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• Problems with cos and sin in Android

  - by bajen micke

  I have a problem with my code in Android. I am using this to moving a ball. If the degree is 90 it should move to the right, if the degree is 180 it should move down etc. This is the code I have done. int degrees=180; int bollspeed=4; bollX += bollspeed*Math.cos(Math.toRadians(degrees)); bollY += bollspeed*Math.sin(Math.toRadians(degrees)); The problem is that when the ball should move 90 degrees it moves 180, and when it should move 180 degrees it moves 270. I have tested all I could come to think... Can anyone see any error in my code or have a expanation I would be really glad. Thanks

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• Java Math.cos() Method Does Not Return 0 When Expected

  - by dimo414

  Using Java on a Windows 7 PC (not sure if that matters) and calling Math.cos() on values that should return 0 (like pi/2) instead returns small values, but small values that, unless I'm misunderstanding, are much greater than 1 ulp off from zero. Math.cos(Math.PI/2) = 6.123233995736766E-17 Math.ulp(Math.cos(Math.PI/2)) = 1.232595164407831E-32 Is this in fact within 1 ulp and I'm simply confused? And would this be an acceptable wrapper method to resolve this minor inaccuracy? public static double cos(double a){ double temp = Math.abs(a % Math.PI); if(temp == Math.PI/2) return 0; return Math.cos(a); }

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• cos result incorrect

  - by suk

  I import "math.h". I can use the cos function, but when I execute cos(0.321139585333178) the result is 0.948876 If I use the calculator in Mac or use a normal calculator, the result is 0.999984292347418 Can anyone help me to solve that problem?

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• info about intel Cos embedded i86 os

  - by Tim Williscroft

  I've got some old Intel printer (Etherexpress XL ) print servers and they seem to be running an Intel OS called Cos aka Intel Client Os i86 I've found out that much just looking in the update files from Intel. It was at least partly written in C. How do I make a custom software image Intel Cos's boot loader will understand ? I know a host PC xmodem's the image to the client device, and I was wondering if anyone had already either reverse-engineered this or had original info ? or is my only recousre to reverse engineer the update file format ?

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• Precision of cos(atan2(y,x)) versus using complex <double>, C++

  - by Ivan

  Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

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• how to make a function recursive

