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  • View matrix question (rotate by 180 degrees)

    - by King Snail
    I am using a third party rendering API on top of OpenGL code and I cannot get my matrices correct. The API states this: We're right handed by default, and we treat y as up by convention. Since IwGx's coordinate system has (0,0) as the top left, you typically need a 180 degree rotation around Z in your view matrix. I think the viewer does this by default. In my OpenGL app I have access to the view and projection matrices separately. How can I convert them to fit the criteria used by my third party rendering API? I don't understand what they mean to rotate 180 degrees around Z, is that in the view matrix itself or something in the camera before making the view matrix. Any code would be helpful, thanks.

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  • Getting the MODELVIEW matrix...

    - by james.ingham
    Hi, I've been pulling my hair out trying to get some matrix calculations working properly and started to wonder. If I have the following: glPushMatrix(); float m[16]; glGetFloatv(GL_MODELVIEW_MATRIX, m); glPopMatrix(); What should I expect the values of m to equal? Currently I'm getting these values and I'm confused as to where they're coming from: -1, 0, 0, 0, 0, -0.6139, 0.7893522, 0, 0, 0.789352238, 0.61394, 0, 0, 0.0955992, -1.344529, 1, I'm assuming there is something which affects this, but I'm not sure what. Could anyone help? I've tried changing pretty much anything but everytime I push the matrix stack I always get this matrix straight away! I don't think this makes a difference but I'm using OpenGLES. Thanks

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  • Use a vector to index a matrix without linear index

    - by David_G
    G'day, I'm trying to find a way to use a vector of [x,y] points to index from a large matrix in MATLAB. Usually, I would convert the subscript points to the linear index of the matrix.(for eg. Use a vector as an index to a matrix in MATLab) However, the matrix is 4-dimensional, and I want to take all of the elements of the 3rd and 4th dimensions that have the same 1st and 2nd dimension. Let me hopefully demonstrate with an example: Matrix = nan(4,4,2,2); % where the dimensions are (x,y,depth,time) Matrix(1,2,:,:) = 999; % note that this value could change in depth (3rd dim) and time (4th time) Matrix(3,4,:,:) = 888; % note that this value could change in depth (3rd dim) and time (4th time) Matrix(4,4,:,:) = 124; Now, I want to be able to index with the subscripts (1,2) and (3,4), etc and return not only the 999 and 888 which exist in Matrix(:,:,1,1) but the contents which exist at Matrix(:,:,1,2),Matrix(:,:,2,1) and Matrix(:,:,2,2), and so on (IRL, the dimensions of Matrix might be more like size(Matrix) = (300 250 30 200) I don't want to use linear indices because I would like the results to be in a similar vector fashion. For example, I would like a result which is something like: ans(time=1) 999 888 124 999 888 124 ans(time=2) etc etc etc etc etc etc I'd also like to add that due to the size of the matrix I'm dealing with, speed is an issue here - thus why I'd like to use subscript indices to index to the data. I should also mention that (unlike this question: Accessing values using subscripts without using sub2ind) since I want all the information stored in the extra dimensions, 3 and 4, of the i and jth indices, I don't think that a slightly faster version of sub2ind still would not cut it..

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  • Faster method for Matrix vector product for large matrix in C or C++ for use in GMRES

