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• applyAngularVelocity causes error when called right after object instantiation

  - by Appeltaart

  I'm trying to make a physicsBody rotate as soon as it is instantiated. CCNode* ball = [CCBReader load:@"Ball"]; [ball.physicsBody applyForce:force]; [ball.physicsBody applyAngularImpulse:arc4random_uniform(360) - 180]; Applying force works fine, the last line however throws an error in cpBody.c line 123: cpAssertHard(body->w == body->w && cpfabs(body->w) != INFINITY, "Body's angular velocity is invalid."); When I don't apply force and merely rotate the problem persists. If I send applyAngularImpulse at some later point (in this case on a touch) it does work. Is this function not supposed to be called right after instantiation, or is this a bug?

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• Corona sdk events dispatched with dispatchEvent() are handled directly upon call. Why so?

  - by Amoxus

  I noticed to my surprise that an event created with dispatchEvent(event) gets handled directly when called, and not together with other events at a specific phase of the frame loop. Two main reasons of having an event system are: so that you can call code B from code A, but still want to prioritize code A. to make sure there are no freaky loopedy loops where code A calls code B calls code A ... I wonder what Ansca's rationale behind having events being handled directly this way is. And does Corona handle loopedy loops and other such pitfalls gracefully? The following code demonstrates dispatchEvent(): T= {} Z = display.newRect(100,100,100,100) function T.doSomething() print("T.doSomething: begun") local event = { name="myEventType", target=T } Z:dispatchEvent( event ) print("T.doSomething: ended") end function Z.sayHello(event) print("Z.sayHello: begun and ended") end Z:addEventListener("myEventType", Z.sayHello) print("Main: begun") T.doSomething() print("Main: ended") However Ansca claims the contrary at http://developer.coronalabs.com/reference/index/objectdispatchevent Can anyone clear this up a little? ( Using Corona simulator V 2012.840 )

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• a flexible data structure for geometries

  - by AkiRoss

  What data structure would you use to represent meshes that are to be altered (e.g. adding or removing new faces, vertices and edges), and that have to be "studied" in different ways (e.g. finding all the triangles intersecting a certain ray, or finding all the triangles "visible" from a given point in the space)? I need to consider multiple aspects of the mesh: their geometry, their topology and spatial information. The meshes are rather big, say 500k triangles, so I am going to use the GPU when computations are heavy. I tried using arrays with vertices and arrays with indices, but I do not love adding and removing vertices from them. Also, using arrays totally ignore spatial and topological information, which I may need studying the mesh. So, I thought about using custom double-linked list data structures, but I believe doing so will require me to copy the data to array buffers before going on the GPU. I also thought about using BST, but not sure it fits. Any help is appreciated. If I have been too fuzzy and you require other information feel free to ask.

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• Any way to edit Warcraft MDX or MDL Animated models?

  - by Aralox

  I have been searching for a while for a way to get an animated mdl or mdx model into any 3D animating software (such as Blender), but so far have not had any success. I found a few methods of getting textured static mdx or mdl models into Blender/Milkshape/Hexagon, but no one seems to have written an importer that deals with the mdl/mdx model's keyframe animation. On that note, if anyone knows of a way of importing a keyframe-animated 3DS model into Blender, me and alot of people would appreciate it if you could let us know. Thanks for any help! :) PS: For anyone curious about static MDL or MDX - Blender, see here: http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Import-Export/WarCraft_MDL

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• OpenGL ES multiple objects not being rendered

  - by ladiesMan217

  I am doing the following to render multiple balls move around the screen but only 1 ball is seen to appear and function. I don't know why the rest (count-1) balls are not being drawn public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glDisable(GL10.GL_DITHER); gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glClientActiveTexture(DRAWING_CACHE_QUALITY_HIGH); gl.glLoadIdentity(); for(int i=0;i<mParticleSystem.getParticleCount();i++){ gl.glPushMatrix(); gl.glTranslatef(mParticleSystem.getPosX(i), mParticleSystem.getPosY(i), -3.0f); gl.glScalef(0.3f, 0.3f, 0.3f); gl.glColor4f(r.nextFloat(), r.nextFloat(), r.nextFloat(), 1); gl.glEnable(GL10.GL_TEXTURE_2D); mParticleSystem.getBall(i).draw(gl); gl.glPopMatrix(); } } Here is my void draw(GL10 gl) method public void draw(GL10 gl){ gl.glEnable(GL10.GL_CULL_FACE); gl.glEnable(GL10.GL_SMOOTH); gl.glEnable(GL10.GL_DEPTH_TEST); // gl.glTranslatef(0.2f, 0.2f, -3.0f); // gl.glScalef(size, size, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); }

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• LibGDX - SpriteBatch's .draw() method requiring float[]

  - by just_a_programmer

  Please excuse my lack of knowledge with LibGDX, as I have just started learning it. I am going through some simple tutorials, and in one of them, I draw a string onto the screen like so: // the following code is in the main file in the core project folder: // this is in the create() method: private SpriteBatch batch; batch = new SpriteBatch(); // this is in the render() method: batch.draw(batch, "Hello world", 200, 200); I am getting an error saying: The method draw(texture, float[], int, int) in the type SpriteBatch is not applicable for the arguments (SpriteBatch, int, int) So, LibGDX wants a float array to draw instead of a string? Thanks in advance.

