Symbolic Posted January 11, 2008 Share Posted January 11, 2008 Hi, I am interested in exploring the fluids. I know that the best way is the H9 help... I tried to render some of the Fluids examples the come with the help... but was not able to see the actual fluids in the final rendered image. I am using the H9.1.118 HD... what might be wrong? ...has any body heard about any future fluids tutorials? Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 15, 2008 Author Share Posted January 15, 2008 I have been struggling for a while with the H9 fluids... it seems like the logic is even more different than the DOPs compared to other contexts in Houdini... I really have hard times understanding which fluid module is for what etc. Is it more efficient to explore Real-Flow? There is more documentation on it I guess... But is the pipeline easy?... from Real-Flow to H9. Or should I try to stick to the H9 fluids? It is new and exciting but... I do not know maybe it is just me being impatient Quote Link to comment Share on other sites More sharing options...
Marc Posted January 15, 2008 Share Posted January 15, 2008 Hey Symbolic The logic shouldn't be that different from other DOPs. Are you having issues in general, or is it just with the rendering of the fluids? Cheers Marc Quote Link to comment Share on other sites More sharing options...
old school Posted January 15, 2008 Share Posted January 15, 2008 SPH (particle based fluids) vs Level set fluids... It's like having Real Flow plus a Volume based fluid solver in a single application. You choose what works best for a given situation. For me, the main issue with SPH is increasing the point count can drastically change the behaviour of the sim (see below). The main issue with Level Set fluids for water is volume loss or gain and a general lack of resolution (unless you go to large resolutions and long sim times). Not a perceptible issue for smoke effects though where this works quite well. After that use the shelf to set up your sims and study the generated networks. None of the example files were built using the shelf and that is both good and bad. Good in that you get to see the bare minimum to get a sim working. Bad in that you have to do a lot of referencing back and forth between DOPs and objects to get things to render with the control you should have (if you had done it from the shelf in the first place ). I use particle based fluids for a lot of water effects. You get better splashes and no boundary box to worry about. You can also run separate level set fluid sims and extract the surface, scatter points then merge and run all the points through the particle based surfacer SOP to get one continuous surface. You can also throw in a dense grid of points and merge that in to have everything blend in together before the particle based surfacer SOP. I like running low point count particle based fluid passes, incrementing the seed and jittering the start sample points with each pass. Then write the particles to disk and merge in the different passes in to a final object. Then surface that with the Particle Fluid Surfacer SOP. I believe this is a common technique in Real Flow for increasing the resolution of a sim without drastically changing the "feel" of the effect. Scale is the only issue but I find running more and more passes increasing the number of particles and upping the drag and lowering the gravity gives the particles a greater sense of scale for example if you want a huge sheet of water. For splashes, you could run subsequent particle fluid sims then merge them in to the final effect. You could create an entire library of particle splashes then copy them in wherever collisions are detected or using Attribute Transfer between objects in the scene and your fluid sim objects. What makes particle based fluids even more attractive to me is the integration of POPs. If you use the shelf to build up your basic sims, all of this is wired up for you and ready to go. A POP network is wired up for you in DOPs and input correctly for you. Actually I can't think of a single sim I have built in the last few months that did NOT start off with the Shelf. I tend to pass everything through the particle based surfacer SOP in H9.1 these days. Break down your fluid effect in to several smaller manageable parts then merge them together as points and surface. You should also dive in to the details view on the DOP network to see what data is added by the various solvers. Merge DOPs allow you to have RBD's interact with particle based fluids, etc. Just remember to wire in the particle based fluids before the RBD objects. Quote Link to comment Share on other sites More sharing options...
