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• How can I achieve strong typing with a component messaging system?

  - by Vaughan Hilts

  I'm looking at implementing a messaging system in my entity component system. I've deduced that I can use an event / queue for passing messages, but right now, I just use a generic object and cast out the data I want. I also considered using a dictionary. I see a lot of information on this, but they all involve a lot of casting and guessing. Is there any way to do this elegantly and keep strong typing on my messages?

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• Which opcodes are faster at the CPU level?

  - by Geotarget

  In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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• Frame timing for GLFW versus GLUT

  - by linello

  I need a library which ensures me that the timing between frames are more constant as possible during an experiment of visual psychophics. This is usually done synchronizing the refresh rate of the screen with the main loop. For example if my monitor runs at 60Hz I would like to specify that frequency to my framework. For example if my gameloop is the following void gameloop() { // do some computation printDeltaT(); Flip buffers } I would like to have printed a constant time interval. Is it possible with GLFW?

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• How do I simulate the mouse and keyboard using C# or C++?

  - by Art

  I want to start develop for Kinect, but hardest theme for it - how to send keyboard and mouse input to any application. In previous question I got an advice to develop my own driver for this devices, but this will take a while. I imagine application like a gate, that can translate SendMessage's into system wide input or driver application with API to send this inputs. So I wonder, is there are drivers or simulators that can interact with C# or C++? Small edition: SendMessage, PostMessage, keybd_event will work only on Windows application with common messages loop. So I need driver application that will work on low, kernel, level.

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• Rotate 3D Model from a custom position

  - by Nipuna Silva

  I have a 3D Model like above in which i want to rotate it from a given location(pointed in red) but I can only rotate it from the middle. How can I rotate it from a custom point. Edit: I successfully able to rotate the model from the below position by getting the radius of the model and applying it to the world matrix Vector3 point = new Vector3(-radius, 0, 0); world = Matrix.CreateTranslation(-radius, 0, 0); But now I cannot change the position of the object and it always centered in middle of the screen. I think that's because i applied the above code. How can I place it anywhere I want?

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• Simple project - make a 3D box tumble and fall to the ground [closed]

  - by Dominic Bou-Samra

  Possible Duplicate: Resources to learn programming rigid body simulation Hi guys, I want to try learning rigid-body dynamic simulation. I have done a fluid and cloth simulation before, but never anything rigid. My maths knowledge is limited in that I don't know the notation that well. Are there any good cliff-notes, tutorials, guides on how I would accomplish a simple task like this? I don't want a super complex pdf that's only a little relevant. Thanks.

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• How do I render only part of a texture to a point sprite in OpenGL ES for Android?

  - by nbolton

  Using the libgdx framework, I've figured out how to render a texture to a point sprite. The problem is, it renders the entire texture to the point sprite, where I only want a small part of it (since it's an isometric tile image). Here's a snippet from some demo code I wrote... create() { renderer = new ImmediateModeRenderer(); tiles = Gdx.graphics.newTexture( Gdx.files.internal("data/tiles2.png"), TextureFilter.MipMap, TextureFilter.Linear, TextureWrap.ClampToEdge, TextureWrap.ClampToEdge); Gdx.gl.glClearColor(0.6f, 0.7f, 0.9f, 1); Gdx.gl.glEnable(GL10.GL_TEXTURE_2D); Gdx.gl.glEnable(GL11.GL_POINT_SPRITE_OES); Gdx.gl11.glTexEnvi( GL11.GL_POINT_SPRITE_OES, GL11.GL_COORD_REPLACE_OES, GL11.GL_TRUE); Gdx.gl10.glPointSize(s); tiles.bind(); } render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); renderer.begin(GL10.GL_POINTS); // render 3 point sprites at various 3d points renderer.vertex(-.1f, 0, -.1f); renderer.vertex(0, 0, 0); renderer.vertex(.1f, 0, .1f); // ... more vertices here if needed (one for each sprite) ... renderer.end(); }

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• error trying to display semi transparent rectangle

  - by scott lafoy

  I am trying to draw a semi transparent rectangle and I keep getting an error when setting the textures data. The size of the data passed in is too large or too small for this resource. dummyRectangle = new Rectangle(0, 0, 8, 8); Byte transparency_amount = 100; //0 transparent; 255 opaque dummyTexture = new Texture2D(ScreenManager.GraphicsDevice, 8, 8); Color[] c = new Color[1]; c[0] = Color.FromNonPremultiplied(255, 255, 255, transparency_amount); dummyTexture.SetData<Color>(0, dummyRectangle, c, 0, 1); the error is on the SetData line: "The size of the data passed in is too large or too small for this resource." Any help would be appreciated. Thank you.

