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char last won the day on May 15 2018

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  1. How could I emit pyro from particles?

    Turn the particles into fuel in order to trigger burn in your pyro sim. I think that would be done through rasterize particle SOP.
  2. Not really, I think you can add a SOP solver in your simulation, combine the two with a Multi solver, then use object merge to bring the source geometry into the sop solver and do your further calculations there, just an idea. The Source is pretty intuitive if you dive into the documentations a bit : quote: Impulse creates a certain number of particles each time the node cooks. Constant creates a certain number of particles per second.
  3. Great, glad it worked. What I'm thinking now if you have Impulse emission, it will spawn a number of points each time it cooks, so essentially every frame. Somehow if you could add an attribute which would be the point number from where the particle spawned. Check if that point number exists on more than one particle spawned meaning there is more than 1 point spawning and delete the excessive points you won't want to use? https://www.sidefx.com/forum/topic/18697/?page=1#post-87850 have a bit of a read in this topic, maybe you can find anything, I'm at work at the moment so I'm a bit constrained to what I can do for you unfortunately!
  4. 1. You need to change the Source type to be Points or All Geometry I think, it's greyed out due to the settings you're using. 2. You'll get that option if you change the source type I believe, I'm not sure what you're trying to achieve with "not every frame while being able to choose the first birth frame", maybe explain a bit more and I'll try and help! 3. You can get the birth frame position by using POP / Geometry Wrangle inside your POP net and just isolate the particle by checking if it was alive on the previous frame and then store that position onto an attribute by choice only for that frame.
  5. I'm going to guess you could implement the techniques from earlier versions of Houdini and use them in 16.5 or 17 (new volume worfklows) with the knowledge we have, shouldn't be too hard as I was still able to open Microsolvers_rnd from 2014 the other day without any problems in Houdini 16.5. Going to explore the examples a bit more, wasn't aware there are more than just the ones in the documents.
  6. Hi @ikoon Which ones are we talking about, I'm only aware of the Example Files provided in the Help Documents for most of the nodes which come with Houdini and can be loaded through F1 Help menu. These Example Files? So guessing I need to find the folder you mentioned and load them in manually due to them being .hda files?
  7. That's some great explanations there, thanks for that. I've been testing a few nodes now and it's a bit clearer how certain calculations are done. Now I just need to figure out where and when this could be implemented in a simulation.
  8. 3D faded trail?

    I'm guessing I'd be easier if you just used particles and mapped the normalized age attribute to be density and then re-fit it so particles born have high density and it's slowly decaying based on how old they get. I could maybe set a scene up till the weekend, bit busy at the moment.
  9. Steven Knipping covers a similar "bombing / shooting" scene in Houdini. I'm guessing if I want to activate something when it hits the ground I'd set up a particle sim from the source (example : airplane), set up Impulse Activation in POP Source to @Frame== 4 && @Frame==6 and so on, meaning it will only spawn on frame 4 AND frame 6, so that way you can set up many things and trigger the activation. I would only emit one particle on the frames you set up on the source. Use the @hit attribute in the POP Solver to isolate that point when it hits the ground (you need POP Collision Detect / Behaviour & Enable Collision Detection ticked on the POP Solver) which you would do with a Delete SOP and an expression using hitnum attribute. After that you can use Copy to points SOP and use these collided particles which only appear on one frame when they hit the ground, copy a source geometry onto these points, turn them into a volume and use that as an emitter for your Pyro Sim. To be completely honest with you I couldn't really pick up what exactly you're going for here so I figured I'd just describe what I would do if I needed to simulate a carpet bombing scene. Let me know if you want me to clarify any part of the description.
  10. 3D faded trail?

