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• What light attenuation function does UDK use?

  - by ananamas

  I'm a big fan of the light attenuation in UDK. Traditionally I've always used the constant-linear-quadratic falloff function to control how "soft" the falloff is, which gives three values to play with. In UDK you can get similar results, but you only need to tweak one value: FalloffExponent. I'm interested in what the actual mathematical function here is. The UDK lighting reference describes it as follows: FalloffExponent: This allows you to modify the falloff of a light. The default falloff is 2. The smaller the number, the sharper the falloff and the more the brightness is maintained until the radius is reached. Does anyone know what it's doing behind the scenes?

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• Basic tutorial/introduction for 3d matrices, idealy in c++, without openGl or directX

  - by René Nyffenegger

  I am wondering if there is a simple tutorial that covers the basics of how to initialize rotation, translation and projection matrices, and how to multiply them, and how to get the screen coordinates afterwards for a 3d point. Idealy, the tutorial comes with compilable code and is not dependent on any 3rd party library. Searching the internet, I found lots of tutorials, so this is not the problem. Yet, it seemed all of these either covered openGl or directX, or they were theoretical in nature.

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• Why am I not getting an sRGB default framebuffer?

  - by Aaron Rotenberg

  I'm trying to make my OpenGL Haskell program gamma correct by making appropriate use of sRGB framebuffers and textures, but I'm running into issues making the default framebuffer sRGB. Consider the following Haskell program, compiled for 32-bit Windows using GHC and linked against 32-bit freeglut: import Foreign.Marshal.Alloc(alloca) import Foreign.Ptr(Ptr) import Foreign.Storable(Storable, peek) import Graphics.Rendering.OpenGL.Raw import qualified Graphics.UI.GLUT as GLUT import Graphics.UI.GLUT(($=)) main :: IO () main = do (_progName, _args) <- GLUT.getArgsAndInitialize GLUT.initialDisplayMode $= [GLUT.SRGBMode] _window <- GLUT.createWindow "sRGB Test" -- To prove that I actually have freeglut working correctly. -- This will fail at runtime under classic GLUT. GLUT.closeCallback $= Just (return ()) glEnable gl_FRAMEBUFFER_SRGB colorEncoding <- allocaOut $ glGetFramebufferAttachmentParameteriv gl_FRAMEBUFFER gl_FRONT_LEFT gl_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING print colorEncoding allocaOut :: Storable a => (Ptr a -> IO b) -> IO a allocaOut f = alloca $ \ptr -> do f ptr peek ptr On my desktop (Windows 8 64-bit with a GeForce GTX 760 graphics card) this program outputs 9729, a.k.a. gl_LINEAR, indicating that the default framebuffer is using linear color space, even though I explicitly requested an sRGB window. This is reflected in the rendering results of the actual program I'm trying to write - everything looks washed out because my linear color values aren't being converted to sRGB before being written to the framebuffer. On the other hand, on my laptop (Windows 7 64-bit with an Intel graphics chip), the program prints 0 (huh?) and I get an sRGB default framebuffer by default whether I request one or not! And on both machines, if I manually create a non-default framebuffer bound to an sRGB texture, the program correctly prints 35904, a.k.a. gl_SRGB. Why am I getting different results on different hardware? Am I doing something wrong? How can I get an sRGB framebuffer consistently on all hardware and target OSes?

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• Calculating instantaneous speed and acceleration for a simple Car software model

  - by Dylan

  I am trying to model a speedometer and tachometer for a simple software model of a car dashboard. I want this to be relatively simple, so for my purposes I won't likely simulate variables such as drag (or, assume that drag is a constant). But I would like to know the general formulas for: 1) Calculating the RPM, depending on a position of a graphical slider representing the accelerator. 2) Using this information to find the instantaneous speed (or, magnitude of instantaneous velocity?). I am not sure, in the case of 2), what other independent variables I need to consider. Do I need to consider the frequency of rotation of the wheels (assuming a fixed radius), in addition to the RPM? If anyone can give me a rough explanation plus relevant formulas, or alternatively direct me to other trusted resources online (I have had a hard time sifting through info and determining the accuracy), it would be much appreciated.

