Tuesday, 13 March 2012

Processing Graphs 3

So based on the stuff in my previous post I decided to ditch the stuff I had already done for work and start with the stuff I worked on in socles on my hack-day as a baseline.

I had to fill out the event management stuff, and then I had to port the few processing nodes I had already ported to my other half-arsed attempt - which apart from a couple of cases was fairly straightforward. I kept the getInputX/getOutputX stuff, implemented some image converters, and wrote a video frame source node (which turned out a bit more involved than I wanted).

Some of the code is a bit messier, and now i've implemented the event stuff I had to go back and fill that out: which was a bit tedious. The 'source' interfaces are a bit of extra mess too but aren't any worse than implementing bound properties and in some cases I can sub-class the implementation.

The graph executor is nice and simple, it visits all nodes and runs every one once in the right order based on the graph. Each execution produces a CLEvent, and takes a CLEventList of the all events from pre-requisite incoming nodes. Each node takes a queue, a CLEventList of conditions, and a CLEventList to which to add it's (one-and-always-one) event output. It wont handle all cases but it will do what I need.

Because input/outputs use simple component-ised syntax, I can auto-connect some of the sources as well using some simple reflective code: this is only run once per graph so isn't expensive.

Possibly I want to allow individual 'source' instances to be able to feed off their own valid-data events too: although I think that's just adding too much complication. If nodes produce partial results the nodes themselves can always be split.

So after all of that (it's been a long day for unrelated reasons), I think it's an improvement ... at least the individual nodes are more re-usable, although some of the glue code to make the stuff I have work is a bit shit. I still have a bunch of cpu-synchronous code because I can't tie in user events with the api I have (I need to update my jocl for that), but with the api i've chosen I should be able to retro-fit that, or other possible design changes later on (e.g. multiple devices? multiple queues?) without needing to change the node code.

Actually I wish I had had more time to play with it in socles before I went with it, because there are always things you don't notice until you try it out. And things are a lot simpler and easier to test in the 'WebcamFX' demo than in a large application. This is also just a side-issue which is keeping me from the main game, so I want to get clear of it ASAP, whereas in socles it's just another idea to play with.

No comments: