gistfile1.txt

Hi Toyos. Thanks for taking the time to read this.

Basically, I have a SCNNode 'Agent' which contain child nodes (maybe a hundred or so) which are simple textured planes which respond to a physics field (or 4).

Every frame, I want to draw a connection between the nodes.

My thought was to :

In the "Agent" node - parent to all the child nodes - override the custom rendering. I would:

A) enumerate the children and get a position of the their presentationNode (so I get correct positions) and make them relative to the Agent nodes coordinate system via convertPosition:

B) Gather that data into a line strip /index for use with something like CPU side Vertex Array (since data changes every frame)

C) Hopefully bind a SCNMaterial I can just make.

D) Draw To GL

E) Happy me!

Right now I think I can gather the positions correctly via presentationNode, but I am unsure of details of C and D, ( I know GL, but it appears i may need a my own shader loaders etc).

Another option was to abuse SCNGeometry and then alter data - but my gut says thats a no-no. I also expect generating SCNGeometry per frame is a bad idea™.

Since the Agent node isn't drawing any SCNGeometry (custom rendering), I don't have a SCNGeometry and thus I don't have an SCNMaterial associated. I assume I would have to call some sort of a 'bind' method, or manually load my own shader into this, no?

I think I would do what you describe with the custom vertex array. But you can't bind a SCNMaterial to it unfortunately. When using a node delegate you have the full control but you loose SceneKit's convenience to render that geometry.
What you would need here is a SCNMutableGeometry that exposes the vertex array data. You should file a request for this.

Awesome. Thanks again. I went with the node render delegate and custom GL. Thanks again for the help!