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• When should a uniform be used in shader programming?

  - by Phineas

  In a vertex shader, I calculate a vector using only uniforms. Therefore, the outcome of this calculation is the same for all instantiations of the vertex shader. Should I just do this calculation on the CPU and upload it as a uniform? What if I have ten such calculations? If I upload a lot of uniforms in this way, does CPU-GPU communication ever get so slow that recomputing such values in the vertex shader is actually faster?

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• ID3D10Device Memory Allocation Strategy and E_OUTOFMEMORY

  - by Buzz

  Hi,guys, I want to know more detail of memory allocation strategy in D3D10Device. Could you give me some help? First questions is: I know D3D10 has done some work on memory virtualization that means client don't need to consider where the buffer was reserved, GPU memory, AGP memory or Process system memory. Is this correct? Second question is: When I use ID3D10Device to CreateBuffer continuously, no matter what buffer desc type is, for example ID3D10Device::CreateBuffer( ... D3D10_USAGE_DEFAULT ... ); ID3D10Device::CreateBuffer( ... D3D10_USAGE_IMMUTABLE ... ); ID3D10Device::CreateBuffer( ... D3D10_USAGE_DYNAMIC ... ); ID3D10Device::CreateBuffer( ... D3D10_USAGE_STAGING ... ); etc, if CreateBuffer return error code "E_OUTOFMEMORY", does that mean process virtual memory is exhausted? And at this time, memory allocation on process default heap would also be failed? Thanks in advance!

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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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• Calculating pixel size on an iPhone

  - by ian1971

  Is there a way in the iPhone SDK to calculate the size (in millimeters) of a single pixel?

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• Fast rectangle to rectangle intersection

  - by Jeremy Rudd

  What's a fast way to test if 2 rectangles are intersecting? A search on the internet came up with this one-liner (WOOT!), but I don't understand how to write it in Javascript, it seems to be written in an ancient form of C++. struct { LONG left; LONG top; LONG right; LONG bottom; } RECT; bool IntersectRect(const RECT * r1, const RECT * r2) { return ! ( r2->left > r1->right || r2->right left || r2->top > r1->bottom || r2->bottom top ); }

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• How to handle alpha in a manual "Overlay" blend operation?

  - by quixoto

  I'm playing with some manual (walk-the-pixels) image processing, and I'm recreating the standard "overlay" blend. I'm looking at the "Photoshop math" macros here: http://www.nathanm.com/photoshop-blending-math/ (See also here for more readable version of Overlay) Both source images are in fairly standard RGBA (8 bits each) format, as is the destination. When both images are fully opaque (alpha is 1.0), the result is blended correctly as expected: But if my "blend" layer (the top image) has transparency in it, I'm a little flummoxed as to how to factor that alpha into the blending equation correctly. I expect it to work such that transparent pixels in the blend layer have no effect on the result, opaque pixels in the blend layer do the overlay blend as normal, and semitransparent blend layer pixels have some scaled effect on the result. Can someone explain to me the blend equations or the concept behind doing this? Bonus points if you can help me do it such that the resulting image has correctly premultiplied alpha (which only comes into play for pixels that are not opaque in both layers, I think.) Thanks! // factor in blendLayerA, (1-blendLayerA) somehow? resultR = ChannelBlend_Overlay(baseLayerR, blendLayerR); resultG = ChannelBlend_Overlay(baseLayerG, blendLayerG); resultB = ChannelBlend_Overlay(baseLayerB, blendLayerB); resultA = 1.0; // also, what should this be??

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• WebSocket support on mobile devices

  - by Marco W.

  For an Android multiplayer game's communication between players I'm using a WebSocket server and TooTallNate's Java library on the client side to enable WebSocket support in the Android app. So just to point it out clearly, WebSocket support in mobile browsers is not important to me. Unfortunately, users report that they're experiencing problems such as connection failures or unreceived messages. Is that a general problem of WebSockets on mobile devices (blocked ports, firewalls, mobile Internet connection) or is that probably a flaw in the client side code? Do you have experience with WebSocket client libraries such as the one above? I've just discovered autobahn.ws for Android - but I don't know if it's worth switching from my current library (see above). What about WAMP? Is WebSocket technology not exactly the adequate solution so that I should use the sub-protocol (?) WAMP?

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• How to draw a drop shadow AND gradient with quartz2d?

  - by Luke

  Hello! I've a custom shape drawing using coregraphics and i want to add a drop shadow and a gradient to it also. I've been trying and searching a lot of informations on how to combine and do this, but i can't get it to work. I'm able to draw only one either. Anyone doing this already or know how to do this? Thank you.