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• What are the most common AI systems implemented in Tower Defense Games

  - by the_Dan

  I'm currently in the middle of researching on the various types of AI techniques used in tower defense type games. If someone could be help me in understanding the different types of techniques and their associated advantages. Using Google I already found several techniques. Random Map traversal Path finding e.g. Cost based Traversing Algorithms i.e. A* I have already found a great answer to this type of question with the below link, but I feel that this answer is tailored to FPS. If anyone could add to this and make it specific to tower defense games then I would be truly great-full. How is AI most commonly implemented in popular games? Example of such games would be: Radiant Defense Plant Vs Zombies - Not truly Intelligent, but there must be an AI system used right? Field Runners Edit: After further research I found an interesting book that may be useful: http://www.amazon.com/dp/0123747317/?tag=stackoverfl08-20

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• Unity GUI not in build, but works fine in editor

  - by Darren

  I have: GUITexture attached to an object A script that has GUIStyles created for the Textfield and Buttons that are created in OnGUI(). This script is attached to the same object in number 1 3 GUIText objects each separate from the above. A script that enables the GUITexture and the script in number 1 and 2 respectively This is how it is supposed to work: When I cross the finish line, number 4 script enables number 1 GUITexture component and number 2 script component. The script component uses one of number 3's GUIText objects to show you your best lap time, and also makes a GUI.Textfield for name entry and 2 GUI.Buttons for "Submit" and "Skip". If you hit "Submit" the script will submit the time. No matter which button you press, The remaining 2 GUIText objects from number 3 will show you the top 10 best times. For some reason, when I run it in editor, everything works 100%, but when I'm in different kinds of builds, the results vary. When I am in a webplayer, The GUITexture and the textfield and buttons appear, but the textfield and buttons are plain and have no evidence of GUIStyles. When I click one of the buttons, the score gets submitted but I do not get the fastest times showing. When I am in a standalone build, the GUITexture shows up, but nothing else does. If I remove the GUIStyle parameter of the GUI.Textfield and GUI.Button, they show up. Why am I getting these variations and how can I fix it? Code below: void Start () { Names.text = ""; Times.text = ""; YourBestTime.text = "Your Best Lap: " + bestTime + "\nEnter your name:"; //StartCoroutine(GetTimes("Test")); } void Update() { if (!ShowButtons && !GettingTimes) { StartCoroutine(GetTimes()); GettingTimes = true; } } IEnumerator GetTimes () { Debug.Log("Getting times"); YourBestTime.text = "Loading Best Lap Times"; WWW times_get = new WWW(GetTimesUrl); yield return times_get; WWW names_get = new WWW(GetNamesUrl); yield return names_get; if(times_get.error != null || names_get.error != null) { print("There was an error retrieiving the data: " + names_get.error + times_get.error); } else { Times.text = times_get.text; Names.text = names_get.text; YourBestTime.text = "Your Best Lap: " + bestTime; } } IEnumerator PostLapTime (string Name, string LapTime) { string hash= MD5.Md5Sum(Name + LapTime + secretKey); string bestTime_url = SubmitTimeUrl + "&Name=" + WWW.EscapeURL(Name) + "&LapTime=" + LapTime + "&hash=" + hash; Debug.Log (bestTime_url); // Post the URL to the site and create a download object to get the result. WWW hs_post = new WWW(bestTime_url); //label = "Submitting..."; yield return hs_post; // Wait until the download is done if (hs_post.error != null) { print("There was an error posting the lap time: " + hs_post.error); //label = "Error: " + hs_post.error; //show = false; } else { Debug.Log("Posted: " + hs_post.text); ShowButtons = false; PostingTime = false; } } void OnGUI() { if (ShowButtons) { //makes text box nameString = GUI.TextField( new Rect((Screen.width/2)-111, (Screen.height/2)-130, 222, 25), nameString, 20, TextboxStyle); if (GUI.Button( new Rect( (Screen.width/2-74.0f), (Screen.height/2)- 90, 64, 32), "Submit", ButtonStyle)) { //SUBMIT TIME if (nameString == "") { nameString = "Player"; } if (!PostingTime) { StartCoroutine(PostLapTime(nameString, bestTime)); PostingTime = true; } } else if (GUI.Button( new Rect( (Screen.width/2+10.0f), (Screen.height/2)- 90, 64, 32), "Skip", ButtonStyle)) { ShowButtons = false; } } } }

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• My grid based collision detection is slow

