Particle render - Line artifacts

[adrianr]

Hi all, hoping someone has had this problem before and can point me to the magical button that fixes it   I have a volume sim advecting circa 60 million particles, and I'm getting some odd lines in the render. Unfortunately there are some project sensitive things in the hip file so I can't upload it (If I get time to recreate it in another scene I'll upload that).  

 

The geometry is animated, and I *may* have had something in mind about particle births being too uniform (There used to be an 'accurate births' setting to overcome this?) but that could be my subconscious playing tricks. 

 

Nothing special about the set up. Pyro sim from the (very, very slightly) animated object, using the vel field with POP advect by volume, wedged in 5 chunks varying the seed by 1 to a total just short of 60 million over 100 or so frames. Pscale 0.005, age decay on the point alpha, opacity around 0.2. Pyro sim division size 0.5 in a box 90 x 120 x 80. 

 

Any clues with that information? 

 

Cheers. 

 

[Juraj]

Hi,

it seems to me that those gaps between lines are caused by low substeps in your particle sim. Maybe particles are born on surface of animated object and particles are born on every frame and therefore there are gaps between frames.

You can try to increase substeps and make sure to have correct animation between frames. You can use Time Blend SOP for that.

 

Another option (and more efficient) may be to deform your surface to mimick motion blur. One way to do it might be to scatter points and stick them to animated surface (using primid and primuv attributes). Then for each point blend its position with previous and next frame's position based on random float value. (-1: prev frame, 0: current frame, 1: next frame). I just got this idea so I am not sure if it will work.

 

Juraj

[adrianr]

Excellent Juraj, thank you. I'll give both a whirl.