I have a question about b2Fixture. I have a body with multiple fixtures (polygons). In my picture you can see a body with multiple fixtures for example. The line in the middle of the body should represent a point. My question is how can i figure out which fixtures are on which site, including the fixtures which are connected.
My first throught was to loop through all vertices of each fixture and find out where the current vertex are located from the line (left or right?).
But this doesn't work because the fixtures on right side can connected with other fixtures which are overlap over the line like here in the image.
So is there a way to find out which fixture are connected with other fixtures? Or can i order the fixtures from left to right?
Hope anyone understand me. And sorry for the bad images (:
Thank you in advance.
Greetings alex
My advice would be to keep track of the fixtures during construction. You have to create these fixtures at some point, right? Because you didn't tag any specific version of box2d I'll assume you're using the c++ version.
box2d allows you to SetUserData for the fixture. If you are not already using the userData then you can use this to refer to an object that stores the fixture's neighbors. A simple structure might look like this:
struct FixtureNeighbors
{
b2Fixture* leftNeighbor;
b2Fixture* rightNeighbor;
};
During construction of the fixtures, you should create a FixtureNeighbors object, cast it as a void*, and call b2Fixture::SetUserData. Then, during the game, whenever you want to find out who a fixture's neighbors are just call b2Fixture::GetUserData, cast the result back to a fixtureNeighbors object, and use that to access the left and right neighbors.
Notes
If you are already using the fixture userData to point to an entity or something else, you should add a GetEntity method to your FixtureNeighbors structure and you can still access the entity if you have the fixture.
If a fixture can be touching more than two neighbors, just use an stl vector to store a list of them.
I hope this helps!
Related
I am reading the Head First Design Patterns book. In Chapter 3 ("Decorating Objects: The Decorator Pattern"), I do not understand this part:
"Wouldn’t it be easy for some
client of a beverage to end up with
a decorator that isn’t the outermost
decorator? Like if I had a DarkRoast with
Mocha, Soy, and Whip, it would be easy
to write code that somehow ended up
with a reference to Soy instead of Whip,
which means it would not include Whip in
the order."
Could someone please help me understand the main point of this section, and what the main issue was that the authors were addressing?
I think what they wanted to point out, is the fact that you can get your references mixed up if you are not careful where and how you create your decorated objects. Consider the example on page 98 (first edition from 2004).
Beverage beverage3 = new HouseBlend();
beverage3 = new Soy(beverage3);
beverage3 = new Mocha(beverage3);
beverage3 = new Whip(beverage3);
If you would do stuff in between those steps of creation, you might end up with a Mocha without Whip.
And like they wrote in the answer section:
However, decorators are typically created by using other patterns like Factory and Builder.
If you automate your object creation, it might prevent you from making reference errors.
I have a Shapefile map of Maryland separated by zipcode. What I'd like to do is color each area based on a value I'm looking up in a database. Currently, I'm using ASP.NET with the SharpMap package. The basic questions are:
1) How do I associate a shape with its zipcode? I can generate the list of zipcodes using SharpMap's ExecuteIntersectionQuery with the BoundingBox set as the extent of the map, but I have no idea how to then connect each row of the resulting table with the shape it represents.
2) Once I have access to an individual shape and know what color I want, how do I assign the color to the shape? In SharpMap, I can color a VectorLayer, but a VectorLayer is generated from a source .shp file, not a shape.
I'm open to using other free map packages besides SharpMap (so no ArcGIS), but for legal reasons I can't use GoogleMaps.
I feel like this should be relatively simple, but trying to find any decent resource for SharpMap is pretty difficult.
EDIT: Alright, I've made a lot of process just by reading over what documentation there is. By setting the FilterDelegate of ShapeFile, I can make a layer consist of only the rows where the zip code matches a certain value. Now my only problem is making the delegate filter look for a different zip code each time. Can I pass another parameter besides the FeatureDataRow? Should I resort to a global variable?
You'll need to use thematics to do this.
I'll assume you already have some code that configures your map and it's layers. Your shapefile is a VectorLayer.
VectorLayer shapefileLayer = GetMyShapefileLayer();
shapefileLayer.Theme = new SharpMap.Rendering.Thematics.CustomTheme(GetStyleForShape);
Then, method GetStyleForShape is called every time the map needs a style for rendering. It looks like this:-
private SharpMap.Styles.VectorStyle GetStyleForShape(SharpMap.Data.FeatureDataRow row, SharpMap.Layers.Layer layer)
{
}
In the method, you create and return a VectorStyle. The table data associated with the feature it's trying to render is passed as a parameter to this method.
So you can use the row parameter to get your zip code, do whatever logic you need to do to calculate it's style, configure that style and return it.
This method (potentially) gets called a lot, so consider storing the styles and reusing them, rather than recreating them every time.
Hope this helps.
In the Flash authoring environment I can edit a library symbol and all on-stage instances based upon it reflect the changes. How can I do the same thing in ActionScript? There seems to be no way to address a library symbol.
For example:
Inside Flash CS3, I have created a Square.swf file that has 100 instances of the library symbol Square.
Now, Square.swf is loaded into another file BlueSquare.swf and I want to change the Square symbol into a blue square so that all instances of Square become blue.
How do I do this using Actionscript?
Thanks for the help.
What's in a clip's library symbol is the author-time definition of that object - you can't change it at runtime. Instead the normal approach would be to dynamically change the contents (not definitions) of the clips you want to change, which can be done in various ways, but all the good ways of doing that involve making the dynamically-changing clip understand how to update its appearance. So you need to be able to re-author the changing clips to suit your needs.
If you're loading in an animation that somebody else made, and trying to go through and replace all instances of object A with object B, the only way to achieve that is to traverse through the content's display list looking for A, and when you find one, remove its children and replace them with the the contents of a B. Mind you, for animations that may not really solve your problem, since animations normally add and remove clips frequently, so at any given point you could replace all the "hand" clips with "hand2", but then a frame later new "hand" clips might come into existence. But short of opening up the SWF and changing the binary data inside, there's no other way to dynamically change all of a given object to something else unless the object knows how to change its contents.
If it is only about making sure that the square you are attaching is blue you could use the colorTransform to change its appearance:
var someSquare:Square = new Square();
someSquare.transform.colorTransform = new ColorTransform(0,0,0,1,0x00,0x00,0xff,0x00 );
addChild( someSquare );
Of course this does not change the color of all instances that you have already attached.
If you really wanted to change the actual SWF symbol in Actionscript the only way I see is to parse the swf with as3swf ( https://github.com/claus/as3swf/wiki ), find the shape tag of the symbol, change it and then load the ByteArray that contains the swf via loader.loadBytes() - but that's admittedly quite a complicated way and you can achieve the same result by simply putting some colorizing code into the shape symbol itself and then trigger the color change via an Event that is broadcasted by your main app.
Of course, if you make custom component, when you change it changes will appear on all instances of that component/class. Here's the example: http://livedocs.adobe.com/flex/3/html/intro_3.html
On the other hand, if you use modules whey pretty much do the same as swf-s you used in Flash, when you rebuild-recompile them changes will reflect on your main application which uses them. Here's th eexample for modules: http://blog.flexexamples.com/2007/08/06/building-a-simple-flex-module/
So MXML/AS component/class are your "symbols" which you can create or drop on stage on fly.
Modules are "movies" you can load and they run on their own with possibility to communicate to main movie.
The closest way of achieving this is to use Bitmaps. If you update the bitmapData they display, they will all update automatically.
However this approach is not good at all. You should maintain application state separately in an object model, and have the visualisation update, if the state changes.
What you want to do, is to misuse a feature for changing graphic appearence at design time, to change application state at runtime. In generally, ideas like these can be thought off as bad.
For example if you take the time to separate the state model and the visualisation layer, it will become fairly easy to save the game state on a server or to synchronize it with other clients to achieve multiuser features.
greetz
back2dos
If you are trying to build an Avatar and user can customize your Avatar parts e.g. hands, legs, face etc. and you want all these assets to be kept in separate swf file, that is pretty straightforward. You keep all the assets, in separate swf or one large swf file and load them at runtime. Now, maintain your Avatar object instance and place the child objects, which are chosen by the user.
You can create inside your class a static List with references all the created instances and then apply a change with static methods. For example:
package
{
import flash.display.MovieClip;
import flash.geom.ColorTransform;
public class Square extends MovieClip
{
public static var instances:Array = new Array();
public function Square():void
{
Square.instances.push(this); // This is the trick. Every time a square is created, it's inserted in the static list.
}
// This property gets the color of the current object (that will be the same of all others because the setter defined below).
public function get color():ColorTransform
{
return this.transform.colorTransform;
}
public function set color(arg:ColorTransform):void
{
// Sets the color transform of all Square instances created.
for each(var sqr:Square in Square.instances)
{
sqr.transform.colorTransform = arg;
}
}
}
}
This is a Qt-specific question.
It's convenient to be able to add new data to a table by typing content into a blank row at the bottom of a table. When the data is committed, a new blank row is added to the table.
Has anyone found a way of implementing this in a generic way, that fits into Qt's model-view programming architecture? My closest attempt involves creating a proxy model, such that the rowCount() returned from the model is always one greater than the source model.
QAbstractTableModel* sourceModel ; // Data is stored here
QBlankRowModel* model ; // Proxy model that adds one to rowCount()
QTableView* view ; // View
view->setModel( model ) ;
model->setSourceModel( sourceModel ) ;
Any suggestions are welcome. Thanks.
From a design-perspective, this should be part of the view, not the model. Therefore, I suggest implementing a view with the functionality and leave the model unchanged. KOffice Kexi does just this with kexitableview (screenshot, documentation). Maybe you want to use some of their code.
BTW, you might still be able to use your hack and combine it with my suggestion by putting it inside a new table view implementation YourTableView:
QBlankRowModel re-implements the
QAbstractTableModel
interface. It returns sourceModel.rowCount()+1 as the QBlankRowModel::rowCount().
It returns a QVariant() if the n+1th row is requested in QBlankRowModel::data().
All the rest within QBlankRowModel is forwarded to the sourceModel (with editing
the n+1th row in QBlankRowModel buffered and replaced with inserting into the
sourceModel when finished).
The new YourTableView inherits from
QTableView and wraps the sourceModel within
YourTableView::setModel(), calling
QTableView::setModel(QBlankRowModel(sourceModel)).
Thereby, your hack is localized at one point.
Your solutions seems a little hackish. Your problem is not only additions, it's also editions. What happens when your user edits a row, the typed data goes directly to your "data layer" even before the user commits his edition?
A better solution would be to restrict the role of your sourceModel. Rather than being a "direct" representation of your data, it should be a "buffered" representation of it. When the sourceModel is created, you make a copy of your data in some kind of Row() instances. The sourceModel, having its own copy of the data can then freely play around, perform editions and additions, and only commit the data to your model layer when the user commits his edits.
If you want a PyQt example of such a table, you can look at the source of a project of mine:
http://hg.hardcoded.net/moneyguru/
You might have to dig around to actually find the "buffering" logic because it's not in the PyQt code itself, but rather the "cross-platform" part of the code:
http://hg.hardcoded.net/moneyguru/src/tip/core/gui/table.py
This logic is then used in my QAbstractItemModel subclass:
http://hg.hardcoded.net/moneyguru/src/tip/qt/controller/table.py
Sounds like a reasonable solution, as it should work for any model that you might want as the actual table model, ie. SqlTableModel or just a plain one. As long as you add the row when the user is done editing and take care not to add the row when the user did not add any data.
I want to get the system icon of a specified folder, but maybe the only way to retrieve the icon is to use SHGetFileInfo() method. The first parameter of SHGetFileInfo() method is a pointer of LPITEMIDLIST.
If I only have the absolute path of the folder, how can I get the pointer according to the path?
SHParseDisplayName().
Welcome to the wonderful world of PIDLs.
You can read more at Introduction to the Shell Namespace, but basically a PIDL is a Pointer to an item ID List. You can think of it as a linked list in contiguous memory, but instead of each node having a pointer to the next node, you instead have the cb member which is the Count of Bytes that are contained the item, so you can add that to the base address to get the next item. IDLists are terminated with an item with { cb = 0, abID = NULL }.
So, what's in these magic lits? Basically you don't care and can't know. Any IShellFolder implementation can create a new type of ID to represent its type of item in the shell namespace. The basic file system view that the Shell implements just stores the parts of the path in these lists, so you have something like "c:\" in the first one "Users\" in the next one, etc. In reality they are serialized structs (or classes) that may contain more data. But they can also represent printers, network shares, database searches (for search folders, stacks, etc).
All you really need to know is you can ask IShellFolders to give you a PIDL that represents the items they contain, and later on you can give that PIDL back to them, and other various Shell functions and interfaces, and they know how to deal with them. What SHParseDisplayName() basically does (I think) is go through the registry looking for all registered IShellFolder implementations and asks them if they know what to do with the string you pass in, and the first one to handle it makes the PIDL and gives it back.