Something like this:
If the camera is to be animated yet not go through the beam of light, how would you do this realistically. I haven’t messed around with it yet but I guess you could texture a cylinder or a plane with an alpha texture that is noisy and put the blend mode on add? Or maybe you would use particles, any advice appreciated since I haven’t really dabbled much with rendering in blender nor any other app.
There are a few solutions to his problem. One of the easiest, least expensive, and fastest to render options is volumetrics.
In Cycles (highly recommend: very realistic, relatively slow to render), you will want to create a very low-density volumetric box containing the entire scene, and then in the materials settings, turn on homogenous.
In Blender Internal, you can simply take your light-source, and turn it into a volume lamp.
The advantage to this is that it takes very little memory, looks perfect from a distance, and is pretty dang fast to render. The disadvantage is that as the camera flies through it, you can’t see the individual dust particles, and therefore looks less like dust and more like mist or fog.
The other, very memory-expensive option is particles. You can make a small object (I’d recommend a single plane, with a texture to make it look like a dust particle), and add a particle system of those, with gravity off and no physics. You can add a little ambient movement by turning on random rotation, global position, and animating the plane itself around a little. I recommend using a ton of child particles for this, because otherwise it’ll take up a TON of memory for the (useless) baking, etc.
Please note that the latter method will need to use a TON of VERY TINY particles, so it will take AGES to render, the shadows will be hard to manage, and can otherwise slow down the whole process a lot. I don’t recommend doing this method unless you want it to be snowing, or something with noticeably visible particles.
You can also do a kind of hybrid method, which basically involves using the second method, but only creating particles near your camera.
I don’t know exactly how to pull it off, but it would have a whole flurry of both technical and aesthetic advantages compared to either one of the two.
