 # Все вопросы: [matrix]

232 вопросов

2ответов
1356 просмотров

### How do i use perspective projection in this library

i found a library called pyeuclid and it seems to do what i want in respect to 3D math. it contins a 3D vector class and a 4X4 matrix class capable of transformations like rotate,translate and scale. matrix creation is simple, simply pass along the arguments and the matrix is created. &gt;&gt...

4ответов
38954 просмотров

### Convert Quaternion rotation to rotation matrix?

Basically, given a quaterion (qx, qy, qz, qw)... How can i convert that to an OpenGL rotation matrix? I'm also interested in which matrix row is "Up", "Right", "Forward" etc... I have a camera rotation in quaternion that I need in vectors...

1ответов
726 просмотров

### CUBLAS or supported libraries, and emphasis for reading for a beginner

I'm trying to harness the power of the GPU (nVidia Quadro NVS140M) to speed up some matrix computations in my project. I'm reading through some documentation (programming guide, best practices guide, and reference manual), but not sure which section(s) I should focus on. It would be great if I ca...

4ответов
55817 просмотров

### Matrix of unknown length in MATLAB?

I'm trying to set up a zero matrix of variable length with two columns into which I can output the results of a while loop (with the intention of using it to store the step data from Euler's method with adjusted time-steps). The length will be determined by the number of iterations of the loop. ...

2ответов
144 просмотров

### Efficient Indexing method for a 2 by 2 matrix

If I fill numbers from 1 to 4 in a 2 by 2 matrix, there are 16 possible combinations. What I want to do is store values in an array of size 24 corresponding to each matrix. So given a 2 by 2 matrix, I want a efficient indexing method to index into the array directly.( I dont want comparing all ...

2ответов
2241 просмотров

### Efficiency of perspective projection vs raytracing/ray casting

I have a very general question. I wish to determine the boundary points of a number of objects (comprising 30-50 closed polygons (z) each having around 300 points(x,y,z)). I am working with a fixed viewport which is rotated about x,y and z-axes (alpha, beta, gamma) wrt origin of coordinate system...

4ответов
8733 просмотров

### FLOPS Intel core and testing it with C (innerproduct)

I have some misconceptions about measuring flops, on Intel architecture, is a FLOP one addition and one multiplication together? I read about this somewhere online and there is no debate that could reject this. I know that FLOP has a different meaning on different types of cpu. How do I calculat...

1ответов
189 просмотров

### How to cycle through matrix blocks?

I have some matrix which I want to cycle through blocks, the matrix could be of many different sizes, but I can know the size, is there a way to fast cycle through blocks? i.e: to fast output the indexes of the blocks, suppose a matrix of 4*4 I should have: Block1: (0,0),(0,1)(1,0)(1,1) Block2:...

1ответов
644 просмотров

### tformfwd and tforminv - what's the difference?

Suppose I have an arbitrary transformation matrix A such as, A = 0.9966 0.0007 -6.5625 0.0027 0.9938 1.0598 0 0 1.0000 And a set of points such that their x and y coordinates are represented by X and Y respectively. And suppose, [Xf Yf] = tformfwd(mak...

2ответов
3760 просмотров

### c++ opengl converting model coordinates to world coordinates for collision detection

(This is all in ortho mode, origin is in the top left corner, x is positive to the right, y is positive down the y axis) I have a rectangle in world space, which can have a rotation m_rotation (in degrees). I can work with the rectangle fine, it rotates, scales, everything you could want it to ...

2ответов
230 просмотров

### Wrong results in JavaScript table

I'm trying to create a matrix for 12-tone music. The numbers between 0-11 show the intervals between pitches. My script shows the matrix correctly as it runs initially with the page; but when we do another calculation with the button, it goes messy, even with the same pitch set. Here is my scri...

7ответов
634 просмотров

### How can I code this problem? (C++)

I am writing a simple game which stores datasets in a 2D grid (like a chess board). Each cell in the grid may contain a single integer (0 means the cell is empty). If the cell contains a number&gt; 0, it is said to be "filled". The set of "filled" cells on the grid is known as a "configuration". ...

2ответов
7306 просмотров

### converting a matrix of lists to a regular matrix

Take the following code: foo &lt;- list() foo[] &lt;- list(a=1, b=2) foo[] &lt;- list(a=11, b=22) foo[] &lt;- list(a=111, b=222) result &lt;- do.call(rbind, foo) result[,'a'] In this case, result[,'a'] shows a list. Is there a more elegant way such that result is a "regular" matrix o...

4ответов
9599 просмотров

### Translate vector by matrix

I have a 4*4 matrix and a 3d vector. I need to translate my vector by the matrix. Not too much crazy maths notation please because I don't understand it. An example in something close to java would be fab!

5ответов
845 просмотров

### The right way to manage a big matrix in Java

I'm working with a big matrix (not sparse), it contains about 10^10 double. Of course I cannot keep it in memory, and I need just 1 row at time. I thought to split it in files, every file 1 row (it requires a lot of files) and just read a file every time I need a row. do you know any more effici...