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• How should I choose quadtree depth?

  - by Evpok

  I'm using a quadtree to prune collision detection pairs in a 2d world. How should I choose to what depth said quadtree is calculated? The world is made mostly of moving objects1, so the cost of dispatching the objects between the quadtree cells matters. What is the relationship between the gain from less collision checking and the loss from more dispatching? How can I strike a balance that performs optimally? 1 To be completely explicit, they are autonomous self-replicating cells competing for food sources. This is an attempt to show my pupils predator-prey dynamics and genetic evolution at work.

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• A way to store potentially infinite 2D map data?

  - by Blam

  I have a 2D platformer that currently can handle chunks with 100 by 100 tiles, with the chunk coordinates are stored as longs, so this is the only limit of maps (maxlong*maxlong). All entity positions etc etc are chunk relevant and so there is no limit there. The problem I'm having is how to store and access these chunks without having thousands of files. Any ideas for a preferably quick & low HD cost archive format that doesn't need to open everything at once?

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• Simple 2D Flight Physics with Box2D

  - by MarkPowell

  I'm trying to build a simple side scroller with an airplane being the player. As such, I want to build simple flight controls with simple but realistic-feeling physics. I'm making use of cocos2D and Box2D. I have a basic system working, but just can't get the physics feeling correct. I am applying force to the plane (which is a b2CircleShape) based on the user's input. So, basically, if the user pushes up, body_->ApplyForce(b2Vec2(10,30), body_->GetPosition()) is called. Similarly, for down -30 is used. This works and the plane flys along with up/down causing it to dive or climb. But it just doesn't feel right. There is no slowdown on climbs, nor speed up during dives. My simple solution is far to simple. How can I get a better feel for a plane climbing/diving? Thanks!

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• Marching squares: Finding multiple contours within one source field?

  - by TravisG

  Principally, this is a follow-up-question to a problem from a few weeks ago, even though this is about the algorithm in general without application to my actual problem. The algorithm basically searches through all lines in the picture, starting from the top left of it, until it finds a pixel that is a border. In pseudo-C++: int start = 0; for(int i=0; i<amount_of_pixels; ++i) { if(pixels[i] == border) { start = i; break; } } When it finds one, it starts the marching squares algorithm and finds the contour to whatever object the pixel belongs to. Let's say I have something like this: Where everything except the color white is a border. And have found the contour points of the first blob: For the general algorithm it's over. It found a contour and has done its job. How can I move on to the other two blobs to find their contours as well?

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• OpenGL Lighting

  - by gopgop

  I have a simple day and night cycle by at day disabling OpenGL lighting and at night enabling openGL Lighting. When I enable everything appears darker. My question is How would I make it that at a specific spot there would be a light that will only light up its surrounding area for example: http://media.giantbomb.com/uploads/0/276/1414275-light_large.png Where the light is is where I want to position my light. My application is in 2D.

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• Edge flicker when moving Camera (2D)

  - by Matthias Reisner

  I have a Orthographic camera. I have a fixed landscape texture and a texture for a moveable object. If the object moves to the right the camera will also move with the object. When I also draw an score text that should have fixed position on the screen, that score text position will be update too if the camera's position gets updated so that it looks like that it is fixed on the screen. But if I do that, I have some edge flickering at the text object. I'am using SpriteBatch! Is there another approach to implement a fixed positioned object on the screen?

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• Why doesn't light continuous on my model?

  - by nosferat

  I created a basic textured cube model with Blender to practice modeling, and then I imported it into Unity. After I put up some lighting it looks pretty ugly. The light is not continuous on a row of textured cubes: What is more odd, the light on the blocks that makes up the floor is continuous. What am I doing wrong? UPDATE This is how it looks like without textures: https://dl.dropbox.com/u/45620018/without%20textures.PNG If I would not know that these are perfect cubes, I'd say there is a slight curve on surface. I also tried lightening the texture but it also didn't help: https://dl.dropbox.com/u/45620018/lighter%20texture.PNG I just simply exported the model from Blender and did not set up any normals or things like that. However I also did not do any special woth the floor brick model.

