How do I create a sparse 3D matrix in C++?
407321
Well, it is easier than you think.  You have to allocate memory, either statically or dynamically on the heap to hold the variable.  It is far too big for use as an auto allocation at 256*256*256*(sizeof [variable type]); or about \n16,777,216*4 bytes at a minimum, over 64 MB of RAM.  A better idea than a matrix may be to keep only boundary or center point coordinate triples in memory and assume that they are on an empty grid.  This way a sphere can be defined as an object with a radius r and a center point triple (x,y,z).  A box becomes a set of two ordered triples, (x,y,z) that represents the two opposite corners in three space.  This will save quite a bit of space.  \nIf a matrix is still required, then you need to allocate as small a matrix as possible and allocate and deallocate memory for the variable arrays at appropriate points in the program.  In C++, this can be done most efficiently with the keywords new and delete.  I hope that this helps you out.  Below are a couple of good forum sites with tutorials and articles.
697721
First up you are going to need a compiler, you can get a free one here.\nhttp://www.borland.com/downloads/download_turbo.html\n\nInformation about it can be found here.\nhttp://www.turboexplorer.com/\n\nSome tutorials for c++ can be found here.\nhttp://www.cs.wustl.edu/~schmidt/C++/\n\nhttp://www.cplusplus.com/doc/tutorial/\n\nYou do not have to worry about memory allocation in C++, you can deal with it if you want, but you can avaoid it by using the keywords, 'new', 'delete', and 'delete[]'.\n\nRegarding the generation of random word segments, it would be done the same way as the random numbers are generated.\n\nIe, make an enum of these word segments,\nstring[] word_segments[5] = {"a", "an", "her", "ot", "etc"}\n\nWhen you get the random number, have it select a value from this array.\n\nword_segments[random_number];
910755
In mathematics, a matrix (plural matrices) is a rectangular table of numbers or, more generally, a table consisting of abstract quantities that can be added and multiplied. Matrices are used to describe linear equations, keep track of the coefficients of linear transformations and to record data that depend on two parameters. Matrices can be added, multiplied, and decomposed in various ways, making them a key concept in linear algebra and matrix theory.
211287
here you find a free download from a book (from the American Mathematical Society):\nhttp://www.ams.org/online_bks/coll17/\n\nThe wikipedia is also a good source\nhttp://en.wikipedia.org/wiki/Matrix_(mathematics)\n\nAnd here's an on-line calculator for matrix operations (it seems cool... I didn't try it)\nhttp://www.quickmath.com/www02/pages/modules/matrices/index.shtml\n\nAnd... mathworld\nhttp://mathworld.wolfram.com/Matrix.html\n\n\nGood work!\n(I'll download the online book myself: I didn't gave a look at it before giving you the link; the book is a little old (1937) but matrices haven't changed so much from that time on...)
246218
Probably something along the lines of it exists in a 3d matrix on an x-axis, y-axis, and z-axis and containing height, depth, and length.
86975
You can try Irrilicht or Ogre. Search for them using yahoo search engine. You should also have some knowledge about 3D programming.
583382
Try the moebius spiral. It's pretty interesting because it's non orientable. \n\nIt's 3d (2 parameters s and t) and described by the parametrized vector components:\n\n[3*cos(s)+t*sin(s/2),\n3*sin(s),\nt*cos(s/2)]\n\n(every component of the vector in a new line)\n\nThe parameter ranges are:\n\ns=-2*Pi...2*Pi,t=-1..1\n\nMAPLE INSTRUCTIONS TO PLOT IT:\n\nwith(plots);\nplot3d([3*cos(s)+t*sin(s/2),3*sin(s),t*cos(s/2)],s=-2*Pi...2*Pi,t=-1..1);\n\nSorry, that instruction is big and not displayed well, but I guess since you know the parametrized vector you can find it.\n\nWHAT DO YOU WANT IT FOR? WANT TO PUBLISH ANYTHING?
30390
go to www.google.com and type in \n\nriemann spaces  3 4 dimensions\n\nit will bring up alot of information for you to look at
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http://www.cplusplus.happycodings.com/Computer_Graphics/code22.html\nhttp://www.wol.net.pk/mtshome/cppComputerGraphics.html#Area%20Filling\n\nThis is C, but close enough:\nhttp://www.programmersheaven.com/download/15200/download.aspx
1126894
This normally means that you are going to be using Gaussian (or Gauss-Jordan) reduction, where ther eare three "moves" that are allowed.\n\n1) You can switch any two rows in the matrix.\n2) You can multiply any row in the matrix by a non-zero scalar.\n3) You can add a multiple of one row to another.\n\nUsing these three "moves," the goal is to reduce the matrix into a usable form (the echelon form, for example).
538201
Here is what I found...\n\nhttp://www.site.uottawa.ca/~laganier/tutorial/opencv+directshow/cvision.htm\n\nhope this helps ...
1077320
My TI-83plus can do that...but it has to be an invertible matrix.  If the determinate is zero, then it can not be done
49374
Wow this question rocks because I found out that search engines like Yahoo and Google use this math trick to figure out which web sites are number one etc in page rank.\n\nIt is also cool for doing stretchy graphics manipulations in graphics programs and  video game designs.\n\nIn so-called "linear algebra" you can make a table or array of numbers (sort of like a spreadsheet) called a matrix. Hey, not "The Matrix" (bullet time rocks!), just "a" matrix.\n\nA matrix can be used for example to stretch, blur, focus, distort or otherwise transform an image. Some programs like PaintShop Pro even let you stuff numbers into a matrix to create a special-effects filter.\n\nIt is very useful to know the quantities called "eigenvectors" and "eigenvalues" for a matrix, because "eigen" is German for"Nuthing happening here dude". This means we can toss them away and make a complicated (big) matrix smaller. That's what "deflation" means. For computer programming you want fast, fast results so it helps to deflate big matrices BEFORE you start computing.\n\nThe Power method is a way to approximately find those pesky eigens using simple arithmetic. The math is not really too hard, you can manually do it with a $1 calculator, just multiplying and adding mostly. But it is best to use a computer program because it can be tedious.\n\nSo get out there and wipe out those eigens!!!
881644
Something like this:\n\nint **myArray;\nint s1,s2,i;\n\nprintf("Input row size: ");\nscanf("%d",&s1);\nprintf("Input column size: ");\nscanf("%d",&s2);\n\nmyArray[0] = malloc(s1*s2*sizeof(int));\nif (myArray[0] != NULL ) {\n  for (i = 0;i<s1,i++) {\n         myArray[i] = (i * s2) + myArray[0];\n  }\n}\n\nmyArray can then be used as normal\n\nmyArray[2][4] = 20;
1043313
It's too cumbersome to rewrite it all here, but check out http://www.euclideanspace.com/maths/algebra/vectors/angleBetween/index.htm\n\nThat's 2D, but the formula is the same for 3D.
331707
search for CBIR on google u will get a no of resources. I had done one project related to this in c++. if u need any help mail me
1069671
yep...scalars multiply vectors component by component just like you have shown.  you can also show it by plotting out the original vectors, scaling them appropriately, adding them, and finding the resukltant components.