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• Making a Camera look at a target Vector

  - by Peteyslatts

  I have a camera that works as long as its stationary. Now I'm trying to create a child class of that camera class that will look at its target. The new addition to the class is a method called SetTarget(). The method takes in a Vector3 target. The camera wont move but I need it to rotate to look at the target. If I just set the target, and then call CreateLookAt() (which takes in position, target, and up), when the object gets far enough away and underneath the camera, it suddenly flips right side up. So I need to transform the up vector, which currently always stays at Vector3.Up. I feel like this has something to do with taking the angle between the old direction vector and the new one (which I know can be expressed by target - position). I feel like this is all really vague, so here's the code for my base camera class: public class BasicCamera : Microsoft.Xna.Framework.GameComponent { public Matrix view { get; protected set; } public Matrix projection { get; protected set; } public Vector3 position { get; protected set; } public Vector3 direction { get; protected set; } public Vector3 up { get; protected set; } public Vector3 side { get { return Vector3.Cross(up, direction); } protected set { } } public BasicCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game) { this.position = position; this.direction = target - position; this.up = up; CreateLookAt(); projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.PiOver4, (float)Game.Window.ClientBounds.Width / (float)Game.Window.ClientBounds.Height, 1, 500); } public override void Update(GameTime gameTime) { // TODO: Add your update code here CreateLookAt(); base.Update(gameTime); } } And this is the code for the class that extends the above class to look at its target. class TargetedCamera : BasicCamera { public Vector3 target { get; protected set; } public TargetedCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game, position, target, up) { this.target = target; } public void SetTarget(Vector3 target) { direction = target - position; } protected override void CreateLookAt() { view = Matrix.CreateLookAt(position, target, up); } }

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• rotating spheres

  - by Dave

  I want to continuously rotate 2 spheres, however the rotation does not seem to work. Here is my code: float angle = 0.0f; void light(){ glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_LIGHT1); // Create light components GLfloat positionlight1[] = { 9.0, 5.0, 1.0, 0.0 }; GLfloat positionlight2[] = {0.2,2.5,1.3,0.0}; GLfloat light_ambient1[] = { 0.0, 0.0, 1.0, 1.0}; GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 }; glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient1); glLightfv(GL_LIGHT1, GL_DIFFUSE, light_diffuse); glLightfv(GL_LIGHT0, GL_POSITION, positionlight1); glLightfv(GL_LIGHT1, GL_POSITION, positionlight2); } void changeSize(int w, int h) { if (h==0) // Prevent A Divide By Zero By { h=1; // Making Height Equal One } glMatrixMode(GL_PROJECTION); // Select The Projection Matrix glLoadIdentity(); // Reset The Projection Matrix glViewport(0,0,w,h);// Reset The Current Viewport // Calculate The Aspect Ratio Of The Window gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f); glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix // Reset The Modelview Matrix } void renderScene(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glPushMatrix(); //set where to start the current object glTranslatef(0.0,1.2,-6); glRotatef(angle,0,1.2,-6); glutSolidSphere(1,50,50); glPopMatrix(); //end the current object transformations glPushMatrix(); //set where to start the current object glTranslatef(0.0,-2,-6); glRotatef(angle,0,-2,-6); glutSolidSphere(0.5,50,50); glPopMatrix(); //end the current object transformations angle=+0.1; glutSwapBuffers(); } int main(int argc, char **argv) { // init GLUT and create window glutInit(&argc, argv); glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA); glutInitWindowPosition(100,100); glutInitWindowSize(500,500); glutCreateWindow("Hello World"); // register callbacks light(); glutDisplayFunc(renderScene); glutReshapeFunc(changeSize); glutIdleFunc(renderScene); // enter GLUT event processing loop glutMainLoop(); return 1; } Graphicstest::Graphicstest(void) { } In the renderscene where i draw,translate and rotate my 2 spheres. It does not seem to rotate the spheres continuously. What am i doing wrong?