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• OpenGL doesn't draw (3.3+) [on hold]

  - by Dhiego Magalhães

  Brief: I've been following this tutorial about OpenGL for 2 days, and I still can't have a triangle drawn, so I'm asking for help here. The tutorial is turned to OpenGL version 3.3 programing, using vertex arrays, buffers, etc. The libraries are: GLFW3 and GLEW, and I setted them by myself. The screen keeps black all the time. Full code: link here (It's just like a Hello World opengl program) Further Details: I get no errors at all. I downloaded a software to test my video card, and it supports OpenGL 4.1+ Standard OpenGL code for drawing (from earlier version) such as this one works normally. I'm using Microsoft Visual Studio 10.0 I presume all the OpenGL implementation was dune right: I added Additional Dependences to the linker as glew32.lib, opengl32.lib, glfw3.lib. The glew.dll was placed at SysWOW64 - because I'm running window 64bits, and glew is 32. Notes: I've been working hard to find out what this is, but I can't find. I would appreciate if anyone could test this code for me, so I can know if I implemented something wrong, and that its not my code.

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• Drawing flaming letters in 3d on OpenGL ES 2.0

  - by Chiquis

  I am a bit confused about how to achieve this. What i want is to "draw with flames". I have achieved this with textures successfully, but now my concern is about doing this with particles to achieve the flaming effect. Am I supposed to have a Path in where i should add many particle emitters along the path that will "be emitting flames"? I understand the concept for 2d, but for 3d are the particles (that are quads) always supposed to be facing the user? Edit: Something else im worried about is the performance hit that will occur by having that many particle emitters, because there can be many letters and drawings at the same time. And each of these elements will have many particle emitters.

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• how to use string::find to look for a word rather each character seperately

  - by RubyKing

  Hello how would I look through a string for a word rather then each character in that word. I have my code here and it always seems to find everything that is .obj even if its o or b or j or "." is there anyway to get passed this here is my code? I checked the docuementation here link but nothing returned any results I craved so hard string &str = *it; if(it->find(".obj")) { cout << "Found .Obj" << endl; } I also tried to use string::compare but that failed :(

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• Set Position of multiple bodies

  - by philipp

  I have a character composed of five bodies which are tied together by a lot of joints. On of them is the overall chassis, to which all forces and impulses are applied to move the whole Character. All in all that works very fine, except one thing: I need to set the Position of the Character so that it get Beamed from one place to the other in one single frame. Unfortunately I cannot get this to work. I tried the following code, without any success… playerbodies.forEach(function (bd) { bd.SetLinearVelocity(new b2.Vec2()); var t = bd.GetTransform(); t.p.x -= 10; bd.SetTransform(t, bd.GetAngle()); }); How can I make that happen?

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• Memory allocation strategy for the vertex buffers (DirectX 10/11)

  - by Alex

  I have the following question. I write CAD system. So I have a 3D scene and there are many different objects (walls, doors, windows and so on). User can add or delete some objects. The question is: how can I organise the keeping of vertices for all my objects. I can create vertex buffer for every object. But I think drawing/switching from one buffer to another would have performance penalty. Another way - I can create several big buffers for every object type. But I don't understand how to update such buffers. It is too big to update whole buffer (for example buffer for all walls). What I need to do if I want to delete the object from the middle of the buffer? Actually I have the similar question: http://stackoverflow.com/questions/5515700/how-to-properly-update-vertex-buffers-in-directx-10 Most examples I've found work with very static models. Therefore, they tend to create a single vertex buffer with their list of points, and then are just manipulated by matrix transformations. I, on the other hand, will be updating the scene very often.

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• Recommended formats to store bitmaps in memory?

  - by Geotarget

  I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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• why specular light is not running?

  - by nkint

  hi, i'm on JOGL this is my method for lighting: private void lights(GL gl) { float[] LightPos = {0.0f, 0.0f, -1.0f, 1.0f}; float[] LightAmb = {0.2f, 0.2f, 0.2f, 1.0f}; float[] LightDif = {0.6f, 0.6f, 0.6f, 1.0f}; float[] LightSpc = {0.9f, 0.9f, 0.9f, 1.0f}; gl.glLightfv(GL.GL_LIGHT1, GL.GL_POSITION, LightPos, 0); gl.glLightfv(GL.GL_LIGHT1, GL.GL_AMBIENT, LightAmb, 0); gl.glLightfv(GL.GL_LIGHT1, GL.GL_DIFFUSE, LightDif, 0); gl.glLightfv(GL.GL_LIGHT1, GL.GL_SPECULAR, LightSpc, 0); gl.glLightfv(GL.GL_LIGHT0, GL.GL_SPECULAR, LightSpc, 0); gl.glEnable(GL.GL_LIGHT0); gl.glEnable(GL.GL_LIGHT1); gl.glShadeModel(GL.GL_SMOOTH); gl.glEnable(GL.GL_LIGHTING); } and i see my objects flat, no specular light.. any ideas? ps. to render my objects: gl.glColor3f(1f,0f,0f); gl.glBegin(GL.GL_TRIANGLES); for(Triangle t : tubeModel.getTriangles()) { gl.glVertex3f(t.v1.x, t.v1.y, t.v1.z); gl.glVertex3f(t.v2.x, t.v2.y, t.v2.z); gl.glVertex3f(t.v3.x, t.v3.y, t.v3.z); } gl.glEnd();

