DOM integration classes

This is some internal notes about COLLADA DOM integration classes.

Integration classes provide a SAX-like approach to using the DOM. My problem with this is that the interdependent links between COLLADA elements has become very complex. Parsing a DOM structure lends itself better to handle these problems. Creating an integration class to process, for example, materials may take the same amount of work as accessing the DOM structures itself. Here's a comparison.

To do with Integration Class:

1. Create class that inherits from daeIntegrationObject.
2. Implement the fromCOLLADA code to do the conversion.
3. Implement the fromCOLLADAPostProcess code to do the processing needed to resolve links to other elements, for example, effect.
4. Make your integration library register with the DOM.

To do with DOM access:

1. Get DOM by calling getDOM() or getDOMRoot from the daeDocument.
   • For each material library
   • For each material
2. Call your conversion function (which would be the same as your fromCOLLADA). Your conversion function can even do the post-processing linking needed since all the data required by the other elements would be available.

Also it is a lot harder to go from custom classes to COLLADA DOM with the integration objects than it would be just with the DOM structures.

DOM structures give you finer-grained control over what to convert; for example, you can spend time converting only the geometries in the scene and not the possible dozens/hundreds/thousands of others which the integration classes convert every single one. This is especially useful to know if you have documents that cross-reference to other documents. For example, imagine loading a document that contains a visual scene where all of the instance_geometry elements reference a geometry from a separate document. This document has only one library_geometries and contains all of the geometry elements used for all of your scenes, not just the one being loaded. Since the COLLADA DOM, by default, loads external documents to resolve the URIs, the integration classes will convert every single geometry found in the second document. There could be lots of geometries and that could take a long time to process, especially since there will be geometries that never get used in the scene.