    - by user35959
    I have a large, dense matrix A, and I aim to find the solution to the linear system Ax=b using an iterative method (in MATLAB was the plan using its built in GMRES). For more than 10,000 rows, this is too much for my computer to store in memory, but I know that the entries in A are constructed by two known vectors x and y of length N and the entries satisfy: A(i,j) = .5*(x[i]-x[j])^2+([y[i]-y[j])^2 * log(x[i]-x[j])^2+([y[i]-y[j]^2). MATLAB's GMRES command accepts as input a function call that can compute the matrix vector product A*x, which allows me to handle larger matrices than I can store in memory. To write the matrix-vecotr product function, I first tried this in matlab by going row by row and using some vectorization, but I avoid spawning the entire array A (since it would be too large). This was fairly slow unfortnately in my application for GMRES. My plan was to write a mex file for MATLAB to, which is in C, and ideally should be significantly faster than the matlab code. I'm rather new to C, so this went rather poorly and my naive attempt at writing the code in C was slower than my partially vectorized attempt in Matlab. #include <math.h> #include "mex.h" void Aproduct(double *x, double *ctrs_x, double *ctrs_y, double *b, mwSize n) { mwSize i; mwSize j; double val; for (i=0; i<n; i++) { for (j=0; j<i; j++) { val = pow(ctrs_x[i]-ctrs_x[j],2)+pow(ctrs_y[i]-ctrs_y[j],2); b[i] = b[i] + .5* val * log(val) * x[j]; } for (j=i+1; j<n; j++) { val = pow(ctrs_x[i]-ctrs_x[j],2)+pow(ctrs_y[i]-ctrs_y[j],2); b[i] = b[i] + .5* val * log(val) * x[j]; } } } The above is the computational portion of the code for the matlab mex file (which is slightly modified C, if I understand correctly). Please note that I skip the case i=j, since in that case the variable val will be a 0*log(0), which should be interpreted as 0 for me, so I just skip it. Is there a more efficient or faster way to write this? When I call this C function via the mex file in matlab, it is quite slow, slower even than the matlab method I used. This surprises me since I suspected that C code should be much faster than matlab. The alternative matlab method which is partially vectorized that I am comparing it with is function Ax = Aprod(x,ctrs) n = length(x); Ax = zeros(n,1); for j=1:(n-3) v = .5*((ctrs(j,1)-ctrs(:,1)).^2+(ctrs(j,2)-ctrs(:,2)).^2).*log((ctrs(j,1)-ctrs(:,1)).^2+(ctrs(j,2)-ctrs(:,2)).^2); v(j)=0; Ax(j) = dot(v,x(1:n-3); end (the n-3 is because there is actually 3 extra components, but they are dealt with separately,so I excluded that code). This is partly vectorized and only needs one for loop, so it makes some sense that it is faster. However, I was hoping I could go even faster with C+mex file. Any suggestions or help would be greatly appreciated! Thanks! EDIT: I should be more clear. I am open to any faster method that can help me use GMRES to invert this matrix that I am interested in, which requires a faster way of doing the matrix vector product without explicitly loading the array into memory. Thanks!

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  • View matrix in opengl

    - by user5584
    Hi! Sorry for my clumsy question. But I don't know where I am wrong at creating view matrix. I have the following code: createMatrix(vec4f(xAxis.x, xAxis.y, xAxis.z, dot(xAxis,eye)), vec4f( yAxis.x_, yAxis.y_, yAxis.z_, dot(yAxis,eye)), vec4f(-zAxis.x_, -zAxis.y_, -zAxis.z_, -dot(zAxis,eye)), vec4f(0, 0, 0, 1)); //column1, column2,... I have tried to transpose it, but with no success. I have also tried to use gluLookAt(...) with success. At the reference page, I watched the remarks about the to-be-created matrix, and it seems the same as mine. Where I am wrong?

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  • Unity3D - Projection matrix camera frustum

    - by MulletDevil
    I've used off centre projection to create a custom projection matrix for my camera. When I run the game I can see the scene correctly in the game view but in the editor view the camera frustum is not correct. It still shows the original frustum shape not the new one. It also appears that Unity is using the original frustum for frustum culling and not the new one as I can see object being culled which are visible to the new frustum but would not be visible in the old one. Am I wrong in thinking that a custom projection matrix would alter the view frustum? Or am I missing something else?

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  • Handling inverse kinematics: animation blending or math?

