Creating a btBvhTriangleMeshShape in libgdx from node of model - libgdx

I want to add nodes of a model to btDynamicsWorld with btBvhTriangleMeshShape. I can do this with the whole model by passing model.meshpart, but nodes does not have meshparts.
I need this because only the required nodes need to be added to btDynamicsWorld.

See the wiki: https://github.com/libgdx/libgdx/wiki/Bullet-Wrapper---Using-models
It's one line:
btCollisionShape shape = Bullet.obtainStaticNodeShape(model.nodes);
You can pass in as many nodes you like (or just one, if you prefer).

Related

combine model on Autodesk Forge

I have couple of questions about combine model on forge viewer (load list urn to 1 viewer):
when i combine model. i only can get data from 1 main model in that combine. for instance, 
var instanceTree = GlobalViewer.model.getData().instanceTree;
var allDbIdsStr = Object.keys(instanceTree.nodeAccess.dbIdToIndex);
var list = allDbIdsStr.map(function (id) { return parseInt(id) });
list will return all dbid of main model, how can i access all data of all model when i combine?
what is the unique id for object in combine model. i do some function with dbid and i realize it can appear in others model too.
When i combine 3d model(revit) with 2d model(autocad). it has 2 case: if 3d model load first i can rotate like normal, if 2d model load first i cant rotate the model any more. how can i force it always can rotate?
Autocad unit seems different with model in viewer. it always scale down compare with the model. how can i fix that?
Appreciate any comments,
Regarding #1: viewer.model obviously only references one of the models (I believe it's the last one you loaded), but you can use viewer.getVisibleModels() or viewer.getHiddenModels() to get other loaded models as well.
Regarding #2: dbIDs are only unique within a single model; many of the viewer methods accept an additional parameter specifying the model on which to operate, for example, you could say viewer.select([123, 456], oneOfMyModels).
Regarding #3: that's a good question; loading a 2D model first puts the viewer into 2D viewing mode (where only zoom and pan is allowed); if you know you will be working with 3D models, I'd recommend always loading those first
Regarding #4: yes, each loaded model can have different units; when loading a model using the loadDocumentNode method you can specify additional options (for example, a placement transform for the loaded geometries), and one of them is an object called applyScaling, for example, like so:
viewer.loadDocumentNode(doc, viewable, {
applyScaling: { to: 'mm' }
});

Is having a single massive class for all data storage OK?

I have created a class that I've been using as the storage for all listings in my applications. The class allows me to "sign" an object to a listing (which can be created on the fly via the sign() method like so):
manager.sign(myObject, "someList");
This stores the index of the element (using it's unique id) in the newly created or previously created listing "someList" as well as the object in a 2D array. So for example, I might end up with this:
trace(_indexes["someList"][objectId]); // 0 - the object is the first in this list
trace(_instances["someList"]); // [object MyObject]
The class has another two methods:
find(signature:String):Array
This method returns an array via slice() containing all of the elements signed with the given signature.
findFirst(signature:String):Object
This method just returns the first object in a given listing
So to retrieve myObject I can either go:
trace(find("someList")[0]); or trace(findFirst("someList"));
Finally, there is an unsign() function which will remove an object from a given listing. This function basically:
Stores the result of pop() in the specified listing against a variable.
Uses the stored index to quickly replace the specified object with the pop()'d item.
Deletes the stored index for the specified object and updates the index for the pop()'d item.
Through all this, using unsign() will remove an object extremely quickly from a listing of any size.
Now this is all well and good, but I've had some thoughts which are making me consider how good this really is? I mean being able to easily list, remove and access lists of anything I want throughout the application like this is awesome - but is there a catch?
A couple of starting thoughts I have had are:
So far I haven't implemented support for listings that are private and only accessible via a given class.
Memory - this doesn't seem very memory efficient. Then again, neither is creating arrays for everything I want to store individually either. Just seems.. Larger.. Somehow.
Any insights?
I've uploaded the class here in case the above doesn't make much sense: https://projectavian.com/AviManager.as
Your solution seems pretty solid. If you're looking to modify it to be a bit more extensible and handle rights management, you might consider moving all those individually indexed properties to a value object for your AV elements. You could perform operations like "sign" and "unsign" internally in the VOs, or check for access rights. Your management class could monitor the collection of these VOs, pass them around, perform the method calls, and the objects would hold the state in a bit more readable format.
Really, though, this is entering into a coding style discussion. Your method works and it's not particularly inefficient. Just make sure the code is readable, encapsulated, and extensible and you're good.

How to display a tree of objects in a JTree?

Imagine a collection of objects such as World, Country, Region and City. World contains a list of Country objects, Country contains a list of Region objects etc.
I would like to represent this structure in a JTree and be able to add, remove and move objects around the tree.
Can I easily create a TableModel from this structure? World would be the root object and I would need to perform some object-specific rendering.
Any one know of an appropriate tutorial that goes beyond building a tree from simple text nodes?
You might start with the examples mentioned in How to Use Trees. You may need profile your code if the intended number of leaf nodes is large. You may want to consider a map as an alternate interface for the uppermost levels. See also the three-part series of articles starting with Creating TreeTables in Swing.
Addendum: Part three in the series cited includes an example TreeTableModelAdapter.
$ ls -1 src/bookmarks/
AbstractTreeTableModel.java
Bookmarks.java
BookmarksModel.java
DynamicTreeTableModel.java
JTreeTable.java
TreeTableExample3.java
TreeTableModel.java
TreeTableModelAdapter.java

What does node mean in MySQL?

Could anyone explain what node means in MySQL?
This one is talking about nested set.
I am reading a document from Codeigniter's wiki and I am not sure what I am supposed to add for $node.
getSubTreeAsHTML (line 704)
Renders the fields for each node starting at the given node
* return: Sample HTML render of tree
string getSubTreeAsHTML (array $node, [array $fields = array()])
* array $node: The node to start with
* array $fields: The fields to display for each node
The code you are looking at is part of BackendPro. The full code of the function can be viewed here.
"Node" in this case refers to a data node of a nested set. Nested sets are nice because they allow you to quickly select a whole branch of a hierarchy with only the starting node.
It looks like the function specified renders part of a tree in HTML starting at the node you specify. The BackendPro interface must render hierarchical data somewhere.
EDIT: Nested sets are not a MySQL-only concept, but there is a good article about nested sets and MySQL here:
http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/

What is the difference between a property and an instance variable?

I think I've been using these terms interchangably / wrongly!
Iain, this is basically a terminology question and is, despite the "language-agnostic" tag associated with this question, very language/environment related.
For design discussions sake, property and instance variable can be used interchangeably, since the idea is that a property is a data item describing an object.
When talking about a specific language these two can be different. For example, in C# a property is actually a function that returns an object, while an instance variable is a non-static member variable of a class.
Hershi is right about this being language specific. But to add to the trail of language specific answers:
In python, an instance variable is an attribute of an instance, (generally) something that is referred to in the instance's dictionary. This is analogous to members or instance variables in Java, except everything is public.
Properties are shortcuts to getter/setter methods that look just like an instance variable. Thus, in the following class definition (modified from Guido's new style object manifesto):
class C(object):
def __init__(self):
self.y = 0
def getx(self):
if self.y < 0: return 0
else: return self.y
def setx(self, x):
self.y = x
x = property(getx, setx)
>>> z = C()
>>> z.x = -3
>>> print z.x
0
>>> print z.y
-3
>>> z.x = 5
>>> print z.x
5
>>> print z.y
5
y is an instance variable of z, x is a property. (In general, where a property is defined, there are some techniques used to obscure the associated instance variable so that other code doesn't directly access it.) The benefit of properties in python is that a designer doesn't have to go around pre-emptively encapsulating all instance variables, since future encapsulation by converting an instance variable to a property should not break any existing code (unless the code is taking advantage of loopholes your encapsulation is trying to fix, or relying on class inspection or some other meta-programming technique).
All this is a very long answer to say that at the design level, it's good to talk about properties. It is agnostic as to what type of encapsulation you may need to perform. I guess this principle isn't language agnostic, but does apply to languages beside python.
In objective c, a property is an instance variable which can take advantage of an overloaded dot operator to call its setter and getter. So my.food = "cheeseburger" is actually interpreted as [my setFood:"cheeseburger"]. This is another case where the definition is definitely not language agnostic because objective-c defines the #property keyword.
code example done in C#
public class ClassName
{
private string variable;
public string property
{
get{ return variable; }
set { variable = value; }
}
}
Maybe thats because you first came from C++ right?!
In my school days I had professors that said class properties or class atributes all the time. Since I moved to the Java C# world, I started hearing about members. Class members, instance members...
And then Properties apear! in Java and .NET. So I think its better for you to call it members. Wheather they are instance members (or as you called it instance variable) or class Members....
Cheers!
A property can, and I suppose mostly does, return an instance variable but it can do more. You could put logic in a property, aggregate values or update other instance variables etc. I think it is best to avoid doing so however. Logic should go into methods.
In Java we have something called JavaBeans Properties, but that is basically a instance variable that follows a certain naming pattern for its getter and setter.
At add to what has been said, in a langauge like C#, a property is essentially a get and set function. As a result, it can have custom logic that runs in addition to the getting/setting. An instance variable cannot do this.
A property is some sort of data associated with an object. For instance, a property of a circle is its diameter, and another is its area.
An instance variable is a piece of data that is stored within an object. It doesn't necessarily need to correspond directly with a property. For instance (heh), a circle may store its radius in an instance variable, and calculate its diameter and area based on that radius. All three are still properties, but only the radius is stored in an instance variable.
Some languages have the concept of "first class" properties. This means that to a client application, the property looks and is used like an instance variable. That is, instead of writing something like circle.getDiameter(), you would write circle.diameter, and instead of circle.setRadius(5), you would write circle.radius = 5.
In contrast to the other answers given, I do think that there is a useful distinction between member variables and properties that is language-agnostic.
The distinction is most apparent in component-oriented programming, which is useful anywhere, but easiest to understand in a graphical UI. In that context, I tend to think of the design-time configuration of a component as manipulating the "properties" of an object. For example, I choose the foreground and background colors, the border style, and font of a text input field by setting its properties. While these properties could be changed at runtime, they typically aren't. At runtime, a different set of variables, representing the content of the field, are much more likely to be read and written. I think of this information as the "state" of the component.
Why is this distinction useful? When creating an abstraction for wiring components together, usually only the "state" variables need to be exposed. Going back to the text field example, you might declare an interface that provides access to the current content. But the "properties" that control the look and feel of the component are only defined on a concrete implementation class.