Divergence Field cause hole in smoke simulation

[ashu_tosh_m]

I was trying to expand the some smoke simulation using divergence field.

the divergence field  create a big hole in the smoke simulation.

any idea why is this happening

Test Smoke.hiplc

[Atom]

I think divergence needs to be negative. Try changing your keyframe value from 20 to -20.

[ashu_tosh_m]

  On 4/2/2020 at 3:43 PM, Atom said:

I think divergence needs to be negative. Try changing your keyframe value from 20 to -20.

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its still creating hole after changing value to -ive

[Atom]

Hmm... That's Od. (rewind to clear old cache..?)

Here is negative divergence using your scene. I made the attraction point, bigger and visualized it.

Edited April 2, 2020 by Atom

[ashu_tosh_m]

  On 4/2/2020 at 3:57 PM, Atom said:

Hmm... That's Od.

Here is negative divergence using your scene. I made the attraction point, bigger and visualized it.

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can u share this hip file?

[Atom]

Sure, here you go.

ap_test_smoke_divergence_040220.hiplc

[ashu_tosh_m]

  On 4/2/2020 at 3:43 PM, Atom said:

I think divergence needs to be negative. Try changing your keyframe value from 20 to -20.

Expand  

Ops i made the value from 20 to -20

not from  0 to -20 :-|

thats why i was creating a hole !

Thank You sooo much :-)

[ashu_tosh_m]

  On 4/2/2020 at 4:23 PM, Atom said:

Sure, here you go.

ap_test_smoke_divergence_040220.hiplcFetching info...

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Hey its working but i want to expand the smoke.. its looking like the divergence field is attracting the smoke ..

how to expand the smoke.. I want to make something like this....

look how the smoke got expanded  in this video..

 

 

 

Edited April 2, 2020 by ashu_tosh_m

[Atom]

A lot of that look is determined by collision objects. Add a ground plane and make your velocity point down.

You can check out my fuel based rocket launch thread here.

 

[ashu_tosh_m]

  On 4/2/2020 at 4:40 PM, Atom said:

A lot of that look is determined by collision objects. Add a ground plane and make your velocity point down.

You can check out my fuel based rocket launch thread here.

 

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BTW I'm not making rocket launch smoke.....

i want to learn how that guy has expanded the smoke.

[toadstorm]

If you want to make smoke expand, source a scalar field with positive values like you'd source any other field (density, etc), and set the destination field to "divergence".

If you're getting holes inside, consider adding more density into the area that you're expanding.

Edited April 2, 2020 by toadstorm

[ashu_tosh_m]

  On 4/2/2020 at 4:56 PM, toadstorm said:

If you want to make smoke expand, source a scalar field with positive values like you'd source any other field (density, etc), and set the destination field to "divergence".

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yes i have done that... its creating hole u can check the screenshot .. or hip file that i had shared..

[toadstorm]

Looks like you're losing density because your divergence scale is enormous, and it's causing the velocities to be too high relative to the time increment. If you increase your max substeps a bit, you should get more accurate results.

[ashu_tosh_m]

  On 4/2/2020 at 5:06 PM, toadstorm said:

Looks like you're losing density because your divergence scale is enormous, and it's causing the velocities to be too high relative to the time increment. If you increase your max substeps a bit, you should get more accurate results.

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u have increased the substep?

may u share this hip file.? 

it will be easy to understand.. bcoz im noob in Pyro

[toadstorm]

It's the same exact file you uploaded. All I did was increase the maximum substeps on the Pyro solver to 4, under the Advanced tab.

[ashu_tosh_m]

  On 4/2/2020 at 5:12 PM, toadstorm said:

It's the same exact file you uploaded. All I did was increase the maximum substeps on the Pyro solver to 4, under the Advanced tab.

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okay thank you.....

let me try 

[Atom]

You can set the Operation of the divergence field to Subtract and the smoke will move away from the divergence field, instead of being drawn in.

 

Upres on right.

 

Animating the scale of the volume might not be the best approach. All that does is increase or decrease the value in the area of the divergence field. To expang and area, you might try want to animate the scale of the divergence field shape at the SOP level and leave the DOP scale set to a constant. That way, when you expand the size from zero and up, the field size area of effect will grow, not the strength.

ap_UPRES_smoke_divergence_040220.hiplcFetching info...

Edited April 2, 2020 by Atom