    - by meds
    I've been working for the past four days on inverse kinematics for my game engine. I'm working on a game with a shoestring budget so when the idea of inverse kinematics came up I knew I had to make it such that the 3D models bones would be mathematically changed to appear to be stepping on objects. This is causing some serious problems with my animation, after it was technically implemented the animations started looking quite bad when the character was wlaking up inclines or steps even though mathematically the stepping was correct and was even smoothly interpolating. So I was wondering, is it actually possible to get a smooth efficient inverse kinematic system based exclusively on math where bones are changed or is this just a wild goose chase and I should either solve the inverse kinematics problem with animation blending or don't do it at all?

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  • Arbitrary projection matrix from 6 arbitrary frustum planes

    - by Doub
    A projection matrix represent a tranformation from the camera view space to the rendering system clip space. In other words, it defines the transormation between a 6-sided frustum to the clip cube. The glOrtho and glFrustum use only 6 parameter to define such a projection, but impose several constraints on the frustum that will get projected to the clip cube: the near and far planes are parallel, the left and right planes intersect on a vertical line, and the top and bottom planes intersect on a horizontal lines, both lines being parallel to the near and far planes. I'd like to lift these restrictions. So, from the definition of the 6 frustum side planes (in whatever representation you see fit), how can I compute a general projection matrix?

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  • projection / view matrix: the object is bigger than it should and depth does not affect vertices