  - by tom smith

  i have this huge function and i am wondering how to make it recursive. i have the base case which should never come true, so it should always go to else and keep calling itself with the variable t increases. any help would be great thanks def draw(x, y, t, planets): if 'Satellites' in planets["Moon"]: print ("fillcircle", x, y, planets["Moon"]['Radius']*scale) else: while True: print("refresh") print("colour 0 0 0") print("clear") print("colour 255 255 255") print("fillcircle",x,y,planets['Sun']['Radius']*scale) print("text ", "\"Sun\"",x+planets['Sun']['Radius']*scale,y) if "Mercury" in planets: r_Mercury=planets['Mercury']['Orbital Radius']*scale; print("circle",x,y,r_Mercury) r_Xmer=x+math.sin(t*2*math.pi/planets['Mercury']['Period'])*r_Mercury r_Ymer=y+math.cos(t*2*math.pi/planets['Mercury']['Period'])*r_Mercury print("fillcircle",r_Xmer,r_Ymer,3) print("text ", "\"Mercury\"",r_Xmer+planets['Mercury']['Radius']*scale,r_Ymer) if "Venus" in planets: r_Venus=planets['Venus']['Orbital Radius']*scale; print("circle",x,y,r_Venus) r_Xven=x+math.sin(t*2*math.pi/planets['Venus']['Period'])*r_Venus r_Yven=y+math.cos(t*2*math.pi/planets['Venus']['Period'])*r_Venus print("fillcircle",r_Xven,r_Yven,3) print("text ", "\"Venus\"",r_Xven+planets['Venus']['Radius']*scale,r_Yven) if "Earth" in planets: r_Earth=planets['Earth']['Orbital Radius']*scale; print("circle",x,y,r_Earth) r_Xe=x+math.sin(t*2*math.pi/planets['Earth']['Period'])*r_Earth r_Ye=y+math.cos(t*2*math.pi/planets['Earth']['Period'])*r_Earth print("fillcircle",r_Xe,r_Ye,3) print("text ", "\"Earth\"",r_Xe+planets['Earth']['Radius']*scale,r_Ye) if "Moon" in planets: r_Moon=planets['Moon']['Orbital Radius']*scale; print("circle",r_Xe,r_Ye,r_Moon) r_Xm=r_Xe+math.sin(t*2*math.pi/planets['Moon']['Period'])*r_Moon r_Ym=r_Ye+math.cos(t*2*math.pi/planets['Moon']['Period'])*r_Moon print("fillcircle",r_Xm,r_Ym,3) print("text ", "\"Moon\"",r_Xm+planets['Moon']['Radius']*scale,r_Ym) if "Mars" in planets: r_Mars=planets['Mars']['Orbital Radius']*scale; print("circle",x,y,r_Mars) r_Xmar=x+math.sin(t*2*math.pi/planets['Mars']['Period'])*r_Mars r_Ymar=y+math.cos(t*2*math.pi/planets['Mars']['Period'])*r_Mars print("fillcircle",r_Xmar,r_Ymar,3) print("text ", "\"Mars\"",r_Xmar+planets['Mars']['Radius']*scale,r_Ymar) if "Phobos" in planets: r_Phobos=planets['Phobos']['Orbital Radius']*scale; print("circle",r_Xmar,r_Ymar,r_Phobos) r_Xpho=r_Xmar+math.sin(t*2*math.pi/planets['Phobos']['Period'])*r_Phobos r_Ypho=r_Ymar+math.cos(t*2*math.pi/planets['Phobos']['Period'])*r_Phobos print("fillcircle",r_Xpho,r_Ypho,3) print("text ", "\"Phobos\"",r_Xpho+planets['Phobos']['Radius']*scale,r_Ypho) if "Deimos" in planets: r_Deimos=planets['Deimos']['Orbital Radius']*scale; print("circle",r_Xmar,r_Ymar,r_Deimos) r_Xdei=r_Xmar+math.sin(t*2*math.pi/planets['Deimos']['Period'])*r_Deimos r_Ydei=r_Ymar+math.cos(t*2*math.pi/planets['Deimos']['Period'])*r_Deimos print("fillcircle",r_Xdei,r_Ydei,3) print("text ", "\"Deimos\"",r_Xpho+planets['Deimos']['Radius']*scale,r_Ydei) if "Ceres" in planets: r_Ceres=planets['Ceres']['Orbital Radius']*scale; print("circle",x,y,r_Ceres) r_Xcer=x+math.sin(t*2*math.pi/planets['Ceres']['Period'])*r_Ceres r_Ycer=y+math.cos(t*2*math.pi/planets['Ceres']['Period'])*r_Ceres print("fillcircle",r_Xcer,r_Ycer,3) print("text ", "\"Ceres\"",r_Xcer+planets['Ceres']['Radius']*scale,r_Ycer) if "Jupiter" in planets: r_Jupiter=planets['Jupiter']['Orbital Radius']*scale; print("circle",x,y,r_Jupiter) r_Xjup=x+math.sin(t*2*math.pi/planets['Jupiter']['Period'])*r_Jupiter r_Yjup=y+math.cos(t*2*math.pi/planets['Jupiter']['Period'])*r_Jupiter print("fillcircle",r_Xjup,r_Yjup,3) print("text ", "\"Jupiter\"",r_Xjup+planets['Jupiter']['Radius']*scale,r_Yjup) if "Io" in planets: r_Io=planets['Io']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Io) r_Xio=r_Xjup+math.sin(t*2*math.pi/planets['Io']['Period'])*r_Io r_Yio=r_Yjup+math.cos(t*2*math.pi/planets['Io']['Period'])*r_Io print("fillcircle",r_Xio,r_Yio,3) print("text ", "\"Io\"",r_Xio+planets['Io']['Radius']*scale,r_Yio) if "Europa" in planets: r_Europa=planets['Europa']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Europa) r_Xeur=r_Xjup+math.sin(t*2*math.pi/planets['Europa']['Period'])*r_Europa r_Yeur=r_Yjup+math.cos(t*2*math.pi/planets['Europa']['Period'])*r_Europa print("fillcircle",r_Xeur,r_Yeur,3) print("text ", "\"Europa\"",r_Xeur+planets['Europa']['Radius']*scale,r_Yeur) if "Ganymede" in planets: r_Ganymede=planets['Ganymede']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Ganymede) r_Xgan=r_Xjup+math.sin(t*2*math.pi/planets['Ganymede']['Period'])*r_Ganymede r_Ygan=r_Yjup+math.cos(t*2*math.pi/planets['Ganymede']['Period'])*r_Ganymede print("fillcircle",r_Xgan,r_Ygan,3) print("text ", "\"Ganymede\"",r_Xgan+planets['Ganymede']['Radius']*scale,r_Ygan) if "Callisto" in planets: r_Callisto=planets['Callisto']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Callisto) r_Xcal=r_Xjup+math.sin(t*2*math.pi/planets['Callisto']['Period'])*r_Callisto r_Ycal=r_Yjup+math.cos(t*2*math.pi/planets['Callisto']['Period'])*r_Callisto print("fillcircle",r_Xcal,r_Ycal,3) print("text ", "\"Callisto\"",r_Xcal+planets['Callisto']['Radius']*scale,r_Ycal) if "Saturn" in planets: r_Saturn=planets['Saturn']['Orbital Radius']*scale; print("circle",x,y,r_Saturn) r_Xsat=x+math.sin(t*2*math.pi/planets['Saturn']['Period'])*r_Saturn r_Ysat=y+math.cos(t*2*math.pi/planets['Saturn']['Period'])*r_Saturn print("fillcircle",r_Xsat,r_Ysat,3) print("text ", "\"Saturn\"",r_Xsat+planets['Saturn']['Radius']*scale,r_Ysat) if "Mimas" in planets: r_Mimas=planets['Mimas']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Mimas) r_Xmim=r_Xsat+math.sin(t*2*math.pi/planets['Mimas']['Period'])*r_Mimas