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• Inverse projection: question about w coordinate

  - by fayeWilly

  I have to perform in shader an inverse projection from a u/v of a render target. What I do is: Get NDC as 2*(u,v,depth) - 1 Then world space as tmp = (P*V)^-1 * (NDC,1.0); world space = tmp/tmp.w; This apparently works, but I am confused about the w division there. Why this work? Shouldn't be a multiplication by a w somewhere (as in the "forward" pipeline there is the perpsective division?) Thank you, Faye

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• Slick 2d scrolling off screen

  - by Peter

  I have something scrolling in and out of the screen. Now when it goes off screen, I want it to scroll into the screen at another location. What I do is I grab the last pixels at the screens edge using g.copyArea and then g.drawImage on the edge of the screen. And then I do a g.translate to create room for the next row which is next render cycle. My problem is that I get a single pixel row, which is not copied onto the canvas. Where as I want each row to be added and then translated, so that the image that scrolled off screen is recreated on the other side of the screen. Here is my code, maybe there is a better way of doing this, open to any suggests, cause I'm totally stuck @Override public void render(GameContainer gc, Graphics g) throws SlickException { //g.setClip(0, 0, 300, gc.getHeight()); g.translate(0, y); g.drawImage(image,0,200); g.resetTransform(); //g.clearClip(); g.copyArea(rightImage, 0, gc.getHeight() - 1); g.drawImage(rightImage, 300, 0); g.translate(0, y); y=y+3; }

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• libgdx arrays onTouch() method and delays for objects

  - by johnny-b

  i am trying to create random bullets but it is not working for some reason. also how can i make a delay so the bullets come every 30 seconds or 1 minute???? also the onTouch method does not work and it is not taking the bullet away???? shall i put the array in the GameRender class? thanks public class GameWorld { public static Ball ball; private Bullet bullet1; private ScrollHandler scroller; private Array<Bullet> bullets = new Array<Bullet>(); public GameWorld() { ball = new Ball(280, 273, 32, 32); bullet = new Bullet(-300, 200); scroller = new ScrollHandler(0); bullets.add(new Bullet(bullet.getX(), bullet.getY())); bullets = new Array<Bullet>(); Bullet bullet = null; float bulletX = 0.0f; float bulletY = 0.0f; for (int i=0; i < 10; i++) { bulletX = MathUtils.random(-10, 10); bulletY = MathUtils.random(-10, 10); bullet = new Bullet(bulletX, bulletY); bullets.add(bullet); } } public void update(float delta) { ball.update(delta); bullet.update(delta); scroller.update(delta); } public static Ball getBall() { return ball; } public ScrollHandler getScroller() { return scroller; } public Bullet getBullet1() { return bullet1; } } i also tried this and it is not working, i used this in the GameRender class Array<Bullet> enemies=new Array<Bullet>(); //in the constructor of the class enemies.add(new Bullet(bullet.getX(), bullet.getY())); // this throws an exception for some reason??? this is in the render method for(int i=0; i<bullet.size; i++) bullet.get(i).draw(batcher); //this i am using in any method that will allow me from the constructor to update to render for(int i=0; i<bullet.size; i++) bullet.get(i).update(delta); this is not taking the bullet out @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { for(int i=0; i<bullet.size; i++) if(bullet.get(i).getBounds().contains(screenX,screenY)) bullet.removeIndex(i--); return false; } thanks for the help anyone.

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• How does a BSP tree work for Z sorting?

  - by Jenko

  I'm developing a 3D engine in software, and so I must compute Z sorting manually. I'm currently using the painters algorithm to sort triangles and then drawing them back-to-front. This causes artifacts that I'm trying to correct. Would using a dynamic BSP-tree ensure "correct Z sorting" of triangles? Why? Because the bounding volumes of triangles would be similar? Since I would have a single "world" BSP tree, would I have to remove and re-add any moved/scaled/rotated object into the tree? Is it possible to add triangles into a BSP tree without the expensive cutting process? Why do you need to cut triangles on the axis planes anyway? Is it faster to traverse a BSP tree from any angle, than to sort all tris each draw like the painters algorithm?