    - by Francesco Noferi
    I'm currently trying to write a C 3D software rendering engine from scratch just for fun and to have an insight on what OpenGL does behind the scene and what 90's programmers had to do on DOS. I have written my own matrix library and tested it without noticing any issues, but when I tried projecting the vertices of a simple 2x2 cube at 0,0 as seen by a basic camera at 0,0,10, the cube seems to appear way bigger than the application's window. If I scale the vertices' coordinates down by 8 times I can see a proper cube centered on the screen. This cube doesn't seem to be in perspective: wheen seen from the front, the back vertices pe rfectly overlap with the front ones, so I'm quite sure it's not correct. this is how I create the view and projection matrices (vec4_initd initializes the vectors with w=0, vec4_initw initializes the vectors with w=1): void mat4_lookatlh(mat4 *m, const vec4 *pos, const vec4 *target, const vec4 *updirection) { vec4 fwd, right, up; // fwd = norm(pos - target) fwd = *target; vec4_sub(&fwd, pos); vec4_norm(&fwd); // right = norm(cross(updirection, fwd)) vec4_cross(updirection, &fwd, &right); vec4_norm(&right); // up = cross(right, forward) vec4_cross(&fwd, &right, &up); // orientation and translation matrices combined vec4_initd(&m->a, right.x, up.x, fwd.x); vec4_initd(&m->b, right.y, up.y, fwd.y); vec4_initd(&m->c, right.z, up.z, fwd.z); vec4_initw(&m->d, -vec4_dot(&right, pos), -vec4_dot(&up, pos), -vec4_dot(&fwd, pos)); } void mat4_perspectivefovrh(mat4 *m, float fovdegrees, float aspectratio, float near, float far) { float h = 1.f / tanf(ftoradians(fovdegrees / 2.f)); float w = h / aspectratio; vec4_initd(&m->a, w, 0.f, 0.f); vec4_initd(&m->b, 0.f, h, 0.f); vec4_initw(&m->c, 0.f, 0.f, -far / (near - far)); vec4_initd(&m->d, 0.f, 0.f, (near * far) / (near - far)); } this is how I project my vertices: void device_project(device *d, const vec4 *coord, const mat4 *transform, int *projx, int *projy) { vec4 result; mat4_mul(transform, coord, &result); *projx = result.x * d->w + d->w / 2; *projy = result.y * d->h + d->h / 2; } void device_rendervertices(device *d, const camera *camera, const mesh meshes[], int nmeshes, const rgba *color) { int i, j; mat4 view, projection, world, transform, projview; mat4 translation, rotx, roty, rotz, transrotz, transrotzy; int projx, projy; // vec4_unity = (0.f, 1.f, 0.f, 0.f) mat4_lookatlh(&view, &camera->pos, &camera->target, &vec4_unity); mat4_perspectivefovrh(&projection, 45.f, (float)d->w / (float)d->h, 0.1f, 1.f); for (i = 0; i < nmeshes; i++) { // world matrix = translation * rotz * roty * rotx mat4_translatev(&translation, meshes[i].pos); mat4_rotatex(&rotx, ftoradians(meshes[i].rotx)); mat4_rotatey(&roty, ftoradians(meshes[i].roty)); mat4_rotatez(&rotz, ftoradians(meshes[i].rotz)); mat4_mulm(&translation, &rotz, &transrotz); // transrotz = translation * rotz mat4_mulm(&transrotz, &roty, &transrotzy); // transrotzy = transrotz * roty = translation * rotz * roty mat4_mulm(&transrotzy, &rotx, &world); // world = transrotzy * rotx = translation * rotz * roty * rotx // transform matrix mat4_mulm(&projection, &view, &projview); // projview = projection * view mat4_mulm(&projview, &world, &transform); // transform = projview * world = projection * view * world for (j = 0; j < meshes[i].nvertices; j++) { device_project(d, &meshes[i].vertices[j], &transform, &projx, &projy); device_putpixel(d, projx, projy, color); } } } this is how the cube and camera are initialized: // test mesh cube = &meshlist[0]; mesh_init(cube, "Cube", 8); cube->rotx = 0.f; cube->roty = 0.f; cube->rotz = 0.f; vec4_initw(&cube->pos, 0.f, 0.f, 0.f); vec4_initw(&cube->vertices[0], -1.f, 1.f, 1.f); vec4_initw(&cube->vertices[1], 1.f, 1.f, 1.f); vec4_initw(&cube->vertices[2], -1.f, -1.f, 1.f); vec4_initw(&cube->vertices[3], -1.f, -1.f, -1.f); vec4_initw(&cube->vertices[4], -1.f, 1.f, -1.f); vec4_initw(&cube->vertices[5], 1.f, 1.f, -1.f); vec4_initw(&cube->vertices[6], 1.f, -1.f, 1.f); vec4_initw(&cube->vertices[7], 1.f, -1.f, -1.f); // main camera vec4_initw(&maincamera.pos, 0.f, 0.f, 10.f); maincamera.target = vec4_zerow; and, just to be sure, this is how I compute matrix multiplications: void mat4_mul(const mat4 *m, const vec4 *va, vec4 *vb) { vb->x = m->a.x * va->x + m->b.x * va->y + m->c.x * va->z + m->d.x * va->w; vb->y = m->a.y * va->x + m->b.y * va->y + m->c.y * va->z + m->d.y * va->w; vb->z = m->a.z * va->x + m->b.z * va->y + m->c.z * va->z + m->d.z * va->w; vb->w = m->a.w * va->x + m->b.w * va->y + m->c.w * va->z + m->d.w * va->w; } void mat4_mulm(const mat4 *ma, const mat4 *mb, mat4 *mc) { mat4_mul(ma, &mb->a, &mc->a); mat4_mul(ma, &mb->b, &mc->b); mat4_mul(ma, &mb->c, &mc->c); mat4_mul(ma, &mb->d, &mc->d); }

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  • Building View Matrix in Direct3D11

    - by Balls
    Am I doing it right? I converted this. m_ViewMatrix = XMMatrixLookAtLH(XMLoadFloat3(&m_Position), lookAtVector, upVector); to this one. XMVECTOR vz = XMVector3Normalize( lookAtVector - XMLoadFloat3(&m_Position) ); XMVECTOR vx = XMVector3Normalize( XMVector3Cross( upVector, vz ) ); XMVECTOR vy = XMVector3Cross( vz, vx ); m_ViewMatrix.r[0] = vx; m_ViewMatrix.r[1] = vy; m_ViewMatrix.r[2] = vz; m_ViewMatrix.r[3] = XMLoadFloat3(&m_Position); m_ViewMatrix.r[0].m128_f32[3] = 0.0f; m_ViewMatrix.r[1].m128_f32[3] = 0.0f; m_ViewMatrix.r[2].m128_f32[3] = 0.0f; m_ViewMatrix.r[3].m128_f32[3] = 1.0f; m_ViewMatrix = XMMatrixInverse( &XMMatrixDeterminant(m_ViewMatrix), m_ViewMatrix ); Everything looks fine when I run it. Another question is, I saw on this site(http://webglfactory.blogspot.com/2011/06/how-to-create-view-matrix.html) that he subtracted lookat from position in his vector vz. I tried it but gave me wrong view matrix. Can anyone check my code. I'm studying linear algebra right now. Sucks my course doesn't have one. Thank you, Balls

