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Hot Asphalt - RnD


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I am still lame in Houdini, so this is unfortunately not much of "knowledge and solution" ... but rather experimenting and appeal for help.

This is what I am trying to achieve, hot asphalt:

I have tried five approaches. All source files are attached below in the zip file. I can explain anything, if anybody wants me to.

Please, if you see a better solution, please let me know.

Visually best solution for me is E - it is fake, not at all physically correct, but the sim is very fast, less then a second for a frame.


A - POP Grain
It works for bigger "rocks", but for small gravel it "flattens" on the ground and it doesnt make a pile.
Preview of my simulation:


B - POP Grain lowres + wrangle upres
Great idea and source files (by rayman) I am not able to set the right scale for search radius and number of neighbors, somewhere it is too low, somewhere too large.
Preview of my simulation:


C - Bullet solver and packed primitives
Works for bigger rocks, but small gravel falls through colliders and the simulation time is too large.
Preview of my simulation:


D - POP follow curve + Colliders + delete the isolated particles
Works quite fine, but the disappearing of some pieces is visible, and it is distracting.
Example help file: houdini\help\examples\nodes\dop\popcurveforce\CurveForce.otl
Preview of my simulation:


E - POP follow curve + Colliders + "average hull of the flow" metaball collider
The best solution, which I can do now.
Preview of my simulation:



Edited by ikoon
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No particles do not disappear. Try setting up a simple emit FLIP from object on a sphere with a ground plain, turn on viscosity on the FLIP solver and increase the amount in the FLIP object until it start to look like molasses. Particles may appear if you have resampling turned on in the FLIP solver so if that's a problem turn that off. What you will have at the end is a particle sim you can mesh for the 'tar' part of the asphalt and a velocity field that you can advect particles with using a POP advect particles by volume. I don't have time to set this up right now but it should be fairly straight forward. Godspeed!

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EDIT: I am sorry, it seems, that the disappearing cubature was some glitch or cache error. I did a sim again and it is fine now, excuse me:

Please, I have tried the FLIP approach and I have run into a problem. I am loosing the "cubature" of the volume. Please look at this video:

Please, I think it will help to "Set Always" higher viscosity of the fluid on the ground (or in that area on the ground). I have tried to set the viscosity by the Gas Viscosity DOP, but I dont know how to feed in the Viscosity Field. Do I have to use the Fluid Source SOP and the Source Volume DOP then? The file is attached.

F - flip - v1.zip

Edited by ikoon
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The previous sim was glitchy, so after restart I did some more development. I used POP VOP Ramp to set the viscosity higher on the ground. I think that I can do some more development on my own now, when I get to it later. I will fake the screw by local velocity field, probably. Thank you very much and I am really sorry for the confusions.

Preview of the attached hiplc:

F - flip - v2.zip

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I did some more development. I did this just with viscous flip and then COPY sop onto Flip Geometry. Hiplc is attached:

I have a question ... in reality, few dry little stones fall apart from the volume and act like a rigid body. Please, do you have an idea, how could I add this behaviour?

I have not succeed with particles being driven by the volume. The POPs fly away from the flip volume.

Also, please, can I set the Flip not to stick to the screw collider? I had to "fake" the screw by local velocity field, because the Flip was sticking and winding around the screw :) even when I set the friction almost to zero.

F - flip - v3.zip

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