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• cocos2d event handler not fired when reentering scene

  - by Adam Freund

  I am encountering a very strange problem with my cocos2d app. I add a sprite to the page and have an event handler linked to it which replaces the scene with another scene. On that page I have another button to take me back to the original scene. When I am back on the original scene, the eventHandler doesn't get fired when I click on the sprite. Below is the relevant code. Thanks for any help! CCMenuItemImage *backBtnImg = [CCMenuItemImage itemWithNormalImage:@"btn_back.png" selectedImage:@"btn_back_pressed.png" target:self selector:@selector(backButtonTapped:)]; backBtnImg.position = ccp(45, 286); CCMenu *backBtn = [CCMenu menuWithItems:backBtnImg, nil]; backBtn.position = CGPointZero; [self addChild:backBtn]; EventHandler method (doesn't get called when the scene is re-entered). (void)backButtonTapped:(id)sender { NSLog(@"backButtonTapped\n"); CCMenuItemImage *backButton = (CCMenuItemImage *)sender; [backButton setNormalImage:[CCSprite spriteWithFile:@"btn_back_pressed.png"]]; [[CCDirector sharedDirector] replaceScene:[CCTransitionFade transitionWithDuration:.25 scene:[MenuView scene] withColor:ccBLACK]]; }

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• Who should map physical keys to abstract keys?

  - by Paul Manta

  How do you bridge the gap between the library's low-level event system and your engine's high-level event system? (I'm not necessarily talking about key events, but also about quit events.) At the top level of my event system, I send out KeyPressedEvents, KeyRelesedEvents and others of this kind. These high-level events only contain the abstract values of the keys (they don't say that Space way pressed, but that the JumpKey was pressed, for example). Whose responsibility should it be to map the "JumpKey" to an actual key on the keyboard?

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• Rotation and translation like in GTA 1 OpenGL

  - by user1876377

  Okay, so I have a figure in XZ plain. I want to move it forward/backward and rotate at it's own Y axis, then move forward again in the rotation's direction, like the character in GTA 1. Code so far: Init: spaceship_position = glm::vec3(0,0,0); spaceship_rotation = glm::vec3(0,0,0); spaceship_scale = glm::vec3(1, 1, 1); Draw: glm::mat4 transform = glm::scale<float>(spaceship_scale) * glm::rotate<float>(spaceship_rotation.x, 1, 0, 0) * glm::rotate<float>(spaceship_rotation.y, 0, 1, 0) * glm::rotate<float>(spaceship_rotation.z, 0, 0, 1) * glm::translate<float>(spaceship_position); drawMesh(spaceship, texture, transform); Update: switch (key.keysym.sym) { case SDLK_UP: spaceship_position.z += 0.1; break; case SDLK_DOWN: spaceship_position.z -= 0.1; break; case SDLK_LEFT: spaceship_rotation.y += 1; break; case SDLK_RIGHT: spaceship_rotation.y -= 1; break; } So this only moves on the Z axis, but how can I move the object on both Z and X axis where the object is facing?

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• libgdx actors and instant actions

  - by vaati

  I'm having trouble with actors and actions. I have a list of actors, they all have either no action, or 1 sequence action This sequence action has either : a couple of actions (some are instant, some have duration 0) a couple of actions followed by a parallel action. My problem is the following: some of the instant actions are used to set the position and the alpha of the actor. So when one of the action is "move to x,y and set alpha to 0" the actor is visible for one frame at position 0,0 , move instantly to x,y for the next frame, and then disappears. Though this behaviours is to be expected, I want to avoid it. How can I achieve that? I tried to intercept the actions before I put actors in the stage but I need the stage width/height for some actions. So something like : Action actionSequence = actor.getActions().get(0); Array<Action> actions = ((SequenceAction) actionSequence).getActions(); for(Action act : actions){ if(act.act(0)) System.out.println("action " + act.toString() + " successfully run"); else System.out.println("action " + act.toString() + " wasn't instant"); } won't work. It gets even more complicated when an actor can also have a repeat action in stead of the sequence action (because you have to only run the actions that have duration 0 once without repeat, and then start the repeat). Any help is appreciated.

