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catchyid

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catchyid last won the day on November 20 2016

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About catchyid

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    Khaled Abdelhay
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    Montreal, QC

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  1. Thanks Tomas! So one way to see pyro density as just a property advected by velocity field, and dissipation parameter removes percentage of it on each frame? As per divergence, can I think of it as a way to adding/removing the density property above? As per vusta, sorry, simple typo
  2. Hi, I am trying to understand the basic physics behind fluid simulation used in Pyro solver. All physics books say that density must be constant (otherwise the equations will be too hard to solve). However, when I do any smoke sim in Pyro, density field is not constant, i.e. one can compute max/min/average density for a Pyro smoke simulation. So my question: how come all books say that density must be constant and yet when I sim smoke in Houdini I have different densities? Thanks,
  3. FLIP Whitewater Spray in H17

    just a quick update, it seems that spray/foam/bubbles have became internal states in the new whitewater sim, you can check their states and control them individually... cheers
  4. Hi, I am doing a whitewater sim in H17 and I could not find the spray tab? I want some whitewater that shoots up a little bit, and gets suspended a little bit in air, I used to do that with spray in H16.5. Tried to change gravity, initial velocity, velocity multiplier but all kept white water "inside" the water volume... Any ideas, thanks
  5. VEX code to create new points

    Oh my god how embarrassing ! not sure what made me thought the seed was different! I did not ask this question
  6. VEX code to create new points

    Hi, I am trying to create random points using VEX. Basically, It's a Geo node with only one Detail Attribute Wrangle node: for(int i = 0; i < 100; ++i) { vector pos=set(rand(0.1*@Frame),rand(@Frame),rand(10*@Frame)); addpoint(geoself(),pos); } I get 100 points, but all have the same location? Any idea why all rand() is producing the same position for all points? Thanks,
  7. C++ Effects Programming ?

    Guys, thaaaaaaaaaaaaaaanks for your for feedback! I am still thinking about your posts (specially I will be busy for the rest of my life thing ) I think my strongest skill set is writing robust logic/behavior! when it comes to math/physics, I have a *good" background but I cannot really compete with SESI tools, or can write something that does not exist in the first place! However, one idea I like is advanced destruction, I find it easy to have a simple destruction shot in Houdini, but to have something like "material" based, easier art directability can be improved... Alright thanks guys for your feedback...
  8. Hi, I have been doing FX using Houdini for almost 1.5 year now, and I have over than 10 years of experience in C++ programming/algorithms. I am wondering what could be improved in Houdini Effects using C++? Is there any kind of effects that require more logic than just using simple VEX or Python scripts? I know there are many translators between Houdini/Arnold/etc. integration that could be written, but I am more interested in Effects programming, i.e. a program that would create hard to create effects using Houdini current built-in tools. Any ideas are really appreciated
  9. Flip fluid forces

    Hi, not sure I entirely understand the question. So, if you want just waves then use ocean tools. But I think you want a real sim? In this case, you can use the ocean tools to create the waves and apply it on FLIP sim (you can use the shelf tool ocean shore to create an example or a simple setup). As for pushing the volume of the water, you just need to have a box, create a static object and plug it in the sim network. Hope this helps...
  10. How to break pieces in animated alembic mesh

    Okay, I got a chance to look at the file, and it does work, thanks As you also questioned, I am not sure why copying @P manually fixes the problem (as you mentioned, @P is already animated). Maybe the assignment itself triggers a flag that position needs to be read. However, I think that setup, i.e. using "Create animated static object", won't work if the there is more than translation only. Meaning, if there is rotation or real deformation (i.e. no actual transformation exist). I've read on other posts that hard constraints should be used instead but I still need to do more research and try it myself first! Once more, thanks for your time and help
  11. Bullet constraints network questions

    Thanks Andrea, I'll look at the example files I guess, it's always good to test them Once more, thaaaanks
  12. Hi, some basic questions on constraints network any feedback is appreciated ! BTW, I am using bullet solver a) what's the main difference between glue constraint and hard constraint? they seem doing the same job for me? 2) on a sop level, primitive, one can set s@constraint_type="all|position|rotation", however in a dop level, we still need to create a constraint specifically by type, i.e. glue or spring, etc ==> why have this redundancy? we have the constraint type twice? thanks
  13. How to break pieces in animated alembic mesh

    Hello! Sorry, I got super distracted by work and could not reply earlier! I will study your file during soon (hmm, in the weekend I guess :)) Just looked at it quickly and really, I am suppper impressed thaaaaaaaaaaaaaaaaaaaaaaaaaaaanks !
  14. How to break pieces in animated alembic mesh

    Okay, I was able to follow the tutorial and produce a similar result, however the motion is wobbly and I need the pieces to stick 100% to the animated constraints (in my actual production, I want the wings to stick 100% to the plane body until the wings hit a tower, then constraints break and the wings fall apart gradually). Any ideas? maybe my whole approach is wrong? Thanks
  15. How to break pieces in animated alembic mesh

    Hi, I am watching the tutorial! I have attached a simple file for the problem, if you have a look, I would really appreciate it Thanks, glue_to_alembic.hip
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