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# Help with a 3D Grid\

 P: n/a Hello!! i'm just a dummie in C/C++ and i need you help for solving my little problem. I have to create a 3D grid of points. Each point has the 3 coordinates and a boolean value. (I made a structure in order to make this). My task is to scan the grid through the x, y and z planes. According to you, which is the best way to create this data structure? I have tried to create a vector of vectors of vectors of point structure, so to access to each point coordinate i just have to do like: Grid[i][j][k].x So the i index will give me all the points which are on the x planes.... but i have now idea about how to build it!!! Does anybody has any clue?! Thank you very much Vito Baldassarre Dec 21 '06 #1
13 Replies

 P: n/a Guardiano del Faro wrote: i'm just a dummie in C/C++ and i need you help for solving my little problem. I have to create a 3D grid of points. Each point has the 3 coordinates and a boolean value. (I made a structure in order to make this). My task is to scan the grid through the x, y and z planes. According to you, which is the best way to create this data structure? I have tried to create a vector of vectors of vectors of point structure, so to access to each point coordinate i just have to do like: Grid[i][j][k].x So the i index will give me all the points which are on the x planes.... but i have now idea about how to build it!!! How to build what? Does anybody has any clue?! What does it mean "to scan the grid"? If points are in arbitrary positions throughout the XYZ space, none of them is guaranteed to have any particular x or y or z coordinate (coincident with your plane). Otherwise, if you have i,j,k _and_ x,y,z of every point, then you don't have a 3-dimensional space (grid), you have six dimensions and are working with a subset of it (hyperplane) for every i or j or k... You don't seem to have a clear understanding of what's required or it's the language barrier that is stopping you from explaining it better. Perhaps if you told us what problem you're solving, it would be easier to suggest something. As an alternative, consider posting to 'comp.graphics.algorithms' newsgroup. They deal with spaces and points every day. V -- Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask Dec 21 '06 #2

 P: n/a Guardiano del Faro wrote: Hello!! i'm just a dummie in C/C++ and i need you help for solving my little problem. I have to create a 3D grid of points. Each point has the 3 coordinates and a boolean value. (I made a structure in order to make this). My task is to scan the grid through the x, y and z planes. According to you, which is the best way to create this data structure? I have tried to create a vector of vectors of vectors of point structure, so to access to each point coordinate i just have to do like: Grid[i][j][k].x So the i index will give me all the points which are on the x planes.... but i have now idea about how to build it!!! Does anybody has any clue?! Thank you very much Vito Baldassarre Try using typedef to create an alternative name for the vector of bool, and then do the same for a vector of that type. -- NOUN:1. Money or property bequeathed to another by will. 2. Something handed down from an ancestor or a predecessor or from the past: a legacy of religious freedom. ETYMOLOGY: MidE legacie, office of a deputy, from OF, from ML legatia, from L legare, to depute, bequeath. www.bartleby.com/61/ Dec 21 '06 #3

 P: n/a Guardiano del Faro wrote in message <11**********************@42g2000cwt.googlegroups. com>... >Hello!!i'm just a dummie in C/C++ and i need you help for solving my littleproblem.I have to create a 3D grid of points. Each point has the 3 coordinatesand a boolean value. (I made a structure in order to make this).My task is to scan the grid through the x, y and z planes.According to you, which is the best way to create this data structure?I have tried to create a vector of vectors of vectors of pointstructure, so to access to each point coordinate i just have to dolike: Grid[i][j][k].xSo the i index will give me all the points which are on the xplanes....but i have now idea about how to build it!!!Does anybody has any clue?!Thank you very muchVito Baldassarre // #includes, // ------------------------------------ void TriVector( std::ostream &cout ){ typedef std::vector(3, int(7)))); for(size_t x(0); x < vec3D.size(); ++x){ for(size_t y(0); y < vec3D.at(x).size(); ++y){ for(size_t z(0); z < vec3D.at(x).at(y).size(); ++z){ cout<<" vec3D.at("<