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• Haskell: OpenGL, how to prevent immediate window closing

  - by Yasir Arsanukaev

  Hello. Whenever I close OpenGL window it makes ghci console from which the app was started to immediately disappear. Is there a way to prevent this behaviour? A sample app. Thanks.

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• Simulating 3D 'cards' with just orthographic rendering

  - by meds

  I am rendering textured quads from an orthographic perspective and would like to simulate 'depth' by modifying UVs and the vertex positions of the quads four points (top left, top right, bottom left, bottom right). I've found if I make the top left and bottom right corners y position be the same I don't get a linear 'skew' but rather a warped one where the texture covering the top triangle (which makes up the quad) seems to get squashed while the bottom triangles texture looks normal. I can change UVs, any of the four points on the quad (but only in 2D space, it's orthographic projection anyway so 3D space won't matter much). So basically I'm trying to simulate perspective on a two dimensional quad in orthographic projection, any ideas? Is it even mathematically possible/feasible? ideally what I'd like is a situation where I can set an x/y rotation as well as a virtual z 'position' (which simulates z depth) through a function and see it internally calclate the positions/uvs to create the 3D effect. It seems like this should all be mathematical where a set of 2D transforms can be applied to each corner of the quad to simulate depth, I just don't know how to make it happen. I'd guess it requires trigonometry or something, I'm trying to crunch the math but not making much progress. here's what I mean: Top left is just the card, center is the card with a y rotation of X degrees and right most is a card with an x and y rotation of different degrees.

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• How to structure class to support imported 3d model ?

  - by brainydexter

  Hello, I've written a C++ library that reads in this 3d model file (collada DAE). uptil now, I would output a list of triangles and handle each at rendering stage. But now, I need to attach some Bounding sphere information with the imported model. I need some advice on how should I organize this in code. Here are some specs of the 3D file format: - 3D model is represented as a Tree consisting of nodes - each node can contain other nodes, geometry information, transformation etc My requirements: - a bounding sphere associated with each node, thereby yielding a tree of bounding sphere hierarchy for the model itself. - actual vertex information What would be the recommended way to deal with this situation? Thanks

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• Asset tracking in "real-time" - how best to display in browser?

  - by mawg

  I am developing an asset tracking system, standard LAMP, and now am wondering how best to present the data to the user in the browser. I expect to track and most a few thousand items, and to refresh them every second or so. I want to draw a floorplan or map of the area and represent the assets the assets symbolically on that (with different symbols for different classes of assets). Additionally, the user should be able to click on an asset to interact with it, and search for a particular asset and centre the screen on it, draw a circle round it, etc http://graphite.wikidot.com/ Looks good - is there any alternative? At its simplest, I suppose I could just generate a JPEG and display it, using CSS to let me know if/where a user clicks ... but what's the "best" way to do it?

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• What is faster with PictureBox? Many small redraws or complete redraw.

  - by kornelijepetak

  I have a PictureBox (WinMobile 6 WinForm) on which I draw some images. There is a background image that goes in the background and it does not change. However objects that are drawn on the picturebox are moving during the application so I need to refresh the background. Since items that are redrawn fill from 50% to 80% of the surface, the question is which of the two is faster: 1) Redraw only parts of the background image that have been changed (previous+next location of the moving object). 2) Redraw complete background and then draw all the objects in their current position. Now, the reason for asking is because I am not sure how much of processor power is needed for a single drawImage operation and what are the time consuming factors. I am aware if there is almost complete coverage of the background, it would be stupid to redraw portions of it, because by drawing portions I will have drawn the complete picture. But since sometimes only half of the image had changed (some objects remained in their old position), it may (perhaps) be benefitial to redraw only those regions. But I need your insight on this... Thanks.

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• Unexplained crashs with coregraphic

