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• Interpolating height for a point inside a grid based on a discrete height function.

  - by fastrack20

  Hi, I have been wracking my brain to come up with a solution to this problem. I have a lookup table that returns height values for various points (x,z) on the grid. For instance I can calculate the height at A, B, C and D in Figure 1. However, I am looking for a way to interpolate the height at P (which has a known (x,z)). The lookup table only has values at the grid intervals, and P lies between these intervals. I am trying to calculate values s and t such that: A'(s) = A + s(C-A) B'(t) = B + t(P-B) I would then use the these two equations to find the intersection point of B'(t) with A'(s) to find a point X on the line A-C. With this I can calculate the height at this point X and with that the height at point P. My issue lies in calculating the values for s and t. Any help would be greatly appreciated.

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• CGGradient Not Displaying Correctly on iPad 1 and 2

  - by daveMac

  I have been experimenting with creating my own gradients for the UI in my iOS app. I first used a CAGradientLayer but I was disappointed with the "stepped" look so I have been trying out CGGradient. enter code here I am having an issue with the Gradient displaying correctly. I have three iPads—one for each generation. The gradient looks right on the iPad 3 but not on the iPad 1 or 2. This is really strange. I was going to take a screenshot and post the two differences but even more strange, the screenshot look the same (and yes, the brightness is the same on both). The colors seem really washed out on the older iPads. I know the iPad 3 is a retina display, but I think it must be something more than that. Here is the code I am using: - (void)drawRect:(CGRect)rect { CGContextRef currentContext = UIGraphicsGetCurrentContext(); CGGradientRef skyGradient; CGColorSpaceRef rgbColorspace; size_t num_locations = 3; CGFloat locations[3] = { 0.0, .5, 1.0 }; CGFloat components[12] = { .106, .73, .93333, 1., 0.0, 0.0 , 1.0, 1., .106, .73, .93333, 1. }; rgbColorspace = CGColorSpaceCreateDeviceRGB(); skyGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations); CGRect currentBounds = self.bounds; CGPoint topLeft = CGPointMake(0.0f, 0.0f); CGPoint bottomRight = CGPointMake(CGRectGetMaxX(currentBounds), CGRectGetMaxY(currentBounds)); CGContextDrawLinearGradient(currentContext, skyGradient, topLeft, bottomRight, 0); CGGradientRelease(skyGradient); CGColorSpaceRelease(rgbColorspace); }

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• How to achieve the same effect like the unlock slider in the welcome screen of iPhone OS?

  - by mystify

  I need to do something similar, where an animation highlights the text of a button to show that it must be slided to do something. Just like that unlock thing on the iPhone. How is that done? Is there a tutorial how to achieve this effect?

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• Monochrome BitMap Library

  - by Asad Jibran Ahmed

  I am trying to create a piece of software that can be used to create VERY large (10000x10000) sized bitmaps. All I need is something that can work in monochrome, since the required output is a matrix containing details of black and white pixels in the bitmap. The closest thing I can think of is a font editor, but the size is a problem. Is there any library out there that I can use to create the software, or will I have to write the whole thing from the start?

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• How can I add graphic elements in android using code?

  - by masterkapu

  How can I add graphic elements in android without the use of drag it into main.xml? I mean using code to make them

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• Blit Queue Optimization Algorithm

  - by martona

  I'm looking to implement a module that manages a blit queue. There's a single surface, and portions of this surface (bounded by rectangles) are copied to elsewhere within the surface: add_blt(rect src, point dst); There can be any number of operations posted, in order, to the queue. Eventually the user of the queue will stop posting blits, and ask for an optimal set of operations to actually perform on the surface. The task of the module is to ensure that no pixel is copied unnecessarily. This gets tricky because of overlaps of course. A blit could re-blit a previously copied pixel. Ideally blit operations would be subdivided in the optimization phase in such a way that every block goes to its final place with a single operation. It's tricky but not impossible to put this together. I'm just trying to not reinvent the wheel. I looked around on the 'net, and the only thing I found was the SDL_BlitPool Library which assumes that the source surface differs from the destination. It also does a lot of grunt work, seemingly unnecessarily: regions and similar building blocks are a given. I'm looking for something higher-level. Of course, I'm not going to look a gift horse in the mouth, and I also don't mind doing actual work... If someone can come forward with a basic idea that makes this problem seem less complex than it does right now, that'd be awesome too. EDIT: Thinking about aaronasterling's answer... could this work? Implement customized region handler code that can maintain metadata for every rectangle it contains. When the region handler splits up a rectangle, it will automatically associate the metadata of this rectangle with the resulting sub-rectangles. When the optimization run starts, create an empty region handled by the above customized code, call this the master region Iterate through the blt queue, and for every entry: Let srcrect be the source rectangle for the blt beng examined Get the intersection of srcrect and master region into temp region Remove temp region from master region, so master region no longer covers temp region Promote srcrect to a region (srcrgn) and subtract temp region from it Offset temp region and srcrgn with the vector of the current blt: their union will cover the destination area of the current blt Add to master region all rects in temp region, retaining the original source metadata (step one of adding the current blt to the master region) Add to master region all rects in srcrgn, adding the source information for the current blt (step two of adding the current blt to the master region) Optimize master region by checking if adjacent sub-rectangles that are merge candidates have the same metadata. Two sub-rectangles are merge candidates if (r1.x1 == r2.x1 && r1.x2 == r2.x2) | (r1.y1 == r2.y1 && r1.y2 == r2.y2). If yes, combine them. Enumerate master region's sub-rectangles. Every rectangle returned is an optimized blt operation destination. The associated metadata is the blt operation`s source.