r_Ymim=r_Ysat+math.cos(t*2*math.pi/planets['Mimas']['Period'])*r_Mimas print("fillcircle",r_Xmim,r_Ymim,3) print("text ", "\"Mimas\"",r_Xmim+planets['Mimas']['Radius']*scale,r_Ymim) if "Enceladus" in planets: r_Enceladus=planets['Enceladus']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Enceladus) r_Xenc=r_Xsat+math.sin(t*2*math.pi/planets['Enceladus']['Period'])*r_Enceladus r_Yenc=r_Ysat+math.cos(t*2*math.pi/planets['Enceladus']['Period'])*r_Enceladus print("fillcircle",r_Xenc,r_Yenc,3) print("text ", "\"Enceladus\"",r_Xenc+planets['Enceladus']['Radius']*scale,r_Yenc) if "Tethys" in planets: r_Tethys=planets['Tethys']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Tethys) r_Xtet=r_Xsat+math.sin(t*2*math.pi/planets['Tethys']['Period'])*r_Tethys r_Ytet=r_Ysat+math.cos(t*2*math.pi/planets['Tethys']['Period'])*r_Tethys print("fillcircle",r_Xtet,r_Ytet,3) print("text ", "\"Tethys\"",r_Xtet+planets['Tethys']['Radius']*scale,r_Ytet) if "Dione" in planets: r_Dione=planets['Dione']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Dione) r_Xdio=r_Xsat+math.sin(t*2*math.pi/planets['Dione']['Period'])*r_Dione r_Ydio=r_Ysat+math.cos(t*2*math.pi/planets['Dione']['Period'])*r_Dione print("fillcircle",r_Xdio,r_Ydio,3) print("text ", "\"Dione\"",r_Xdio+planets['Dione']['Radius']*scale,r_Ydio) if "Rhea" in planets: r_Rhea=planets['Rhea']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Rhea) r_Xrhe=r_Xsat+math.sin(t*2*math.pi/planets['Rhea']['Period'])*r_Rhea r_Yrhe=r_Ysat+math.cos(t*2*math.pi/planets['Rhea']['Period'])*r_Rhea print("fillcircle",r_Xrhe,r_Yrhe,3) print("text ", "\"Rhea\"",r_Xrhe+planets['Rhea']['Radius']*scale,r_Yrhe) if "Titan" in planets: r_Titan=planets['Titan']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Titan) r_Xtit=r_Xsat+math.sin(t*2*math.pi/planets['Titan']['Period'])*r_Titan r_Ytit=r_Ysat+math.cos(t*2*math.pi/planets['Titan']['Period'])*r_Titan print("fillcircle",r_Xtit,r_Ytit,3) print("text ", "\"Titan\"",r_Xtit+planets['Titan']['Radius']*scale,r_Ytit) if "Iapetus" in planets: r_Iapetus=planets['Iapetus']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Iapetus) r_Xiap=r_Xsat+math.sin(t*2*math.pi/planets['Iapetus']['Period'])*r_Iapetus r_Yiap=r_Ysat+math.cos(t*2*math.pi/planets['Iapetus']['Period'])*r_Iapetus print("fillcircle",r_Xiap,r_Yiap,3) print("text ", "\"Iapetus\"",r_Xiap+planets['Iapetus']['Radius']*scale,r_Yiap) if "Uranus" in planets: r_Uranus=planets['Uranus']['Orbital Radius']*scale; print("circle",x,y,r_Uranus) r_Xura=x+math.sin(t*2*math.pi/planets['Uranus']['Period'])*r_Uranus r_Yura=y+math.cos(t*2*math.pi/planets['Uranus']['Period'])*r_Uranus print("fillcircle",r_Xura,r_Yura,3) print("text ", "\"Uranus\"",r_Xura+planets['Uranus']['Radius']*scale,r_Yura) if "Puck" in planets: r_Puck=planets['Puck']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Puck) r_Xpuc=r_Xura+math.sin(t*2*math.pi/planets['Puck']['Period'])*r_Puck r_Ypuc=r_Yura+math.cos(t*2*math.pi/planets['Puck']['Period'])*r_Puck print("fillcircle",r_Xpuc,r_Ypuc,3) print("text ", "\"Puck\"",r_Xpuc+planets['Puck']['Radius']*scale,r_Ypuc) if "Miranda" in planets: r_Miranda=planets['Miranda']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Miranda) r_Xmira=r_Xura+math.sin(t*2*math.pi/planets['Miranda']['Period'])*r_Miranda r_Ymira=r_Yura+math.cos(t*2*math.pi/planets['Miranda']['Period'])*r_Miranda print("fillcircle",r_Xmira,r_Ymira,3) print("text ", "\"Miranda\"",r_Xmira+planets['Miranda']['Radius']*scale,r_Ymira) if "Ariel" in planets: r_Ariel=planets['Ariel']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Ariel) r_Xari=r_Xura+math.sin(t*2*math.pi/planets['Ariel']['Period'])*r_Ariel r_Yari=r_Yura+math.cos(t*2*math.pi/planets['Ariel']['Period'])*r_Ariel print("fillcircle",r_Xari,r_Yari,3) print("text ", "\"Ariel\"",r_Xari+planets['Ariel']['Radius']*scale,r_Yari) if "Umbriel" in planets: r_Umbriel=planets['Umbriel']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Umbriel) r_Xumb=r_Xura+math.sin(t*2*math.pi/planets['Umbriel']['Period'])*r_Umbriel r_Yumb=r_Yura+math.cos(t*2*math.pi/planets['Umbriel']['Period'])*r_Umbriel print("fillcircle",r_Xumb,r_Yumb,3) print("text ", "\"Umbriel\"",r_Xumb+planets['Umbriel']['Radius']*scale,r_Yumb) if "Titania" in planets: r_Titania=planets['Titania']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Titania) r_Xtita=r_Xura+math.sin(t*2*math.pi/planets['Titania']['Period'])*r_Titania r_Ytita=r_Yura+math.cos(t*2*math.pi/planets['Titania']['Period'])*r_Titania print("fillcircle",r_Xtita,r_Ytita,3) print("text ", "\"Titania\"",r_Xtita+planets['Titania']['Radius']*scale,r_Ytita) if "Oberon" in planets: r_Oberon=planets['Oberon']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Oberon) r_Xober=r_Xura+math.sin(t*2*math.pi/planets['Oberon']['Period'])*r_Oberon r_Yober=r_Yura+math.cos(t*2*math.pi/planets['Oberon']['Period'])*r_Oberon print("fillcircle",r_Xober,r_Yober,3) print("text ", "\"Oberon\"",r_Xober+planets['Oberon']['Radius']*scale,r_Yober) if "Neptune" in planets: r_Neptune=planets['Neptune']['Orbital Radius']*scale; print("circle",x,y,r_Neptune) r_Xnep=x+math.sin(t*2*math.pi/planets['Neptune']['Period'])*r_Neptune r_Ynep=y+math.cos(t*2*math.pi/planets['Neptune']['Period'])*r_Neptune print("fillcircle",r_Xnep,r_Ynep,3) print("text ", "\"Neptune\"",r_Xnep+planets['Neptune']['Radius']*scale,r_Ynep) if "Titan" in planets: r_Titan=planets['Titan']['Orbital Radius']*scale; print("circle",r_Xnep,r_Ynep,r_Titan) r_Xtita=r_Xnep+math.sin(t*2*math.pi/planets['Titan']['Period'])*r_Titan r_Ytita=r_Ynep+math.cos(t*2*math.pi/planets['Titan']['Period'])*r_Titan print("fillcircle",r_Xtita,r_Ytita,3) print("text ", "\"Titan\"",r_Xtita+planets['Titan']['Radius']*scale,r_Ytita) t += 0.003 print(draw(x, y, t, planets))