  - by Fibericon

  Something about my implementation of a basic 2x4 grid for collision detection is slow - so slow in fact, that it's actually faster to simply check every bullet from every enemy to see if the BoundingSphere intersects with that of my ship. It becomes noticeably slow when I have approximately 1000 bullets on the screen (36 enemies shooting 3 bullets every .5 seconds). By commenting it out bit by bit, I've determined that the code used to add them to the grid is what's slowest. Here's how I add them to the grid: for (int i = 0; i < enemy[x].gun.NumBullets; i++) { if (enemy[x].gun.bulletList[i].isActive) { enemy[x].gun.bulletList[i].Update(timeDelta); int bulletPosition = 0; if (enemy[x].gun.bulletList[i].position.Y < 0) { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450); } else { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450) + 4; } GridItem bulletItem = new GridItem(); bulletItem.index = i; bulletItem.type = 5; bulletItem.parentIndex = x; if (bulletPosition > -1 && bulletPosition < 8) { if (!grid[bulletPosition].Contains(bulletItem)) { for (int j = 0; j < grid.Length; j++) { grid[j].Remove(bulletItem); } grid[bulletPosition].Add(bulletItem); } } } } And here's how I check if it collides with the ship: if (ship.isActive && !ship.invincible) { BoundingSphere shipSphere = new BoundingSphere( ship.Position, ship.Model.Meshes[0].BoundingSphere.Radius * 9.0f); for (int i = 0; i < grid.Length; i++) { if (grid[i].Contains(shipItem)) { for (int j = 0; j < grid[i].Count; j++) { //Other collision types omitted else if (grid[i][j].type == 5) { if (enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive) { BoundingSphere bulletSphere = new BoundingSphere(enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].position, enemy[grid[i][j].parentIndex].gun.bulletModel.Meshes[0].BoundingSphere.Radius); if (shipSphere.Intersects(bulletSphere)) { ship.health -= enemy[grid[i][j].parentIndex].gun.damage; enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive = false; grid[i].RemoveAt(j); break; //no need to check other bullets } } else { grid[i].RemoveAt(j); } } What am I doing wrong here? I thought a grid implementation would be faster than checking each one.

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• Can I use DllImport/PInvoke in libraries loaded as Assets in Unity Free?

  - by sebf

  I am interested in using utilising third-party libraries in Unity Free. I know Unity can use managed libraries as Assets, but only the Pro version supports using native libraries. (DllImport within scripts). This thread however suggests that it is possible to import DLLs in the free version. I would like to utilise native libraries (as a hobbyist I cannot afford Pro), but want to do it the supported way so I don't have to worry about Unity 'fixing' this hole if that is what it is. Is there any supported way to use native libraries with Unity free? (i.e. does that thread suggest a workaround or is it a 'bug'? Is it supported to use DllImport/PInvoke in libraries loaded as assets? (could I create a wrapper myself?)

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• Group arrival steering

  - by ltjax

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

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• First Minecraft mod not working: make a new sword

  - by yamikoWebs

  I am making my first mod and cannot see what is wrong with it. I am using MCP and Modloader. For my first mod I was going to make swords. I started with making a new EnumToolMaterials WOOD(0, 59, 2.0F, 0, 15), STONE(1, 131, 4.0F, 1, 5), IRON(2, 250, 6.0F, 2, 14), LAPIS(3, 750, 7.0F, 2, 14), OBSIDIAN(3, 1000, 7.5F, 3, 12), EMERALD(3, 1561, 8.0F, 3, 10),//diamond GREEN(3, 2000, 9.0F, 4, 10),//emerald GOLD(0, 200, 12.0F, 0, 22); then here is the mod class public class _Mod_Yamiko extends BaseMod{ /* mod itemts */ public static final Item swordLapis = (new ItemSword(600, EnumToolMaterial.LAPIS)).setItemName("swordLapis"); public static final Item swordObsidian = (new ItemSword(601, EnumToolMaterial.OBSIDIAN)).setItemName("swordObsidian"); public static final Item swordGreen = (new ItemSword(602, EnumToolMaterial.GREEN)).setItemName("swordGreen"); public void load(){ //set images swordLapis.iconIndex = ModLoader.addOverride("/gui/items.png","/gui/swordLapis.png"); ModLoader.addName(swordLapis, "Lapis Sword"); //craft ModLoader.addRecipe(new ItemStack(_Mod_Yamiko.swordLapis, 1), new Object[]{ " X ", " X ", " Y ", 'X', Block.dirt, 'Y', Item.stick }); } public String getVersion(){ return "0.1"; } } Then I made a 16×16 .png image. I am not sure where to save it so I recompiled and reobfuscated, took the mod files and put it in my local Minecraft install, added the image where it be should be. No problems when playing but I cannot make the new sword.

