Using Phoenix to simulate a gas cloud

[magarlick]

Dear all

I am a freelance animator and illustrator, working in Max. I specialise in astronomy simulations. I have been commissioned to create a simulation of a gas cloud as it approaches a black hole and is pulled around it and stretched out by its gravity. This link shows what I mean:

http://www.eso.org/public/videos/eso1151c/

I have never used Phoenix FD but I am considering getting it. I just want to make sure that it can do the job I need and that the learning curve is not too steep before I part with any cash. Does anybody know if it can indeed be used to recreate something that looks like the simulation in the link above?

Thanks a lot.

[Ivaylo Katev]

Hi Magarlick,
the simulation seems possible,you can use Phoenix to produce similar effect like in the video.
However, you can't use Phoenix to make physically plausible simulations, because there are some differences in the nebula dynamics and the one used to produce fire and explosions for CG. The most important difference is that the nebula is moving in empty space and this produces different look of the surface. In your reference video there are small vortexes that hint for external invisible dense environment, so i would say it's not physically correct, and therefore is fully achievable with Phoenix. If your goal is a scientific plausible simulation, i think you have to write the software on your own.
Here is the result that i achieved with few attempts:

Regards,
Ivaylo Katev

[magarlick]

Dear Ivaylo

I can't thank you enough for your reply. Your simulation is close enough to what I am trying to achieve. No it doesn't have to be ultra realistic. The only question I have now is how did you do it? Would you be so kind as to give me some pointers as to where to start?

Kind regards,

Mark

[Paul Oblomov]

I think he used 2D mode (when one of the grid dimension is 1). Then some force to point smoke tosomething. Maybe it is an emiter with low temp or just a force field.

[Ivaylo Katev]

Take the scene as a gift
The important points:
- Phoenix is used in 2d simulation mode (your video seems to be also a 2d sim)
- The initialization is made by script
- To make the simulation closer to gas in vacuum liquid in air is simulated. The liquid is much denser than the air and keeps its movement like the nebula in the space. If you try to simulate smoke in air, it will loose the movement after short distance, because the drag.
- to simulate the disappearing of the gas in the black hole, a source with negative discharge is used. Without this source, the smoke does not disappear and finally forms something like rotating gaseous planet.

[magarlick]

Thank you once again. For some reason I am not permitted to download that link you sent via this forum. Would you be able to place the file on Dropbox or something, or email it to mag at markgarlick dot com?

Which version of Max did you use to create it? I use Max 2013. Also, is it the scanline version of Phoenix or Vray? I have not purchased the software yet.

Cheers again.

[Ivaylo Katev]

you didn't have rights to download, but now you have.
the scene is made by vray version of phoenix, but there is nothing requiring vray in it, you can use scanline too

[magarlick]

Thanks again, very grateful.

[magarlick]

Hello again. I have downloaded the demo of Phoenix FD and played a little with the file you sent me. At this stage I am wondering if it is possible to do this simulation without using MaxScript, which I have never used. Can it be done another way? If not, how can I modify the script to make the initial blob smaller, further from the black hole and moving on a trajectory not so close to the hole?

Thanks again.

[Ivaylo Katev]

yes you can do it without script.
create a simple cylindrical source and select to emit from polygon id=1, this will make only the upper cap to emit liquid. animate the source discharge to emit few frames, the source parameters are T=1 smoke=1

[magarlick]

Hello again. I have been playing with the scene file that you made for me, but I just can't seem to undo the reliance on MaxScript. I have unticked the 'use script' button, and created a cylinder, which I added to the list of target objects in the PhoenixSource. But when I start the simulation nothing appears, no liquid. I must have misunderstood something. I also don't know what you mean by T=1, smoke=1.

I have looked at several of the tutorials but this scene seems different in that the 'smoke' is not coming out of something that I can see. There is a sphere added to the PhoenixSource but the liquid does not come out of it.

Thanks.

[Ivaylo Katev]

T=1 means temperature=1. In Phoenix the temperature and the liquid share a common channel, usually just liquid source is used and it sets the temperature to 1, but your case is very rare - you need actually gaseous simulation, and if the simple liquid source was used, the transparency curve have to be arranged to work with pure liquid content.

[magarlick]

Ok, thanks. But right now my main problem is getting this to work without MaxScript, as I said in my previous post. I have unticked the 'use script' button, and created a cylinder, which I added to the list of target objects in the PhoenixSource. But when I start the simulation nothing appears, no liquid. I must have misunderstood something? Remember I only just found this software and, although I have been looking at tutorials and reading help, most of it is not understood yet. Thanks again.

[Ivaylo Katev]

perhaps your source is not set properly, it must be temperature=1,smoke=1

[magarlick]

Ok, here's what I have done.

Created a cylinder. Added it to the target objects in the source. Changed polygon id to 1. Deleted sphere from target objects. (Including it made no difference). Ticked boxes temp and smoke and set them both to 1.

In Phoenix FD01, I unticked use script. This is the only change I made there.

I click start, and the simulation proceeds but no liquid appears either in the viewport on when rendering.

Any other changes that need to be made?

Kind regards,

Mark