Unfortunately there is no Spline-Operator for Particle Flow in 3ds Max and Path-Follow SpaceWarp don’t work with the Force-Operator in PFlow. So we need a particle flow script to control the position of each particle with splines. Here is my solution of this problem.

1. Create a group of shapes (e.g. 20 splines) and attach them to one object. Copy the object name.
2. Create a Standard-PFlow-System.
3. Set the “Amount” of particles in the Birth-Operator equal to the amount of spline curves in the shape object (in this case: 20) and turn down “Emit Start” and “Emit Stop” to 0.
4. Delete the Position Icon and Speed-Operator of the first event
5. Add a “Delete” operator and set your life span to a particle age (e.g. 100)
6. Add a Script-Operator with following script and paste the name of your target spline in line 18:

on ChannelsUsed pCont do
(
 pCont.useAge = true
 pCont.useLifespan = true
 pCont.useSpeed = true
 pCont.usePosition = true
)

on Init pCont do
(
 seed 12345
 global weightArray = #()
 global particleLifeArray = #()
)

on Proceed pCont do
(
 splinePath = $Line001
 particleCount = pCont.NumParticles()
 curveCount = numSplines splinePath
 particleTime = pCont.getTimeStart()
 minSpeed = 50
 maxSpeed = 60

 for i in 1 to particleCount do
 (
 pCont.particleIndex = i

 if weightArray[pCont.particleID] == undefined do
 (
 weight = for s = 1 to curveCount collect 1.0
 sum = 0
 for s in weight do sum += s
 weightArray[pCont.particleID] = for s in weight collect s/sum
 )

 if particleLifeArray[pCont.particleID] == undefined do
 (
 for s = 1 to curveCount do
 (
 pathLength = (curveLength splinePath s) / random minSpeed maxSpeed
 particleLifeArray[pCont.particleID] = pathLength
 )
 )

 actualSplineProgress = mod  (pCont.particleAge.frame / particleLifeArray[pCont.particleID]) 1.0
 nextSplineProgress = mod ((pCont.particleAge.frame + 1) / particleLifeArray[pCont.particleID]) 1.0

 actualPosition = [0,0,0]
 nextPosition = [0,0,0]

 for s = 1 to curveCount do
 (
 at time particleTime
 (           
 actualPosition += (lengthInterp splinePath i actualSplineProgress) * weightArray[pCont.particleID][s]
 nextPosition += (lengthInterp splinePath i nextSplineProgress) * weightArray[pCont.particleID][s]
 )   
 )
 pCont.particleSpeed = (nextPosition-actualPosition) / TicksPerFrame
 pCont.particlePosition = nextPosition
 )
)

on Release pCont do
(

)

Press CTRL-E to evaluate your script. You can open the MAXScript Listener Window to see all values. You can use the “Cache” operator in your PF Source for faster results.

Cheers!

Vali