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  • Matrix.CreateBillboard centre rotation problem

    - by Chris88
    I'm having an issue with Matrix.CreateBillboard and a textured Quad where the center axis seems to be positioned incorrectly to the quad object which is rotating around a center point: Using: BasicEffect quadEffect; Drawing the quad shape: Left = Vector3.Cross(Normal, Up); Vector3 uppercenter = (Up * height / 2) + origin; LowerLeft = uppercenter + (Left * width / 2); LowerRight = uppercenter - (Left * width / 2); UpperLeft = LowerLeft - (Up * height); UpperRight = LowerRight - (Up * height); Where height and width are float values passed in (it draws a square) Draw method: quadEffect.View = camera.view; quadEffect.Projection = camera.projection; quadEffect.World = Matrix.CreateBillboard(Origin, camera.cameraPosition, Vector3.Up, camera.cameraDirection); GraphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass pass in quadEffect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawUserIndexedPrimitives <VertexPositionNormalTexture>( PrimitiveType.TriangleList, Vertices, 0, 4, Indexes, 0, 2); } GraphicsDevice.BlendState = BlendState.Opaque; In the screenshots below i draw the image at Vector3(32f, 0f, 32f) The screenshots below show you the position of the quad in relation to the red cross. The red cross shows where it should be drawn http://i.imgur.com/YwRYj.jpg http://i.imgur.com/ZtoHL.jpg It rotates around the red cross position

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  • What is Chain Matrix Multiplication ?

    - by Hellnar
    Hello, I am trying to understand what is a chain matrix multiplication and how it is different from a regular multiplication. I have checked several sourcers yet all seem to be very academically explained for me to understand. I guess it is a form of dynamic programming algorithm to achieve the operation in an optimised way but I didn't go any further. Thanks

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  • Latex Inverse search from a pdf in Okular to TexMaker

    - by Kayton
    I am using TexMaker of Karmic Ubuntu with Okular. I use pdfLatex to compile and I view the PDFs in Okular. How can I configure Okular to inverse search with TexMaker? I have tried the following code: texmaker %f -line %l but it does not work. I have tried double clicking, ctrl+click, shift+click, ctrl+shift+click, ctrl+alt+click, alt+shift+click, still nothing. Perhaps I simply don't know what the action is to initiate the inverse search from within Okular. How can I configure Okular to inverse search with TexMaker?

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  • WebGL First Person Camera - Matrix issues

