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  • Html 5 ping pong game side collision problem

    - by Gurjit
    I am making a simple ping pong game where I am facing a side collision problem means when the ball collides with the either side of the paddle . Although I have written code for making it works but something is failing....I want plz someone to give suggestions and tell how to avoid it. Means while trying to hit the ball with side face of the paddle poses a problem.!! Here is the main part of the code causing problem function checkCollision(){ ///// This is collision detection for the upper part ///// if( cy + radius >= paddleTop && cx + radius > paddleLeft && cy + radius >= paddleTop + 5 && cx - radius <= paddleLeft + paddleWidth ) { dy = -dy; ++hits; /// On collision we are increasing the Score playSound(); } else if( cy + radius >= paddleTop && cy + radius <= paddleTop + paddleHeight && cx + radius >= paddleLeft && cy - radius <= paddleLeft - (radius + 1) ) { dx = -dx; } } here is working fiddle for it :- http://jsfiddle.net/gurjitmehta/orzpzf69/

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  • Find a Hash Collision, Win $100

    - by Mike C
    Margarity Kerns recently published a very nice article at SQL Server Central on using hash functions to detect changes in rows during the data warehouse load ETL process. On the discussion page for the article I noticed a lot of the same old arguments against using hash functions to detect change. After having this same discussion several times over the past several months in public and private forums, I've decided to see if we can't put this argument to rest for a while. To that end I'm going to...(read more)

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  • Does Oracle re-hash the driving table for each join on the same table columns?

    - by thecoop
    Say you've got the following query on 9i: SELECT /*+ USE_HASH(t2 t3) */ * FROM table1 t1 -- this has lots of rows LEFT JOIN table2 t2 ON t1.col1 = t2.col1 AND t1.col2 = t2.col2 LEFT JOIN table3 t3 ON t1.col1 = t3.col1 AND t1.col2 = t3.col2 Due to 9i not having RIGHT OUTER HASH JOIN, it needs to hash table1 for both joins. Does it re-hash table1 between joining t2 and t3 (even though it's using the same join columns), or does it keep the same hash information for both joins?

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  • How do I detect and handle collisions using a tile property with Slick2D?

    - by oracleCreeper
    I am trying to set up collision detection in Slick2D based on a tilemap. I currently have two layers on the maps I'm using, a background layer, and a collision layer. The collision layer has a tile with a 'blocked' property, painted over the areas the player can't walk on. I have looked through the Slick documentation, but do not understand how to read a tile property and use it as a flag for collision detection. My method of 'moving' the player is somewhat different, and might affect how collisions are handled. Instead of updating the player's location on the window, the player always stays in the same spot, updating the x and y the map is rendered at. I am working on collisions with objects by restricting the player's movement when its hitbox intersects an object's hitbox. The code for the player hitting the right side of an object, for example, would look like this: if(Player.bounds.intersects(object.bounds)&&(Player.x<=(object.x+object.width+0.5))&&Player.isMovingLeft){ isInCollision=true; level.moveMapRight(); } else if(Player.bounds.intersects(object.bounds)&&(Player.x<=(object.x+object.width+0.5))&&Player.isMovingRight){ isInCollision=true; level.moveMapRight(); } else if(Player.bounds.intersects(object.bounds)&&(Player.x<=(object.x+object.width+0.5))&&Player.isMovingUp){ isInCollision=true; level.moveMapRight(); } else if(Player.bounds.intersects(object.bounds)&&(Player.x<=(object.x+object.width+0.5))&&Player.isMovingDown){ isInCollision=true; level.moveMapRight(); } and in the level's update code: if(!Player.isInCollision) Player.manageMovementInput(map, i); However, this method still has some errors. For example, when hitting the object from the right, the player will move up and to the left, clipping through the object and becoming stuck inside its hitbox. If there is a more effective way of handling this, any advice would be greatly appreciated.

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  • How do I handle specific tile/object collisions?

