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  • How do I find hash value of a 3D vector ?

    - by brainydexter
    I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any) collisions. So, here is what I am doing: Grid-cell's position: (int type) (Gx, Gy, Gz) = (x / M, y / M, z / M) where M is the size of the grid. Once, I have a cell, I'd like to add it to a hash-table with its key being a unique hash based on (Gx, Gy, Gz) and the value being the cell itself. Now, I cannot think of a good hash function and I need some help with that. Can someone please suggest me a good hash function? Thanks

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  • NSPredicate by NSManagedObject for many-to-one lookups

    - by niklassaers
    Hi guys, I've got the scenario with two NSManagedObjects, Arm and Person. Between them is a many-to-one relationship Person.arms and inverse Arm.owner. I'd like to write a simple NSPredicate where I've got the NSManagedObject *arm and I'd like to fetch the NSManagedObject *person that this arm belongs to. I could make a textual representation and look for that, but is there a better way where I can look it up by identity? Something like this perhaps? NSEntityDescription *person = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:MOC]; NSPredicate *personPredicate = [NSPredicate predicateWithFormat:@"%@ IN arms", arm]; Cheers Nik

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  • JavaScript: Achieving precise animation end values?

    - by bobthabuilda
    I'm currently trying to write my own JavaScript library. I'm in the middle of writing an animation callback, but I'm having trouble getting precise end values, especially when animation duration times are smaller. Right now, I'm only targeting positional animation (left, top, right, bottom). When my animations complete, they end up having an error margin of 5px~ on faster animations, and 0.5px~ on animations 1000+ ms or greater. Here's the bulk of the callback, with notes following. var current = parseFloat( this[0].style[prop] || 0 ) // If our target value is greater than the current , gt = !!( value > current ) , delta = ( Math.abs(current - value) / (duration / 13) ) * (gt ? 1 : -1) , elem = this[0] , anim = setInterval( function(){ elem.style[prop] = ( current + delta ) + 'px'; current = parseFloat( elem.style[prop] ); if ( gt && current >= value || !gt && current <= value ) clearInterval( anim ); }, 13 ); this[0] and elem both reference the target DOM element. prop references the property to animate, left, top, bottom, right, etc. current is the current value of the DOM element's property. value is the desired value to animate to. duration is the specified duration (in ms) that the animation should last. 13 is the setInterval delay (which should roughly be the absolute minimal for all browsers). gt is a var that is true if value exceeds the initial current, else it is false. How can I resolve the error margin?

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  • Simulating graphing paper on iPhone

    - by Rick
    I need to implement 'graphing paper' in an iPhone app. The user should be presented with a grid. They user can touch individual squares to turn them on, or if they're already on, off.The user can pinch to zoom and scroll around the paper as well.. So far I'm thinking Quartz 2D + UIScrollView is the way to do this but these are both areas of iPhone development that I'm unfamiliar with. Does this seem like a reasonable strategy?

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  • Understanding colors

    - by Ankur Gupta
    Hello everyone, Kindly point towards theory/material to read for understanding colors and what makes a good color combinations. Mind it that I am not interested in say "Color combinations for web application" etc. More of the lines of say "Colors and humans". Material free to read is what i am looking for. Thanks

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  • Zoom image to pixel level

    - by zaf
    For an art project, one of the things I'll be doing is zooming in on an image to a particular pixel. I've been rubbing my chin and would love some advice on how to proceed. Here are the input parameters: Screen: sw - screen width sh - screen height Image: iw - image width ih - image height Pixel: px - x position of pixel in image py - y position of pixel in image Zoom: zf - zoom factor (0.0 to 1.0) Background colour: bc - background colour to use when screen and image aspect ratios are different Outputs: The zoomed image (no anti-aliasing) The screen position/dimensions of the pixel we are zooming to. When zf is 0 the image must fit the screen with correct aspect ratio. When zf is 1 the selected pixel fits the screen with correct aspect ratio. One idea I had was to use something like povray and move the camera towards a big image texture or some library (e.g. pygame) to do the zooming. Anyone think of something more clever with simple pseudo code? To keep it more simple you can make the image and screen have the same aspect ratio. I can live with that. I'll update with more info as its required.