    - by Ryan Welsh
    I have been trying to make a WebGL FPS camera.I have all the inputs working correctly (I think) but when it comes to applying the position and rotation data to the view matrix I am a little lost. The results can be viewed here http://thistlestaffing.net/masters/camera/index.html and the code here var camera = { yaw: 0.0, pitch: 0.0, moveVelocity: 1.0, position: [0.0, 0.0, -70.0] }; var viewMatrix = mat4.create(); var rotSpeed = 0.1; camera.init = function(canvas){ var ratio = canvas.clientWidth / canvas.clientHeight; var left = -1; var right = 1; var bottom = -1.0; var top = 1.0; var near = 1.0; var far = 1000.0; mat4.frustum(projectionMatrix, left, right, bottom, top, near, far); viewMatrix = mat4.create(); mat4.rotateY(viewMatrix, viewMatrix, camera.yaw); mat4.rotateX(viewMatrix, viewMatrix, camera.pitch); mat4.translate(viewMatrix, viewMatrix, camera.position); } camera.update = function(){ viewMatrix = mat4.create(); mat4.rotateY(viewMatrix, viewMatrix, camera.yaw); mat4.rotateX(viewMatrix, viewMatrix, camera.pitch); mat4.translate(viewMatrix, viewMatrix, camera.position); } //prevent camera pitch from going above 90 and reset yaw when it goes over 360 camera.lockCamera = function(){ if(camera.pitch > 90.0){ camera.pitch = 90; } if(camera.pitch < -90){ camera.pitch = -90; } if(camera.yaw <0.0){ camera.yaw = camera.yaw + 360; } if(camera.yaw >360.0){ camera.yaw = camera.yaw - 0.0; } } camera.translateCamera = function(distance, direction){ //calculate where we are looking at in radians and add the direction we want to go in ie WASD keys var radian = glMatrix.toRadian(camera.yaw + direction); //console.log(camera.position[3], radian, distance, direction); //calc X coord camera.position[0] = camera.position[0] - Math.sin(radian) * distance; //calc Z coord camera.position[2] = camera.position [2] - Math.cos(radian) * distance; console.log(camera.position [2] - (Math.cos(radian) * distance)); } camera.rotateUp = function(distance, direction){ var radian = glMatrix.toRadian(camera.pitch + direction); //calc Y coord camera.position[1] = camera.position[1] + Math.sin(radian) * distance; } camera.moveForward = function(){ if(camera.pitch!=90 && camera.pitch!=-90){ camera.translateCamera(-camera.moveVelocity, 0.0); } camera.rotateUp(camera.moveVelocity, 0.0); } camera.moveBack = function(){ if(camera.pitch!=90 && camera.pitch!=-90){ camera.translateCamera(-camera.moveVelocity, 180.0); } camera.rotateUp(camera.moveVelocity, 180.0); } camera.moveLeft = function(){ camera.translateCamera(-camera.moveVelocity, 270.0); } camera.moveRight = function(){ camera.translateCamera(-camera.moveVelocity, 90.0); } camera.lookUp = function(){ camera.pitch = camera.pitch + rotSpeed; camera.lockCamera(); } camera.lookDown = function(){ camera.pitch = camera.pitch - rotSpeed; camera.lockCamera(); } camera.lookLeft = function(){ camera.yaw= camera.yaw - rotSpeed; camera.lockCamera(); } camera.lookRight = function(){ camera.yaw = camera.yaw + rotSpeed; camera.lockCamera(); } . If there is no problem with my camera then I am doing some matrix calculations within my draw function where a problem might be. //position cube 1 worldMatrix = mat4.create(); mvMatrix = mat4.create(); mat4.translate(worldMatrix, worldMatrix, [-20.0, 0.0, -30.0]); mat4.multiply(mvMatrix, worldMatrix, viewMatrix); setShaderMatrix(); gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer); gl.vertexAttribPointer(shaderProgram.attPosition, 3, gl.FLOAT, false, 8*4,0); gl.vertexAttribPointer(shaderProgram.attTexCoord, 2, gl.FLOAT, false, 8*4, 3*4); gl.vertexAttribPointer(shaderProgram.attNormal, 3, gl.FLOAT, false, 8*4, 5*4); gl.activeTexture(gl.TEXTURE0); gl.bindTexture(gl.TEXTURE_2D, myTexture); gl.uniform1i(shaderProgram.uniSampler, 0); gl.useProgram(shaderProgram); gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.numItems); //position cube 2 worldMatrix = mat4.create(); mvMatrix = mat4.create(); mat4.multiply(mvMatrix, worldMatrix, viewMatrix); mat4.translate(worldMatrix, worldMatrix, [40.0, 0.0, -30.0]); setShaderMatrix(); gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.numItems); //position cube 3 worldMatrix = mat4.create(); mvMatrix = mat4.create(); mat4.multiply(mvMatrix, worldMatrix, viewMatrix); mat4.translate(worldMatrix, worldMatrix, [20.0, 0.0, -100.0]); setShaderMatrix(); gl.drawArrays(gl.TRIANGLES, 0, vertexBuffer.numItems); camera.update();

