Comments on: QuadTree (Source Included) http://www.kyleschouviller.com/wsuxna/quadtree-source-included/ Fri, 12 Mar 2010 00:36:11 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Mathieu http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-24499 Mathieu Thu, 24 Dec 2009 12:31:14 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-24499 gg dude gg dude

]]> By: Aaron Schultz http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-24107 Aaron Schultz Sun, 25 Oct 2009 07:12:55 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-24107 Just wondering, but you mentioned changing the passing of Lists to use the ref keyword. Isn't that unnecessary, since List is a reference type? As far as I understand it, adding the keyword is only necessary when dealing with value types, which are copied by default. Otherwise, great post. Probably the best run-down and tutorial on Quadtrees I have ever read. I implemented your system awhile back on a game project for class that had several hundred moving particles of different scales all doing collision, and with modifications to handle position changing it worked amazingly well. There was a point where having lots of empty nodes was a problem, but running a quick cull on all empty nodes each frame solved the issue. Just wondering, but you mentioned changing the passing of Lists to use the ref keyword. Isn’t that unnecessary, since List is a reference type? As far as I understand it, adding the keyword is only necessary when dealing with value types, which are copied by default.

Otherwise, great post. Probably the best run-down and tutorial on Quadtrees I have ever read. I implemented your system awhile back on a game project for class that had several hundred moving particles of different scales all doing collision, and with modifications to handle position changing it worked amazingly well. There was a point where having lots of empty nodes was a problem, but running a quick cull on all empty nodes each frame solved the issue.

]]> By: TruongThanhTung http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-24093 TruongThanhTung Tue, 20 Oct 2009 17:03:57 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-24093 thank you so much, it helps me how to make store my world game. Thanks, thank you so much, it helps me how to make store my world game. Thanks,

]]> By: [XNA] Detección de colisiones por descomposición del espacio en una rejilla de vóxeles - Jesús Bosch http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-24020 [XNA] Detección de colisiones por descomposición del espacio en una rejilla de vóxeles - Jesús Bosch Sat, 26 Sep 2009 10:15:04 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-24020 [...] en el caso en el que dos objetos se encuentren en el mismo voxel. ¿Parecido con el Quadtree? Bastante, la diferencia está en que aquí no hay voxels [...] [...] en el caso en el que dos objetos se encuentren en el mismo voxel. ¿Parecido con el Quadtree? Bastante, la diferencia está en que aquí no hay voxels [...]

]]> By: Edward http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-23920 Edward Mon, 14 Sep 2009 23:58:18 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-23920 Nice tutorial it helped me alot! but i still got a question. Just like your example above I have a quadtree with nodes that hold 1 object each, what happen if i add 2 objects to the tree and both of them cannot fit entirely into the lower level, and both of them got to stay in level. Nice tutorial it helped me alot! but i still got a question.
Just like your example above I have a quadtree with nodes that hold 1 object each, what happen if i add 2 objects to the tree and both of them cannot fit entirely into the lower level, and both of them got to stay in level.

]]> By: Kyle Schouviller http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-23518 Kyle Schouviller Tue, 16 Jun 2009 19:18:10 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-23518 Jack, Thanks for the "good article" comments. You're correct that items spanning dividing lines will be allocated in the level above the dividing line, which may be as high as level 0. If this isn't optimal for the type of objects in the scene, then a quadtree probably isn't a good solution. My implementation is pretty old, and doesn't implement a lot of performance considerations you'd want to make for XNA and especially the Xbox. However, that's not the purpose of the implementation, or this article. A quadtree is a good introduction to spatial trees, and can in fact be fairly useful in certain situations. The tree I've described isn't optimal for most situations, but it's not meant to explore those - just the basic concepts of a quadtree. I leave the specific variation as an exercise to the reader. Jack,

Thanks for the “good article” comments.

You’re correct that items spanning dividing lines will be allocated in the level above the dividing line, which may be as high as level 0. If this isn’t optimal for the type of objects in the scene, then a quadtree probably isn’t a good solution.

My implementation is pretty old, and doesn’t implement a lot of performance considerations you’d want to make for XNA and especially the Xbox.

However, that’s not the purpose of the implementation, or this article. A quadtree is a good introduction to spatial trees, and can in fact be fairly useful in certain situations. The tree I’ve described isn’t optimal for most situations, but it’s not meant to explore those - just the basic concepts of a quadtree. I leave the specific variation as an exercise to the reader.

]]> By: Jack http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-23491 Jack Mon, 08 Jun 2009 22:37:04 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-23491 What happens to a tiny square which spans the centre of the quadtree? it will always be allocated to level 0 ?? and that means it will be returned even for your query above and that is true for all objects spanning dividing lines in the quadtree it does not work plus it is no good for dynamic objects as it takes too long to shuffle everything about when things move the classic quadtree you describe is almost no use in real life why not think up a variation that works properly and then write a good article about a good spatial index instead of a good article about a bad spatial index What happens to a tiny square which spans the centre of the quadtree?

it will always be allocated to level 0 ??

and that means it will be returned even for your query above

and that is true for all objects spanning dividing lines in the quadtree

it does not work

plus it is no good for dynamic objects as it takes too long to shuffle everything about when things move

the classic quadtree you describe is almost no use in real life

why not think up a variation that works properly and then write a good article about a good spatial index

instead of a good article about a bad spatial index

]]> By: Game Rendering » Quadtree http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-1393 Game Rendering » Quadtree Tue, 16 Dec 2008 19:31:25 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-1393 [...] More info about quadtrees, including source: http://www.kyleschouviller.com/wsuxna/quadtree-source-included/ [...] [...] More info about quadtrees, including source: http://www.kyleschouviller.com/wsuxna/quadtree-source-included/ [...]

]]> By: Kyle Schouviller http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-551 Kyle Schouviller Mon, 02 Jun 2008 01:12:39 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-551 Yah, you can have the objects in any level of the tree - it's just best if they're in the leaf nodes, since you can eliminate the most collision checks if they are (in fact, the closer to the leaves the better). Yah, you can have the objects in any level of the tree - it’s just best if they’re in the leaf nodes, since you can eliminate the most collision checks if they are (in fact, the closer to the leaves the better).

]]> By: Josh http://www.kyleschouviller.com/wsuxna/quadtree-source-included/comment-page-1/#comment-544 Josh Thu, 29 May 2008 03:29:14 +0000 http://www.kyleschouviller.com/index.php/quadtree-source-included/#comment-544 Hey Kyle! Thanks for the excellent article with very readable code to boot! I am curious about a few things at the moment... I am planning to use a quad tree for collision detection and and considering pre-partitioning the tree as to not require many objects to be created during run-time. That being said, would all objects have to be in leaf nodes of the tree for this to be feasible, or could the larger sized objects remain in higher level nodes, while smaller ones exist in leaf nodes? I am not sure if the question actually makes sense, but it is something that I am trying to work through semantically at the moment. Thanks again! -Josh Hey Kyle!

Thanks for the excellent article with very readable code to boot! I am curious about a few things at the moment…

I am planning to use a quad tree for collision detection and and considering pre-partitioning the tree as to not require many objects to be created during run-time. That being said, would all objects have to be in leaf nodes of the tree for this to be feasible, or could the larger sized objects remain in higher level nodes, while smaller ones exist in leaf nodes? I am not sure if the question actually makes sense, but it is something that I am trying to work through semantically at the moment. Thanks again!

-Josh

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