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• NET Math Libraries

  - by JoshReuben

  NET Mathematical Libraries   .NET Builder for Matlab The MathWorks Inc. - http://www.mathworks.com/products/netbuilder/ MATLAB Builder NE generates MATLAB based .NET and COM components royalty-free deployment creates the components by encrypting MATLAB functions and generating either a .NET or COM wrapper around them. .NET/Link for Mathematica www.wolfram.com a product that 2-way integrates Mathematica and Microsoft's .NET platform call .NET from Mathematica - use arbitrary .NET types directly from the Mathematica language. use and control the Mathematica kernel from a .NET program. turns Mathematica into a scripting shell to leverage the computational services of Mathematica. write custom front ends for Mathematica or use Mathematica as a computational engine for another program comes with full source code. Leverages MathLink - a Wolfram Research's protocol for sending data and commands back and forth between Mathematica and other programs. .NET/Link abstracts the low-level details of the MathLink C API. Extreme Optimization http://www.extremeoptimization.com/ a collection of general-purpose mathematical and statistical classes built for the.NET framework. It combines a math library, a vector and matrix library, and a statistics library in one package. download the trial of version 4.0 to try it out. Multi-core ready - Full support for Task Parallel Library features including cancellation. Broad base of algorithms covering a wide range of numerical techniques, including: linear algebra (BLAS and LAPACK routines), numerical analysis (integration and differentiation), equation solvers. Mathematics leverages parallelism using .NET 4.0's Task Parallel Library. Basic math: Complex numbers, 'special functions' like Gamma and Bessel functions, numerical differentiation. Solving equations: Solve equations in one variable, or solve systems of linear or nonlinear equations. Curve fitting: Linear and nonlinear curve fitting, cubic splines, polynomials, orthogonal polynomials. Optimization: find the minimum or maximum of a function in one or more variables, linear programming and mixed integer programming. Numerical integration: Compute integrals over finite or infinite intervals, over 2D and higher dimensional regions. Integrate systems of ordinary differential equations (ODE's). Fast Fourier Transforms: 1D and 2D FFT's using managed or fast native code (32 and 64 bit) BigInteger, BigRational, and BigFloat: Perform operations with arbitrary precision. Vector and Matrix Library Real and complex vectors and matrices. Single and double precision for elements. Structured matrix types: including triangular, symmetrical and band matrices. Sparse matrices. Matrix factorizations: LU decomposition, QR decomposition, singular value decomposition, Cholesky decomposition, eigenvalue decomposition. Portability and performance: Calculations can be done in 100% managed code, or in hand-optimized processor-specific native code (32 and 64 bit). Statistics Data manipulation: Sort and filter data, process missing values, remove outliers, etc. Supports .NET data binding. Statistical Models: Simple, multiple, nonlinear, logistic, Poisson regression. Generalized Linear Models. One and two-way ANOVA. Hypothesis Tests: 12 14 hypothesis tests, including the z-test, t-test, F-test, runs test, and more advanced tests, such as the Anderson-Darling test for normality, one and two-sample Kolmogorov-Smirnov test, and Levene's test for homogeneity of variances. Multivariate Statistics: K-means cluster analysis, hierarchical cluster analysis, principal component analysis (PCA), multivariate probability distributions. Statistical Distributions: 25 29 continuous and discrete statistical distributions, including uniform, Poisson, normal, lognormal, Weibull and Gumbel (extreme value) distributions. Random numbers: Random variates from any distribution, 4 high-quality random number generators, low discrepancy sequences, shufflers. New in version 4.0 (November, 2010) Support for .NET Framework Version 4.0 and Visual Studio 2010 TPL Parallellized – multicore ready sparse linear program solver - can solve problems with more than 1 million variables. Mixed integer linear programming using a branch and bound algorithm. special functions: hypergeometric, Riemann zeta, elliptic integrals, Frensel functions, Dawson's integral. Full set of window functions for FFT's. Product  Price Update subscription Single Developer License $999  $399  Team License (3 developers) $1999  $799  Department License (8 developers) $3999  $1599  Site License (Unlimited developers in one physical location) $7999  $3199    NMath http://www.centerspace.net .NET math and statistics libraries matrix and vector classes random number generators Fast Fourier Transforms (FFTs) numerical integration linear programming linear regression curve and surface fitting optimization hypothesis tests analysis of variance (ANOVA) probability distributions principal component analysis cluster analysis built on the Intel Math Kernel Library (MKL), which contains highly-optimized, extensively-threaded versions of BLAS (Basic Linear Algebra Subroutines) and LAPACK (Linear Algebra PACKage). Product  Price Update subscription Single Developer License $1295 $388 Team License (5 developers) $5180 $1554   DotNumerics http://www.dotnumerics.com/NumericalLibraries/Default.aspx free DotNumerics is a website dedicated to numerical computing for .NET that includes a C# Numerical Library for .NET containing algorithms for Linear Algebra, Differential Equations and Optimization problems. The Linear Algebra library includes CSLapack, CSBlas and CSEispack, ports from Fortran to C# of LAPACK, BLAS and EISPACK, respectively. Linear Algebra (CSLapack, CSBlas and CSEispack). Systems of linear equations, eigenvalue problems, least-squares solutions of linear systems and singular value problems. Differential Equations. Initial-value problem for nonstiff and stiff ordinary differential equations ODEs (explicit Runge-Kutta, implicit Runge-Kutta, Gear's BDF and Adams-Moulton). Optimization. Unconstrained and bounded constrained optimization of multivariate functions (L-BFGS-B, Truncated Newton and Simplex methods).   Math.NET Numerics http://numerics.mathdotnet.com/ free an open source numerical library - includes special functions, linear algebra, probability models, random numbers, interpolation, integral transforms. A merger of dnAnalytics with Math.NET Iridium in addition to a purely managed implementation will also support native hardware optimization. constants & special functions complex type support real and complex, dense and sparse linear algebra (with LU, QR, eigenvalues, ... decompositions) non-uniform probability distributions, multivariate distributions, sample generation alternative uniform random number generators descriptive statistics, including order statistics various interpolation methods, including barycentric approaches and splines numerical function integration (quadrature) routines integral transforms, like fourier transform (FFT) with arbitrary lengths support, and hartley spectral-space aware sequence manipulation (signal processing) combinatorics, polynomials, quaternions, basic number theory. parallelized where appropriate, to leverage multi-core and multi-processor systems fully managed or (if available) using native libraries (Intel MKL, ACMS, CUDA, FFTW) provides a native facade for F# developers

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• Issues passing values to shader