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  • iPhone Rendering Question

    - by slythic
    Hi all, I'm new to iPhone/Objective-C development. I "jumped the gun" and started reading and implementing some chapters from O'Reilly's iPhone Development. I was following the ebook's code exactly and my code was generating the following error: CGContextSetFillColorWithColor: invalid context CGContextFillRects: invalid context CGContextSetFillColorWithColor: invalid context CGContextGetShouldSmoothFonts: invalid context However, when I downloaded the sample code for the same chapter the code is different. Book Code: - (void) Render { CGContextRef g = UIGraphicsGetCurrentContext(); //fill background with gray CGContextSetFillColorWithColor(g, [UIColor grayColor].CGColor); CGContextFillRect(g, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)); //draw text in black. CGContextSetFillColorWithColor(g, [UIColor blackColor].CGColor); [@"O'Reilly Rules!" drawAtPoint:CGPointMake(10.0, 20.0) withFont:[UIFont systemFontOfSize:[UIFont systemFontSize]]]; } Actual Project Code from the website (works): - (void) Render { [self setNeedsDisplay]; //this sets up a deferred call to drawRect. } - (void)drawRect:(CGRect)rect { CGContextRef g = UIGraphicsGetCurrentContext(); //fill background with gray CGContextSetFillColorWithColor(g, [UIColor grayColor].CGColor); CGContextFillRect(g, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)); //draw text in black. CGContextSetFillColorWithColor(g, [UIColor blackColor].CGColor); [@"O'Reilly Rules!" drawAtPoint:CGPointMake(10.0, 20.0) withFont:[UIFont systemFontOfSize:[UIFont systemFontSize]]]; } What is it about these lines of code that make the app render correctly? - (void) Render { [self setNeedsDisplay]; //this sets up a deferred call to drawRect. } - (void)drawRect:(CGRect)rect { Thanks in advance for helping out a newbie!

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  • Malloc to a CGPoint Pointer throwing EXC_BAD_ACCESS when accessing

    - by kdbdallas
    I am trying to use a snippet of code from a Apple programming guide, and I am getting a EXC_BAD_ACCESS when trying to pass a pointer to a function, right after doing a malloc. (For Reference: iPhone Application Programming Guide: Event Handling - Listing 3-6) The code in question is really simple: CFMutableDictionaryRef touchBeginPoints; UITouch *touch; .... CGPoint *point = (CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch); if (point == NULL) { point = (CGPoint *)malloc(sizeof(CGPoint)); CFDictionarySetValue(touchBeginPoints, touch, point); } Now when the program goes into the if statement it assigns the 'output' of malloc into the point variable/pointer. Then when it tries to pass point into the CFDictionarySetValue function it crashes the application with: Program received signal: “EXC_BAD_ACCESS”. Someone suggested not doing the malloc and pass the point var/pointer as: &point, however that still gave me a EXC_BAD_ACCESS. What I am (and it looks like Apple) doing wrong??? Thanks in advance.

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  • Java2d: Set gradient for a lines

    - by Algorist
    Hi, I am having multiple points in a plane and some hundreds of lines pass through those points. Some points can have more lines passing through them than other points. I want to show some kind of more gradient or brightness associated with lines crowded together. Is this possible to do in java2d. Please refer to this : http://ft.ornl.gov/doku/_media/ft/projects/paraxis.jpg Thank you.

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  • iPhone OS: Is there a way to set up KVO between two ManagedObject Entities?

    - by nickthedude
    I have 2 entities I want to link with KVO, one a single statTracker class that keeps track of different stats and the other an achievement class that contains information about achievements. Ideally what I want to be able to do is set up KVO by having an instance of the achievement class observe a value on the statTracker class and also set up a threshold value at which the achievement instance should be "triggered"(triggering in this case would mean showing a UIAlertView and changing a property on the achievement class.) I'd like to also set these relationships up on instantiation of the achievement class if possible so kind of like this: Achievement *achievement1 = (Achievement *)[NSEntityDescription insertNewObjectForEntityForName:@"Achievement" inManagedObjectContext:[[CoreDataSingleton sharedCoreDataSingleton] managedObjectContext]]; [achievement1 setAchievementName:@"2 time launcher"]; [achievement1 setAchievementDescription:@"So you've decided to come back for more eh? Here are some achievement points to get you going"]; [achievement1 setAchievementPoints:[NSNumber numberWithInt:300]; [achievement1 setObjectToObserve:@"statTrackerInstace" propertyToObserve:@"timesLaunched" valueOfPropertToSatisfyAchievement:2] Anyone out there know how I would set this up? Is there some way I could do this by way of relationships that I'm not seeing? Thanks, Nick