    - by Thomas William Cannady
    What do I do after the bounding box test against a tile to determine whether there is a real collision against the contents of that tile? And if there is, how should I move the object in response to that collision? I have a small object, and test for collisions against the tiles that each corner of it is on. Here's my current code, which I run for each of those (up to) four tiles: // get the bounding box of the object, in world space objectBounds = object->bounds + object->position; if ( (objectBounds.right >= tileBounds.left) && (objectBounds.left <= tileBounds.right) && (objectBounds.top >= tileBounds.bottom) && (objectBounds.bottom <= tileBounds.top)) { // perform specific test to see if it's a left, top , bottom // or right collision. If so, I check to see the nature of it // and where I need to place the object to respond to that collision... // [THIS IS THE PART THAT NEEDS WORK] // if( lastkey==keydown[right] && ((objectBounds.right >= tileBounds.left) && (objectBounds.right <= tileBounds.right) && (objectBounds.bottom >= tileBounds.bottom) && (objectBounds.bottom <= tileBounds.top)) ) { object->position.x = tileBounds.left - objectBounds.width; } // etc.

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  • Bounding volume hierarchy - linked nodes (linear model)

    - by teodron
    The scenario A chain of points: (Pi)i=0,N where Pi is linked to its direct neighbours (Pi-1 and Pi+1). The goal: perform efficient collision detection between any two, non-adjacent links: (PiPi+1) vs. (PjPj+1). The question: it's highly recommended in all works treating this subject of collision detection to use a broad phase and to implement it via a bounding volume hierarchy. For a chain made out of Pi nodes, it can look like this: I imagine the big blue sphere to contain all links, the green half of them, the reds a quarter and so on (the picture is not accurate, but it's there to help understand the question). What I do not understand is: How can such a hierarchy speed up computations between segments collision pairs if one has to update it for a deformable linear object such as a chain/wire/etc. each frame? More clearly, what is the actual principle of collision detection broad phases in this particular case/ how can it work when the actual computation of bounding spheres is in itself a time consuming task and has to be done (since the geometry changes) in each frame update? I think I am missing a key point - if we look at the picture where the chain is in a spiral pose, we see that most spheres are already contained within half of others or do intersect them.. it's odd if this is the way it should work.

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  • Unity, changing gravity game & stopping character when he hit a wall.

    - by Sylario
    i am currently working on a 2d puzzle game in the unity engine. One of the aspect of this game is the possibility to rotate the level of 90°. It also rotate the gravity. The main character is not directly controlled by the player, but instead fall when the level is rotated. When the main character hit a wall, he should stop to move. If i do not stop it, it kind of blink ans shake against the wall. To stop it i detect collision and depending on the current rotation state, the player will stop at "vertical" or "horizontal" tags when a OnCollisonEnter occurs. I must do that because when the player fall on his relative ground, He must not stop like if he had touch a wall. My problem is the 'side' of platform, or the 'top' of wall, they use the same tag and thus do not give the correct tag to my character. I tried to put a very small invisible box on top/side of elements but the collision occurs nevertheless. It seems when the player falls and hit something he go through a bit before being replaced at correct position by unity. Is there a way : 1 ) to doesn't stop my character but to make it appear immobile on screen 2 ) To detect a "i cannot move anymore" collision other than by using collision?

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  • Using Bullet physics engine to find the moment of object contact before penetration

    - by MooMoo
    I would like to use Bullet Physics engine to simulate the objects in 3D world. One of the objects in the world will move using the position from 3D mouse control. I will call it "Mouse Object" and any object in the world as "Object A" I define the time before "mouse object" and "Object A" collide as t-1 The time "mouse object" penetrate "Object A" as t Now there is a problem about rendering the scene because when I move the mouse very fast, "Mouse object" will reside in "Object A" before "Object A" start to move. I would like the "Mouse Object" to stop right away attach to the "Object A". Also If the "Object A" move, the "Mouse object" should move following (attach) the "Object A" without stop at the first collision take place. This is what i did I find the position of the "Mouse Object" at time t-1 and time t. I will name it as pos(t-1) and pos(t) The contact time will be sometime between t-1 to t, which the time of contact I name it as t_contact, therefore the contact position (without penetration) between "Mouse object" and "Object A" will be pos(t_contact) then I create multiple "Mouse object"s using this equation pos[n] = pos(t-1) * C * ( pos(t) - pos(t-1) ) where 0 <= C <= 1 if I choose C = 0.1, 0.2, 0.3,0.4..... 1.0, I will get pos[n] for 10 values Then I test collision for all of these 10 "Mouse Objects" and choose the one that seperate between "no collision" and "collision". I feel this method is super non-efficient. I am not sure the way other people find the time-of-contact or the position-of-contact when "Object A" can move.