  - by numerical25

  I am having issues passing values to my shader. My application compiles fine, but my cube object won't shade. Below is majority of my code. Most of my code for communicating with my shader is in createObject method myGame.cpp #include "MyGame.h" #include "OneColorCube.h" /* This code sets a projection and shows a turning cube. What has been added is the project, rotation and a rasterizer to change the rasterization of the cube. The issue that was going on was something with the effect file which was causing the vertices not to be rendered correctly.*/ typedef struct { ID3D10Effect* pEffect; ID3D10EffectTechnique* pTechnique; //vertex information ID3D10Buffer* pVertexBuffer; ID3D10Buffer* pIndicesBuffer; ID3D10InputLayout* pVertexLayout; UINT numVertices; UINT numIndices; }ModelObject; ModelObject modelObject; // World Matrix D3DXMATRIX WorldMatrix; // View Matrix D3DXMATRIX ViewMatrix; // Projection Matrix D3DXMATRIX ProjectionMatrix; ID3D10EffectMatrixVariable* pProjectionMatrixVariable = NULL; ID3D10EffectVectorVariable* pLightVarible = NULL; bool MyGame::InitDirect3D() { if(!DX3dApp::InitDirect3D()) { return false; } D3D10_RASTERIZER_DESC rastDesc; rastDesc.FillMode = D3D10_FILL_WIREFRAME; rastDesc.CullMode = D3D10_CULL_FRONT; rastDesc.FrontCounterClockwise = true; rastDesc.DepthBias = false; rastDesc.DepthBiasClamp = 0; rastDesc.SlopeScaledDepthBias = 0; rastDesc.DepthClipEnable = false; rastDesc.ScissorEnable = false; rastDesc.MultisampleEnable = false; rastDesc.AntialiasedLineEnable = false; ID3D10RasterizerState *g_pRasterizerState; mpD3DDevice->CreateRasterizerState(&rastDesc, &g_pRasterizerState); //mpD3DDevice->RSSetState(g_pRasterizerState); // Set up the World Matrix D3DXMatrixIdentity(&WorldMatrix); D3DXMatrixLookAtLH(&ViewMatrix, new D3DXVECTOR3(0.0f, 10.0f, -20.0f), new D3DXVECTOR3(0.0f, 0.0f, 0.0f), new D3DXVECTOR3(0.0f, 1.0f, 0.0f)); // Set up the projection matrix D3DXMatrixPerspectiveFovLH(&ProjectionMatrix, (float)D3DX_PI * 0.5f, (float)mWidth/(float)mHeight, 0.1f, 100.0f); if(!CreateObject()) { return false; } return true; } //These are actions that take place after the clearing of the buffer and before the present void MyGame::GameDraw() { static float rotationAngleY = 15.0f; static float rotationAngleX = 0.0f; static D3DXMATRIX rotationXMatrix; static D3DXMATRIX rotationYMatrix; // create the rotation matrix using the rotation angle D3DXMatrixRotationY(&rotationYMatrix, rotationAngleY); D3DXMatrixRotationX(&rotationXMatrix, rotationAngleX); //rotationAngleY += (float)D3DX_PI * 0.002f; //rotationAngleX += (float)D3DX_PI * 0.001f; WorldMatrix = rotationYMatrix * rotationXMatrix; // Set the input layout mpD3DDevice->IASetInputLayout(modelObject.pVertexLayout); // Set vertex buffer UINT stride = sizeof(VertexPos); UINT offset = 0; mpD3DDevice->IASetVertexBuffers(0, 1, &modelObject.pVertexBuffer, &stride, &offset); // Set primitive topology mpD3DDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST); //ViewMatrix._43 += 0.005f; // Combine and send the final matrix to the shader D3DXMATRIX finalMatrix = (WorldMatrix * ViewMatrix * ProjectionMatrix); pProjectionMatrixVariable->SetMatrix((float*)&finalMatrix); // make sure modelObject is valid // Render a model object D3D10_TECHNIQUE_DESC techniqueDescription; modelObject.pTechnique->GetDesc(&techniqueDescription); // Loop through the technique passes for(UINT p=0; p < techniqueDescription.Passes; ++p) { modelObject.pTechnique->GetPassByIndex(p)->Apply(0); // draw the cube using all 36 vertices and 12 triangles mpD3DDevice->Draw(36,0); } } //Render actually incapsulates Gamedraw, so you can call data before you actually clear the buffer or after you //present data void MyGame::Render() { DX3dApp::Render(); } bool MyGame::CreateObject() { //Create Layout D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"NORMAL",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 24, D3D10_INPUT_PER_VERTEX_DATA, 0} }; UINT numElements = (sizeof(layout)/sizeof(layout[0])); modelObject.numVertices = sizeof(vertices)/sizeof(VertexPos); for(int i = 0; i < modelObject.numVertices; i += 3) { D3DXVECTOR3 out; D3DXVECTOR3 v1 = vertices[0 + i].pos; D3DXVECTOR3 v2 = vertices[1 + i].pos; D3DXVECTOR3 v3 = vertices[2 + i].pos; D3DXVECTOR3 u = v2 - v1; D3DXVECTOR3 v = v3 - v1; D3DXVec3Cross(&out, &u, &v); D3DXVec3Normalize(&out, &out); vertices[0 + i].normal = out; vertices[1 + i].normal = out; vertices[2 + i].normal = out; } //Create buffer desc D3D10_BUFFER_DESC bufferDesc; bufferDesc.Usage = D3D10_USAGE_DEFAULT; bufferDesc.ByteWidth = sizeof(VertexPos) * modelObject.numVertices; bufferDesc.BindFlags = D3D10_BIND_VERTEX_BUFFER; bufferDesc.CPUAccessFlags = 0; bufferDesc.MiscFlags = 0; D3D10_SUBRESOURCE_DATA initData; initData.pSysMem = vertices; //Create the buffer HRESULT hr = mpD3DDevice->CreateBuffer(&bufferDesc, &initData, &modelObject.pVertexBuffer); if(FAILED(hr)) return false; /* //Create indices DWORD indices[] = { 0,1,3, 1,2,3 }; ModelObject.numIndices = sizeof(indices)/sizeof(DWORD); bufferDesc.ByteWidth = sizeof(DWORD) * ModelObject.numIndices; bufferDesc.BindFlags = D3D10_BIND_INDEX_BUFFER; initData.pSysMem = indices; hr = mpD3DDevice->CreateBuffer(&bufferDesc, &initData, &ModelObject.pIndicesBuffer); if(FAILED(hr)) return false;*/ ///////////////////////////////////////////////////////////////////////////// //Set up fx files LPCWSTR effectFilename = L"effect.fx"; modelObject.pEffect = NULL; hr = D3DX10CreateEffectFromFile(effectFilename, NULL, NULL, "fx_4_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, mpD3DDevice, NULL, NULL, &modelObject.pEffect, NULL, NULL); if(FAILED(hr)) return false; pProjectionMatrixVariable = modelObject.pEffect->GetVariableByName("Projection")->AsMatrix(); pLightVarible = modelObject.pEffect->GetVariableByName("lightSource")->AsVector(); //Dont sweat the technique. Get it! LPCSTR effectTechniqueName = "Render"; D3DXVECTOR3 vLight(10.0f, 10.0f, 10.0f); pLightVarible->SetFloatVector(vLight); modelObject.pTechnique = modelObject.pEffect->GetTechniqueByName(effectTechniqueName); if(modelObject.pTechnique == NULL) return false; //Create Vertex layout D3D10_PASS_DESC passDesc; modelObject.pTechnique->GetPassByIndex(0)->GetDesc(&passDesc); hr = mpD3DDevice->CreateInputLayout(layout, numElements, passDesc.pIAInputSignature, passDesc.IAInputSignatureSize, &modelObject.pVertexLayout); if(FAILED(hr)) return false; return true; } And below is my shader effect.fx matrix Projection; float3 lightSource; float4 lightColor = {0.5, 0.5, 0.5, 0.5}; // PS_INPUT - input variables to the pixel shader // This struct is created and fill in by the // vertex shader struct PS_INPUT { float4 Pos : SV_POSITION; float4 Color : COLOR0; float4 Normal : NORMAL; }; //////////////////////////////////////////////// // Vertex Shader - Main Function /////////////////////////////////////////////// PS_INPUT VS(float4 Pos : POSITION, float4 Color : COLOR, float4 Normal : NORMAL) { PS_INPUT psInput; // Pass through both the position and the color psInput.Pos = mul( Pos, Projection ); psInput.Color = Color; psInput.Normal = Normal; return psInput; } /////////////////////////////////////////////// // Pixel Shader /////////////////////////////////////////////// float4 PS(PS_INPUT psInput) : SV_Target { float4 finalColor = 0; finalColor = saturate(dot(lightSource, psInput.Normal) * lightColor); return finalColor; } // Define the technique technique10 Render { pass P0 { SetVertexShader( CompileShader( vs_4_0, VS() ) ); SetGeometryShader( NULL ); SetPixelShader( CompileShader( ps_4_0, PS() ) ); } }