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  • Add shading to clipped UIView

    - by huggie
    I'm creating an iphone application. I have this UIView whose content is clipped with a path. I want to add shading and/or shadow to it. What's the best way to do this? For shadow, I tried CGContextSetShadow() but it doesn't seem to have an effect (perhaps it's drawing outside the shown region?) . How about shading? I want it to appear along the path. What's the best way to go about it? Is it to create another narrow clip strip along the original clipping path (if it's possible to have two clip path... ) Or does this need to be done in another CALayer? I am not even sure what that is yet.

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  • Custom UIView using CALayers disappears after 180º rotation or navigation controller pop

    - by Steve Madsen
    I have a created a custom UIView subclass that is exhibiting some strange behavior. It is a spinning wheel selector, and for performance reasons it is drawn entirely into two CALayer instances. The bottom layer is the wheel itself, which is rotated using setAffineTransform: according to touches. The top layer is eye candy. drawRect: is fairly simple. If the control hasn't been drawn yet (or it's been invalidated), it calls a method that creates the images and assigns them to the layer contents property. - (void) drawRect:(CGRect)rect { if (imageLayer == nil) { [self drawIntoImageLayer]; } [self updateWheelRotation]; } When the view controller using this view first appears, everything is fine. There are two instances where the view completely disappears, however: If the device is rotated a full 180°. After a view controller is popped off the navigation stack and the view becomes visible again. drawRect: is not called either time. Interestingly enough, it IS called after a 90° orientation change, and that causes the view to re-appear. How can I ensure that a custom view using CALayers is redrawn properly in these situations?

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  • How decompose NSPredicate into components?

    - by Victor
    Is there any common way to decompose an expression created by [NSPredicate predicateWithFormat] to objects NSComprasionPredicate, NSExpression and other? For below example need to disassemble into components. [NSPredicate predicateWithFormat:@"(0 != SUBQUERY(collection, $x, $x.name == "Name").@Count)"];

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  • Can't block capslock with CGEventTap

    - by Thor Frølich
    I'm using Quartz CGEventTap in an attempt to globally intercept capslock presses and block them (to have them do something useful instead). I succesfully detect capslock presses but have so far been unable to block them. My code (originating from this stackoverflow answer) is something like this: eventTap = CGEventTapCreate(kCGHIDEventTap, kCGTailAppendEventTap, kCGEventTapOptionDefault, eventMask, myCGEventCallback, &oldFlags); runLoopSource = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopCommonModes); CGEventTapEnable(eventTap, true); CGEventRef myCGEventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef theEvent, void *refcon) { CGEventFlags *oldFlags = (CGEventFlags *)refcon; switch (type) { case kCGEventFlagsChanged: { CGEventFlags newFlags = CGEventGetFlags(theEvent); CGEventFlags changedFlags = *oldFlags ^ newFlags; *oldFlags = newFlags; if (changedFlags == 65536) { NSLog(@"Capslock pressed. Let's not return the event"); return NULL; } break; } default: break; } NSLog(@"Different modifier than capslock. Returning the event"); return theEvent; } If I understand correctly returning NULL should effectively block the keypress from propagating. Indeed it also does for "normal" keyup and -down events. However capslock toggles regardless. Any ideas why that is? Am I making incorrect assumptions? And/or how can I do things differently to achieve my goal? Thanks, Thor

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  • Merge overlapping triangles into a polygon

    - by nornagon
    I've got a bunch of overlapping triangles from a 3D model projected into a 2D plane. I need to merge each island of touching triangles into a closed, non-convex polygon. The resultant polygons shouldn't have any holes in them (since the source data doesn't). Many of the source triangles share (floating point identical) edges with other triangles in the source data. What's the easiest way to do this? Performance isn't particularly important, since this will be done at design time.