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• How to calculate Sin function quicker and more precisely?

  - by user1297181

  I want to calculate y(n)=32677Sin(45/1024•n), where y is an integer and n ranges from 0 to 2048. How can I make this process quicker and more precisely? Now I want to show you a reference answer: Since Sin(a+b)=Sin(a)Cos(b)+Cos(a)Sin(b) And Cos(a+b)=Cos(a)Cos(b)-Sin(a)Cos(b). So I can store Sin(45/1024•1) andCos(45/1024•1) ` only.Then use this formula: Sin(45/1024•2)=Sin(45/1024•1+45/1024•1), Cos(45/1024•2)=Cos(45/1024•1+45/1024•1), .... `Sin(45/1024•n)=Sin(45/1024•(n-1)+45/1024•1) `, `Cos(45/1024•n)=Cos(45/1024•(n-1)+45/1024•1) `, This way maybe quicker without storing large array.

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• ActionScript applying rotation of sprite to startDrag()'s rectangle bounds

  - by TheDarkIn1978

  i've added a square sprite to the stage which, when dragged, is contained within set boundaries. private function swatchBounds():Rectangle { var stageBounds = new Rectangle ( 0 - defaultSwatchRect.x, 0 - defaultSwatchRect.y, stage.stageWidth - defaultSwatchRect.width, stage.stageHeight - defaultSwatchRect.height ); return stageBounds; } if the square sprite is scaled, the following returned rectangle boundary works private function swatchBounds():Rectangle { var stageBounds = new Rectangle ( 0 - defaultSwatchRect.x * swatchObject.scaleX, 0 - defaultSwatchRect.y * swatchObject.scaleY, stage.stageWidth - defaultSwatchRect.width * swatchObject.scaleX, stage.stageHeight - defaultSwatchRect.height * swatchObject.scaleY ); return stageBounds; } now i'm trying to include the square sprites rotation into the mix. math certainly isn't my forté, but i feel i'm on the write track. however, i just can't seem to wrap my head around it to get it right private function swatchBounds():Rectangle { var stageBounds = new Rectangle ( 0 - defaultSwatchRect.x * swatchObject.scaleX * Math.cos(defaultSwatchRect.x * swatchObject.rotation), 0 - defaultSwatchRect.y * swatchObject.scaleY * Math.sin(defaultSwatchRect.y * swatchObject.rotation), stage.stageWidth - defaultSwatchRect.width * swatchObject.scaleX * Math.cos(defaultSwatchRect.width * swatchObject.rotation), stage.stageHeight - defaultSwatchRect.height * swatchObject.scaleY * Math.sin(defaultSwatchRect.height * swatchObject.rotation) ); return stageBounds; }

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• Rotate point in rectangle

  - by Dested

  I have a point in a rectangle that I need to rotate an arbitrary degree and find the x y of the point. How can I do this using javascript. Below the x,y would be something like 1,3 and after I pass 90 into the method it will return 3,1. |-------------| | * | | | | | |-------------| _____ | *| | | | | | | | | _____ |-------------| | | | | | *| |-------------| _____ | | | | | | | | |* | _____ Basically I am looking for the guts to this method function Rotate(pointX,pointY,rectWidth,rectHeight,angle){ /*magic*/ return {newX:x,newY:y}; }

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• How can I run a (16-bit) .COM executable that has been renamed to .COS?