    I'm guessing it would work with volumes as well, as it's quicker to set up fading density, right?
  11. Hoping this topic picks up and more people engage in the conversation as well @ikoon That's interesting, haven't really been looking into vortex confinement too much so seeing this is encouraging enough to try and dissect it later. I'm guessing a\ll that (curl, grad,...) is essentially a representation of Rotation, Magnitude, Direction and then normalization in a simulation, correct me if I'm wrong. Been watching Khan videos on Gradients and Curl yesterday, really wish I found his content earlier, loads of gems right there. The examples from 2011 are still quite relevant in H16.5, all opens up normally and I did have a quick peek just now, so recommending it to anyone learning like me.
  12. Hi @ikoon & @loudsubs Thanks a lot for both of your replies. Where on earth have you been all this time, that's probably the most useful script that exists, thanks so much for sending out the links. I've watched the masterclass and a few other videos, some of which you posted are still new so I'll surely adding them to my watch later list. Would you mind if I continue this topic a bit further? Both clarifications helped to understand the whole thing quite a lot. So let's say in your example, you have a Gradient built from the surface of your FLIP sim, where / how would that vector field be used? Would this just be a case of filling the Gas Calculate > Dest Field with vel and your Source Field with the name of the field created and using a specific Calculation method? Even the quote from that fluid masterclass : "advect velocity by velocity" is messing with my head at this point. I'm only aware of a method where you feed a certain field to control where for example GAS Turbulence affects the simulation but even that is not really intuitive because in order to use a mask in a simulation you need to put the name of the field into Gas Turbulence > Bindings > Density Field and I'm finding it a bit hard to understand why that should be placed there in order to work. An example for that would be a dotproduct of the gradient and velocity to mask only the top part of the smoke (if it's moving up), but again, I've read about it but there isn't much of an explanation why certain things are done the way they are. Second question would be; to understand Curl, Gradient, Laplacian a bit more than just the document explanation: "The simple case of a scalar field results in a vector field which points in the direction of increasing scalar values." would it be worth just watching a few Khan Academy videos on physics to really get a grasp of all these aspects? I'm pretty comfortable with most of the aspects of Houdini, but understanding a few things above was my goal for the past year of researching. Thanks again!
  13. Hi people, been lurking around here and gathering all the knowledge you are sharing, so thanks to each of you contributing to the forum. Lately I've been trying to understand another side of Smoke simulations and ways of controlling them. Before posting this I've gone through the most popular posts on the forum like "getting rid of mushroom" and others where there is tons of knowledge to pick up, I've also read the documentation on Microsolvers (Analysis, Match Field,...) multiple times in hope to understand which nodes to use and how to properly set them up. Could somebody point me to any resource to understand the workflow on building custom fields, how to use Gas Analysis, how it's related to Gas Match Field and some other aspects of these MS. I've been trying to understand what the documentation is saying and it's still a bit blurry to me compared to how other nodes are so well explained. A few days ago I've only read a quick post about building one but it doesn't explain much, it's more in the likes of "click this and click that, done". Apart from cracking open the Pyro Solver and individual Gas Microsolvers, where have you people picked up the knowledge / workflow on building custom fields. For what I've noticed people making tutorials and forum posts tend to steer away from anything that isn't Gas Turbulence, Shredding, Disturbance. Even a quick clarification on Gas Analysis / Calculate and it's common uses from you experienced people would be a massive help. Many Thanks!
  14. Captain Marvel FX?

    My best guess would be a particle sim (a lot of particles), convert them into a volume and use a pyro shader to add colors going from red, to yellow, orange and blue. Then just feed the age attribute into that ramp on the shader. You will have to play with the particle sim a lot and I'm sure it's not just one basic sim creating the effect. You do have to understand replicating an effect from a Marvel movie isn't going to be a 5 minute thing.
  15. Ripple

    Create a rest on your non animated geometry. Subtract the animated P vector (ripple animation) from the rest P vector in an attribute wrangle. The difference produces a vector that you can measure using length vex function. Using the float value from the length function you can delete points that exceed a certain threshold. That will give you starting geometry to source your pop sim from. You can calculate the velocity before the sim to use it to push particles in that direction rather than using the random velocity inside the simulation. I can post an example later if you want.