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• Point line collision reaction

  - by user4523

  I am trying to program point line segment collision detection and reaction. I am doing this for fun and to learn. The point moves (it has a velocity, and can be controlled by the user), whilst the lines are strait and stationary. The lines are not axis aligned. Everything is in 2D. It is quite straight forward to work out if a collision has occurred. For each frame, the point moves from A to B. AB is a line, and if it crosses the line segment, a collision has occurred (or will occur) and I am able to work out the point of intersection (poi). The problem I am having is with the reaction. Ideally I would like the point to be prevented from moving across the line. In one frame, I can move the point back to the poi (or only alow it to move as far as the poi), and alter the velocity. The problem I am having with this approach (I think) is that, next frame the user may try to cross the line again. Although the point is on the poi, the point may not be exactly on the line. Since it is not axis aligned, I think there is always some subtle rounding issue (A float representation of a point on a line might be rounded to a point that is slightly on one side or the other). Because of this, next frame the path might not intersect the line (because it can start on the other side and move away from it) and the point is effectively allowed to cross the line. Firstly, does the analysis sound correct? Having accepted (maybe) that I cannot always exactly position the point on the line, I tried to move the point away from the line slightly (either along the normal to the line, or along the path vector). I then get a problem at edges. Attempting to fix one collision by moving the point away from the line (even slightly) can cause it to cross another line (one shape I am dealing with is a star, with sharp corners). This can mean that the solution to one collision inadvertently creates another collision, which is ignored. Again, does this sound correct? Anyway, whatever I try, I am having difficulty with edges, and the point is occasionally able to penetrate the polygons and cross lines, which is undesirable. Whilst I can find a lot of information about collision detection on the web (and on this site) I can find precious little information on collision reaction. Does any one know of any good point line collision reaction tutorials? Or is my approach too flawed/over complicated?

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• Best approach to get clicked objects from a display list (2D)

  - by Ixx

  I'm implementing a display list to manage my visuals on screen. I want to know which object is clicked. My objects already have z-order variable. With my current knowledge (almost nothing) the only thing which comes to my mind is make a linear search and get all the objects which contains the clicked point. And then select the object with the highest z-order. But I know there are far better approaches. I think it's something with trees (binary search?). - container display objects and search recursively? just don't know where to start looking, for this concrete case. Any hint link or concrete solution is welcome.

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• How to apply Data Oriented Design with Object Oriented Programming?

  - by Pombal

  Hi. I've read lots of articles about DOD and I understand it but I can't design an Object Oriented system with DOD in mind, I think my OOP education is blocking me. How should I think to mix the two? The objective is to have a nice OO interface while using DOD behind the scenes. I saw this too but didn't help much: http://stackoverflow.com/questions/3872354/how-to-apply-dop-and-keep-a-nice-user-interface

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• how to organize rendering

  - by Irbis

  I use a deferred rendering. During g-buffer stage my rendering loop for a sponza model (obj format) looks like this: int i = 0; int sum = 0; map<string, mtlItem *>::const_iterator itrEnd = mtl.getIteratorEnd(); for(map<string, mtlItem *>::const_iterator itr = mtl.getIteratorBegin(); itr != itrEnd; ++itr) { glActiveTexture(GL_TEXTURE0 + 0); glBindTexture(GL_TEXTURE_2D, itr->second->map_KdId); glDrawElements(GL_TRIANGLES, indicesCount[i], GL_UNSIGNED_INT, (GLvoid*)(sum * 4)); sum += indicesCount[i]; ++i; glBindTexture(GL_TEXTURE_2D, 0); } I sorted faces based on materials. I switch only a diffuse texture but I can place there more material properties. Is it a good approach ? I also wonder how to handle a different kind of materials, for example: some material use a normal map, other doesn't use. Should I have a different shaders for them ?

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• Speed up content loading

  - by user1806687

  I am using WinForms Sample downloaded from microsoft website. The problem is, that the model loading time is quite long, using: contentBuilder.Add(ModelPath, ModelName, null, "ModelProcessor"); contentManager.Load<Model>(ModelName); even a simple model, such as a cube with no textures, takes 4+ seconds to load. Now, I am no expert on this, but is there anyway to decrease loading time? EDIT: I've gone thru the code and found out that calling contentBuilder.Build(); ,which comes right after contentBuilder.Add() method takes up most of the time.

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