  - by max16bit

  I'm trying to run a couple of 16-bit legacy DOS programs from a standard windows XP dos prompt. The problem is that the file extensions have been renamed from .COM to .COS and they are stored on read-only media and I can't copy them (special environment). Any tips on how to invoke such files despite the weird extension? If they had been 32-bit EXEs, it wouldn't have been an issue running them even without their proper extensions, but with these COM files, I'm unable to find a way to run them.

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• What is the fastest way to compute sin and cos together?

  - by Danvil

  I would like to compute both the sine and co-sine of a value together (for example to create a rotation matrix). Of course I could compute them separately one after another like a = cos(x); b = sin(x);, but I wonder if there is a faster way when needing both values.

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• 3D rotation matrices deform object while rotating

  - by Kevin

  I'm writing a small 3D renderer (using an orthographic projection right now). I've run into some trouble with my 3D rotation matrices. They seem to squeeze my 3D object (a box primitive) at certain angles. Here's a live demo (only tested in Google Chrome): http://dl.dropbox.com/u/109400107/3D/index.html The box is viewed from the top along the Y axis and is rotating around the X and Z axis. These are my 3 rotation matrices (Only rX and rZ are being used): var rX = new Matrix([ [1, 0, 0], [0, Math.cos(radiants), -Math.sin(radiants)], [0, Math.sin(radiants), Math.cos(radiants)] ]); var rY = new Matrix([ [Math.cos(radiants), 0, Math.sin(radiants)], [0, 1, 0], [-Math.sin(radiants), 0, Math.cos(radiants)] ]); var rZ = new Matrix([ [Math.cos(radiants), -Math.sin(radiants), 0], [Math.sin(radiants), Math.cos(radiants), 0], [0, 0, 1] ]); Before projecting the verticies I multiply them by rZ and rX like so: vert1.multiply(rZ); vert1.multiply(rX); vert2.multiply(rZ); vert2.multiply(rX); vert3.multiply(rZ); vert3.multiply(rX); The projection itself looks like this: bX = (pos.x + (vert1.x*scale)); bY = (pos.y + (vert1.z*scale)); Where "pos.x" and "pos.y" is an offset for centering the box on the screen. I just can't seem to find a solution to this and I'm still relativly new to working with Matricies. You can view the source-code of the demo page if you want to see the whole thing.

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• Calculating 3d rotation around random axis

  - by mitim

  This is actually a solved problem, but I want to understand why my original method didn't work (hoping someone with more knowledge can explain). (Keep in mind, I've not very experienced in 3d programming, having only played with the very basic for a little bit...nor do I have a lot of mathematical experience in this area). I wanted to animate a point rotating around another point at a random axis, say a 45 degrees along the y axis (think of an electron around a nucleus). I know how to rotate using the transform matrix along the X, Y and Z axis, but not an arbitrary (45 degree) axis. Eventually after some research I found a suggestion: Rotate the point by -45 degrees around the Z so that it is aligned. Then rotate by some increment along the Y axis, then rotate it back +45 degrees for every frame tick. While this certainly worked, I felt that it seemed to be more work then needed (too many method calls, math, etc) and would probably be pretty slow at runtime with many points to deal with. I thought maybe it was possible to combine all the rotation matrixes involve into 1 rotation matrix and use that as a single operation. Something like: [ cos(-45) -sin(-45) 0] [ sin(-45) cos(-45) 0] rotate by -45 along Z [ 0 0 1] multiply by [ cos(2) 0 -sin(2)] [ 0 1 0 ] rotate by 2 degrees (my increment) along Y [ sin(2) 0 cos(2)] then multiply that result by (in that order) [ cos(45) -sin(45) 0] [ sin(45) cos(45) 0] rotate by 45 along Z [ 0 0 1] I get 1 mess of a matrix of numbers (since I was working with unknowns and 2 angles), but I felt like it should work. It did not and I found a solution on wiki using a different matirx, but that is something else. I'm not sure if maybe I made an error in multiplying, but my question is: this is actually a viable way to solve the problem, to take all the separate transformations, combine them via multiplying, then use that or not?

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• Java: substitute for ArrayList cos primitive types not allowed in ArrayList?

  - by HH

  Primitive types are not allowed in ArrayList, source. Partial solution: you can wrap prim.types such as int to Integer to form an extra class but a side effect. I want to index data, is there some substitute for ArrayList that allows primitive types?

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• Drupal 6: using too many Views module causing site to go down cos of too many mysql connection.

  - by artmania

  Hi friends, I have HostGator Baby Shared Plan . I develop Drupal site on. everything was fine at the beginning, then by the time i go further with development, site started ti work really slow. now it is not working at all. giving my sql errors like TOO many connections, etc... I created so many blocks, pages with View. so it makes my site to so much depend on database. should not I do that? can it be the reason of my site's no working now. appreciate helps!!!!