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• add collision detection to sprite?

  - by xBroak

  bassically im trying to add collision detection to the sprite below, using the following: self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") However it seems that when the collide is triggered it continuously prints 'collide' over and over when instead i want them to simply not be able to walk through the object, any help? def update(self, time_passed): """ Update the creep. time_passed: The time passed (in ms) since the previous update. """ if self.state == Creep.ALIVE: # Maybe it's time to change the direction ? # self._change_direction(time_passed) # Make the creep point in the correct direction. # Since our direction vector is in screen coordinates # (i.e. right bottom is 1, 1), and rotate() rotates # counter-clockwise, the angle must be inverted to # work correctly. # self.image = pygame.transform.rotate( self.base_image, -self.direction.angle) # Compute and apply the displacement to the position # vector. The displacement is a vector, having the angle # of self.direction (which is normalized to not affect # the magnitude of the displacement) # displacement = vec2d( self.direction.x * self.speed * time_passed, self.direction.y * self.speed * time_passed) self.pos += displacement # When the image is rotated, its size is changed. # We must take the size into account for detecting # collisions with the walls. # self.image_w, self.image_h = self.image.get_size() global bounds_rect bounds_rect = self.field.inflate( -self.image_w, -self.image_h) if self.pos.x < bounds_rect.left: self.pos.x = bounds_rect.left self.direction.x *= -1 elif self.pos.x > bounds_rect.right: self.pos.x = bounds_rect.right self.direction.x *= -1 elif self.pos.y < bounds_rect.top: self.pos.y = bounds_rect.top self.direction.y *= -1 elif self.pos.y > bounds_rect.bottom: self.pos.y = bounds_rect.bottom self.direction.y *= -1 self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") elif self.state == Creep.EXPLODING: if self.explode_animation.active: self.explode_animation.update(time_passed) else: self.state = Creep.DEAD self.kill() elif self.state == Creep.DEAD: pass #------------------ PRIVATE PARTS ------------------# # States the creep can be in. # # ALIVE: The creep is roaming around the screen # EXPLODING: # The creep is now exploding, just a moment before dying. # DEAD: The creep is dead and inactive # (ALIVE, EXPLODING, DEAD) = range(3) _counter = 0 def _change_direction(self, time_passed): """ Turn by 45 degrees in a random direction once per 0.4 to 0.5 seconds. """ self._counter += time_passed if self._counter > randint(400, 500): self.direction.rotate(45 * randint(-1, 1)) self._counter = 0 def _point_is_inside(self, point): """ Is the point (given as a vec2d) inside our creep's body? """ img_point = point - vec2d( int(self.pos.x - self.image_w / 2), int(self.pos.y - self.image_h / 2)) try: pix = self.image.get_at(img_point) return pix[3] > 0 except IndexError: return False def _decrease_health(self, n): """ Decrease my health by n (or to 0, if it's currently less than n) """ self.health = max(0, self.health - n) if self.health == 0: self._explode() def _explode(self): """ Starts the explosion animation that ends the Creep's life. """ self.state = Creep.EXPLODING pos = ( self.pos.x - self.explosion_images[0].get_width() / 2, self.pos.y - self.explosion_images[0].get_height() / 2) self.explode_animation = SimpleAnimation( self.screen, pos, self.explosion_images, 100, 300) global remainingCreeps remainingCreeps-=1 if remainingCreeps == 0: print("all dead")

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• Partial recalculation of visibility on a 2D uniform grid