 P: n/a In article <11**********************@42g2000cwt.googlegroups. com>, "Guardiano del Faro" ::reference reference; typedef std::vector::const_reference const_reference; Grid3D( unsigned x, unsigned y, unsigned z ): h( x ), w( y ), d( z ), rep( x * y * z ) { } reference at( unsigned x, unsigned y, unsigned z ) { assert( x < h && y < w && z < d ); return rep[ x*w*d + y*d + z ] != 0; } const_reference at( unsigned x, unsigned y, unsigned z ) const { assert( x < h && y < w && z < d ); return rep[ x*w*d + y*d + z ] != 0; } // other functions to taste }; use like this: int main() { Grid3D g( 10, 10, 10 ); g.at( 3, 4, 6 ) = true; if ( g.at( 7, 5, 9 ) ) { cout << "should not print"; } } Caution: I wrote the above with a puppy in my lap, so there may be some errors. :-) Dec 22 '06 #5

 P: n/a Victor Bazarov ha scritto: Guardiano del Faro wrote: Hello everybody and thanks for your help! How to build what? the data structure! > Does anybody has any clue?! You don't seem to have a clear understanding of what's required or it's the language barrier that is stopping you [...] Ok, i will try to explain it better! I have a protein, which is a set of spheras (i have a file which contains the 3d coords of the atoms). So, let suppose the protein is just a set of point. I know the MIN and the MAX, which are the left-bottom and the right-up vertex. I have to build a grind which contain this protein, and after that i must scan the grid through the x direction, then the y direction, and then the z direction if a point of the grid is inside the protein (i already know how to check it) it has a TRUE value, otherwise it's FALSE. It's quite a simple idea, the problem is that i wanted to have a dynamic allocation of the vectors...maybe it can be easier if i calculate the dimensions of them... Thanks a lot, i hope it's clear now Buon Natale, Marry christmas Dec 22 '06 #6

 P: n/a Daniel T. wrote: In article <11**********************@42g2000cwt.googlegroups. com>, "Guardiano del Faro" Hello!!i'm just a dummie in C/C++ and i need you help for solving my littleproblem.I have to create a 3D grid of points. Each point has the 3coordinates and a boolean value. (I made a structure in order tomake this).My task is to scan the grid through the x, y and z planes.According to you, which is the best way to create this datastructure?I have tried to create a vector of vectors of vectors of pointstructure, so to access to each point coordinate i just have to dolike:Grid[i][j][k].xSo the i index will give me all the points which are on the xplanes....but i have now idea about how to build it!!!Does anybody has any clue?! My suggestion: class Grid3D { std::vector::reference reference; typedef std::vector::const_reference const_reference; Grid3D( unsigned x, unsigned y, unsigned z ): h( x ), w( y ), d( z ), rep( x * y * z ) { } reference at( unsigned x, unsigned y, unsigned z ) { assert( x < h && y < w && z < d ); return rep[ x*w*d + y*d + z ] != 0; I am not sure 'reference' will work as the return value here or the 'return' statement should just be return rep[ x*w*d + y*d + z ]; } const_reference at( unsigned x, unsigned y, unsigned z ) const { assert( x < h && y < w && z < d ); return rep[ x*w*d + y*d + z ] != 0; I'd probably just do return rep[ x*w*d + y*d + z ]; here as well. } // other functions to taste }; use like this: int main() { Grid3D g( 10, 10, 10 ); g.at( 3, 4, 6 ) = true; if ( g.at( 7, 5, 9 ) ) { cout << "should not print"; } } Caution: I wrote the above with a puppy in my lap, so there may be some errors. :-) V -- Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask Dec 22 '06 #7

 P: n/a Guardiano del Faro wrote: Victor Bazarov ha scritto: >Guardiano del Faro wrote: Hello everybody and thanks for your help! >How to build what? the data structure! >> >>Does anybody has any clue?! >You don't seem to have a clear understanding of what's required orit's the language barrier that is stopping you [...] Ok, i will try to explain it better! I have a protein, which is a set of spheras (i have a file which contains the 3d coords of the atoms). So, let suppose the protein is just a set of point. I know the MIN and the MAX, which are the left-bottom and the right-up vertex. I have to build a grind which contain this protein, and after that i must scan the grid through the x direction, then the y direction, and then the z direction if a point of the grid is inside the protein (i already know how to check it) it has a TRUE value, otherwise it's FALSE. It's quite a simple idea, the problem is that i wanted to have a dynamic allocation of the vectors...maybe it can be easier if i calculate the dimensions of them... Thanks a lot, i hope it's clear now Coupling with Daniel T.'s suggestion, scanning through the grid would be done by nested loops: unsigned const H = ??; unsigned const W = ??; unsigned const D = ??; double stepx = (xmax-xmin)/(H-1), stepy = (ymax-ymin)/(W-1); double stepz = (zmax-zmin)/(D-1); Grid3D inside(H, W, D); // see Daniel's suggestion for (unsigned x = 0; x < H; ++x) { for (unsigned y = 0; y < W; ++y) { for (unsigned z = 0; z < D; ++z) { // generate the point of the grid double xP = xmin + x*stepx; double yP = ymin + y*stepy; double zP = zmin + z*stepz; inside.at(x,y,z) = CheckIfInsideProtein(xP, yP, zP); } } } If your grid is supposedly regular, you essentially need a structure that keeps the inside/outside flag (Daniel's Grid3D) and a way to convert Grid3D into X,Y,Z for checking. You can, of course, make Grid3D keep the min and max coordinate values and let it convert indices into coordinates and values. V -- Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask Dec 22 '06 #8