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• Adding a computed column to an ActiveRecord query

  - by bmwbzz

  Hi, I am running a query using a scope and some conditions. Something like this: conditions[:offset] = (options[:page].to_i - 1) * PAGE_SIZE unless options[:page].blank? conditions[:limit] = options[:limit] ||= PAGE_SIZE scope = Promo.enabled.active results = scope.all conditions I'd like to add a computed column to the query (at the point when I'm now calling scope.all). Something like this: (ACOS(least(1,COS(0.71106459055501)*COS(-1.2915436464758)*COS(RADIANS(addresses.lat))*COS(RADIANS(addresses.lng))+ COS(0.71106459055501)*SIN(-1.2915436464758)*COS(RADIANS(addresses.lat))*SIN(RADIANS(addresses.lng))+ SIN(0.71106459055501)*SIN(RADIANS(addresses.lat))))*3963.19) as accurate_distance Is there a way to do that without just using find_by_sql and rewriting the whole existing query? Thanks!

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• Android Can't get two virtual joysticks to move independently and at the same time

  - by Cole

  @Override public boolean onTouch(View v, MotionEvent event) { // TODO Auto-generated method stub float r = 70; float centerLx = (float) (screenWidth*.3425); float centerLy = (float) (screenHeight*.4958); float centerRx = (float) (screenWidth*.6538); float centerRy = (float) (screenHeight*.4917); float dx = 0; float dy = 0; float theta; float c; int action = event.getAction(); int actionCode = action & MotionEvent.ACTION_MASK; int pid = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; int fingerid = event.getPointerId(pid); int x = (int) event.getX(pid); int y = (int) event.getY(pid); c = FloatMath.sqrt(dx*dx + dy*dy); theta = (float) Math.atan(Math.abs(dy/dx)); switch (actionCode) { case MotionEvent.ACTION_DOWN: case MotionEvent.ACTION_POINTER_DOWN: //if touching down on left stick, set leftstick ID to this fingerid. if(x < screenWidth/2 && c<r*.8) { lsId = fingerid; dx = x-centerLx; dy = y-centerLy; touchingLs = true; } else if(x > screenWidth/2 && c<r*.8) { rsId = fingerid; dx = x-centerRx; dy = y-centerRy; touchingRs = true; } break; case MotionEvent.ACTION_MOVE: if (touchingLs && fingerid == lsId) { dx = x - centerLx; dy = y - centerLy; }else if (touchingRs && fingerid == rsId) { dx = x - centerRx; dy = y - centerRy; } c = FloatMath.sqrt(dx*dx + dy*dy); theta = (float) Math.atan(Math.abs(dy/dx)); //if touching outside left radius and moving left stick if(c >= r && touchingLs && fingerid == lsId) { if(dx>0 && dy<0) { //top right quadrant lsX = r * FloatMath.cos(theta); lsY = -(r * FloatMath.sin(theta)); Log.i("message", "top right"); } if(dx<0 && dy<0) { //top left quadrant lsX = -(r * FloatMath.cos(theta)); lsY = -(r * FloatMath.sin(theta)); Log.i("message", "top left"); } if(dx<0 && dy>0) { //bottom left quadrant lsX = -(r * FloatMath.cos(theta)); lsY = r * FloatMath.sin(theta); Log.i("message", "bottom left"); } else if(dx > 0 && dy > 0){ //bottom right quadrant lsX = r * FloatMath.cos(theta); lsY = r * FloatMath.sin(theta); Log.i("message", "bottom right"); } } if(c >= r && touchingRs && fingerid == rsId) { if(dx>0 && dy<0) { //top right quadrant rsX = r * FloatMath.cos(theta); rsY = -(r * FloatMath.sin(theta)); Log.i("message", "top right"); } if(dx<0 && dy<0) { //top left quadrant rsX = -(r * FloatMath.cos(theta)); rsY = -(r * FloatMath.sin(theta)); Log.i("message", "top left"); } if(dx<0 && dy>0) { //bottom left quadrant rsX = -(r * FloatMath.cos(theta)); rsY = r * FloatMath.sin(theta); Log.i("message", "bottom left"); } else if(dx > 0 && dy > 0) { rsX = r * FloatMath.cos(theta); rsY = r * FloatMath.sin(theta); Log.i("message", "bottom right"); } } else { if(c < r && touchingLs && fingerid == lsId) { lsX = dx; lsY = dy; } if(c < r && touchingRs && fingerid == rsId){ rsX = dx; rsY = dy; } } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_POINTER_UP: if (fingerid == lsId) { lsId = -1; lsX = 0; lsY = 0; touchingLs = false; } else if (fingerid == rsId) { rsId = -1; rsX = 0; rsY = 0; touchingRs = false; } break; } return true; } There's a left joystick and a right joystick. Right now only one will move at a time. If someone could set me on the right track I would be incredibly grateful cause I've been having nightmares about this problem.