  - by Martin Källman

  Problem Imagine that we have a 2D uniform grid of dimensions N x N. For this grid we have also pre-computed a visibility look-up table, e.g. with DDA, which answers the boolean query is cell X visible from cell Y? The look-up table is a complete graph KN of the cells V in the grid, with each edge E being a binary value denoting the visibility between its vertices. Question If any given cell has its visibility modified, is it possible to extract the subset Edelta of edges which must have their visibility recomputed due to the change, so as to avoid a full-on recomputation for the entire grid? (Which is N(N-1) / 2 or N2 depending on the implementation) Update If is not possible to solve thi in closed form, then maintaining a separate mapping of each cell and every cell pair who's line intersects said cell might also be an option. This obviously consumes more memory, but the data is static. The increased memory requirement could be reduced by introducing a hierarchy, subdividing the grid into smaller parts, and by doing so the above mapping can be reused for each sub-grid. This would come at a cost in terms of increased computation relative to the number of subdivisions; also requiring a resumable ray-casting algorithm.

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• Gap in parallaxing background loop

  - by CinetiK

  The bug here is that my background kind of offset a bit itself from where it should draw and so I have this line. I have some troubles understanding why I get this bug when I set a speed that is different then 1,2,4,8,16,... In main class I set the speed depending on the player speed bgSpeed = -(int)playerMoveSpeed.X / 10; and here's my background class class ParallaxingBackground { Texture2D texture; Vector2[] positions; public int Speed { get; set;} public void Initialize(ContentManager content, String texturePath, int screenWidth, int speed) { texture = content.Load<Texture2D>(texturePath); this.Speed = speed; positions = new Vector2[screenWidth / texture.Width + 2]; for (int i = 0; i < positions.Length; i++) { positions[i] = new Vector2(i * texture.Width, 0); } } public void Update() { for (int i = 0; i < positions.Length; i++) { positions[i].X += Speed; if (Speed <= 0) { if (positions[i].X <= -texture.Width) { positions[i].X = texture.Width * (positions.Length - 1); } } else { if (positions[i].X >= texture.Width*(positions.Length - 1)) { positions[i].X = -texture.Width; } } } } public void Draw(SpriteBatch spriteBatch) { for (int i = 0; i < positions.Length; i++) { spriteBatch.Draw(texture, positions[i], Color.White); } } }

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• How can I view an R32G32B32 texture?

  - by bobobobo

  I have a texture with R32G32B32 floats. I create this texture in-program on D3D11, using DXGI_FORMAT_R32G32B32_FLOAT. Now I need to see the texture data for debug purposes, but it will not save to anything but dds, showing the error in debug output, "Can't find matching WIC format, please save this file to a DDS". So, I write it to DDS but I can't open it now! The DirectX texture tool says "An error occurred trying to open that file". I know the texture is working because I can read it in the GPU and the colors seem correct. How can I view an R32G32B32 texture in an image viewer?

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• How do I simplify terrain with tunnels or overhangs?

  - by KKlouzal

  I'm attempting to store vertex data in a quadtree with C++, such that far-away vertices can be combined to simplify the object and speed up rendering. This works well with a reasonably flat mesh, but what about terrain with overhangs or tunnels? How should I represent such a mesh in a quadtree? After the initial generation, each mesh is roughly 130,000 polygons and about 300 of these meshes are lined up to create the surface of a planetary body. A fully generated planet is upwards of 10,000,000 polygons before applying any culling to the individual meshes. Therefore, this second optimization is vital for the project. The rest of my confusion focuses around my inexperience with vertex data: How do I properly loop through the vertex data to group them into specific quads? How do I conclude from vertex data what a quad's maximum size should be? How many quads should the quadtree include?

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• How to fix bad Collada produced by FBX?

  - by David

  I tried to use the FBX SDK (2011.3.1) to load FBX files and save them as Collada files in order to be able to import FBX files in Panda3D. Unfortunately the resulting Collada files are not usable for several reasons, among them: There's a Maya specific extra technique diffuse <diffuse> <texture texture="Map__2-image" texcoord="CHANNEL0"> <extra> <technique profile="MAYA"> <wrapU sid="wrapU0">TRUE</wrapU> <wrapV sid="wrapV0">TRUE</wrapV> <blend_mode>ADD</blend_mode> </technique> </extra> </texture> </diffuse> It assigns a texcoord channel name that isn't referenced anywhere else in the file (in the previous code sample, no geometry uses "CHANNEL0"...) Every polygon is exported twice, a first time with a basic material (only diffuse color, specular color, etc.) and a second time with a textured material -- this doubles the number of polygons of each model without any valuable reason Anyway, the resulting Collada file cannot be opened correctly either with OpenCOLLADA or Panda3D's "dae2egg". Anyone has any experience on how to "fix" it and make it understandable by common and well-reputed Collada importers such as OpenCOLLADA?