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• Filtering spectrum using FIR filters

  - by Alex Hoppus

  If i have signal values x[T] and filter coefficients b[i], i can perform filtering using convolution. Suppose i have spectrum of x (after FFT) and i need to perform filtering using filters coefficients, how can i perform this? I heard that in frequency domain it will be multiplying, rather than convolution (time domain). But i can't find an equation to use it. I have 614000 values in y = fft(x[T]) vector and 119 filter coefficients (generated using fdatool), i can't multiply them directly ... Thanks.

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• How can I create matrices of data in Excel?

  - by sandeep

  I want to create a 4*4 matrix in excel 2007 by taking three or more columns or conditions for example Column index Row index Name 1 2 x 2 3 y 3 4 z 4 1 p this is how data looks and i want it for 1*1 cell as p and 1*2 cell as x and so on. and I want out put as follows matrix 1 2 3 4 1 p x y z 2 p x y z 3 p x y z 4 p x y z and I have very huge data like this some times the matrix size goes up to 60*60 also.

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• Java code optimization leads to numerical inaccuracies and errors

  - by rano

  I'm trying to implement a version of the Fuzzy C-Means algorithm in Java and I'm trying to do some optimization by computing just once everything that can be computed just once. This is an iterative algorithm and regarding the updating of a matrix, the clusters x pixels membership matrix U, this is the update rule I want to optimize: where the x are the element of a matrix X (pixels x features) and v belongs to the matrix V (clusters x features). And m is a parameter that ranges from 1.1 to infinity. The distance used is the euclidean norm. If I had to implement this formula in a banal way I'd do: for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < V.length; j++) { double num = D[i][j]; double sumTerms = 0; for(int k = 0; k < V.length; k++) { double thisDistance = D[i][k]; sumTerms += Math.pow(num / thisDistance, (1.0 / (m - 1.0))); } U[i][j] = (float) (1f / sumTerms); } } In this way some optimization is already done, I precomputed all the possible squared distances between X and V and stored them in a matrix D but that is not enough, since I'm cycling througn the elements of V two times resulting in two nested loops. Looking at the formula the numerator of the fraction is independent of the sum so I can compute numerator and denominator independently and the denominator can be computed just once for each pixel. So I came to a solution like this: int nClusters = V.length; double exp = (1.0 / (m - 1.0)); for(int i = 0; i < X.length; i++) { int count = 0; for(int j = 0; j < nClusters; j++) { double distance = D[i][j]; double denominator = D[i][nClusters]; double numerator = Math.pow(distance, exp); U[i][j] = (float) (1f / (numerator * denominator)); } } Where I precomputed the denominator into an additional column of the matrix D while I was computing the distances: for (int i = 0; i < X.length; i++) { for (int j = 0; j < V.length; j++) { double sum = 0; for (int k = 0; k < nDims; k++) { final double d = X[i][k] - V[j][k]; sum += d * d; } D[i][j] = sum; D[i][B.length] += Math.pow(1 / D[i][j], exp); } } By doing so I encounter numerical differences between the 'banal' computation and the second one that leads to different numerical value in U (not in the first iterates but soon enough). I guess that the problem is that exponentiate very small numbers to high values (the elements of U can range from 0.0 to 1.0 and exp , for m = 1.1, is 10) leads to ver y small values, whereas by dividing the numerator and the denominator and THEN exponentiating the result seems to be better numerically. The problem is it involves much more operations. Am I doing something wrong? Is there a possible solution to get both the code optimized and numerically stable? Any suggestion or criticism will be appreciated.