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• Managing constant buffers without FX interface

  - by xcrypt

  I am aware that there is a sample on working without FX in the samplebrowser, and I already checked that one. However, some questions arise: In the sample: D3DXMATRIXA16 mWorldViewProj; D3DXMATRIXA16 mWorld; D3DXMATRIXA16 mView; D3DXMATRIXA16 mProj; mWorld = g_World; mView = g_View; mProj = g_Projection; mWorldViewProj = mWorld * mView * mProj; VS_CONSTANT_BUFFER* pConstData; g_pConstantBuffer10->Map( D3D10_MAP_WRITE_DISCARD, NULL, ( void** )&pConstData ); pConstData->mWorldViewProj = mWorldViewProj; pConstData->fTime = fBoundedTime; g_pConstantBuffer10->Unmap(); They are copying their D3DXMATRIX'es to D3DXMATRIXA16. Checked on msdn, these new matrices are 16 byte aligned and optimised for intel pentium 4. So as my first question: 1) Is it necessary to copy matrices to D3DXMATRIXA16 before sending them to the constant buffer? And if no, why don't we just use D3DXMATRIXA16 all the time? I have another question about managing multiple constant buffers within one shader. Suppose that, within your shader, you have multiple constant buffers that need to be updated at different times: cbuffer cbNeverChanges { matrix View; }; cbuffer cbChangeOnResize { matrix Projection; }; cbuffer cbChangesEveryFrame { matrix World; float4 vMeshColor; }; Then how would I set these buffers all at different times? g_pd3dDevice->VSSetConstantBuffers( 0, 1, &g_pConstantBuffer10 ); gives me the possibility to set multiple buffers, but that is within one call. 2) Is that okay even if my constant buffers are updated at different times? And do I suppose I have to make sure the constantbuffers are in the same position in the array as the order they appear in the shader?

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• 2D shader to draw representation of rotating sphere.

  - by TheBigO

  I want to display a 3D textured sphere, and then rotate it in one direction. The direction will never change, and the camera will never move. One way is to actually create a spherical mesh, map a texture to it, rotate the sphere, and render in 3D. My question is, is there a way to display a 2D circle, that looks like a rotating sphere, with just a 2D shader. In other words, can someone think of a trick, like mapping a texture to the circle in a particular way, to give the appearance of an in-place rotating sphere, that is always viewed from the side? I don't need exact shader code, I'm just looking for the right idea.

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• CW/CCW Rotation of a Vector

  - by user23132

  Considering that I have a vector A, and after an arbitrary rotation I get vector B. I want to use this rotation operation in others vectors as well, but I'm having problems in doing that. My idea do that is to calculate the perpendicular vector C of the plane AB (by calculating AxB). This vector C is the axis that I'll need to rotate. To discover the angle I used the dot product between A and B, the acos of the dot product will return the lowest angle between A and B, the angle ang. The rotation I need to do is then: -rotate *ang*º around the C axis. The problem is that I dont know if this rotation is a CW or CCW rotation, since the cos of the dot product does not give me information of the sign of the angle. There's a tip discover that in 2D ( A.x * B.y - A.y * B.x) that you can use to discover if the vector A is at left/right of vector B. But I dont know how to do this in 3D space. Can anyone help me?

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• Directx and Open Libraries list? [closed]

  - by OVERTONE

  I've just been looking for comparissons between open and proprietary frameworks and libraries. More so just to get an idea of what exists than how they compare. For example: We have DirectX (graphics) and its open counterpart OpenGL DirectX (sound) and OpenAL But there are other DirectX libraries that I can't find open alternatives to such as DirectInput DXGI Direct2D DirectWrite Doe's anyone have any list's or Comparisons between Directx and their open counterparts?

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• How to do directional per fragment lighting in world space?

  - by user

  I am attempting to create a GLSL shader for simple, per-fragment directional light. So far, after following many tutorials, I have continually ran into the issue: my light is specified in world coordinates, however, the shader treats the light's position as being in eye space, thus, the light direction changes when I move the camera. My question is, how to I transform a directional light position such as (50, 50, 50, 0) into eye space, or, would doing things this way be the incorrect approach to the problem?

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• Creating a frozen bubble clone