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  • How to create projection/view matrix for hole in the monitor effect

    - by Mr Bell
    Lets say I have my XNA app window that is sized at 640 x 480 pixels. Now lets say I have a cube model with its poly's facing in to make a room. This cube is sized 640 units wide by 480 units high by 480 units deep. Lets say the camera is somewhere in front of the box looking at it. How can I set up the view and projection matrices such that the front edge of the box lines up exactly with the edges of the application window? It seems like this should probably involve the Matrix.CreatePerspectiveOffCenter method, but I don't fully understand how the parameters translate on to the screen. For reference, the end result will be something like Johhny Lee's wii head tracking demo: http://www.youtube.com/watch?v=Jd3-eiid-Uw&feature=player_embedded P.S. I realize that his source code is available, but I am afraid I haven't been able to make heads or tails out of it.

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  • Rotate view matrix based on touch coordinates

    - by user1055947
    I'm working on an Android game where I need to rotate the camera around the origin based on the user dragging their finger. My view matrix has initial position of sitting on the negative z and facing origin. I have succeeded in moving the camera through rotation left or right, up or down based on the user dragging the finger, but my problem is obviously that after I drag my finger up/down and rotate say 90 degrees so my intial position of -z is now +y and still facing origin, if I drag my finger left/right I want to rotate from +y to +x, but what happens is it rotates around the pole +y. This is to be expected as I am mapping 2D touch drag coords to 3D space, but I dont know where to start trying to do what I want. Perhaps someone can point me in the right direction, I've been googling for a while now but I don't know what I want to do is called! Edit __ What I was looking for is called an ArcBall, google it for lots of info on it.

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  • Unity3d vector and matrix operations

    - by brandon
    I have the following three vectors: posA: (1,2,3) normal: (0,1,0) offset: (2,3,1) I want to get the vector representing the position which is offset in the direction of the normal from posA. I know how to do this by cheating (not using matrix operations): Vector3 result = new Vector3(posA.x + normal.x*offset.x posA.y + normal.y*offset.y, posA.z + normal.z*offset.z); I know how to do this mathematically Note: [] indicates a column vector, {} indicates a row vector result = [1,2,3] + {2,3,1}*{[0,0,0],[0,1,0],[0,0,0]} What I don't know is which is better to use and if it's the latter how do I do this in unity? I only know of 4x4 matrices in unity. I don't like the first option because you are instantiating a new vector instead of just modifying the original. Suggestions? Note: by asking which is better, I am asking for a quantifiable reason, not just a preference.

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  • Restoring projection matrix

    - by brainydexter
    I am learning to use FBOs and one of the things that I need to do when rendering something onto user defined FBO, I have to setup the projection, modelview and viewport for it. Once I am done rendering to the FBO, I need to restore these matrices. I found: glPushAttrib(GL_VIEWPORT_BIT); glPopAttrib(); to restore the viewport to its old state. Is there a way to restore the projection and modelview matrix to whatever it was earlier ? Tech: C++/OpenGL Thanks!

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  • convert orientation vec3 to a rotation matrix

    - by lapin
    I've got a normalized vec3 that represents an orientation. Each frame of animation, an object's orientation changes slightly, so I add a delta vector to the orientation vector and then normalize to find the new orientation. I'd like to convert the vec3 that represents an orientation into a rotation matrix that I can use to orient my object. If it helps, my object is a cone, and I'd like to rotate it about the pointy end, not from its center :) PS I know I should use quaternions because of the gimbal lock problem. If someone can explain quats too, that'd be great :)

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  • Transformation matrix that maps a window

    - by gbhall
    I'm currently learning OpenGL at uni, and they give us questions to help us learn (these are not worth anything), however I'm stuck on this one question and would have to travel over an hour and a half to uni for an answer. How do I do this question? Please include as many steps as you can, I want to be able to follow exactly how to do this. Find the transformation that maps a window whose lower left corner is at (1,1) and upper right corner is at (3,5) onto: The entire device screen whose dimension is (600, 500) A viewport that has lower left corner at (100,100) and upper right corner at (400,400) Edit: Damn sorry I should have added I am meant to find the matrix, so no code.

