issues when removing and readding View3D to stage

[david-gregory]

Away3D, as is, causes this error when adding, removing, and re-adding View3D to the stage.

Main Thread (Suspended: Error: A Stage3D instance was already assigned!)

• away3d.core.render::RendererBase/set stage3DProxy
• away3d.containers::View3D/onAddedToStage
• flash.display::DisplayObjectContainer/addChild [no source]

This is caused by the renderer's 3D proxy not being set to null. To fix this, we should be calling _renderer.dispose() and _depthRenderer.dispose() in the View3D.onRemovedFromStage() function. Note that RendererBase.dispose() does nothing except set this pointer to null.

After doing so, we get a successful call to onAddedToStage the 2nd time. However, the next call to render() bombs with the following callstack:

Main Thread (Suspended: Error: Error #3698: The back buffer is not configured.)

• flash.display3D::Context3D/clear [no source]
• away3d.core.render::RendererBase/executeRender
• away3d.core.render::RendererBase/render
• away3d.containers::View3D/render