 P: n/a "Victor Bazarov" i'm just a dummie in C/C++ and i need you help for solving my little problem. > I have to create a 3D grid of points. Each point has the 3 coordinates and a boolean value. (I made a structure in order to make this). > My task is to scan the grid through the x, y and z planes. > According to you, which is the best way to create this data structure? > I have tried to create a vector of vectors of vectors of point structure, so to access to each point coordinate i just have to do like: > Grid[i][j][k].x > So the i index will give me all the points which are on the x planes.... > but i have now idea about how to build it!!! Does anybody has any clue?! My suggestion: class Grid3D { std::vector::reference reference; typedef std::vector::const_reference const_reference; Grid3D( unsigned x, unsigned y, unsigned z ): h( x ), w( y ), d( z ), rep( x * y * z ) { } reference at( unsigned x, unsigned y, unsigned z ) { assert( x < h && y < w && z < d ); return rep[ x*w*d + y*d + z ] != 0; I am not sure 'reference' will work as the return value here or the 'return' statement should just be return rep[ x*w*d + y*d + z ]; Good catch. I originally was going to hold a vector of chars to avoid the vector

 P: n/a Victor Bazarov ha scritto: i solved the problem in a different way!! :D i realized that that grid needs a lot of space (because it's a 1000x1000x1000 points grid!!) and i can have some memory problems, and the point is that i dont actually need to memorize the grid, but only the points which have the boolean value 1!! So i scan a "virtual"grid (3 for cycles) and i store the points that i need! Much more easier, simple and light! thank you for you help! ViTo Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask Dec 22 '06 #10

 P: n/a "Guardiano del Faro" ::reference reference; typedef std::map::const_reference const_reference; Grid3D( unsigned x, unsigned y, unsigned z ): h( x ), w( y ), d( z ), rep( x * y * z ) { } const_reference at( unsigned x, unsigned y, unsigned z ) const { assert( x < h && y < w && z < d ); return rep.find( Vector3( x, y, z ) != rep.end(); } void set( unsigned x, unsigned y, unsigned z ) { assert( x < h && y < w && z < d ); rep.insert( Vector3( x, y, z ) ); } void unset( unsigned x, unsigned y, unsigned z ) { assert( x < h && y < w && z < d ); rep.erase( Vector3( x, y, z ) ); } // other functions to taste }; Dec 22 '06 #11

 P: n/a Guardiano del Faro wrote: Victor Bazarov ha scritto: i solved the problem in a different way!! :D i realized that that grid needs a lot of space (because it's a 1000x1000x1000 points grid!!) and i can have some memory problems, and the point is that i dont actually need to memorize the grid, but only the points which have the boolean value 1!! So i scan a "virtual"grid (3 for cycles) and i store the points that i need! Much more easier, simple and light! thank you for you help! ViTo You have just rediscovered the "sparse matrix". Dec 22 '06 #12

 P: n/a r ha scritto: > You have just rediscovered the "sparse matrix". did i win something?! :) Dec 23 '06 #13

 P: n/a Guardiano del Faro wrote: r ha scritto: You have just rediscovered the "sparse matrix". did i win something?! :) You don't win anything, but you could save yourself a lot of programming. The problem you've just solved is a well-known problem in engineering. So you might want to google: sparse matrix "C++" and see what you come up with. Dec 23 '06 #14

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