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• Error in Ordinary Differential Equation representation

  - by Priya M

  UPDATE I am trying to find the Lyapunov Exponents given in link LE. I am trying to figure it out and understand it by taking the following eqs for my case. These are a set of ordinary differential equations (these are just for testing how to work with cos and sin as ODE) f(1)=ALPHA*(y-x); f(2)=x*(R-z)-y; f(3) = 10*cos(x); and x=X(1); y=X(2); cos(y)=X(3); f1 means dx/dt;f2 dy/dt and f3 in this case would be -10sinx. However,when expressing as x=X(1);y=X(2);i am unsure how to express for cos.This is just a trial example i was doing so as to know how to work with equations where we have a cos,sin etc terms as a function of another variable. When using ode45 to solve these Eqs [T,Res]=sol(3,@test_eq,@ode45,0,0.01,20,[7 2 100 ],10); it throws the following error ??? Attempted to access (2); index must be a positive integer or logical. Error in ==> Eq at 19 x=X(1); y=X(2); cos(x)=X(3); Is my representation x=X(1); y=X(2); cos(y)=X(3); alright? How to resolve the error? Thank you

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• Rotation Matrix calculates by column not by row

  - by pinnacler

  I have a class called forest and a property called fixedPositions that stores 100 points (x,y) and they are stored 250x2 (rows x columns) in MatLab. When I select 'fixedPositions', I can click scatter and it will plot the points. Now, I want to rotate the plotted points and I have a rotation matrix that will allow me to do that. The below code should work: theta = obj.heading * pi/180; apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; But it wont. I get this error. ??? Error using == mtimes Inner matrix dimensions must agree. Error in == landmarkslandmarks.get.apparentPositions at 22 apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; When I alter forest.fixedPositions to store the variables 2x250 instead of 250x2, the above code will work, but it wont plot. I'm going to be plotting fixedPositions constantly in a simulation, so I'd prefer to leave it as it, and make the rotation work instead. Any ideas? Also, fixed positions, is the position of the xy points as if you were looking straight ahead. i.e. heading = 0. heading is set to 45, meaning I want to rotate points clockwise 45 degrees. Here is my code: classdef landmarks properties fixedPositions %# positions in a fixed coordinate system. [x, y] heading = 45; %# direction in which the robot is facing end properties (Dependent) apparentPositions end methods function obj = landmarks(numberOfTrees) %# randomly generates numberOfTrees amount of x,y coordinates and set %the array or matrix (not sure which) to fixedPositions obj.fixedPositions = 100 * rand([numberOfTrees,2]) .* sign(rand([numberOfTrees,2]) - 0.5); end function obj = set.apparentPositions(obj,~) theta = obj.heading * pi/180; [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; end function apparent = get.apparentPositions(obj) %# rotate obj.positions using obj.facing to generate the output theta = obj.heading * pi/180; apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; end end end P.S. If you change one line to this: obj.fixedPositions = 100 * rand([2,numberOfTrees]) .* sign(rand([2,numberOfTrees]) - 0.5); Everything will work fine... it just wont plot.

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• Inserting text in TextBox at cursor

  - by Anil

  Hi all I have a textbox in aspx page in which the user enters text. Now when user clicks on a button called "Sin" the textbox should show "Sin[]" and the cursor has to be placed in between brackets.Like as follows "Sin[<cursor here]" Now when the user clicks on some other button say "Cos" the textbox text should show "Sin[Cos[]]" and the cursor has be placed between the brackets of Cos as follows: "Sin[Cos[<cursor here]]". How is this handled. Any simple code please.. Thanks in advance

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• how to animate 2 surfaces in Matlab?

  - by Kate

  Hi everyone, I've written this code which makes an animation of 2 ellipsoids. Parameter k1 of these ellipsoids must depend on time (so they'd move asynchronously), but I need to animate them in one figure. Can I use loop for it or is it better to use timer & some kind of callback functions? The second problem - I need to move inner ellipsoid so they would have one common side. How can I do this? a=5; b=a; c=10; u = (0:0.05*pi:2*pi)'; v = [0:0.05*pi:2*pi]; X = a*sin(u)*cos(v); Y = a*sin(u)*sin(v); Z = c*cos(u)*ones(size(v)); Z(Z0)=0; % cut upper V1=4/3*pi*a*b*c; d=1/2; e=2^d; a2=a/e; b2=a/e; c2=c; V2=4/3*pi*a2*b2*c2; X2 = a2*sin(u)*cos(v);%-2.5; Y2 = b2*sin(u)*sin(v); Z2 = c2*cos(u)*ones(size(v));%+0.25; Z2(Z20)=0; % cut h=1/3; for j = 1:20 k1=(sin(pi*j/20)+0.5)^h; a=a*k1; c=c*k1; X = a*sin(u)*cos(v); Y = a*sin(u)*sin(v); Z = c*cos(u)*ones(size(v)); Z(Z0)=0; a2=a2*k1; b2=a2*k1; c2=c2*k1; X2 = a2*sin(u)*cos(v)+5;%-2.5; Y2 = b2*sin(u)*sin(v); Z2 = c2*cos(u)*ones(size(v));%+0.25; Z2(Z20)=0; hS1=surf(X,Y,Z); alpha(.11) hold on hS2=surf(X2,Y2,Z2); hold off axis([-20 20 -20 20 -20 20]); F(j) = getframe; end movie(F,4)

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• Python: x-y-plot with matplotlib