michael Posted January 15, 2008 Share Posted January 15, 2008 Jeff, I know I'll not get much of an answer but... why is SESI so reluctant to release the files that created all the examples we've seen in the past months? I know that perhaps some of them might break with the changes that have happened 9.0 > 9.1 but isn't it worth a tiny amount of time on SESI's end to quickly fix them up and release them with a note saying "these are old demo/test files - use at own risk" this goes for the pbr stuff also... I just don't get it... the Procedural Girl promotion from last year could have been zippped up and released 'as-is' and everyone would have lots of neat examples to dig through...but what is any of that being used for now? - nothing. Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 16, 2008 Author Share Posted January 16, 2008 (edited) Hi old school, Thanks for the detailed answer. It will take me a while to understand your post... I guess it will get more and more clear as I practice... So the fluids in H9.1 are SPH? ...it means that an particle infrastructure is used to drive the final geometry? right? But then, what are Level set fluids? Hi michael and Marc, I tried to setup some examples... I managed to render some of them... For example: a teapot made of fluid that splashes on the ground... it kind of worked. Then I tried to collide two fluid teapots ...and everything got creazy. Right now, I am trying to have an object falling into a liquid... and control the character of the fluid. Something like that: nikeairforceone_fluid.mov // Just to keep things clear: (Project credits) Director: Christopher Riggert Producer: Michael Hilliard Production Co: @ Radical Design & VFX Co: Resolution Design Creative Director: Tim Dyroff Head of 3D: Max McMullin 3D Animator: Tom Corbett Compositors/Designers: Maxence Peillon & Lisha Tan Post producer: Will Alexander Sound Design: Supersonic Composer: Jono Ma Producer: Charlton hill (A link to the original video) http://motionographermedia.com/radicalmedi...airforceone.mov // It is obvious that this sample is from a professional project... It probably required lots of tweaking, we do not know anything about the tool used etc. I do not want to sound like I want to achieve this look with a press of a botton... Just used it as a visual example for the kind of the effect that I might aim for... Anyway... thanks for your help... Edited January 16, 2008 by Symbolic Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 18, 2008 Author Share Posted January 18, 2008 any ideas about this? What are the main things that control the character and the behavior of the fluid? Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 24, 2008 Author Share Posted January 24, 2008 (edited) Finally Digital Tutors releases a Houdini Dynamics set of tutorials... It has a great section on basic fluids... It helped me a lot to understand the logic. I am really happy about those tutorials... Most of us have been waiting for fresh educational materials for a long time.. at least me. And now it is happening! More! More! The first tutorial set is also very good... wraps up most of the basic things... Edited January 24, 2008 by Symbolic Quote Link to comment Share on other sites More sharing options...
Smithjoe1 Posted January 27, 2008 Share Posted January 27, 2008 I'm still having a tricky time understanding how to get it all working sometimes. I've finally understood the logic of using the merge node to change the kind of relationships between each of the nodes and trying to get them to actually work, its a slow learning process now to try and understand the fluids, took me a while to pick out the source selection in the merge to kind of make them all finally work. I've been most interested with the Sand Object, haven't seen anything with it yet and theres such little resources about it, but seems to be cool, I'm just trying now to understand how to have a keyframed object reacting with it instead of just leaving it to its own devices. Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 27, 2008 Author Share Posted January 27, 2008 I'm still having a tricky time understanding how to get it all working sometimes. I've finally understood the logic of using the merge node to change the kind of relationships between each of the nodes and trying to get them to actually work, its a slow learning process now to try and understand the fluids, took me a while to pick out the source selection in the merge to kind of make them all finally work.I've been most interested with the Sand Object, haven't seen anything with it yet and theres such little resources about it, but seems to be cool, I'm just trying now to understand how to have a keyframed object reacting with it instead of just leaving it to its own devices. Yeah... fluids... i can not say that I understand them yet... But kind of started to get clues and work my way around. One should give him/her self time. Hopefully as the resources grow, it will get faster to learn. Quote Link to comment Share on other sites More sharing options...
Smithjoe1 Posted January 27, 2008 Share Posted January 27, 2008 Yeah... fluids... i can not say that I understand them yet... But kind of started to get clues and work my way around. One should give him/her self time. Hopefully as the resources grow, it will get faster to learn. I most certainly agree, once I found out about the merge node for the different kind of relationships to set up different, the examples are sort of there for basic things, but the amount of recourses there for anything slightly advanced just dont exist there yet, perhaps the DT stuff or the Gnomon DVDs have information in it for fluids and the likes, but really the amount of stuff available for it is limited. I wanted to do the fluid previews from the SideFX website with all the boxes and the fluid rushing out around it, the example files for those would be fantastic to learn from. Quote Link to comment Share on other sites More sharing options...
Symbolic Posted January 29, 2008 Author Share Posted January 29, 2008 Yes. I agree... I wish we had access to those files. Maybe one day. Quote Link to comment Share on other sites More sharing options...
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