flat/horizontal lines in smoke

[finalight]

Hi Kresimir,

I believe we discussed this years ago and now that I'm back to working with detailed blast sims, I'm running into this issue again. It only seems to occur for these blasts when cubic or advanced advection is used + the expansion is animated down or burn rate is animated down. I've been tweaking everything I can think of: quality, iterations, sensitivity 0, stride, the help file suggestions, etc. The only way I can get rid of them is to go with a non-cubic sim which is inferior in detail and motion. Any ideas on how these can be resolved? I was thinking of even using effectors testing for 'no temp, no velocity' and then add noise to break them up - if that would even work. Here's a screen shot, however you'll recognize the features from the issue noted in the help file under: UI / Simulation (the brown smoke image with arrows in it). In the help file it talks about fast moving smoke however I notice they only show up when the smoke slows down. Thanks. Best regards, Brian

[sitnisati]

Hello,

This is expected with Advanced advection and it's mentioned inside the help file as well.

Regards,
Kresimir Tkalcec

[finalight]

Hi Kresimir,

It also occurs with cubic-on but advanced advection off. Are there any ways to get rid of it? The only way I have found is to sim without cubic which yields poor results in the detail. Thanks.

[sitnisati]

The problem with cubic interpolation that it can overshoot the data and then the values have to be somethow returned into the normal range.
I suppose that those lines are the cause of this cubic interpolation nature and cannot be avoided.

Regards,
Kresimir Tkalcec

[finalight]

Roger that. So any ideas on how it can be avoided? Quality, iterations, effectors, any tricks? This seems to be a major roadblock to get realistic/detailed explosion behavior. Thanks.

[sitnisati]

Some velocity diffusion might be able fix that, but that would lower the amount of detail.
Have you maybe tried Advanced advection (fields only)?

Regards,
Kresimir Tkalcec

[finalight]

Interesting, I'll try that - the vel diffusion. I've also tried turning off cubic and using Advanced advection fields and it still exhibits the problem - I'm guessing because cubic turns back on in 'advanced advec', correct? Thanks.

Best,
Brian

[sitnisati]

Advanced advection and cubic interpolation are two separated pieces of code, but both can cause visible problems (Advanced adv. more than cubic).

Regards,
Kresimir Tkalcec

[finalight]

Thanks Kresimir - great to know.