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• Finding the centroid of a polygon?

  - by user146780

  I have tried: for each vertex, add to total, divide by number of verities to get center. I'v also tried: Find the topmost, bottommost - get midpoint... find leftmost, rightmost, find midpoint. Both of these did not return the perfect center because I'm relying on the center to scale a polygon. I want to scale my polygons so I may put a border around them. What is the best way to find the centroid of a polygon given that the polygon may be concave, convex and have many many sides of various lengths. Thanks

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• Is there a table of OpenGL extensions, versions, and hardware support somewhere?

  - by Thomas

  I'm looking for some resource that can help me decide what OpenGL version my game needs at minimum, and what features to support through extensions. Ideally, a table of the following format: 1.0 1.1 1.2 1.2.1 1.3 ... multitexture - ARB ARB core core texture_float - EXT EXT ARB ARB ... (Not sure about the values I put in, but you get the idea.) The extension specs themselves, at opengl.org, list the minimum OpenGL version they need, so that part is easy. However, many extensions have been accepted and became core standard in subsequent OpenGL versions, but it is very hard to find when that happened. The only way I could find is to compare the full OpenGL standards document for each version. On a related note, I would also very much like to know which extensions/features are supported by which hardware, to help me decide what features I can safely use in my game, and which ones I need to make optional. For example, a big honkin' table like this: MAX_TEXTURE_IMAGE_UNITS MAX_VERTEX_TEXTURE_IMAGE_UNITS ... GeForce 6xxx 8 4 GeForce 7xxx 16 8 ATi x300 8 4 ... (Again, I'm making the values up.) The table could list hardware limitations from glGet but also support for particular extensions, and limitations of such extension support (e.g. what floating-point texture formats are supported in hardware). Any pointers to these or similar resources would be hugely appreciated!

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• Point to point linear gradient?

  - by user146780

  I want to make an application that can generate point to point gradient (like Photoshop does). I'm familiar with how to generate an up to down gradient but not point to point. How is this conceptually done. Thanks

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• When not to do maximum compression in png?

  - by user1444680

  Intro When saving png images through GIMP, I've always used level 9 (maximum) compression, as I knew that it's lossless. Now I've to specify compression level when saving png format image through GD extension of PHP. Question Is there any case when I shouldn't compress PNG to maximum level? Like any compatibility issues? If there's no problem then why to ask user; why not automatically compress to max?

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• How can I tell if a closed path contains a given point?

  - by Tom Seago

  In Android, I have a Path object which I happen to know defines a closed path, and I need to figure out if a given point is contained within the path. What I was hoping for was something along the lines of path.contains(int x, int y) but that doesn't seem to exist. The specific reason I'm looking for this is because I have a collection of shapes on screen defined as paths, and I want to figure out which one the user clicked on. If there is a better way to be approaching this such as using different UI elements rather than doing it "the hard way" myself, I'm open to suggestions. I'm open to writing an algorithm myself if I have to, but that means different research I guess.

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• Codebase for making a Flash-based interactive map with SVG vector data?

  - by Mike

  I'm looking for a way to take SVG path info (basically a string of coordinates) and dynamically draw it with Actionscript. Icing on the cake would be if those shapes could detect mouse events to trigger JS and dynamically change their appearance (fill, stroke, etc...). I'm currently trying something similar to this (http://raphaeljs.com/australia.html) using SVG but it's just too slow in IE. I've also tried Google's SVG Web (http://code.google.com/p/svgweb/) which basically does exactly what I'm looking for (it converts SVG to Flash in IE) but again, it's sloooooow - which is why I'm considering doing the whole shebang in Flash. Anyone know of some links to point me in the right direction?

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• How to force Mac window to foreground?

  - by Thomi

  How can I programmatically force a mac window to be the front window? I have the window handle, and want to ensure that my window is displayed above all other windows. I can use both Carbon & Cocoa for this.

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• What's the simplest and fastest way to draw a parse tree using .Net?

  - by mp

  I've written a simple top down parser using c#. It's a console application. I'd like the parser could save, at the end of the computation, an image file of the parse tree. I think I could use graphviz, but I'd like to know your opinion. Thanks.

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• Writing BMP image in pure c/c++ without other libraries

  - by den bardadym

  In my algorithm i need create information output. I must to write boolean matrix in bmp file. It must be monocromic image, where pixel is white if matrix on such element is true. Main problem is bmp header and how to write this. Thanks.