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  • X (close) shape in SVG

    - by danke
    I'm trying to make this SVG shape (ignore the color background, just the X shape) Close SVG Path but don't have Illustrator and wouldn't know how to use it. Can someone help out with the general idea, or point me to alternatives. I'm using it in flex.

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  • Importing large datasets on iPhone using CoreData

    - by Matthes
    Hi there, I'm facing very annoying problem. My iPhone app is loading it's data from a network server. Data are sent as plist and when parsed, it neeeds to be stored to SQLite db using CoreData. Issue is that in some cases those datasets are too big (5000+ records) and import takes way too long. More on that, when iPhone tries to suspend the screen, Watchdog kills the app because it's still processing the import and does not respond up to 5 seconds, so import is never finished. I used all recommended techniques according to article "Efficiently Importing Data" http://developer.apple.com/mac/library/DOCUMENTATION/Cocoa/Conceptual/CoreData/Articles/cdImporting.html and other docs concerning this, but it's still awfully slow. Solution I'm looking for is to let app suspend, but let import run in behind (better one) or to prevent attempts to suspend the app at all. Or any better idea is welcomed too. Any tips on how to overcome these issues are highly appreciated! Thanks

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  • Lighting does not work with gluSphere

    - by badcodenotreat
    This is a simple issue that I'm somewhat ashamed to ask for help on. I'm making a simple call to gluSphere to render a sphere, however, it does not light properly even though I'm pretty sure I added the normals and lighting correctly. If, however, I add a texture, the model lights normally, except it seems to be always SMOOTH, and I cannot change it to flat. This is the lighting code in my init() function: gl.glLightfv( GL.GL_LIGHT0, GL.GL_AMBIENT , AMBIENT_LIGHT, 0 ); gl.glLightfv( GL.GL_LIGHT0, GL.GL_DIFFUSE , DIFFUSE_LIGHT, 0 ); gl.glLightfv( GL.GL_LIGHT0, GL.GL_POSITION, light_pos , 0 ); gl.glEnable ( GL.GL_LIGHT0 ); gl.glEnable ( GL.GL_LIGHTING ); this is my sphere code in my display() function: gl.glColor3d(1.0, 1.0, 1.0); glu.gluQuadricDrawStyle (quad, GLU.GLU_FILL); glu.gluQuadricNormals (quad, GLU.GLU_FLAT); glu.gluQuadricOrientation(quad, GLU.GLU_OUTSIDE); glu.gluSphere(quad, 1.0, lat, lon); Please advise.

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  • Literature and Tutorials for Writing a Ray Tracer

    - by grrussel
    I am interested in finding recommendations on books on writing a raytracer, simple and clear implementations of ray tracing that can be seen on the web, and online resources on introductory raytracing. Ideally, the approach would be incremental and tutorial in style, and explain both the programming techniques and underyling mathematics, starting from the basics.

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  • iPhone OS: Why is my managedModelObject not complying with Key Value Coding?

    - by nickthedude
    Ok so I'm trying to build this stat tracker for my app and I have built a data model object called statTracker that keeps track of all the stuff I want it to. I can set and retrieve values using the selectors, but if I try and use KVC (ie setValue: forKey: ) everything goes bad and says my StatTracker class is not KVC compliant: valueForUndefinedKey:]: the entity StatTracker is not key value coding-compliant for the key "timesLauched".' 2010-05-18 15:55:08.573 here's the code that is triggering it: NSArray *statTrackerArray = [[NSArray alloc] init]; statTrackerArray = [[CoreDataSingleton sharedCoreDataSingleton] getStatTracker]; NSNumber *number1 = [[NSNumber alloc] init]; number1 = [NSNumber numberWithInt:(1 + [[(StatTracker *)[statTrackerArray objectAtIndex:0] valueForKey:@"timesLauched"] intValue])]; [(StatTracker *)[statTrackerArray objectAtIndex:0] setValue:number1 forKey:@"timesLaunched" ]; NSError *error; if (![[[CoreDataSingleton sharedCoreDataSingleton] managedObjectContext] save:&error]) { NSLog(@"error writing to db"); } Not sure if this is enough code for you folks let me know what you need if you do need more. This would be so sweet if I could use KVC because I could then abstract all this stat tracking stuff into a single method call with a string argument for the value in question. At least that is what I hope to accomplish here. I'm actually now understanding the power of KVC but now I'm just trying to figure out how to make it work. Thanks! Nick

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  • A way to enable a LaunchDaemon to output sound?

