x4000 - Developer IT

Fixed point math in c#?

- by x4000

Hi there, I was wondering if anyone here knows of any good resources for fixed point math in c#? I've seen things like this (http://2ddev.72dpiarmy.com/viewtopic.php?id=156) and this (http://stackoverflow.com/questions/79677/whats-the-best-way-to-do-fixed-point-math), and a number of discussions about whether decimal is really fixed point or actually floating point (update: responders have confirmed that it's definitely floating point), but I haven't seen a solid C# library for things like calculating cosine and sine. My needs are simple -- I need the basic operators, plus cosine, sine, arctan2, PI... I think that's about it. Maybe sqrt. I'm programming a 2D RTS game, which I have largely working, but the unit movement when using floating-point math (doubles) has very small inaccuracies over time (10-30 minutes) across multiple machines, leading to desyncs. This is presently only between a 32 bit OS and a 64 bit OS, all the 32 bit machines seem to stay in sync without issue, which is what makes me think this is a floating point issue. I was aware from this as a possible issue from the outset, and so have limited my use of non-integer position math as much as possible, but for smooth diagonal movement at varying speeds I'm calculating the angle between points in radians, then getting the x and y components of movement with sin and cos. That's the main issue. I'm also doing some calculations for line segment intersections, line-circle intersections, circle-rect intersections, etc, that also probably need to move from floating-point to fixed-point to avoid cross-machine issues. If there's something open source in Java or VB or another comparable language, I could probably convert the code for my uses. The main priority for me is accuracy, although I'd like as little speed loss over present performance as possible. This whole fixed point math thing is very new to me, and I'm surprised by how little practical information on it there is on google -- most stuff seems to be either theory or dense C++ header files. Anything you could do to point me in the right direction is much appreciated; if I can get this working, I plan to open-source the math functions I put together so that there will be a resource for other C# programmers out there. UPDATE: I could definitely make a cosine/sine lookup table work for my purposes, but I don't think that would work for arctan2, since I'd need to generate a table with about 64,000x64,000 entries (yikes). If you know any programmatic explanations of efficient ways to calculate things like arctan2, that would be awesome. My math background is all right, but the advanced formulas and traditional math notation are very difficult for me to translate into code.

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HDMI output issue in Ubuntu

- by xsznix

Hi, I am using Ubuntu 10.04 on a HP notebook with a nVidia GT 130M graphics card. Whenever I connect a HDTV using the HDMI output and set all of the settings in the nVidia Control Panel, it will output to the HDTV, but cut off about 24 pixels on each side. Sometimes (but not often), it will work properly (display the entire screen), but I cannot get it to work thus consistently. I have tried using resolutions of 1920x1080, 1360x768, 800x600 with two HDTVs of different brands, with and without forcing full GPU scaling, with and without syncing to VBlank (what is this?), etc., and also using a Linux Mint 9 computer with integrated Intel (X4000-ish, don't remember exactly) graphics. The problem persists no matter what, but only with HDMI output (VGA works fine). The same computers works fine with HDTVs in Windows. Any ideas?

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Error when compiling FXAA shader

- by mulletdevil

I am getting the following error when compiling the FXAA shader downloaded from here http://timothylottes.blogspot.co.uk/2011/07/fxaa-311-released.html Fxaa3_11.h(934,5): error x4000: Use of potentially uninitialized variable (FxaaPixelShader) Here is the line in the shader if(earlyExit) #if (FXAA_DISCARD == 1) FxaaDiscard; #else return rgbyM; #endif Does anyone know what may be causing this? I have not changed any values in that shader. Here is a snippet from my current pixel shader #define FXAA_GREEN_AS_LUMA 1 #define FXAA_HLSL_4 1 #define FXAA_PC 1 #define FXAA_QUALITY__PRESET 12 #include "Fxaa3_11.h" PS_OUTPUT main(PS_INPUT fragment) { PS_OUTPUT output; const float2 pos = fragment.hPosition.xy; const float4 notUsedFloat4 = float4(0.0f, 0.0f, 0.0f, 0.0f); const float fxaaQualitySubpix = 0; const float fxaaQualityEdgeThreshold = 0.333; const float fxaaQualityEdgeThresholdMin = 0.0833; const float notUsedFloat = 0.0f; FxaaTex fxaaTex; fxaaTex.smpl = SampleType; fxaaTex.tex = inputTexture; output.colour = FxaaPixelShader(pos, //1 notUsedFloat4, //2 fxaaTex, //3 fxaaTex, //4 fxaaTex, //5 rcpFrame, //6 notUsedFloat4, //7 rcpFrameOpt, //8 notUsedFloat4, //9 fxaaQualitySubpix, //10 fxaaQualityEdgeThreshold, //11 fxaaQualityEdgeThresholdMin, //12 notUsedFloat, //13 notUsedFloat, //14 notUsedFloat, //15 notUsedFloat //16 ); return output; } Am I passing a wrong value into the shader?

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