essencevfx Posted July 14, 2009 Share Posted July 14, 2009 Hey all, I'm trying to use a particle stream to add velocity to a pyro sim. Has anyone sucessfully got this to work (adding extra source velocity ) without changing the source options on the original pyro object ? Is it possible to pump along an objects normal direction , that way the fluid would always push along the pumps facing direction ? I suppose that would work as well for what I'm trying to accomplish ( push fluid very quickly ,like a hose, but the source is animated so I cant just set_velocity in a single direction in a motion dop ) Thanks for any insight ! Quote Link to comment Share on other sites More sharing options...
Fomal Posted July 15, 2009 Share Posted July 15, 2009 So if I'm correct, you're trying to add velocity from a particle sim on top of your original source velocity? Cause that can be added and scaled by using the sources point velocity attribute. Quote Link to comment Share on other sites More sharing options...
essencevfx Posted July 15, 2009 Author Share Posted July 15, 2009 yes, basically I've got a particle system sourcing fuel/temp/smoke and I'm using point velocity for that source, but I want to add the extra velocity from a separate source, ( ( in effect , a 'pump',with velocities set up in sops, not in the motion dop) unless there is a way to have motion dop set velocitys along an objects normal or something like that, so even when animated it will flow properly)... Quote Link to comment Share on other sites More sharing options...
essencevfx Posted July 15, 2009 Author Share Posted July 15, 2009 so , basically, I'm trying to use a separate particle source for fuel/smoke/temp , and one to introduce velocities. That was much simpler to say Quote Link to comment Share on other sites More sharing options...
Fomal Posted July 15, 2009 Share Posted July 15, 2009 Ah okay Sure, what you can do is create your extra velocity volumes in sops and add those to the original velocity. I've made a quick file to demonstrate this. Alternatively you could use a gasParticleToField microsolver. To directly add point attributes. But I prefer the volume approach since this doesn't create any direct scaling issues when changing the resolution and solves faster. A third method is creating a second source relationship and a second index field (with source scalar field) for storing the addidtion attributes. And use that. But that's a bit more tricky. add_2nd_vel.hipnc Quote Link to comment Share on other sites More sharing options...
essencevfx Posted July 15, 2009 Author Share Posted July 15, 2009 wicked, excellent Coen, thanks I'll have a look ! I was just playing with a SOP_vector field dop but wasn't getting very far yet. Nice work on this solver, from a long time maya fluid user, its nice to have the 'handcuffs' off so to speak. Cheers ! Quote Link to comment Share on other sites More sharing options...
Fomal Posted July 15, 2009 Share Posted July 15, 2009 (edited) No Problem. I made a quick new one that let's you select the way you want to add extra data to vel. Using either points or Sop Volumes. Or Both When adding data, make sure the information that you read in is updated over time in DOPS. So set the time to $T and the method to always. This way you can have animated geometry updating the fields over time. add_2nd_vel_both_ways.hipnc Edited July 15, 2009 by Fomal Quote Link to comment Share on other sites More sharing options...
essencevfx Posted July 15, 2009 Author Share Posted July 15, 2009 the particle field dop worked perfectly for this. Thanks again... One other thing thats been on my mind working with this is the upres process. I seem to be adding a whole lot of resolution, but I would expect more detail in the sim then I'm getting with this many divisions ( 500) . Is this something I need to mess with in the up-res/turbulence , or is there some other place I might look at first to get a good upres. cheers j. Quote Link to comment Share on other sites More sharing options...
Fomal Posted July 16, 2009 Share Posted July 16, 2009 On the upres solver there are a couple of options to tweak for that. First, make sure your Peak turbulence is set up correctly. Every low res sim will have it's own characteristics, so the calculated turbulence scale in the upres solver will behave different as well. You can check if you have the right range by visualizing the turbscale field. Once this is within decent bounds you can remap this effect. With feedback in the viewport. Next, by default the frequence of turbulence (detail) is scaled according to the low res sim. Filling in a lower number in freq scale gives you bigger chunks of noise applied to your simulation. If you don't compute Freq cutoff the result is not linked to the low res sim, which can generate interesting results as well. The danger is that the calculated turbulence will push your fluid in a direction where it will not be advected anymore. But for more randomness this is a good option. Next to this the amplitude and overall turbulence settings can be very handy increasing the detail after you have got a good idea where and how the turbulence will be applied. Hope this helps a bit Quote Link to comment Share on other sites More sharing options...
essencevfx Posted July 16, 2009 Author Share Posted July 16, 2009 (edited) thanks man, I'll put all those tips to work today and see what I end up with. Edited August 6, 2009 by essencevfx Quote Link to comment Share on other sites More sharing options...
essencevfx Posted August 6, 2009 Author Share Posted August 6, 2009 Hey Coen ,thanks for all the help so far. I understand the upres process now much better, but I'm still having a hard time making the up-res not errode away at my lo res fields. I've got nice details in my lo res sim that Id like to preserve but they just get eaten away seems durring upres....Is this negative noise values perhaps removing field values ? Quote Link to comment Share on other sites More sharing options...
Fomal Posted August 18, 2009 Share Posted August 18, 2009 Sorry for my late reply, been busy at work But this issue comes down to how the turbulence scale is calculated, since this defines the magnitude of the added noise. Not the frequency or actual amplitude. Just where to start adding detail. Basically there are three options, curl, wavelets and constant. Constant is what it says but with the others the low res velocity field is used to calculate the magnitude of the noise. This gets stored in the turbscale field and can be remapped. That's where you can get a lot of control. You can even create your own method, to define where to add the detail, as long as you store the results in the turbscale scalar field. Scaling the calculated turbscale field by density will help as well. The ramp gives you a remapping option for the low res density. The output of that function is multiplied with the previously calculated turbscale, to create the final magnitude for the noise. By remapping the scale by density ramp you can actually control where on your sim the noise is added and where not. This will also result in a smoother result, as the bounds are being controlled by the original density field. Quote Link to comment Share on other sites More sharing options...
essencevfx Posted August 18, 2009 Author Share Posted August 18, 2009 Cool, I was beginning to think that it might be my (very) high velocities in the lo-res sim thst happen to be in the area where I'm seeing the most noise,... the whole sim is very fast moving fire, so I'll try and work out a method using my own mappings for the turbscale scalar field and see where that takes me . But , besides that , Ive been getting some sweet looking fire here, Thanks ! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.