = * ( long * ) &y; i = 0x5f3759df - ( i >> 1 ); y = * ( float * ) &i; y = y * ( threehalfs - ( x2 * y * y ) ); return y; }

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  • What is a right datatype in C++ for OpenGL scene representation with use of GLSL

    - by Rarach
    I am programming in C++ OpenGl with GLSL. Until now I have been using a data structure that is composed of std::vector filled with structures of vertexes and with their parameters (position , normal, color ...) as a global variable for all the code. My question is, as I am using VBOs for drawing - is this a good approach to this problem? I am asking because I happen to have a lot of memory related trouble with this structure. I am trying to generate a terrain with a lot of vertices - more than 1 million. This seems to work, but as I refill the buffer I get memory related issues (crushes that occur, more or less randomly). So again the question is, is this a good data structure to use / and look for the faults in my code, or should I change to something else? Or what data structure would be advisable?

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  • GLSL, all in one or many shader programs?

    - by stjepano
    I am doing some 3D demos using OpenGL and I noticed that GLSL is somewhat "limited" (or is it just me?). Anyway I have many different types of materials. Some materials have ambient and diffuse color, some materials have ambient occlusion map, some have specular map and bump map etc. Is it better to support everything in one vertex/fragment shader pair or is it better to create many vertex/fragment shaders and select them based on currently selected material? What is the usual shader strategy in OpenGL or D3D?

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  • Creating new games on Android and/or iPhone

    - by James Clifton
    I have a succesfull facebook poker game that is running very nicely, now some people have asked if I can port this to other platforms - mainly mobile devices (and I have been asked to make a tablet version, do I really need a seperate version?) I am currently a PHP programmer (and game designer) and I simply dont' have the time to learn Android and other languages - so I have decided to pay third parties to program them (if viable). The information I need to know is what programming language is needed for the following four devices - Android mobile phone, iPhone, iPad and tablets? Can they all run off a central sql database? If they can't then i'm not interested :( Do any of these run FLASH? Have I covered all my main bases here? For example if a person programs for a ANDROID mobile phone is that to much differant to an ANDROID tablet? They will have slightly differant graphics (because the tablet has a greater screen area might as well use it) but do they need to be started from scratch? Same goes for iPhone/iPad, do they really need to be programmed differantly if the only differance is the graphics?

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  • 2D game big background images for maps

    - by WhiteCat
    Update: this question is general, not specific to Sprite Kit or a single language/platform. I'm toying with Sprite Kit with an idea to make a 2D side-scroller. Now the backgrounds for the maps are going to be hand-drawn and surely bigger than retina display, so the maps could span more than 1 screen in both axis. I imagine loading such a huge image could mean trouble and I don't plan to use tiling. I'm not sure how Sprite Kit splits images bigger than max texture size, if it does. I could split the images myself and use more sprites for each part of the background. What is the usual way to handle this?

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  • Using box2d DrawDebugData with multi layer scene ?

    - by Mr.Gando
    In my Game, a Scene is composed by several layers. Each layer has different camera transformations. This way I can have a layer at z=3 (GUI), z=2 (Monsters), z=1 (scrolling background), and this 3 layers compose my whole Scene. My render loop looks something like: renderLayer() applyTransformations() renderVisibleEntities() renderChildLayers() end If I call DrawDebugData() in the render loop, the whole b2world debug data will be rendered once for each layer in my scene, this generates a mess, because the "debug boxes" get duplicated, some of them get the camera transformations applied and some of them don't, etc. What I would like to do, would be to make DrawDebugData to draw only certain debug boxes. In that way, I could call something like b2world->DrawDebugDataForLayer(int layer_id) and call that on each layer like : renderLayer() applyTransformations() renderVisibleEntities() //Only render my corresponding layer debug data b2world->DrawDebugDataForLayer(layer_id) renderChildLayers() end Is there a way to subclass b2World so I could add this functionality ( specific to my game ) ? If not, what would be the best way to achieve this (Cocos2d uses a similar scene graph approach and box2d, but I'm not sure if debugDraw works in Cocos2d... ) Thanks

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  • Pathfinding with MicroPather : costs calculations with sectors and portals

