Particle Paint is a unique and novel creative tool with which you can paint using live particles. Since these particles always remain live, the user can continue to modify them and change their attributes indefinitely until they're ready to bake into an image. This means color can be changed over and over again, as can position, visibility, transparency. Dynamic motion effects can be applied to the particles using physics, forces and filters. Particles can spawn additional particles manually, by age or by speed, each capable of inheriting brush or parent forces.
Particle paint emits particles like any particles simulator does during the course of an evolving timeline. Particles are sprayed using a rate and speed that is affected by forces such as air resistance (paper absorption), brush direction, etc. At any time, the user can rewind the timeline and redo those particles. Alternately, one can select any section within a timeline and make modifications to it.
Making full use of Adobe Photoshop's integration, Particle Paint can use image information as emitters or colliders. A specific area can be drawn, for instance, and then used to emit particles. Likewise, a specific area can be draw, and when particles collide with it, any number of operations can occur such as bouncing, stopping, dying or spawning.
As with any professional paint software, Particle Paint provides layers to work with. Particles can be overlayed on top of each other, modified within their layer only, or modified across all layers at the same time. Layers provide transparency tools and blending modes for indefinite possibilities.
Particle Paint features inter-particle collision checking so that particles can interact and bounce off each other, or they can blend their colors together. Gravitational forces can be applied, as well as brush forces allowing the user to specify a brush size and interactively apply forces over a particular area of particles.
Because of their indefinite lifespans, particles can be continually modified using the tools section until the user chooses to bake the particles and generate the final image.
Particle Paint is very much an experimental beta application at this time and it suffers from poor performance issues. There may be glitches but for the most part it is a powerful and unique, fully-functional, dynamics-driven painting application. Have fun.