  - by Ziggy

  Hello there, i'm on this bug for a week now, and i can't solve it. I have some crash with coregraphic calls, it happen randomly (sometimes after 2 mn, or just at the start), but often at the same places in the code. I have a class that just wrap a CGContext, it have a CGContextRef as member. This Object is re-created each time DrawRect() is called, so the CGContextRef is always up-to-date. The draw calls came from the main thread, only After looking for this kind of error, it appear that it should be object Release related. Here is an example of an error : #0 0x90d8a7a7 in ___forwarding___ #1 0x90d8a8b2 in __forwarding_prep_0___ #2 0x90d0d0b6 in CFRetain #3 0x95e54a5d in CGColorRetain #4 0x95e5491d in CGGStateCreateCopy #5 0x95e5486d in CGGStackSave #6 0x95e54846 in CGContextSaveGState #7 0x00073500 in CAutoContextState::CAutoContextState at Context.cpp:47 the AutoContextSave() class look like this : class CAutoContextState { private: CGContextRef m_Hdc; public: CAutoContextState(const CGContextRef& Hdc) { m_Hdc = Hdc; CGContextSaveGState(m_Hdc); } virtual ~CAutoContextState() { CGContextRestoreGState(m_Hdc); } }; It crash at CGContextSaveGState(m_Hdc). Here is what i see into GDB: * -[Not A Type retain]: message sent to deallocated instance 0x16a148b0. When i type malloc-history on the address, i have this : 0: 0x954cf10c in malloc_zone_malloc 1: 0x90d0d201 in _CFRuntimeCreateInstance 2: 0x95e3fe88 in CGTypeCreateInstanceWithAllocator 3: 0x95e44297 in CGTypeCreateInstance 4: 0x95e58f57 in CGColorCreate 5: 0x71fdd in _ZN4Flux4Draw8CContext10DrawStringERKNS_7CStringEPKNS0_5CFontEPKNS0_6CBrushERKNS_5CRectENS0_12tagAlignmentESE_NS0_17tagStringTrimmingEfiPKf at /Volumes/Sources Mac/Flux/Sources/DotFlux/Projects/../Draw/CoreGraphic/Context.cpp:1029 Which point me at this line of code : f32 components[] = {pSolidBrush->GetColor().GetfRed(), pSolidBrush->GetColor().GetfGreen(), pSolidBrush->GetColor().GetfBlue(), pSolidBrush->GetColor().GetfAlpha()}; //{ 1.0, 0.0, 0.0, 0.8 }; CGColorRef TextColor = CGColorCreate(rgbColorSpace, components); Point this func : CGColorCreate(); Any help would be appreciated, i need to finish this task very soon, but i don't know how to resolve this :( Thanks.

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• Remote Service Vs. Local Service

  - by Nguyen Dai Son

  Dear All, I am a newbiew to Android. I had read a lot of articles about Android Service but I am not clearly understanding what defferent between Local Service and Remote Service (except for "Local Service run in the same process as the lunching activity; remote services run in their own process" - The Busy Coder's Guide to Android Development - Mark L. Murphy ). Please shows me what different between Local Service and Remote Service. What's the advantage/disadvantage of using Local Service. What's the advantage/disadvantage of using Remote Service. Thanks & best regards Dai Son

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• Alpha blending colors in .NET Compact Framwork 2.0

  - by Adam Haile

  In the Full .NET framework you can use the Color.FromArgb() method to create a new color with alpha blending, like this: Color blended = Color.FromArgb(alpha, color); or Color blended = Color.FromArgb(alpha, red, green , blue); However in the Compact Framework (2.0 specifically), neither of those prototypes are valid, you only get: Color.FromArgb(int red, int green, int blue); and Color.FromArgb(int val); The first one, obviously, doesn't even let you enter an alpha value, but the documentation for the latter shows that "val" is a 32bit ARGB value (as 0xAARRGGBB as opposed to the standard 24bit 0xRRGGBB), so it would make sense that you could just build the ARGB value and pass it to the function. I tried this with the following: private Color FromARGB(byte alpha, byte red, byte green, byte blue) { int val = (alpha << 24) | (red << 16) | (green << 8) | blue; return Color.FromArgb(val); } But no matter what I do, the alpha blending never works, the resulting color always as full opacity, even when setting the alpha value to 0. Has anyone gotten this to work on Compact Framework?

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• Issue when I'm trying to draw gradient in swift

  - by bagusflyer

  I got an error when I was trying to draw gradient in Swift code: GradientView.swift:31:40: Could not find an overload for '__conversion' that accepts the supplied arguments Here is my code: let context : CGContextRef = UIGraphicsGetCurrentContext() let locations :CGFloat[] = [ 0.0, 0.25, 0.5, 0.75 ] let colors = [UIColor.redColor().CGColor,UIColor.greenColor().CGColor,UIColor.blueColor().CGColor, UIColor.yellowColor().CGColor] let colorspace : CGColorSpaceRef = CGColorSpaceCreateDeviceRGB() let gradient : CGGradientRef = CGGradientCreateWithColors(colorspace, colors, locations) //CGGradientCreateWithColors(colorspace,colors,locations) let startPoint : CGPoint = CGPointMake(0, 0) let endPoint : CGPoint = CGPointMake(500,500) CGContextDrawLinearGradient(context, gradient,startPoint, endPoint, 0); The problem is the CGGradientCreateWithColors takes CFArray not a normal Swift Array. I have no idea how to convert CFArray to Array and can't find anything in Apple's document. Any idea? Thanks

