I am trying to animate flames on a bipedal transformer-esque character with wings and assorted thrusters on his back (think starscream: http://tfarchive.com/creative/content/590/fh_starscream.jpg). [tfarchive.com] The character is running along, then hits the jets and takes off. I am using a pops network to generate the thruster flames and exhaust, which I want to keep very tight behind the jet. The problem I am having is that once my particles are emitted, they leave an unsightly and lengthy trail as the character speeds away. I have tried a variety of methods inside of pops to get the effect I am looking for (turning the sampling up, decreasing the life expectancy and increasing impulse birth, restricting the flames to a bounding box around the jet, etc). I think to achieve the affect I am looking for I need to add the acceleration of the source geometry to each particle, so that no matter where the source moves the particles will follow. My question is, what is the best way to do this? I was using the point sop, which will give me the CURRENT position of the geometry, but it won't let me go back one frame to get the difference. Should I add an attribute node after the POP network and store the position there, and read it back in POPs?

You need to do only two things for fast moving particle sources:

- Increase oversampling
- Turn on Accurate Births

I think you are missing the latter. It is found in the Source POP's Birth folder. Using this will increase POP cook times as each particle birthed at a sub-frame interval will cause the POP network to cook.

Then dial up oversampling until you get a solid column of particles.

Also make sure your particles are in world space: the object birthing particles inherits no transforms from your particle source geometry. Object Merge SOP your particle source geometry in to the particle object with Transform object set to . or here.

P.S.: I have a “thing” for transformers so let's see your finished animation soon.