# Implement a rendering graph model

[fughilli]

Ideas:

• Specify port types. Perhaps ports can be one of kModel, kRender, or kRaster
  • Model ports are for model data (verts, UVs, etc.)
  • Render ports have backwards-facing attributes for applying transforms before rendering and specifying the raster to render to
  • Raster ports are for raster data and metadata (size)

[fughilli]

Initial design document

Started work in the graphs branch

[fughilli]

conversion declaration, opaque data storage, and a minimal graph model are implemented (the graph model only supports linear graphs, which is not very useful at the moment).

I think a nice short-term goal to be able to start playing with the features consists of:

• support arbitrary render graphs (implement an actual graph representation in opendrop::Graph with appropriate edge storage/aliasing)
• support constructing graphs from textproto files (and saving them, too?)
• finish the "minimum satistfaction" feature for arbitrary graphs where there are dangling inputs

[fughilli]

An initial model is now implemented and merged. There is a lot of cruft left over that should be cleaned up:

The OpaqueTuple abstraction should not own memory. It should be just a mechanism for converting from a set of pointers to data to a tuple of typed references and back. The outputs of all nodes in the graph will have memory owned by the graph itself; the nodes will only own memory used to track their internal state. The input to the whole graph is provided by reference at the time of Graph::Evaluate(), and thus does not need to be owned by the graph.

Types should be default-constructible--it was a complete headache trying to work around how to be able to construct memory for a Type without statically knowing its C++ class type. All memory for a graph will be default-constructed and then initialized appropriately on first mutation.

The implementation should be revised to achieve this simpler model.