When I use 3D particles, I typically create a looping animation and use that in Particular Set the particle to loop with a random start time. Just keep your precomp size pretty small so AE doesn’t bog down.
I’ve never tried it, but I would think that you probably would have to build the planes of the building in your particle comp, and then turn on Collapse Transformations so that it would be a 3D element in your main comp. Even then Particular might do something that would flatten your particle image, since it, like many things in AE, is not truly operating in a 3D space – more like 2.5D
Create your building in a precomp and nest it into the comp with Particular. Using Particular’s custom particle, you can select the 3Dbuilding that you created in Particular. The only tricky bit is setting the Time Sampling for Particular. Usually you will set it to Random Loop.
Random Loop will force Particular to emit particles with a random start point and when the particle reaches its inherent end-point, the particle will loop to its inherent start point and continue again in this manner until it dies off. Also keep an eye out for the size of your particles – too small and they may pixelate if they get too close to the camera and too big and they’ll bog Particular down to a crawl.
For this to work, ensure that your particle is created in such a way that it is seamlessly loopable. Also, you can use renders from 3D software as 3D particles with Particular or even Particle Playground.
broadcastGEMs.com – the leader in customizable royalty-free animated backdrops