SceneGraph_Knob

This is a general purpose knob that can be used to show a hierarchical tree of primitives. It can also be used when loading a file using the “R” hotkey. In order to allow populating this menu, the following procedure needs to be followed.

1. A SceneReaderPlugin needs to be subclassed

2. A SceneReaders::PluginDescription needs to be instantiated, registering

1. the name of the plugin class,

2. the file extensions that should be handled by the plugin,

3. and the constructor of the plugin.

1. The SceneReaderPlugin::query populates the out stream

There’s two query commands, SceneGraph::kSceneGraphKnobCommand which gives the following input:

“command:scene_graph””path_to_file”

And expects the following output:

no of keys | key2 | no of items for key1 | items for key1 … | key2 | no of items for key2 | items for key2… For example, a stringstream that had two objects, with type sphere, cube and name a, b and an enabled state on and off looks like “3””name””2””a””b””type””2””sphere””cube””enabled””2””1””0”

And SceneGraph::kSceneGraphTypeCommand, which gives the following input:

“command:op_type””some_type”

And expects the following response:

“name_of_node_to_instantiate_for_some_type”

Two helper functions are provided to help serialise and deserialise primitive data into the stream:

void SceneGraph::SerialiseSceneData(const DD::Image::SceneItems& data, std::ostream &out); bool SceneGraph::createBrowser(const char* fileName, DD::Image::SceneGraph_KnobI* pSceneGraphKnob, const DD::Image::SceneItems& items);

For an example of the SceneReaderPlugin, see NukeUSDPlugins SceneReaderPlugin.h