hi all!!

i have a particle system /otl as follows…

particles spawned from a point group - which is created when spawn geometry enters a bounding box..

the velocity of the spawn geometry is passed into chops (via an object chop then a slope chop, channels are then split into x, y and z) where the user has access to multipliers and limits on the x, y and z velocity, these are then passed up to the particle systems birth rate and dvelocity attributes (throwing the partiles in the direction of th emoving geometry)

it all appears to work beautifully until a trail sop is applied (for motion blur) when this reveals that particles are zooming off at large velocities in random directions on some frames.. i have applied numerous limits to the particle velocites that are passed back up to the source pop, also there are no spikes in the slope data being passed through chops… i`vwe been trying to solve this for 2 days now with no luck..

anyone got any idea what might be causing this?

otherwise is there a way to use deformation / transformation motion blur on particles to see if its the trail sop causing the problem?

cheers all…

Your point count is changing and particles are dying, right? If so then that's the issue you are dealing with. Trail SOP just connects the point number dots from the previous frame. The first particle that dies causes the point numbers to move around.

Your solution is to try to use velocity based motion blur. Just calculate velocity vectors on your points based on it's previous position if the velocity isn't already there then turn on velocity blur.