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• What is the format of DXGI_FORMAT_D24_UNORM_S8_UINT?

  - by bobobobo

  I'm trying to read the values in a depth texture of type DXGI_FORMAT_D24_UNORM_S8_UINT. I know this means "24 bits for depth, 8 bits for stencil" "A 32-bit z-buffer format that supports 24 bits for depth and 8 bits for stencil.", but how do you interpret those 24 bits? It's clearly not going to be a 32-bit int, and it's not going to be a 32-bit float. If it is an integer value, how "far away" is a value of "1" in the depth texture?

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• Does DirectX implement Triple Buffering?

  - by Asik

  As AnandTech put it best in this 2009 article: In render ahead, frames cannot be dropped. This means that when the queue is full, what is displayed can have a lot more lag. Microsoft doesn't implement triple buffering in DirectX, they implement render ahead (from 0 to 8 frames with 3 being the default). The major difference in the technique we've described here is the ability to drop frames when they are outdated. Render ahead forces older frames to be displayed. Queues can help smoothness and stuttering as a few really quick frames followed by a slow frame end up being evened out and spread over more frames. But the price you pay is in lag (the more frames in the queue, the longer it takes to empty the queue and the older the frames are that are displayed). As I understand it, DirectX "Swap Chain" is merely a render ahead queue, i.e. buffers cannot be dropped; the longer the chain, the greater the input latency. At the same time, I find it hard to believe that the most widely used graphics API would not implement such fundamental functionality correctly. Is there a way to get proper triple buffered vertical synchronisation in DirectX?

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• How to store character moves (sprite animations)?

  - by Saad

  So I'm thinking about making a small rpg, mainly to test out different design patterns I've been learning about. But the one question that I'm not too sure on how to approach is how to store an array of character moves in the best way possible. So let's say I have arrays of different sprites. This is how I'm thinking about implementing it: array attack = new array (10); array attack2 = new array(5); (loop) //blit some image attack.push(imageInstance); (end loop) Now every time I want the animation I call on attack or attack2; is there a better structure? The problem with this is let's say there are 100 different attacks, and a player can have up to 10 attacks equipped. So how do I tell which attack the user has; should I use a hash map?

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• Shader optimization - cg/hlsl pseudo and via multiplication

  - by teodron

  Since HLSL/Cg do not allow texture fetching inside conditional blocks, I am first checking a variable and performing some computations, afterwards setting a float flag to 0.0 or 1.0, depending on the computations. I'd like to trigger a texture fetch only if the flag is 1.0 or not null, for that matter of fact. I kind of hoped this would do the trick: float4 TU0_atlas_colour = pseudoBool * tex2Dlod(TU0_texture, float4(tileCoord, 0, mipLevel)); That is, if pseudoBool is 0, will the texture fetch function still be called and produce overhead? I was hoping to prevent it from getting executed via this trick that usually works in plain C/C++.

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• runtime error: invalid memory address or nil pointer dereference

