Pivy/ja

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Revision as of 12:11, 8 January 2019 by Luc (talk | contribs) (Created page with "シーンの直下の子ノードを調べることもできます。 for node in sg.getChildren(): print node")

PivyはFreeCADで使われている3DレンダリングライブラリであるCoin3d用のPythonのバインディングライブラリです。実行中のPythonインタプリタにインポートするとFreeCADの3DビューアーなどのCoin3dシーングラフと直に対話処理を行ったり、新しい3Dビューアーを作成することさえできます。Pivyは標準のFreeCADインストールに同梱されています。

Coinライブラリはいくつかに分割されています。Coin自体はシーングラフの操作を担い、Windowsといった複数のGUIシステム用のパッケージがありますが私たちの場合はQt用になります。これらの分割されたモジュールもシステム上に存在する場合にはPivyから利用することができます。Coinモジュールは常駐していて自由に利用することができます。既にFreeCADによって行われているので3D表示をどのインターフェイスに紐付けするのか気にする必要はありません。私たちがやらなければならないのは以下のコマンドを実行することだけです:

from pivy import coin
from pivy import coin

シーングラフへのアクセスと変更

典型的なCoinシーンがどの様に構成されているかはシーングラフページで見ました。FreeCADの3Dビューに表示されているものは全てCoinシーングラフであり、同じやり方で構成されています。ルートのノードが一つあり、画面上のオブジェクトは全てその子ノードです。

FreeCADでは3Dビューシーングラフのルートノードに簡単にアクセスすることができます:

sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()
print sg
sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()
print sg

こうするとルートノードが返されます。

<pivy.coin.SoSelection; proxy of <Swig Object of type 'SoSelection *' at 0x360cb60> >
<pivy.coin.SoSelection; proxy of <Swig Object of type 'SoSelection *' at 0x360cb60> >

シーンの直下の子ノードを調べることもできます。

for node in sg.getChildren():
    print node
for node in sg.getChildren():
    print node

Some of those nodes, such as SoSeparators or SoGroups, can have children themselves. The complete list of the available coin objects can be found in the official coin documentation.

Let's try to add something to our scenegraph now. We'll add a nice red cube:

col = coin.SoBaseColor()
col.rgb=(1,0,0)
cub = coin.SoCube()
myCustomNode = coin.SoSeparator()
myCustomNode.addChild(col)
myCustomNode.addChild(cub)
sg.addChild(myCustomNode)

and here is our (nice) red cube. Now, let's try this:

col.rgb=(1,1,0)

See? everything is still accessible and modifiable on-the-fly. No need to recompute or redraw anything, coin takes care of everything. You can add stuff to your scenegraph, change properties, hide stuff, show temporary objects, anything. Of course, this only concerns the display in the 3D view. That display gets recomputed by FreeCAD on file open, and when an object needs recomputing. So, if you change the aspect of an existing FreeCAD object, those changes will be lost if the object gets recomputed or when you reopen the file.

A key to work with scenegraphs in your scripts is to be able to access certain properties of the nodes you added when needed. For example, if we wanted to move our cube, we would have added a SoTranslation node to our custom node, and it would have looked like this:

col = coin.SoBaseColor()
col.rgb=(1,0,0)
trans = coin.SoTranslation()
trans.translation.setValue([0,0,0])
cub = coin.SoCube()
myCustomNode = coin.SoSeparator()
myCustomNode.addChild(col)
mtCustomNode.addChild(trans)
myCustomNode.addChild(cub)
sg.addChild(myCustomNode)

Remember that in an openInventor scenegraph, the order is important. A node affects what comes next, so you can say something like: color red, cube, color yellow, sphere, and you will get a red cube and a yellow sphere. If we added the translation now to our existing custom node, it would come after the cube, and not affect it. If we had inserted it when creating it, like here above, we could now do:

trans.translation.setValue([2,0,0])

And our cube would jump 2 units to the right. Finally, removing something is done with:

sg.removeChild(myCustomNode)

Using callback mechanisms

A callback mechanism is a system that permits a library that you are using, such as our coin library, to call you back, that is, to call a certain function from your currently running python object. This is extremely useful, because that way coin can notify you if some specific event occurs in the scene. Coin can watch very different things, such as mouse position, clicks of a mouse button, keyboard keys being pressed, and many other things.

FreeCAD features an easy way to use such callbacks:

class ButtonTest:
  def __init__(self):
    self.view = FreeCADGui.ActiveDocument.ActiveView
    self.callback = self.view.addEventCallbackPivy(SoMouseButtonEvent.getClassTypeId(),self.getMouseClick) 
  def getMouseClick(self,event_cb):
    event = event_cb.getEvent()
    if event.getState() == SoMouseButtonEvent.DOWN:
      print "Alert!!! A mouse button has been improperly clicked!!!"
      self.view.removeEventCallbackSWIG(SoMouseButtonEvent.getClassTypeId(),self.callback) 
 
ButtonTest()

The callback has to be initiated from an object, because that object must still be running when the callback will occur. See also a complete list of possible events and their parameters, or the official coin documentation.

Documentation

Unfortunately pivy itself still doesn't have a proper documentation, but since it is an accurate translation of coin, you can safely use the coin documentation as reference, and use python style instead of c++ style (for example SoFile::getClassTypeId() would in pivy be SoFile.getClassId())

Scenegraph
PySide