  - by kame

  I want to plot some data. The first column contains the x-data. But matplotlib doesnt plot this. Where is my mistake? #fresnel formula import numpy as np from numpy import cos from scipy import * from pylab import plot, show, ylim, yticks from matplotlib import * from pprint import pprint n1 = 1.0 n2 = 1.5 #alpha, beta, intensity data = [ [10, 22, 4.3], [20, 42, 4.2], [30, 62, 3.6], [40, 83, 1.3], [45, 102, 2.8], [50, 123, 3.0], [60, 143, 3.2], [70, 163, 3.8], ] for i in range(len(data)): rhotang1 = (n1 * cos(data[i][0]) - n2 * cos(data[i][1])) rhotang2 = (n1 * cos(data[i][0]) + n2 * cos(data[i][1])) rhotang = rhotang1 / rhotang2 data[i].append(rhotang) #append 4th value pprint(data) x = data[:][0] y1 = data[:][2] y3 = data[:][3] plot(x, y1, x, y3) show() EDIT: http://paste.pocoo.org/show/205534/ But it doesnt work.

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• calculating a gps coordinate given a point, bearing and distance

  - by user530509

  Hello, I have a problem which draws my back in some project for some time now. Im basically looking to trap a polygon using x,y points drawn by some script ive written. lat1,lon1 are the center gps cords of the polygon and im looking for its surrounding polygon. here is a part of my code in python: def getcords(lat1,lon1,dr,bearing): lat2=asin(sin(lat1)*cos(dr)+cos(lat1)*sin(dr)*cos(bearing)) lon2=lon1+atan2(sin(bearing)*sin(dr)*cos(lat1),cos(dr)-sin(lat1)*sin(lat2)) return [lat2,lon2] my input goes like this: lat1,lon1 - are given in decimal degrees. -dr is the angular computed by dividing the distance in miles by the earth's -raiuds(=3958.82) -bearing between 0-360 degrees. however for the input getcorsds1(42.189275,-76.85823,0.5/3958.82,30) i get [-1.3485899508698462, -76.8576637627568], however [42.2516666666667,-76.8097222222222] is the right answer. as for the angular distance i calculate it simply by dividing the distance in miles by the earth's raiuds(=3958.82). anybody?

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• postgresql error - ERROR: input is out of range

  - by CaffeineIV

  The function below keeps returning this error message. I thought that maybe the double_precision field type was what was causing this, and I tried to use CAST, but either that's not it, or I didn't do it right... Help? Here's the error: ERROR: input is out of range CONTEXT: PL/pgSQL function "calculate_distance" line 7 at RETURN ********** Error ********** ERROR: input is out of range SQL state: 22003 Context: PL/pgSQL function "calculate_distance" line 7 at RETURN And here's the function: CREATE OR REPLACE FUNCTION calculate_distance(character varying, double precision, double precision, double precision, double precision) RETURNS double precision AS $BODY$ DECLARE earth_radius double precision; BEGIN earth_radius := 3959.0; RETURN earth_radius * acos(sin($2 / 57.2958) * sin($4 / 57.2958) + cos($2/ 57.2958) * cos($4 / 57.2958) * cos(($5 / 57.2958) - ($3 / 57.2958))); END; $BODY$ LANGUAGE 'plpgsql' VOLATILE COST 100; ALTER FUNCTION calculate_distance(character varying, double precision, double precision, double precision, double precision) OWNER TO postgres; //I tried changing (unsuccessfully) that RETURN line to: RETURN CAST( (earth_radius * acos(sin($2 / 57.2958) * sin($4 / 57.2958) + cos($2/ 57.2958) * cos($4 / 57.2958) * cos(($5 / 57.2958) - ($3 / 57.2958))) ) AS text);

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• When is a>a true ?

  - by Cricri

  Right, I think I really am living a dream. I have the following piece of code which I compile and run on an AIX machine: AIX 3 5 PowerPC_POWER5 processor type IBM XL C/C++ for AIX, V10.1 Version: 10.01.0000.0003 #include <stdio.h> #include <math.h> #define RADIAN(x) ((x) * acos(0.0) / 90.0) double nearest_distance(double radius,double lon1, double lat1, double lon2, double lat2){ double rlat1=RADIAN(lat1); double rlat2=RADIAN(lat2); double rlon1=lon1; double rlon2=lon2; double a=0,b=0,c=0; a = sin(rlat1)*sin(rlat2)+ cos(rlat1)*cos(rlat2)*cos(rlon2-rlon1); printf("%lf\n",a); if (a > 1) { printf("aaaaaaaaaaaaaaaa\n"); } b = acos(a); c = radius * b; return radius*(acos(sin(rlat1)*sin(rlat2)+ cos(rlat1)*cos(rlat2)*cos(rlon2-rlon1))); } int main(int argc, char** argv) { nearest_distance(6367.47,10,64,10,64); return 0; } Now, the value of 'a' after the calculation is reported as being '1'. And, on this AIX machine, it looks like 1 1 is true as my 'if' is entered !!! And my acos of what I think is '1' returns NanQ since 1 is bigger than 1. May I ask how that is even possible ? I do not know what to think anymore ! The code works just fine on other architectures where 'a' really takes the value of what I think is 1 and acos(a) is 0.

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