  - by Klink

  I want to learn OpenGL 3.0 with golang. But when i try to compile some code, i get many errors. package main import ( "os" //"errors" "fmt" //gl "github.com/chsc/gogl/gl33" //"github.com/jteeuwen/glfw" "github.com/go-gl/gl" "github.com/go-gl/glfw" "runtime" "time" ) var ( width int = 640 height int = 480 ) var ( points = []float32{0.0, 0.8, -0.8, -0.8, 0.8, -0.8} ) func initScene() { gl.Init() gl.ClearColor(0.0, 0.5, 1.0, 1.0) gl.Enable(gl.CULL_FACE) gl.Viewport(0, 0, 800, 600) } func glfwInitWindowContext() { if err := glfw.Init(); err != nil { fmt.Fprintf(os.Stderr, "glfw_Init: %s\n", err) glfw.Terminate() } glfw.OpenWindowHint(glfw.FsaaSamples, 1) glfw.OpenWindowHint(glfw.WindowNoResize, 1) if err := glfw.OpenWindow(width, height, 0, 0, 0, 0, 32, 0, glfw.Windowed); err != nil { fmt.Fprintf(os.Stderr, "glfw_Window: %s\n", err) glfw.CloseWindow() } glfw.SetSwapInterval(1) glfw.SetWindowTitle("Title") } func drawScene() { for glfw.WindowParam(glfw.Opened) == 1 { gl.Clear(gl.COLOR_BUFFER_BIT) vertexShaderSrc := `#version 120 attribute vec2 coord2d; void main(void) { gl_Position = vec4(coord2d, 0.0, 1.0); }` vertexShader := gl.CreateShader(gl.VERTEX_SHADER) vertexShader.Source(vertexShaderSrc) vertexShader.Compile() fragmentShaderSrc := `#version 120 void main(void) { gl_FragColor[0] = 0.0; gl_FragColor[1] = 0.0; gl_FragColor[2] = 1.0; }` fragmentShader := gl.CreateShader(gl.FRAGMENT_SHADER) fragmentShader.Source(fragmentShaderSrc) fragmentShader.Compile() program := gl.CreateProgram() program.AttachShader(vertexShader) program.AttachShader(fragmentShader) program.Link() attribute_coord2d := program.GetAttribLocation("coord2d") program.Use() //attribute_coord2d.AttribPointer(size, typ, normalized, stride, pointer) attribute_coord2d.EnableArray() attribute_coord2d.AttribPointer(0, 3, false, 0, &(points[0])) //gl.DrawArrays(gl.TRIANGLES, 0, len(points)) gl.DrawArrays(gl.TRIANGLES, 0, 3) glfw.SwapBuffers() inputHandler() time.Sleep(100 * time.Millisecond) } } func inputHandler() { glfw.Enable(glfw.StickyKeys) if glfw.Key(glfw.KeyEsc) == glfw.KeyPress { //gl.DeleteBuffers(2, &uiVBO[0]) glfw.Terminate() } if glfw.Key(glfw.KeyF2) == glfw.KeyPress { glfw.SetWindowTitle("Title2") fmt.Println("Changed to 'Title2'") fmt.Println(len(points)) } if glfw.Key(glfw.KeyF1) == glfw.KeyPress { glfw.SetWindowTitle("Title1") fmt.Println("Changed to 'Title1'") } } func main() { runtime.LockOSThread() glfwInitWindowContext() initScene() drawScene() } And after that: panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x0 pc=0x41bc6f74] goroutine 1 [syscall]: github.com/go-gl/gl._Cfunc_glDrawArrays(0x4, 0x7f8500000003) /tmp/go-build463568685/github.com/go-gl/gl/_obj/_cgo_defun.c:610 +0x2f github.com/go-gl/gl.DrawArrays(0x4, 0x3, 0x0, 0x45bd70) /tmp/go-build463568685/github.com/go-gl/gl/_obj/gl.cgo1.go:1922 +0x33 main.drawScene() /home/klink/Dev/Go/gogl/gopher/exper.go:85 +0x1e6 main.main() /home/klink/Dev/Go/gogl/gopher/exper.go:116 +0x27 goroutine 2 [syscall]: created by runtime.main /build/buildd/golang-1/src/pkg/runtime/proc.c:221 exit status 2

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• libgdx ActorGestureListener.pan() parameters not moving actor in smooth line

  - by Roar Skullestad

  I override the pan method in ActorGestureListener to implement dragging actors in libgdx (scene2d). When I move individual pieces on a board they move smoothly, but when moving the whole board, the x and y coordinates that is sent to pan is "jumping", and in an increasingly amount the longer it is dragged. These are an example of the deltaY coordinates sent to pan when dragging smoothly downwards: 1.1156368 -0.13125038 -1.0500145 0.98439217 -1.0500202 0.91877174 -0.984396 0.9187679 -0.98439026 0.9187641 -0.13125038 This is how I move the camera: public void pan (InputEvent event, float x, float y, float deltaX, float deltaY) { cam.translate(-deltaX, -deltaY); I have been using both the delta values sent to pan and the real position values, but similar results. And since it is the coordinates that are wrong, it doesn't matter whether I move the board itself or the camera. What could the cause be for this and what is the solution? When I move camera only half the delta-values, it moves smoothly but only at half the speed of the mouse pointer: cam.translate(-deltaX / 2, -deltaY / 2); It seems like the moving of camera or board affects the mouse input coordinates. How can I drag at "mouse speed" and still get smooth movements? (This question was also posted on stackoverflow: http://stackoverflow.com/questions/20693020/libgdx-actorgesturelistener-pan-parameters-not-moving-actor-in-smooth-line)

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• Execute code at specific intervals, only once?