3ответов
2441 просмотров

### read matrix from a file in C C++

Just wonder, for a matrix stored in a file as what it is, i.e. each line in the file being a row of the matrix where elements are separated by space(s), how can I predetermine the size of the matrix, then create an array of the same size and read it into the array in C and C++? If you have some c...

2ответов
3601 просмотров

### Transforming a NxN binary matrix to a zero matrix using minimum row and column toggles

This is about the question i posted regarding converting one NxN binary matrix to another . The question i asked is a code-challenge problem . However, a similar question was asked at How to do matrix conversions by row and columns toggles?. I went through that thread,and have gained some idea ab...

2ответов
2613 просмотров

### print a jpg

I've been trying to print a dynamically loaded jpg and for some reason it's never printing to scale, not sure what I'm doing wrong so here's what I've done so far var request:URLRequest = new URLRequest(getAbsPath("pages/" + pagePrint + "_big.jpg")); var loader:Loader = new Loader(); loader.load...

1ответов
1689 просмотров

### Limited matrices in Ruby

How come the Matrix class has no methods to edit its vectors and components? It seems like everything inside a matrix can be read but not written. Am I mistaken? Is there some third-party elegant Matrix-like class that would allow me to delete rows and intentionally edit them? Please, notify me ...

1ответов
735 просмотров

### Troubles: Matrices, Vectors and Arrays

As far as I understood, matrices are very inflexible to work with. Therefor, I'm trying to get an array of vectors do deal with. My needs are: to be able to add vectors and make arithmetical operations on their components. Writing the code below, require 'matrix' x = Matrix.rows( IO.readlines(...

6ответов
4953 просмотров

### Matrix Circular Shift

Does anyone know an efficient way to right circular-shift a matrix? Btw, the matrix is binary but a method to solve a non-binary matrix is also fine. Right now, I'm thinking of implementing a circular array for the rows of my matrix and updating each row whenever a shift operation is required. ...

2ответов
10812 просмотров

### Calculating vertices of a rotated rectangle

Hey guys, I am trying to calculate the vertices of a rotated rectangle (2D). It's easy enough if the rectangle has not been rotated, I figured that part out. If the rectangle has been rotated, I thought of two possible ways to calculate the vertices. 1) Figure out how to transform the vertices ...

5ответов
1155 просмотров

### Java: Cache results of computation?

I'm writing a program to calculate a value that is a measure of the similarity between two objects. The comparison is commutative, so compare(a, b) == compare(b, a). The program's output to the console is a matrix of all results. However, since the matrix has each comparison twice ((a, b) and (b...

1ответов
4297 просмотров

### Hide matrix Gridlines SQL Server Reporting Services 2005

I am creating a report using SQL Server Reporting Services in Visual Studio 2005 (SSRS). I have placed a matrix in a list. The data and the matrix are working fine. However I can't seem to find a way to hide the matrix grid lines at runtime. Also, I have set the visibility of the static 1st colu...

1ответов
1679 просмотров

### Read a txt file containing a matrix of numbers separated by spaces and lines into an array

I've been trying to read a txt file containing a formatted matrix (9x9) into an int array. The txt file is selected by the user using NSOpenPanel. An example txt file: 2 7 9 1 6 2 1 1 1 9 1 3 3 4 0 6 8 5 5 3 2 9 3 8 6 7 0 6 0 9 2 5 6 4 8 0 3 2 0 4 0 5 0 6 0 4 0 5 4 0 3 9 0 0 6 4 1 3 2 5 7 2 ...

5ответов
4140 просмотров

### Rotating cordinates around pivot? (tetris)

I'm attempting to design my very own tetris clone but have run into a little problem with shape rotations. I have a 2 dimensional array representing a 10 x 20 game grid and individual shape objects which when initialised contain coordinates of where on the grid the shape will start falling from....

2ответов
282 просмотров

### Speed up text comparisons (with sparse matrices)

I have a function which takes two strings and gives out the cosine similarity value which shows the relationship between both texts. If I want to compare 75 texts with each other, I need to make 5,625 single comparisons to have all texts compared with each other. Is there a way to reduce this n...

6ответов
5971 просмотров

### Transpose a 2D array

How do you efficiently transpose a matrix? Are there libraries for this, or what algorithm would you use? E.g.: short src[W*H] = { {1,2,3}, {4,5,6} }; short dest[W*H]; rotate_90_clockwise(dest,src,W,H); //&lt;-- magic in here, no need for in-place //dest is now: { {4, 1}, {5, 2}, ...

1ответов
1939 просмотров

### Making Dynamic and Static columns play nicely in Matrix in SSRS 2005

I have a report that shows financial data by year along with a few other bits of static data: every time I try to put in a Column group, it does either above or below the static data: FiscalYear StaticData1 | StaticData2 | StaticData3 | StaticData4 Or: StaticData1 | StaticData2 | StaticData3 ...

4ответов
13844 просмотров

### What is a good free (open source) BLAS/LAPACK library for .net (C#)?

I have a project written in C# where I need to do various linear algebraic operations on matrices (like LU-factorization). Since the program is mainly a prototype created to confirm a theory, a C# implementation will suffice (compared to a possibly speedier C++ one), but I would still like a goo...