Right now Yngine Scene-graph implements nodes with loose attributes. Attributes
represent node states, like transformation, render geometry, etc. This has a
big disadvantage: An engine subsystem has to query for attributes of known
type, e.g. renderer queries for TransformationAttribute and GeometryAttribute
to draw the primitives. As a result, all data in Scene-graph structure merge
together and become hard to distinguish.
This should be changed. Scene-graph will define structure of the world and keep
a list of active world-subsystems. Every subsystem will register specific
attributes for each node. At Scene-graph traversal, each subsystem receives the
corresponding attributes automatically at invocation time.
Example:
The world will activate OpenGL renderer, custom world logic (currently
implemented as GLRenderers "Strategy" classes) and JBullet physics sub-systems.
We add a camera, lights and a few objects into the Scene-graph as abstract
nodes.
For OpenGL renderer we register a CameraAttribute for the camera node,
LightAttribute for the lights and GeometryAttributes for the world objects. For
JBullet subsystem we register only RigidBodyAttributes for the world objects
and connect MotionState to the OpenGLRenderer's TransformAttributes.
The custom world logic subsystem will get a "StrategyAttribute" registered for
every logic-controlled world object. These strategies will get applied based on
a given conditions, e.g.: Time-based invocation.
This example shows, how complex this refactoring can become. Attributes become
assigned to specific parts of the engine, while comunicating together. They
start having inputs and outputs. The update/render pipeline has to invoke every
subsystem for specific nodes, or for the whole Scene-graph at a correct time
durring the main loop. Physics subsystem has to dispatch events, like
touch-event, so the whole world can react.
End of example.
This is just the basic idea. Think about the best way of doing such separation
and describe the best solution in this issue before implementation.
Original issue reported on code.google.com by yinotaurus on 28 Mar 2011 at 2:02
Original issue reported on code.google.com by
yinotauruson 28 Mar 2011 at 2:02