    - by Adan
    Hello, I'm considering using micropather to help me with pathfinding. I'm not using a discrete map : I'm working in 2d with sectors and portales. However, I'm just wondering what is the best way to compute costs with this library in this context. Just to be more clear about geometrical shapes I'm using : sectors are basically convex polygons, and portals are segments that lies on sector's edge. Micropather exposes a pure virtual Graph class that you must inherate and overrides 3 functions. I understand how pathfinding works, so there's no problem in overriding those functions. Right now, my implementation give me results, i.e I'm able to find a path in my map, but I'm not sure I'm using an optimal solution. For the AdjacentCost method : I just take the distance between sector's centers as the cost. I think a better solution should be to use the portal between the two sectors, compute its center, and then the cost should be : distance( sector A center, portal center ) + distance ( sector B center, portal center ). I'm pretty sure the approximation I'm using with just sector's center is enough for most cases, but maybe with thin and long sectors that are perpendicular, this approximation could mislead the A* algorithm. For the LeastCostEstimate method : I just take the midpoint of the two sectors. So, as you understand, I'm always working with sectors' centers, and it's working fine. And I'm pretty sure there's a better way to work. Any suggestions or feedbacks? Thanks in advance!

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  • (Where) Can I learn creating art for my 2D games?

    - by Poorly paid coder
    I'm currently bad at drawing. If I want to create something looking acceptable, it usually takes me hours and hours to fiddle around just to get the basic looks right. I think that I'm not completely skill-less, I just lack simple drawing techniques.. Am I a hopeless case? Where is a good place to start out in drawing for 2D games? I'd like to be able to create acceptably good backgrounds, terrains / tilemaps, characters and weapons

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  • C# XNA Make rendered screen a texture2d

    - by redcodefinal
    I am working on a cool little city generator which makes cities in the isometric perspective. However, a problem arose where if the grid size was over a certain limit it would have awful lag. I found the main problem to be in the draw method. So I took the precautionary step of rendering only items that were onscreen. This fixed the lag but, not by much. The idea I have is to render the frame once and take a snapshot. Then, display that as a texture2d on screen. This way I don't have to render 1,000,000 objects every frame since they don't change anyways. TL;DR - I want to Take a snapshot of an already rendered frame Turn it into a Texture2D Render that to the screen instead of all the objects. Any help appreciated.

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  • Syncing properties across a game server

    - by Vaughan Hilts
    I'm beginning to implement a simple scripting system into my networked server, and I've hit a snag. Before, I've been wrapping my calls into functions on objects that manipulate objects, but lately I've been finding this to be a pain for simple things. For example, if I set 'player.HP = 1'.. this works server-side. But the player side never sees this change unless I explicitly send a packet to inform the client. For many things like map swapping that require more complicated changes, like change X, Y, Map and do this.. I have a function. That's fine. But what about these small properties I want to sync?

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  • "Time Control" in a 2d Platformer

    - by Woody Zantzinger
    I am making a 2d platformer where the player can press a button, and restart the level, only their previous character will also run the level at the same time, like they are traveling back in time. I know other games have done this before, and the way I have thought of doing it is to make the game character have a set of actions (Idle, Jumping, Walking Left etc.) and then detect changes in those actions and log them into a list along with the game time. So then when I need the character to run the level again on its own, I can just go through the list changing its actions at the right time. Is this the best way to do it? Does anyone have any experience in this? Thanks.

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  • Setting a leader from a sprite array

    - by Craig
    I'm looking to set a leader from an array of sprites, I keep on getting a NullReferenceException was unhandled error from within my main game class when calling the UpdateMouse Method. What have I dont wrong here? class MouseSprite { Random random = new Random(); private MouseSprite leader; public void UpdateBoundaryBox() { mouseBounds.X = (int)mousePosition.X - mouseTexture.Width / 2; mouseBounds.Y = (int)mousePosition.Y - mouseTexture.Height / 2; } public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; this.alive = true; mice[random.Next(0, mice.Length)] = leader;

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  • Entiity System with C++

    - by Dono
    I'm working on a game engine using the Entity System and I have some questions. How i see Entity System : Components : A class with attributs, set and get. Sprite Physicbody SpaceShip ... System : A class with a list of components. (Component logic) EntityManager Renderer Input Camera ... Entity : Just a empty class with a list of components. What i've done : Currently, i've got a program who allow me to do that : // Create a new entity/ Entity* entity = game.createEntity(); // Add some components. entity->addComponent( new TransformableComponent() ) ->setPosition( 15, 50 ) ->setRotation( 90 ) ->addComponent( new PhysicComponent() ) ->setMass( 70 ) ->addComponent( new SpriteComponent() ) ->setTexture( "name.png" ) ->addToSystem( new RendererSystem() ); My questions Did the system stock a list of components or a list of entities ? In the case where I stock a list of entities, I need to get the component of this entities on each frame, that's probably heavy isn't it ? Did the system stock a list of components or a list of entities ? In the case where I stock a list of entities, I need to get the component of this entities on each frame, that's probably heavy isn't it ?