  - by Vaughan Hilts

  This photo illustrates the environment: http://i.imgur.com/V4wbp.png I'll shoot the cannon, it'll bounce off the wall and it's SUPPOSED to stick to the bubble. It does at pretty much every other angle. The problem is always reproduced here, when hit off the wall into those bubbles. It also exists in other cases, but I'm not sure what triggers it. What actually happens: The ball will sometimes set to the wrong cell, and my "dropping" code will detect it as a loner and drop it off the stage. *There are many implementations of "Frozen Bubble" on the web, but I can't for the life of me find a good explanation as to how the algorithm for the "Bubble Sticking" works. * I see this: http://www.wikiflashed.com/wiki/BubbleBobble https://frozenbubblexna.svn.codeplex.com/svn/FrozenBubble/ But I can't figure out the algorithims... could anyone explain possibly the general idea behind getting the balls to stick? Code in question: //Counstruct our bounding rectangle for use var nX = currentBall.x + ballvX * gameTime; var nY = currentBall.y - ballvY * gameTime; var movingRect = new BoundingRectangle(nX, nY, 32, 32); var able = false; //Iterate over the cells and draw our bubbles for (var x = 0; x < 8; x++) { for (var y = 0; y < 12; y++) { //Get the bubble at this layout var bubble = bubbleLayout[x][y]; var rowHeight = 27; //If this slot isn't empty, draw if (bubble != null) { var bx = 0, by = 0; if (y % 2 == 0) { bx = x * 32 + 270; by = y * 32 + 45; } else { bx = x * 32 + 270 + 16; by = y * 32 + 45; } //Check var targetBox = new BoundingRectangle(bx, by, 32, 32); if (targetBox.intersects(movingRect)) { able = true; } } } } cellY = Math.round((currentBall.y - 45) / 32); if (cellY % 2 == 0) cellX = Math.round((currentBall.x - 270) / 32); else cellX = Math.round((currentBall.x - 270 - 16) / 32); Any ideas are very much welcome. Things I've tried: Flooring and Ceiling values Changing the wall bounce to a lower value Slowing down the ball None of these seem to affect it. Is there something in my math I'm not getting?

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• Path tables or real time searching for AI?

  - by SirYakalot

  What is the more common practice in commercial games; path lookup tables or real time searches? I've read that in many games path lookup tables are pre-calculated and baked into each map, so to speak, then steering behaviour is used to handle dynamic obstacles. or is it better practice to use optimised hierarchical A* searches? I understand the pro's and cons of each, I'm just curious as to what is most often used in the industry.

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• determine collision angle on a rotating body

  - by jorb

  update: new diagram and updated description I have a contact listener set up to try and determine the side that a collision happened at relative to the a bodies rotation. One way to solve this is to find the value of the yellow angle between the red and blue vectors drawn above. The angle can be found by taking the arc cosine of the dot product of the two vectors (Evan pointed this out). One of my points of confusion is the difference in domain of the atan2 function html canvas coordinates and the Box2d rotation information. I know I have to account for this somehow... SS below questions: Does Box2D provide these angles more directly in the collision information? Am I even on the right track? If so, any hints? I have the following javascript so far: Ship.prototype.onCollide = function (other_ent,cx,cy) { var pos = this.body.GetPosition(); //collision position relative to body var d_cx = pos.x - cx; var d_cy = pos.y - cy; //length of initial vector var len = Math.sqrt(Math.pow(pos.x -cx,2) + Math.pow(pos.y-cy,2)); //body angle - can over rotate hence mod 2*Pi var ang = this.body.GetAngle() % (Math.PI * 2); //vector representing body's angle - same magnitude as the first var b_vx = len * Math.cos(ang); var b_vy = len * Math.sin(ang); //dot product of the two vectors var dot_prod = d_cx * b_vx + d_cy * b_vy; //new calculation of difference in angle - NOT WORKING! var d_ang = Math.acos(dot_prod); var side; if (Math.abs(d_ang) < Math.PI/2 ) side = "front"; else side = "back"; console.log("length",len); console.log("pos:",pos.x,pos.y); console.log("offs:",d_cx,d_cy); console.log("body vec",b_vx,b_vy); console.log("body angle:",ang); console.log("dot product",dot_prod); console.log("result:",d_ang); console.log("side",side); console.log("------------------------"); }

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• Interesting 3d zooming technique

  - by stark

  Is it possible to zoom to a certain point on screen by modifying the field of view and rotating the camera as to keep that point/object in the same place on screen while zooming ? Changing the camera position is not allowed.. I projected the 3d pos of the object on screen and remembered it. Then on each frame I calculate the direction to it in camera space and then I construct a rotation matrix to align this direction to Z axis (in cam space). After this, I calculate the direction from the camera to the object in world space and transform this vector with the matrix I obtained earlier and then use this final vector as the camera's new direction. And it's actually "kinda working", the problem is that it is more/less off than the camera's rotation before starting to zoom depending on the area you are trying to zoom in (larger error on edges/corners). It looks acceptable, but I'm not settling for only this. Any suggestions/resources for doing this technique perfectly ? If some of you want to explain the math in detail, be my guests, I can understand these things well. Thanks. Edit: I'll check often for responses, I'm really curious about this :D

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