    - by Varun Mehta
    I have a small Foundation application that checks a website and plays a sound if it sees a certain value. This application successfully plays a sound when I run it as my user from the Terminal. I've configured this app to run as a LaunchDaemon, with the following plist: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Label</key> <string>org.myorg.appidentifier</string> <key>ProgramArguments</key> <array> <string>/Users/varunm/path/to/cli/application</string> </array> <key>KeepAlive</key> <true/> <key>RunAtLoad</key> <true/> </dict> </plist> When I have this service launched I can see it successfully read in and log values from the website, but it never generates any sound. The sound files are located in the same directory as the binary, and I use the following code: NSSound *soundToPlay = [[NSSound alloc] initWithContentsOfFile:@"sound.wav" byReference:NO]; [soundToPlay setDelegate:stopper]; [soundToPlay play]; while (g_keepRunning) { [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1.0]]; } [soundToPlay setCurrentTime:0.0]; Is there any way to get my LaunchDaemon application to play sound? This machine gets run by different people, and sometimes has no one logged in, which is why I have to configure it as a LaunchDaemon.

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  • How to- NSAttributedString to CGImageRef

    - by kroko
    Hello! I'm writing a QuickLook plugin. Well, everything works. Just want to try it make better ;). Thus the question. Here is a function that returns thumbnail image and that I'm using now. QLThumbnailRequestSetImageWithData( QLThumbnailRequestRef thumbnail, CFDataRef data, CFDictionaryRef properties); ); http://developer.apple.com/mac/library/documentation/UserExperience/Reference/QLThumbnailRequest_Ref/Reference/reference.html#//apple_ref/c/func/QLThumbnailRequestSetImageWithData Right now I'm creating a TIFF - encapsulated it into NSData. An example // Setting CFDataRef CGSize thumbnailMaxSize = QLThumbnailRequestGetMaximumSize(thumbnail); NSMutableAttributedString *attributedString = [[[NSMutableAttributedString alloc] initWithString:@"dummy" attributes:[NSDictionary dictionaryWithObjectsAndKeys: [NSFont fontWithName:@"Monaco" size:10], NSFontAttributeName, [NSColor colorWithCalibratedRed:0.0 green:0.0 blue:0.0 alpha:1.0], NSForegroundColorAttributeName, nil] ] autorelease]; NSImage *thumbnailImage = [[[NSImage alloc] initWithSize:NSMakeSize(thumbnailMaxSize.width, thumbnailMaxSize.height)] autorelease]; [thumbnailImage lockFocus]; [[NSColor whiteColor] set]; NSRectFill(NSMakeRect(0, 0, thumbnailMaxSize.width, thumbnailMaxSize.height)); [attributedString drawInRect:NSMakeRect(0, 0, thumbnailMaxSize.width, thumbnailMaxSize.height)]; [thumbnailImage unlockFocus]; (CFDataRef)[thumbnailImage TIFFRepresentation]; // This is data // Setting CFDictionaryRef (CFDictionaryRef)[NSDictionary dictionaryWithObjectsAndKeys:@"kUTTypeTIFF", (NSString *)kCGImageSourceTypeIdentifierHint, nil ]; // this is properties However QuickLook provides another function to return thumbnail image, namely QLThumbnailRequestSetImage( QLThumbnailRequestRef thumbnail, CGImageRef image, CFDictionaryRef properties); ); http://developer.apple.com/mac/library/documentation/UserExperience/Reference/QLThumbnailRequest_Ref/Reference/reference.html#//apple_ref/c/func/QLThumbnailRequestSetImage I have a feeling that passing CGImage to the QL instead of TIFF data would help in speeding things up. However- I have never worked with CG context before. I know, the documentation is there :), but anyways- could anyone give an example how to turn that NSAttributed string into CGImageRef. An example is worth 10 times reading the documentation ;) Any help appreciated. Thanks in advance!

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