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• Can't get Jacobi algorithm to work in Objective-C

  - by Chris Long

  Hi, For some reason, I can't get this program to work. I've had other CS majors look at it and they can't figure it out either. This program performs the Jacobi algorithm (you can see step-by-step instructions and a MATLAB implementation here). BTW, it's different from the Wikipedia article of the same name. Since NSArray is one-dimensional, I added a method that makes it act like a two-dimensional C array. After running the Jacobi algorithm many times, the diagonal entries in the NSArray (i[0][0], i[1][1], etc.) are supposed to get bigger and the others approach 0. For some reason though, they all increase exponentially. For instance, i[2][4] should equal 0.0000009, not 9999999, while i[2][2] should be big. Thanks in advance, Chris NSArray+Matrix.m @implementation NSArray (Matrix) @dynamic offValue, transposed; - (double)offValue { double sum = 0.0; for ( MatrixItem *item in self ) if ( item.nonDiagonal ) sum += pow( item.value, 2.0 ); return sum; } - (NSMutableArray *)transposed { NSMutableArray *transpose = [[[NSMutableArray alloc] init] autorelease]; int i, j; for ( i = 0; i < 5; i++ ) { for ( j = 0; j < 5; j++ ) { [transpose addObject:[self objectAtRow:j andColumn:i]]; } } return transpose; } - (id)objectAtRow:(NSUInteger)row andColumn:(NSUInteger)column { NSUInteger index = 5 * row + column; return [self objectAtIndex:index]; } - (NSMutableArray *)multiplyWithMatrix:(NSArray *)array { NSMutableArray *result = [[NSMutableArray alloc] init]; int i = 0, j = 0, k = 0; double value; for ( i = 0; i < 5; i++ ) { value = 0.0; for ( j = 0; j < 5; j++ ) { for ( k = 0; k < 5; k++ ) { MatrixItem *firstItem = [self objectAtRow:i andColumn:k]; MatrixItem *secondItem = [array objectAtRow:k andColumn:j]; value += firstItem.value * secondItem.value; } MatrixItem *item = [[MatrixItem alloc] initWithValue:value]; item.row = i; item.column = j; [result addObject:item]; } } return result; } @end Jacobi_AlgorithmAppDelegate.m // ... - (void)jacobiAlgorithmWithEntry:(MatrixItem *)entry { MatrixItem *b11 = [matrix objectAtRow:entry.row andColumn:entry.row]; MatrixItem *b22 = [matrix objectAtRow:entry.column andColumn:entry.column]; double muPlus = ( b22.value + b11.value ) / 2.0; muPlus += sqrt( pow((b22.value - b11.value), 2.0) + 4.0 * pow(entry.value, 2.0) ); Vector *u1 = [[[Vector alloc] initWithX:(-1.0 * entry.value) andY:(b11.value - muPlus)] autorelease]; [u1 normalize]; Vector *u2 = [[[Vector alloc] initWithX:-u1.y andY:u1.x] autorelease]; NSMutableArray *g = [[[NSMutableArray alloc] init] autorelease]; for ( int i = 0; i <= 24; i++ ) { MatrixItem *item = [[[MatrixItem alloc] init] autorelease]; if ( i == 6*entry.row ) item.value = u1.x; else if ( i == 6*entry.column ) item.value = u2.y; else if ( i == ( 5*entry.row + entry.column ) || i == ( 5*entry.column + entry.row ) ) item.value = u1.y; else if ( i % 6 == 0 ) item.value = 1.0; else item.value = 0.0; [g addObject:item]; } NSMutableArray *firstResult = [[g.transposed multiplyWithMatrix:matrix] autorelease]; matrix = [firstResult multiplyWithMatrix:g]; } // ...

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• Camera wont stay behind model after pitch, then rotation

  - by ChocoMan

  I have a camera position behind a model. Currently, if I push the left thumbstick making my model move forward, backward, or strafe, the camera stays with the model. If I push the right thumbstick left or right, the model rotates in those directions fine along with the camera rotating while maintaining its position relatively behind the model. But when I pitch the model up or down, then rotate the model afterwards, the camera moves slightly rotates in a clock-like fashion behind the model. If I do a few rotations of the model and try to pitch the camera, the camera will eventually be looking at the side, then eventually the front of the model while also rotating in a clock-like fashion. My question is, how do I keep the camera to pitch up and down behind the model no matter how much the model has rotated? Here is what I got: // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { // Rotates Camera with model Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(angularSpeed); // Pitches Camera around model Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(angularSpeed); AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); } // Orbit (yaw) Camera around with model (only seeing back of model) public void cameraYaw(Vector3 axisYaw, float yaw) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; } // Raise camera above or below model's shoulders public void cameraPitch(Vector3 axisPitch, float pitch) { ModelLoad.CameraPos = Vector3.Transform(ModelLoad.CameraPos - ModelLoad.camTarget, Matrix.CreateFromAxisAngle(axisPitch, pitch)) + ModelLoad.camTarget; } // Call in update method public void updateCamera() { cameraYaw(Vector3.Up, Yaw); cameraPitch(Vector3.Right, Pitch); } NOTE: I tried to use addPitch just like addRotation but it didn't work...

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• Keep 3d model facing the camera at all angles

  - by Sparky41

  I'm trying to keep a 3d plane facing the camera at all angles but while i have some success with this: Vector3 gunToCam = cam.cameraPosition - getWorld.Translation; Vector3 beamRight = Vector3.Cross(torpDirection, gunToCam); beamRight.Normalize(); Vector3 beamUp = Vector3.Cross(beamRight, torpDirection); shipeffect.beamWorld = Matrix.Identity; shipeffect.beamWorld.Forward = (torpDirection) * 1f; shipeffect.beamWorld.Right = beamRight; shipeffect.beamWorld.Up = beamUp; shipeffect.beamWorld.Translation = shipeffect.beamPosition; *Note: Logic not wrote by me i just found this rather useful It seems to only face the camera at certain angles. For example if i place the camera behind the plane you can see it that only Roll's around the axis like this: http://i.imgur.com/FOKLx.png (imagine if you are looking from behind where you have fired from. Any idea what to what the problem is (angles are not my specialty) shipeffect is an object that holds this class variables: public Texture2D altBeam; public Model beam; public Matrix beamWorld; public Matrix[] gunTransforms; public Vector3 beamPosition;

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• Move a 2D square on y axis on android GLES2