  - by Mathias Lykkegaard Lorenzen

  I am having an issue with XNA, where I want to execute some code in my Update method, but only at a given interval, and only once. I would like to avoid booleans to check if I've already called it once, if possible. My code is here: if ((gameTime.TotalGameTime.TotalMilliseconds % 500) == 0) { Caret.Visible = !Caret.Visible; } As you may have guessed, it's for a TextBox control, to animate the caret between invisible and visible states. I just have reason to believe that it is called twice or maybe even 3 times in a single update-call, which is bad, and makes it look unstable and jumpy.

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• Effective way to check if an Entity/Player enters a region/trigger

  - by Chris

  I was wondering how multiplayer games detect if you enter a special region. Let's assume there is a huge map that is so big that simply checking it would become a huge performance issue. I've seen bukkit (a modding API for Minecraft servers) firing an Event on every single move. I don't think that larger games do the same because even if you have only a few coordinates you are interested in, you have to loop through a few trigger zone to see if the player is inside your region - for every player. This seems like an extremely CPU-intense operation to me even though I've never developed something like that. Is there a special algorithm that is used by larger games to accomplish this? The only thing I could imagine is to split up the world into multiple parts and to register the event not on the movement itself but on all the parts that are covered by your area and only check for areas that are registered in the current part. And another thing I would like to know: How could you detect when someone must have entered a trigger but you never saw him directly in it since his client only sent you an move packet shortly before entering and after leaving the trigger area. Drawing a line and calculate all colliding parts seems rather CPU intensive if you have to perform it every time.

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• Problems Rendering Text in OpenGL Using FreeType

  - by Sean M.

  I've been following both the FreeType2 tutorial and the WikiBooks tuorial, trying to combine things from them both in order to load and render fonts using the FreeType library. I used the font loading code from the FreeType2 tutorial and tried to implement the rendering code from the wikibooks tutorial (tried being the keyword as I'm still trying to learn model OpenGL, I'm using 3.2). Everything loads correctly and I have the shader program to render the text with working, but I can't get the text to render. I'm 99% sure that it has something to do with how I cam passing data to the shader, or how I set up the screen. These are the code segments that handle OpenGL initialization, as well as Font initialization and rendering: //Init glfw if (!glfwInit()) { fprintf(stderr, "GLFW Initialization has failed!\n"); exit(EXIT_FAILURE); } printf("GLFW Initialized.\n"); //Process the command line arguments processCmdArgs(argc, argv); //Create the window glfwWindowHint(GLFW_SAMPLES, g_aaSamples); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2); g_mainWindow = glfwCreateWindow(g_screenWidth, g_screenHeight, "Voxel Shipyard", g_fullScreen ? glfwGetPrimaryMonitor() : nullptr, nullptr); if (!g_mainWindow) { fprintf(stderr, "Could not create GLFW window!\n"); closeOGL(); exit(EXIT_FAILURE); } glfwMakeContextCurrent(g_mainWindow); printf("Window and OpenGL rendering context created.\n"); glClearColor(0.2f, 0.2f, 0.2f, 1.0f); //Are these necessary for Modern OpenGL (3.0+)? glViewport(0, 0, g_screenWidth, g_screenHeight); glOrtho(0, g_screenWidth, g_screenHeight, 0, -1, 1); //Init glew int err = glewInit(); if (err != GLEW_OK) { fprintf(stderr, "GLEW initialization failed!\n"); fprintf(stderr, "%s\n", glewGetErrorString(err)); closeOGL(); exit(EXIT_FAILURE); } printf("GLEW initialized.\n"); Here is the font file (it's slightly too big to post): CFont.h/CFont.cpp Here is the solution zipped up: [solution] (https://dl.dropboxusercontent.com/u/36062916/VoxelShipyard.zip), if anyone feels they need the entire solution. If anyone could take a look at the code, it would be greatly appreciated. Also if someone has a tutorial that is a little more user friendly, that would also be appreciated. Thanks.

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