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• Border in DrawRectangle

  - by undsoft

  Well, I'm coding the OnPaint event for my own control and it is very nescessary for me to make it pixel-accurate. I've got a little problem with borders of rectangles. See picture: These two rectangles were drawn with the same location and size parameters, but using different size of the pen. See what happend? When border became larger it has eaten the free space before the rectangle (on the left). I wonder if there is some kind of property which makes border be drawn inside of the rectangle, so that the distance to rectangle will always be the same. Thanks.

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• Simple question about the lunarlander example.

  - by Smills

  I am basing my game off the lunarlander example. This is the run loop I am using (very similar to what is used in lunarlander). I am getting considerable performance issues associated with my drawing, even if I draw almost nothing. I noticed the below method. Why is the canvas being created and set to null each cycle? @Override public void run() { while (mRun) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas();//null synchronized (mSurfaceHolder) { updatePhysics(); doDraw(c); } } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } Most of the times I have read anything about canvases it is more along the lines of: mField = new Bitmap(...dimensions...); Canvas c = new Canvas(mField); My question is: why is Google's example done that way (null canvas), what are the benefits of this, and is there a faster way to do it?

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• Level of Detail for 3D terrains/models in Mobile Devices (Android / XNA )

  - by afriza

  I am planning to develop for WP7 and Android. What is the better way to display (and traverse) 3D scene/models in term of LoD? The data is planned to be island-wide (Singapore). 1) Real-Time Dynamic Level of Detail Terrain Rendering 2) Discrete LoD 3) Others? And please advice some considerations/algorithms/resources/source codes. something like LoD book also Okay. Side note: I am a beginner in this area but pretty well-versed in C/C++. And I haven't read the LoD book. Related posts: - Distant 3D object rendering [games]

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• Why are all my masked views unmasked in my view snapshot?

  - by mystify

  I'm taking a snapshot of an view. This view has got some subviews which have layer masks applied to them. For some reason, those masks take no effect in the snapshot and the masked parts are completely visible. UIGraphicsBeginImageContext(theView.frame.size); [theView.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); I assume this is a bug in the framework. But maybe it's not? Did I do anything wrong here?

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• Displaying bitmaps in relative positions

  - by JonF

  I'd like to put a couple images on a surfaceview. I understand that the screen sizes of android devices can vary, so I don't think I can just use an x y position or I might end up placing it off different screens. Say I want to put two boxes in the center of the screen, a blue one and a red one. The blue one is to the left of the red one. How can I accomplish that while accounting for different screen sizes?

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• How can I capture the amount of surface area that the user is making contact with the iPhone screen?

  - by BeachRunnerJoe

  Is there a way to capture the amount of screen that is making contact with the users? I assume there is since this finger painting app shows the ipad responding to only the pixels that the user makes contact with. Thanks so much in advance for your help!

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• Simulating brush strokes for painting application

  - by DrRobot

  I'm trying to write an application that can be used to create pictures that look like paintings using simulated brush strokes. Are there any good sources for simple ways of simulating brush strokes? For example, given a list of mouse positions that the user has dragged the mouse through, a brush width and a brush texture, how do I determine what to draw to the canvas? I've tried angling the brush texture in the direction of the mouse movement and dabbing several brush texture images along the path, but it doesn't look great. I think I'm missing something where the brush texture should shrink and grow on corners. Any simple to follow links would be appreciated. I've found complex academic papers on simulating e.g. oil paints but I just want a basic algorithm to use that produces OK results if possible.

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• How do I integrate a BSDF into a ray caster.

  - by pelb

  I'm trying to implement sub surface scattering at isosurfaces and looked up how a BSDF works mathematically. Implementing the reflective and diffuse part seems to be quite easy as i just have to evaluate phong at the isosurface intersection, but how do you I apply the transmissive part of the BSDF? In what way do i have to modify the ray direction. Any pointers to a practical implementation are welcome. Thanks and So long!

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• iPhone animated banner : which framework to use

  - by Julien

  Hi folks, I'm willing to create a little frame to display animated ads in my app. It could be simple little animations, or "3D" transition between ads, or combination of both. I'm not familiar with graphic frameworks, I just used CoreGraphics, which I think is not optimized for that. I thought of OpenGL, but maybe that's too much and takes too much ressources just for this little thing. What do you think ?

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• [CA_COLOR_OPAQUE] things that make a layer non-opaque. scaled CAGradientLayer?

  - by mahal tertin

  i spent some time with the environment variable CA_COLOR_OPAQUE = 1 and have my findings to share. things that make a CALayer non-opaque (slow, more memory, ...): * contents with alpha (like an NSImage with an icon) * NSImage/CGImage from a pdf as contents (even when the pdf does not contain any alpha and opaque=YES) * backgroundColor = nil * CATextLayer with text in a (because it is contents with alpha) * rounded corners? maybe/sometimes * masksToBounds? not necessarily as we scale most of tree with CATransform3DScale on sublayerTransform i found also these rather irritating non-opaque: * CAGradientLayer that is somewhere down in this scaled tree (even when set all the gradient colors without alpha) * edgeAntialiasingMask != 0 of a layer that is somewhere down in this scaled tree the last two do not make sense to me. why should it be non opaque? what do i see? if anyone has any thoughts on these findings, i'm happy to learn as i couldn't find such a list yet.

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