  - by Dan

  I am trying to create a simple game for android, to start i am trying to make the square move down the y axis but the way i am doing it dosent move the square at all and i cant find any tutorials for GLES20 The on draw frame function in the render class updates the users position based on accleration dew to gravity, gets the transform matrix from the user class which is used to move the square down, then the program draws it. All that happens is that the square is drawn, no motion happens public void onDrawFrame(GL10 gl) { user.update(0.0, phy.AccelerationDewToGravity); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT); // Re draws black background GLES20.glVertexAttribPointer(maPositionHandle, 3, GLES20.GL_FLOAT, false, 12, user.SquareVB);//triangleVB); GLES20.glEnableVertexAttribArray(maPositionHandle); GLES20.glUniformMatrix4fv(maPositionHandle, 1, false, user.getTransformMatrix(), 0); GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4); } The update function in the player class is public void update(double vh, double vv) { Vh += vh; // Increase horrzontal Velosity Vv += vv; // Increase vertical velosity //Matrix.translateM(mMMatrix, 0, (int)Vh, (int)Vv, 0); Matrix.translateM(mMMatrix, 0, mMMatrix, 0, (float)Vh, (float)Vv, 0); }

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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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• Quaternion LookAt for camera

  - by Homar

  I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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• Managing constant buffers without FX interface

  - by xcrypt

  I am aware that there is a sample on working without FX in the samplebrowser, and I already checked that one. However, some questions arise: In the sample: D3DXMATRIXA16 mWorldViewProj; D3DXMATRIXA16 mWorld; D3DXMATRIXA16 mView; D3DXMATRIXA16 mProj; mWorld = g_World; mView = g_View; mProj = g_Projection; mWorldViewProj = mWorld * mView * mProj; VS_CONSTANT_BUFFER* pConstData; g_pConstantBuffer10->Map( D3D10_MAP_WRITE_DISCARD, NULL, ( void** )&pConstData ); pConstData->mWorldViewProj = mWorldViewProj; pConstData->fTime = fBoundedTime; g_pConstantBuffer10->Unmap(); They are copying their D3DXMATRIX'es to D3DXMATRIXA16. Checked on msdn, these new matrices are 16 byte aligned and optimised for intel pentium 4. So as my first question: 1) Is it necessary to copy matrices to D3DXMATRIXA16 before sending them to the constant buffer? And if no, why don't we just use D3DXMATRIXA16 all the time? I have another question about managing multiple constant buffers within one shader. Suppose that, within your shader, you have multiple constant buffers that need to be updated at different times: cbuffer cbNeverChanges { matrix View; }; cbuffer cbChangeOnResize { matrix Projection; }; cbuffer cbChangesEveryFrame { matrix World; float4 vMeshColor; }; Then how would I set these buffers all at different times? g_pd3dDevice->VSSetConstantBuffers( 0, 1, &g_pConstantBuffer10 ); gives me the possibility to set multiple buffers, but that is within one call. 2) Is that okay even if my constant buffers are updated at different times? And do I suppose I have to make sure the constantbuffers are in the same position in the array as the order they appear in the shader?

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• Sorting objects before rendering

  - by dreta

  I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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• How to use mount points in MilkShape models?

  - by vividos

  I have bought the Warriors & Commoners model pack from Frogames and the pack contains (among other formats) two animated models and several non-animated objects (axe, shield, pilosities, etc.) in MilkShape3D format. I looked at the official "MilkShape 3D Viewer v2.0" (msViewer2.zip at http://www.chumba.ch/chumbalum-soft/ms3d/download.html) source code and implemented loading the model, calculating the joint matrices and everything looks fine. In the model there are several joints that are designated as the "mount points" for the static objects like axe and shield. I now want to "put" the axe into the hand of the animated model, and I couldn't quite figure out how. I put the animated vertices in a VBO that gets updated every frame (I know I should do this with a shader, but I didn't have time to do this yet). I put the static vertices in another VBO that I want to keep static and not updated every frame. I now tried to render the animated vertices first, then use the joint matrix for the "mount joint" to calculate the location of the static object. I tried many things, and what about seems to be right is to transpose the joint matrix, then use glMatrixMult() to transform the modelview matrix. For some objects like the axe this is working, but not for others, e.g. the pilosities. Now my question: How is this generally implemented when using bone/joint models, and especially with MilkShape3D models? Am I on the right track?

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• Extracting Frustum Planes (Hartmann & Gribbs method)

  - by DAVco

  I have been grappling with the Hartmann/Gribbs method of extracting the Frustum planes for some time now, with little success. There doesn't appear to be a "definitive" topic or tutorial which combines all the necessary information, so perhaps this can be it First of all, I am attempting to do this in C# (For Playstation Mobile), using OpenGL style Column-Major matrices in a Right-Handed coordinate system but obviously the math will work in any language. My projection matrix has a Near plane at 1.0, Far plane at 1000, FOV of 45.0 and Aspect of 1.7647. I want to get my planes in World-Space, so I build my frustum from the View-Projection Matrix (that's projectionMatrix * viewMatrix). The view Matrix is the inverse of the camera's World-Transform. The problem is; regardless of what I tweak, I can't seem to get a correct frustum. I think that I may be missing something obvious. Focusing on the Near and Far planes for the moment (since they have the most obvious normals when correct), when my camera is positioned looking down the negative z-axis, I get two planes facing in the same direction, rather than opposite directions. If i strafe my camera left and right (while still looking along the z axis) the x value of the normal vector changes. Obviously, something is fundamentally wrong here; I just can't figure out what - maybe someone here can?