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• CALayer and Off-Screen Rendering

  - by Luke Mcneice

  I have a Paging UIScrollView with a contentSize large enough to hold a number of small UIScrollViews for zooming, The viewForZoomingInScrollView is a viewController that holds a CALayer for drawing a PDF page onto. This allows me to navigate through a PDF much like the ibooks PDF reader. The code that draws the PDF (Tiled Layers) is located in: - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx; And simply adding a 'page' to the visible screen calls this method automatically. When I change page there is some delay before all the tiles are drawn, even though the object (page) has already been created. What i want to be able to do is render the next page before the user scrolls to it, thus preventing the visible tiling effect. However, i have found that if the layer is located offscreen adding it to the scrollview doesn't call the drawLayer. Any Ideas/common gotchas here? I have tried: [viewController.view.layer setNeedsLayout]; [viewController.view.layer setNeedsDisplay]; NB: The fact that this is replicating the ibooks functionally is irrelevant within the context of the full app.

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• minimum enclosing rectangle of fixed aspect ratio

  - by Ramya Narasimha

  I have an Image with many rectangles at different positions in the image and of different sizes (both overlapping and non-overlapping). I also have a non-negative scores associated with each of these rectangles. My problem now is to find one larger rectangle *of a fixed (given) aspect ratio* that encloses as many of these rectangles as possible. I am looking for an algorithm to do this, if anyone has a solution, even a partial one it would be helpful. Please note that the positions of the rectangles in the image is fixed and cannot be moved around and there is no orientation issue as all of them are upright.

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• RAW key generation in IOS with AES

  - by sudheer

  I am novice to the cryptography in ios . I got a requirement to convert android encryption code into IOS . Below is the android code part. I need that in IOS . Can any one please help me out in this . I need this below android code in IOS. private static byte[] getRawKey(byte[] seed) throws Exception { KeyGenerator kgen = KeyGenerator.getInstance("AES"); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed(seed); kgen.init(256, sr); SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); return raw; }

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• What are the names of network interfaces on the Motorola CLIQ?

  - by RS

  The network interfaces on Android interfaces are listed as directories in the file system in /sys/class/net/. For most Android devices the network interface for gprs traffic is called rmnet0 and for Wi-Fi it's usually eth0 or tiwlan0. I suspect that the cell interface for the Motorola CLIQ is rmnet0, but I would like to have this confirmed + know the name of the Wi-Fi interface. Also it would be good to know the device id for this model. This is the value available as android.os.Build.DEVICE in the Java SDK. (E.g. T-Mobile G1 uses dream, Samsung Galaxy uses GT-I7500, and Motorolda Droid uses sholes.)

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• Writing to a java socket channel which should be closed does not generate an exception

  - by Dan Serfaty

  Hi all, We have a java server that keeps a socket channel open with an Android client in order to provide push capabilities to our client application. However, after putting the Android in airplane mode, which I expected would sever the connection, the server can still write to the SocketChannel object associated with that Android client and no error is thrown. Calling SocketChannel.isConnected() before writing to it returns true. What are we missing? Is the handling of sockets different with mobile devices? Thanks in advance for your help.

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• Pango Cursor Rendering and Highlighting....

  - by user367255

  How do you render the cursor and create highlighting for selected text in Pango? Also, can I use PangoCairo to render parts of a layout at a time, so I can draw it in different ways (such as with an outline)? Finally, how did you get your understanding of Pango, there doesn't seem to be very many tutorials and the technical documentation only describes the functions. Thanks!

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• How i access the array of CGPoints to draw the graph?

  - by Rajendra Bhole

  Hi, I have the code in which i want to develop the graph.The code is, NSArray *coordinate = [[NSArray alloc] initWithObjects: @"42,213", @"75,173", @"108,153", @"141,133", @"174,113", @"207,73", @"240,33", nil]; CGContextSetRGBFillColor(ctx, 255, 0, 0, 1.0); CGContextSetLineWidth(ctx, 8.0); for(int intIndex = 0; intIndex < [coordinate count]; fltX1+=33, intIndex++) { CGContextMoveToPoint(ctx, fltX1+37, fltY2+18); CGPoint point = [[coordinate objectAtIndex:intIndex] CGPointValue]; CGContextAddLineToPoint(ctx, point); CGContextStrokePath(ctx); } The problem is that the function of CGContextAddLineToPoint(ctx, point); not working properly. How i drawing the line in the graph using above code????????

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