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Particle Effects for Animated Exeter

January 22, 2011

Now I have a fairly robust camera tracking system, I want to start looking at the front end particles which will act as the fireflies for the project. We decided that we would like to map the fireflies to the architectural details of the cathedral window. The problem we have at the moment is that we don’t know the angle which the projector will be at and therefore we can’t really map it without knowing what we’re projecting on. We need an exact image of what we’re using. So for now I wanted to create a dynamic particle system which I can change easily, so for example I can use a basic image of the window, then all I need to do is change the image and the particles will adapt to move to the right positions.


Fortunately Ralph Hauwart has just released an excellent blog post on particle systems and he has released the source code which I am able to use. I have tweaked it slightly at so I am able to use sprites instead of filling pixels so I am able to use Billy’s graphics.  Ralph’s code runs much better in terms of performance, but doesn’t allow any customisation in terms of graphics.

Ralph’s code uses vectors to colour individual pixels which means flash can render 30k + particles at a time with no problem. I have to reduce mine to around 1000 to make sure it runs nicely.

My version This is my version with the custimisable particles, it doesn’t look as good at the moment, but needs a bit of tweaking, hopefully when I put Billy’s graphics in it will look nice.




Basically what happens is the individual particles get attracted to the white areas of the background image that I am using. This is what the background image looks like:

background imageThe projection will never see this image, but basically I can change the white areas in the image and the particles will get attracted to it. Which means I can change pattern which the particles follow really easily.

It also makes it really easy to implement the next part of the project: camera tracking. What I am doing is producing white dots where the people are, which means when the dots appear on the image, the particles should follow, which means the particles should follow the audience.



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