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• Questions before I revamp my rendering engine to use shaders (GLSL)

  - by stephelton

  I've written a fairly robust rendering engine using OpenGL ES 1.1 (fixed-function.) I've been looking into revamping the engine to use OpenGL ES 2.0, which necessitates that I use shaders. I've been absorbing information all day long and still have some questions. Firstly, lighting. The fixed-function pipeline is guaranteed to have at least 8 lights available. My current engine finds lights that are "close" to the primitives being drawn and enables them; I don't know how many lights are going to be enabled until I draw a given model. Nothing is dynamically allocated in GLSL, so I have to define in a shader some number of lights to be used, right? So if I want to stick with 8, should I write my general purpose shader to have 8 lights and then use uniforms to tell it how many / which lights to use? Which brings me to another question: should I be concerned with the amount of data I'm allocating in a shader? Recent video cards have hundreds of "stream processors." If I've got a fragment shader being used on some number of fragments in a given triangle, I assume they must each have their own stack to work on. Are read-only variables copied here, or read when needed? My initial goal is to rework my code so that it is virtually identical to the current implementation. What I have in mind is to create my own matrix stack so that I can implement something along the lines of push/popMatrix and apply all my translations, rotations, and scales to this matrix, then provide the matrix to the vertex shader so that it can make very quick vertex translations. Is this approach sound? Edit: My original intention was to ask if there was a tutorial that would explain the bare minimum necessary to jump from fixed-function to using shaders. Thanks!

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• Create a rectangle struct to be rotated and have a .Intersects() function

  - by MintyAnt

  In my XNA program, I am trying to swing a sword. The sword starts at an angle of 180 degrees, then rotates (clockwise) to an angle of 90 degrees. The Rectangle struct that XNA provides, Rectangle mAttackBox = new Rectangle(int x, int y, int width, int height); However, this struct has two problems: Holds position and size in Integers, not Floats Cannot be rotated I was hoping someone could help me in either telling me that i'm wrong and the Rectangle can be used for both these methods, or can lead me down the right path for rotating a rectangle. I know how to create a Struct. I believe that I can make methods like classes. I can determine the 4 vertices of a 2D rectangle by calculating out the x,y of the other 3 given the length, width. I'm sure theres a Matrix class I can use to multiply each point against a Rotation matrix. But once i have my 4 vertices, I got two other problems: - How do I test other rectangles against it? How does .Intersects() work for the rectangle struct? - Is this even the fastest way to do it? I'd be constantly doing matrix multiplication, wouldnt that slow things down?

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• Quaternions, Axis Angles and Rotation Matrices. Which of these should I use for FP Camera?

  - by Afonso Lage

  After 2 weeks of reading many math formulas and such I know what is a Quaternion, an Axis Angles and Matrices. I have made my own math libary (Java) to use on my game (LWJGL). But I'm really confused about all this. I want to have a 3D first person camera. The move (translation) is working fine but the rotation isnt working like I need. I need a camera to rotate arround world Axis and not about its own axis. But even using Quaternions, this doesnt work and no matter how much I read about Euler Angles, everybody says to me dont touch on it! This is a little piece of code that i'm using to make the rotation: Quaternion qPitch = Quaternion.createFromAxis(cameraRotate.x, 1.0f, 0.0f, 0.0f); Quaternion qYaw = Quaternion.createFromAxis(cameraRotate.y, 0.0f, 1.0f, 0.0f); this.multiplicate(qPitch.toMatrix4f().toArray()); this.multiplicate(qYaw.toMatrix4f().toArray()); Where this is a Matrix4f view matrix and cameraRotate is a Vector3f that just handle the angles to rotate obtained from mouse move. So I think I'm doing everything right: Translate the view Matrix Rotate the Move Matrix So, after reading all this, I just want to know: To obtain a correct first person camera rotate, I must need to use Quaternios to make the rotations, but how to rotate around world axis? Thanks for reading it. Best regards, Afonso Lage

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• Split up a screen into regions

  - by nexen

  My task: I want to split up a screen into 3 regions for buffs-bar (with picked items), score-info and a game-map. It doesn't matter are regions intersect with each other or not. For example: I have a screen with width=1; height=1 and the origin of coordinates (0;0) is the left bottom point. I have 3 functions: draw items, draw info, draw map. If I use it without any matrix transformations, it draws fullscreen, because it's vertex coordinates are from 0;0 to 1;1. (pseudo-code) drawItems(); drawInfo(); drawMap(); And after that I see only map onto info onto items. My goal: I have some matrixes for transformation vertexes with 0;0-1;1 coordinates to strict regions. There is only one thing, what I need to do - set matrix before drawing. So my call of drawItems-function is like: (pseudo-code) adjustViewMatrixes_andSomethingElse(items.position_of_the_region_there_it_should_be_drawn, items.sizes_of_region_to_draw); setItemsMatrix(); drawItems(); //the same function with vertex coordinates 0;0->1;1, //but it draws in other coordinates, //because I have just set the matrix for region I know only some people will understand me, so there is a picture with regions which I need to make. Every region has 0;0 - 1;1 inner coordinates.

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• How do I classify using SVM Classifier?

  - by Gomathi

  I'm doing a project in liver tumor classification. Actually I initially used Region Growing method for liver segmentation and from that I segmented tumor using FCM. I,then, obtained the texture features using Gray Level Co-occurence Matrix. My output for that was stats = autoc: [1.857855266614132e+000 1.857955341199538e+000] contr: [5.103143332457753e-002 5.030548650257343e-002] corrm: [9.512661919561399e-001 9.519459060378332e-001] corrp: [9.512661919561385e-001 9.519459060378338e-001] cprom: [7.885631654779597e+001 7.905268525471267e+001] Now how should I give this as an input to the SVM program. function [itr] = multisvm( T,C,tst ) %MULTISVM(2.0) classifies the class of given training vector according to the % given group and gives us result that which class it belongs. % We have also to input the testing matrix %Inputs: T=Training Matrix, C=Group, tst=Testing matrix %Outputs: itr=Resultant class(Group,USE ROW VECTOR MATRIX) to which tst set belongs %----------------------------------------------------------------------% % IMPORTANT: DON'T USE THIS PROGRAM FOR CLASS LESS THAN 3, % % OTHERWISE USE svmtrain,svmclassify DIRECTLY or % % add an else condition also for that case in this program. % % Modify required data to use Kernel Functions and Plot also% %----------------------------------------------------------------------% % Date:11-08-2011(DD-MM-YYYY) % % This function for multiclass Support Vector Machine is written by % ANAND MISHRA (Machine Vision Lab. CEERI, Pilani, India) % and this is free to use. email: [email protected] % Updated version 2.0 Date:14-10-2011(DD-MM-YYYY) u=unique(C); N=length(u); c4=[]; c3=[]; j=1; k=1; if(N>2) itr=1; classes=0; cond=max(C)-min(C); while((classes~=1)&&(itr<=length(u))&& size(C,2)>1 && cond>0) %This while loop is the multiclass SVM Trick c1=(C==u(itr)); newClass=c1; svmStruct = svmtrain(T,newClass); classes = svmclassify(svmStruct,tst); % This is the loop for Reduction of Training Set for i=1:size(newClass,2) if newClass(1,i)==0; c3(k,:)=T(i,:); k=k+1; end end T=c3; c3=[]; k=1; % This is the loop for reduction of group for i=1:size(newClass,2) if newClass(1,i)==0; c4(1,j)=C(1,i); j=j+1; end end C=c4; c4=[]; j=1; cond=max(C)-min(C); % Condition for avoiding group %to contain similar type of values %and the reduce them to process % This condition can select the particular value of iteration % base on classes if classes~=1 itr=itr+1; end end end end Kindly guide me. Images:

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• Multiplying matrices: error: expected primary-expression before 'struct'

  - by justin

  I am trying to write a program that is supposed to multiply matrices using threads. I am supposed to fill the matrices using random numbers in a thread. I am compiling in g++ and using PTHREADS. I have also created a struct to pass the data from my command line input to the thread so it can generate the matrix of random numbers. The sizes of the two matrices are also passed in the command line as well. I keep getting: main.cpp:7: error: expected primary-expression before 'struct' my code @ line 7 =: struct a{ int Arow; int Acol; int low; int high; }; My inpust are : Sizes of two matrices ( 4 arguments) high and low ranges in which o generate the random numbers between. Complete code: [headers] using namespace std; void *matrixACreate(struct *); void *status; int main(int argc, char * argv[]) { int Arow = atoi(argv[1]); // Matrix A int Acol = atoi(argv[2]); // WxX int Brow = atoi(argv[3]); // Matrix B int Bcol = atoi(argv[4]); // XxZ, int low = atoi(argv[5]); // Range low int high = atoi(argv[6]); struct a{ int Arow; // Matrix A int Acol; // WxX int low; // Range low int high; }; pthread_t matrixAthread; //pthread_t matrixBthread; pthread_t runner; int error, retValue; if (Acol != Brow) { cout << " This matrix cannot be multiplied. FAIL" << endl; return 0; } error = pthread_create(&matrixAthread, NULL, matrixACreate, struct *a); //error = pthread_create(&matrixAthread, NULL, matrixBCreate, sendB); retValue = pthread_join(matrixAthread, &status); //retValue = pthread_join(matrixBthread, &status); return 0; } void matrixACreate(struct * a) { struct a *data = (struct a *) malloc(sizeof(struct a)); data->Arow = Arow; data->Acol = Acol; data->low = low; data->high = high; int range = ((high - low) + 1); cout << Arow << endl<< Acol << endl; }// just trying to print to see if I am in the thread

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• Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

  - by voxelizr

  TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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• OpenGL Fast-Object Instancing Error

  - by HJ Media Studios

  I have some code that loops through a set of objects and renders instances of those objects. The list of objects that needs to be rendered is stored as a std::map, where an object of class MeshResource contains the vertices and indices with the actual data, and an object of classMeshRenderer defines the point in space the mesh is to be rendered at. My rendering code is as follows: glDisable(GL_BLEND); glEnable(GL_CULL_FACE); glDepthMask(GL_TRUE); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); for (std::map<MeshResource*, std::vector<MeshRenderer*> >::iterator it = renderables.begin(); it != renderables.end(); it++) { it->first->setupBeforeRendering(); cout << "<"; for (unsigned long i =0; i < it->second.size(); i++) { //Pass in an identity matrix to the vertex shader- used here only for debugging purposes; the real code correctly inputs any matrix. uniformizeModelMatrix(Matrix4::IDENTITY); /** * StartHere fix rendering problem. * Ruled out: * Vertex buffers correctly. * Index buffers correctly. * Matrices correct? */ it->first->render(); } it->first->cleanupAfterRendering(); } geometryPassShader->disable(); glDepthMask(GL_FALSE); glDisable(GL_CULL_FACE); glDisable(GL_DEPTH_TEST); The function in MeshResource that handles setting up the uniforms is as follows: void MeshResource::setupBeforeRendering() { glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glEnableVertexAttribArray(2); glEnableVertexAttribArray(3); glEnableVertexAttribArray(4); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID); glBindBuffer(GL_ARRAY_BUFFER, vboID); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0); // Vertex position glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 12); // Vertex normal glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 24); // UV layer 0 glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 32); // Vertex color glVertexAttribPointer(4, 1, GL_UNSIGNED_SHORT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 44); //Material index } The code that renders the object is this: void MeshResource::render() { glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } And the code that cleans up is this: void MeshResource::cleanupAfterRendering() { glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); glDisableVertexAttribArray(2); glDisableVertexAttribArray(3); glDisableVertexAttribArray(4); } The end result of this is that I get a black screen, although the end of my rendering pipeline after the rendering code (essentially just drawing axes and lines on the screen) works properly, so I'm fairly sure it's not an issue with the passing of uniforms. If, however, I change the code slightly so that the rendering code calls the setup immediately before rendering, like so: void MeshResource::render() { setupBeforeRendering(); glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } The program works as desired. I don't want to have to do this, though, as my aim is to set up vertex, material, etc. data once per object type and then render each instance updating only the transformation information. The uniformizeModelMatrix works as follows: void RenderManager::uniformizeModelMatrix(Matrix4 matrix) { glBindBuffer(GL_UNIFORM_BUFFER, globalMatrixUBOID); glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(Matrix4), matrix.ptr()); glBindBuffer(GL_UNIFORM_BUFFER, 0); }

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