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  • 128-Bit Hash Method

    - by Kyle Rozendo
    Hi All, Does anyone know of a hashing method that you can use with .NET, that will output 128 Bytes? I cannot use SHA-2+ generation hashes, as it's not supported on many client machines. Thanks, Kyle

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  • How are hash functions like MD5 unique?

    - by Aly
    Im aware that MD5 has had some collisions but this is more of a high level question about hashing functions. If MD5 hashes any arbitrary string into a 32-digit hex value, then according to the Pigeonhole Principle surely this can not be unique as there are more unique arbitrary strings than there are unique 32-digit hex values

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  • Converting a md5 hash byte array to a string

    - by Blankman
    How can I convert the hashed result, which a byte array, to a string? byte[] bytePassword = Encoding.UTF8.GetBytes(password); using (MD5 md5 = MD5.Create()) { byte[] byteHashedPassword = md5.ComputeHash(bytePassword); } So I need to convert byteHashedPassword to a string

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  • MD5 hash with salt for keeping password in DB in C#

    - by abatishchev
    Could you please advise me some easy algorithm for hashing user password by MD5, but with salt for increasing reliability. Now I have this one: private static string GenerateHash(string value) { var data = System.Text.Encoding.ASCII.GetBytes(value); data = System.Security.Cryptography.MD5.Create().ComputeHash(data); return Convert.ToBase64String(data); }

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  • How can I keep a hash sorted?

    - by srk
    use strict; use warnings; my @aoh =( { 3 => 15, 4 => 8, 5 => 9, }, { 3 => 11, 4 => 25, 5 => 6, }, { 3 => 5, 4 => 18, 5 => 5, }, { 0 => 16, 1 => 11, 2 => 7, }, { 0 => 21, 1 => 13, 2 => 31, }, { 0 => 11, 1 => 14, 2 => 31, }, ); #declaring a new array to store the sorted hashes my @new; print "\n-------------expected output------------\n"; foreach my $href (@aoh) { #i want a new array of hashes where the hashes are sorted my %newhash; my @sorted_keys = sort {$href->{$b} <=> $href->{$a} || $b <=> $a} keys %$href; foreach my $key (@sorted_keys) { print "$key => $href->{$key}\n"; $newhash{$key} = $href->{$key}; } print "\n"; push(@new,\%newhash); } print "-----------output i am getting---------------\n"; foreach my $ref(@new) { my @skeys = skeys %$ref; foreach my $key (@skeys) { print "$key => $ref->{$key}\n" } print "\n"; } The output of the program : -------------expected output------------ 3 => 15 5 => 9 4 => 8 4 => 25 3 => 11 5 => 6 4 => 18 5 => 5 3 => 5 0 => 16 1 => 11 2 => 7 2 => 31 0 => 21 1 => 13 2 => 31 1 => 14 0 => 11 -----------output i am getting--------------- 4 => 8 3 => 15 5 => 9 4 => 25 3 => 11 5 => 6 4 => 18 3 => 5 5 => 5 1 => 11 0 => 16 2 => 7 1 => 13 0 => 21 2 => 31 1 => 14 0 => 11 2 => 31 Please tell me what am i doing wrong in storing the hashes into a new array.. how do i achieve what i want.. ? Thanks in advance...

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  • Generate fixed length hash in python for url parameter

    - by LeRoy
    I am working in python on appengine. I am trying to create what is equivalent to the "v" value in the youtube url's (http://www.youtube.com/watch?v=XhMN0wlITLk) for retrieving specific entities. The datastore auto generates a key but it is way too long (34 digits). I have experimented with hashlib to build my own, but again I get a long string. I would like to keep it to under 11 digits (I am not dealing with a huge number of entities) and letters and numbers are acceptable. It seems like there should be a pretty standard solution. I am probably just missing it.

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  • How do I find hash value of a 3D vector ?

    - by brainydexter
    I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any) collisions. So, here is what I am doing: Grid-cell's position: (int type) (Gx, Gy, Gz) = (x / M, y / M, z / M) where M is the size of the grid. Once, I have a cell, I'd like to add it to a hash-table with its key being a unique hash based on (Gx, Gy, Gz) and the value being the cell itself. Now, I cannot think of a good hash function and I need some help with that. Can someone please suggest me a good hash function? Thanks

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  • Passing hash as values in hidden_field_tag

    - by funkymunky
    I am trying to pass some filters in my params through a form like so: hidden_field_tag "filters", params[:filters] For some reason the params get changed in the next page. For example, if params[:filters] used to be... "filters"={"name_like_any"=["apple"]} [1] ...it gets changed to... "filters"="{\"name_like_any\"=[\"apple\"]}" [2] note the extra quotations and backslashes in [2] when compared to [1]. Any ideas? I'm attempting to use this with searchlogic for some filtering, but I need it to persist when I change change objects in forms. I would prefer not to have to store it in session.

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  • Better way to fill a Ruby hash?

    - by sardaukar
    Is there a better way to do this? (it looks clunky) form_params = {} form_params['tid'] = tid form_params['qid'] = qid form_params['pri'] = pri form_params['sec'] = sec form_params['to_u'] = to_u form_params['to_d'] = to_d form_params['from'] = from form_params['wl'] = wl

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  • Using hash to check if page with $_POST values was refreshed

    - by Dieseltime
    When posting a form to the same PHP page, what is the correct method to find if the page was accidentally refreshed instead of submitted again? Here's what I'm using right now: $tmp = implode('',$_POST); $myHash = md5($tmp); if(isset($_SESSION["myHash"]) && $_SESSION["myHash"] == $myHash) { header("Location: index.php"); // page refreshed, send user somewhere else die(); } else { $_SESSION["myHash"] = $myHash; } // continue processing... Is there anything wrong with this solution?

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  • C# hash password create salt question

    - by 5YrsLaterDBA
    If I create salt by using something like this: public class User { private const int Hash_Salt_Length = 8; private byte[] saltBytes = new byte[Hash_Salt_Length]; public User() { RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); rng.GetNonZeroBytes(saltBytes); } .... } The saltBytes bytes array will be different for each session (restart the application). How can I check password to allow user login our application?

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  • RoR: Output Hash, getting correct parameters?

    - by andrewliu
    I have output something like this: #<Hashie::Mash created_time="1366008641" from=#<Hashie::Mash full_name="Cor Valen" id="22340" username="_corin"> id="4344344286" text="Look Who It Is, My Brother, My Favorite Deputy"> This was an output if I did this: <%= media.caption %> I wanted to get the text part, and I did this: <%= media.caption.text %> gets me error: undefined method `text' for nil:NilClass <%= media.caption[:text] %> gets me error: undefined method `[]' for nil:NilClass I don't get it? Thanks

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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  • Ruby Hash.merge with specified keys only

    - by ba
    I'm pretty sure I saw on a Rails related site something along the lines of: def my_function(*opts) opts.require_keys(:first, :second, :third) end And if one of the keys in require_keys weren't specified, or if there were keys that weren't specified, an exception was raised. I've been looking through ActiveSupport and I guess I might be looking for something like the inverse of except. I like to try and use as much of the framework as possible compared to writing my own code, that's the reason I'm asking when I know how to make the same functionality on my own. :) At the moment I'm doing it through the normal merge routine and making sure that I have what I need with some IFs.

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