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  • Optimizing hierarchical transform

    - by Geotarget
    I'm transforming objects in 3D space by transforming each vector with the object's 4x4 transform matrix. In order to achieve hierarchical transform, I transform the child by its own matrix, and then the child by the parent matrix. This becomes costly because objects deeper in the display tree have to be transformed by all the parent objects. This is what's happening, in summary: Root -- transform its verts by Root matrix Parent -- transform its verts by Parent, Root matrix Child -- transform its verts by Child, Parent, Root matrix Is there a faster way to transform vertices to achieve hierarchical transform? What If I first concatenated each transform matrix with the parent matrices, and then transform verts by that final resulting matrix, would that work and wouldn't that be faster? Root -- transform its verts by Root matrix Parent -- concat Parent, Root matrices, transform its verts by Concated matrix Child -- concat Child, Parent, Root matrices, transform its verts by Concated matrix

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  • Transform coordinates from 3d to 2d without matrix or built in methods

    - by Thomas
    Not to long ago i started to create a small 3D engine in javascript to combine this with an html5 canvas. One of the issues I run into is how can you transform 3d to 2d coords. Since I cannot use matrices or built in transformation methods I need another way. I've tried implementing the next explanation + pseudo code: http://freespace.virgin.net/hugo.elias/routines/3d_to_2d.htm Unfortunately no luck there. I've replace all the input variables with data from my own camera and object classes. I have the following data: An object with a rotation, position vector and an array of 4 3d coords (its just a plane) a camera with a position and rotation vector the viewport - a square 600 x 600 surface. The example uses a zoom factor which I've set as 1 Most hits on google use either matrix calculations or don't implement camera rotation. Basic transformation should be like this: screen.x = x / z * zoom screen.y = y / z * zoom Can anyone point me in the right direction or explain to me howto achieve this? edit: Thanks for all your posts, I haven't been able to apply all this to my project yet but I hope to do this soon.

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  • Algorithm for computing the inverse of a polynomial

    - by Neville
    I'm looking for an algorithm (or code) to help me compute the inverse a polynomial, I need it for implementing NTRUEncrypt. An algorithm that is easily understandable is what I prefer, there are pseudo-codes for doing this, but they are confusing and difficult to implement, furthermore I can not really understand the procedure from pseudo-code alone. Any algorithms for computing the inverse of a polynomial with respect to a ring of truncated polynomials?

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  • C Programming matrix

    - by Bilal Khan
    In this program the user enters the # of columns of the matrix and then the entries of the matrix. So, for example, if the user enters 2 for column # and 1 2 3 4 for entries then the program develops a 2 by 2 matrix with 1 2 3 4 as entries. My program works perfectly in such a case. However, if the user for example had only entered 1 2 3 then my program makes a matrix with garbage values. I would like the program in such a case to exit the program. It is a simple question, but it has me baffled. #include<stdio.h> #include<stdlib.h> int main() { int m,x, n, c = 0, d,k, matrix[10][10], transpose[10][10], product[10][10]; printf("Enter the number of columns of matrix "); scanf("%d",&m); if(m<=0){ printf("You entered a invalid value."); exit(0); } else{ printf("Enter the elements of matrix \n"); for( c = 0 ; c < 10 ; c++ ) { for( d = 0 ; d < m ; d++ ) { scanf("%d",&matrix[c][d]); if (matrix[c][d] == 99) // 'x' is character variable I declared to use as a break break; // c = c+1; } if (matrix[c][d] == 99) break; } } printf("\nHere is your matrix:\n"); int i; for(i=0;i<c;i++) { for(d=0;d<m;d++) { printf("%3d ",matrix[i][d]); } printf("\n"); }

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