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2014/10/15 ¤U¤È 10:12:51
iphone Programming Glossary: precisionIntercepting/Hijacking iPhone Touch Events for MKMapView http://stackoverflow.com/questions/1121889/intercepting-hijacking-iphone-touch-events-for-mkmapview the user has put a finger down anywhere in the MKMapView. If you need to detect zooming or panning with 100 recall and precision it might be more complicated than this. What we really need is an open source implementation of MKMapView so we can add..
How to detect iPhone 5 (widescreen devices)? http://stackoverflow.com/questions/12446990/how-to-detect-iphone-5-widescreen-devices UIScreen mainScreen bounds .size.height double 568 DBL_EPSILON The use of fabs with the epsilon is here to prevent precision errors when comparing floating points as pointed in the comments by H2CO3. So from now on you can use it in standard if..
What's the difference between NSNumber and NSInteger? http://stackoverflow.com/questions/1285098/whats-the-difference-between-nsnumber-and-nsinteger bits vs 64 bits so you might as well use 64 bits. If you've declared things as CGFloat 's you suddenly get that extra precision for free when you recompile. And as iKenndac has pointed out NSNumber is a wrapper class for all of these and other primitive..
What does the Tiler Utilization statistic mean in the iPhone OpenGL ES instrument? http://stackoverflow.com/questions/1287811/what-does-the-tiler-utilization-statistic-mean-in-the-iphone-opengl-es-instrumen given appropriate scaling. You might also have to bin by position in this case if shorts scaled to provide sufficient precision aren ™t covering the range you need. These sorts of techniques might require additional draw calls but I suspect the improvement..
http://stackoverflow.com/questions/1622729/double-vs-float-on-the-iphone much slower that regular float. Is this true Evidence I am very interested in the issue because my program needs high precision calculations and I will have to compromise on speed. iphone cocoa touch floating point ieee 754 share improve this question.. iphone cocoa touch floating point ieee 754 share improve this question The iPhone can do both single and double precision arithmetic in hardware. On the 1176 original iPhone and iPhone3G they operate at approximately the same speed though you.. On the 1176 original iPhone and iPhone3G they operate at approximately the same speed though you can fit more single precision data in the caches. On the Cortex A8 iPhone3GS iPhone4 and iPad single precision arithmetic is done on the NEON unit instead..
Measuring velocity via iPhone SDK http://stackoverflow.com/questions/1994018/measuring-velocity-via-iphone-sdk from a user interaction standpoint. Also I need to feed velocity into some other calculations that I'm doing and the precision is not really what I need. It seems possible based on very few other apps I've seen notably gMeter which claims to make..
How Do I write a Timer in Objective-C? http://stackoverflow.com/questions/3519562/how-do-i-write-a-timer-in-objective-c Don't use NSTimer that way. NSTimer is normally used to fire a selector at some time interval. It isn't high precision and isn't suited to what you want to do. What you want is a High resolution timer class using NSDate Output Total time was..
Comparing float and double data types in objective C http://stackoverflow.com/questions/5024913/comparing-float-and-double-data-types-in-objective-c if f 4.2 this block of code is not executed. f is exactly 4.19999980926513671875 but you're comparing it to the double precision literal 4.2 which has the value 4.20000000000000017763568394002504646778106689453125 so the comparison fails. If instead.. so the comparison fails. If instead you compare against the single precision literal 4.2f float f 4.2 if f 4.2f this block of code is exectued. the comparison succeeds because the values are exactly.. but it is entirely deterministic one of the simplest things you can do to make it more intuitive is to not mix precisions. If you're working with float make sure all of your literals are suffixed with f to make them single precision too. This..
How can I optimize the rendering of a large model in OpenGL ES 1.1? http://stackoverflow.com/questions/5718846/how-can-i-optimize-the-rendering-of-a-large-model-in-opengl-es-1-1 information. I found that I could use GLshort instead of GLfloat for my vertices and normals without losing much precision in the rendering. This will significantly compact your geometry and lead to a nice speed boost in rendering. Bin similarly..
How can I improve the performance of my custom OpenGL ES 2.0 depth texture generation? http://stackoverflow.com/questions/6051237/how-can-i-improve-the-performance-of-my-custom-opengl-es-2-0-depth-texture-gener Instruments is pegged at 99 indicating that I'm limited by fragment processing . It currently looks like the following precision mediump float varying mediump vec2 impostorSpaceCoordinate varying mediump float normalizedDepth varying mediump float adjustedSphereRadius.. not to use branching in a shader but in this case that led to better performance than otherwise. When I simplify it to precision mediump float varying mediump vec2 impostorSpaceCoordinate varying mediump float normalizedDepth varying mediump float adjustedSphereRadius.. cycles. The change in render time based on cycle count doesn't seem linear. Finally if I just output a constant color precision mediump float void main gl_FragColor vec4 0.5 0.5 0.5 1.0 the rendering time drops to 1.1 2.3 ms on iPad 1 1.3 ms on iPhone..
track small movements of iphone with no GPS http://stackoverflow.com/questions/6158176/track-small-movements-of-iphone-with-no-gps use data provided by the gyroscope and the accelerometer. The distances I need to measure are rather small and the precision I'm looking for is 40 50cm ~2 feet at the very most. Is this possible If so what's the best way to go about it Also do you..
Is programmatically inverting the colors of an image possible? http://stackoverflow.com/questions/6672517/is-programmatically-inverting-the-colors-of-an-image-possible we need to divide by the alpha channel if it isn't zero of course to get uninflected RGB. We multiply by 255 to keep precision while still using integers int r g b if linePointer 3 r linePointer 0 255 linePointer 3 g linePointer 1 255 linePointer..
Getting the time elapsed (Objective-c) http://stackoverflow.com/questions/741830/getting-the-time-elapsed-objective-c
How can I get a precise time, for example in milliseconds in Objective-C? http://stackoverflow.com/questions/889380/how-can-i-get-a-precise-time-for-example-in-milliseconds-in-objective-c is a double with sub millisecond accuracy. NSTimeInterval is in seconds but it uses the double to give you greater precision. In order to calculate millisecond time accuracy you can do Get a current time for where you want to start measuring from..
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