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  • Extracting Frustum Planes (Hartmann & Gribbs method)

    - by DAVco
    I have been grappling with the Hartmann/Gribbs method of extracting the Frustum planes for some time now, with little success. There doesn't appear to be a "definitive" topic or tutorial which combines all the necessary information, so perhaps this can be it First of all, I am attempting to do this in C# (For Playstation Mobile), using OpenGL style Column-Major matrices in a Right-Handed coordinate system but obviously the math will work in any language. My projection matrix has a Near plane at 1.0, Far plane at 1000, FOV of 45.0 and Aspect of 1.7647. I want to get my planes in World-Space, so I build my frustum from the View-Projection Matrix (that's projectionMatrix * viewMatrix). The view Matrix is the inverse of the camera's World-Transform. The problem is; regardless of what I tweak, I can't seem to get a correct frustum. I think that I may be missing something obvious. Focusing on the Near and Far planes for the moment (since they have the most obvious normals when correct), when my camera is positioned looking down the negative z-axis, I get two planes facing in the same direction, rather than opposite directions. If i strafe my camera left and right (while still looking along the z axis) the x value of the normal vector changes. Obviously, something is fundamentally wrong here; I just can't figure out what - maybe someone here can?

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  • how to keep display tick rate steady when using continuous collision detection?

    - by nas Ns
    (I've just found about this forum). I hope it is ok to repost my question again here. I posted this question at stackoverflow, but it looks like I might get better help here. Here is the question: I've implemented basic particles motion simulation with continuous collision detection. But there is small issue in display. Assume simple case of circles moving inside square. All elastic collisions. no firction. All motion is constant speed. No forces are involved, no gravity. So when a particle is moving, it is always moving at constant speed (in between collisions) What I do now is this: Let the simulation time step be 1 second (for example). This is the time step simulation is advanced before displaying the new state (unless there is a collision sooner than this). At start of each time step, time for the next collision between any particles or a particle with a wall is determined. Call this the TOC time; let’s say TOC was .5 seconds in this case. Since TOC is smaller than the standard time step, then the system is moved by TOC and the new system is displayed so that the new display shows any collisions as just taking place (say 2 circles just touched each other’s, or a circle just touched a wall) Next, the collision(s) are resolved (i.e. speeds updated, changed directions etc..). A new step is started. The same thing happens. Now assume there is no collision detected within the next 1 second (those 2 circles above will not be in collision any more, even though they are still touching, due to their speeds showing they are moving apart now), Hence, simulation time is advanced now by the full one second, the standard time step, and particles are moved on the screen using 1 second simulation time and new display is shown. You see what has just happened: One frame ran for .5 seconds, but the next frame runs for 1 second, may be the 3rd frame is displayed after 2 seconds, may be the 4th frame is displayed after 2.8 seconds (because TOC was .8 seconds then) and so on. What happens is that the motion of a particle on the screen appears to speed up or slow down, even though it is moving at constant speed and was not even involved in a collision. i.e. Looking at one particle on its own, I see it suddenly speeding up or slowing down, becuase another particle had hit a wall. This is because the display tick is not uniform. i.e. the frame rate update is changing, giving the false illusion that a particle is moving at non-constant speed while in fact it is moving at constant speed. The motion on the screen is not smooth, since the screen is not updating at constant rate. I am not able to figure how to fix this. If I want to show 2 particles at the moment of the collision, I must draw the screen at different times. Drawing the screen always at the same tick interval, results in seeing 2 particles before the collision, and then after the collision, and not just when they colliding, which looked bad when I tried it. So, how do real games handle this issue? How to display things in order to show collisions when it happen, yet keep the display tick constant? These 2 requirements seem to contradict each other’s.

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