in accurate surface offset boundaries ?

[o.delellis@gmail.com]

hullo,,,,


so i got negative offsets working, kind of, but it seems the collision boundary not only is a bit vague (in high pressure areas the particles push further in the object than on low pressure areas) but it might not be frame precise???

i offset the collision object animation by 0.5 frames in 3dsmax, and this looks better than the non offset animation. (the simulation was done with the no offset mesh)

as i have retimed this particles (h2 sim), regardless of the GFC files not being able to be retimed ( i have asked this question before, if they are needed in some way, but had no answer! ) i am meshing the un retimed original sim to see if the issue is on the simulation itself, or the retime process.

i realise this might not be what H2 was desinged to do, ie: monster coming out of water, boat wake, 1,000,000,0000 particles at hight speed, etc. etc ....

But it would be good , specially since SPH has had no development in what...5+ years? if H2 could be used in medium shot / Cu , low turbulence, subtler forms of fluid sims.

anyway,,,here r the pics
frame 035

offset_f035.jpg

frame 043

offset_f043.jpg

frame 156

offset_f156.jpg

[atena]

Hello, sorry for the delay in the answer, I needed some time to check your issues. Please let me go through your questions.

(1) “Surface offset” with negative values just doesn’t work right now. Maybe sometimes kind of seems to work but it doesn’t. Now it is fixed and working properly. As you can imagine a bug fix patch will be available very soon.

(2) There is indeed a 1 frame offset with the animated geometry. This was kind of known issue that we wanted to fix before the release but we didn’t have time. For medium-large scales this offset is negligible. But for close-up shots might be a problem as you pointed out. In theory this problem kind of alleviated if you do more than 1 step per frame for the Hybrido fluid, but still is something that we will fix for the pacth. The thing that surprises me is that you have to offset the Sd by 0.5 frames when the offset should be -1.0 frames, i.e. the geometry is one frame ahead of the fluid. Maybe this is because the retiming. Please note that GFC files don’t need to be retimed as they are used only for the generation of the secondary elements but not used at all for meshing. Generation of secondary elements from a retimed sequence is something you just can’t do, but wonder if that makes any sense as the secondary elements should match the timing of the original fluid.

Thank you for your comments, hope you just can work around the above issues until the next patch comes out. There is a simulation graph that you can use for adding more particles to the closest points on the animated geo and then mesh all particles together resulting in a filling of the gaps. I believe my colleague Gus sent you the scene/graph if not just let me know, I might be of help.

Cheers.

[o.delellis@gmail.com]

ok, well now i know it is a known bug.

i am simulating at 1/6 of the speed and the re timing to x6 so the offset of 0.5 is 3 frames in the simulation (1f = 6f)...

still doesn't seem to conform to the -1 frame offcial offset..but it looks right in most of the frames.

the negative offset, i do find it works, but it takes a couple of frames for the particles to get closer to the object. So if you are comparing the first frame of a sim, the results will look the same for offset 0.0 to -0.14 (what i am using).

[atena]

Glad is kind of working for you, hopefully with the upcoming patch you don't have to do this workarounds.

[izo]

Thank you for your comments, hope you just can work around the above issues until the next patch comes out. There is a simulation graph that you can use for adding more particles to the closest points on the animated geo and then mesh all particles together resulting in a filling of the gaps. I believe my colleague Gus sent you the scene/graph if not just let me know, I might be of help.

Sorry to barge in here, but that graph sounds like something I would love to get my hands on Where can I find it?

[o.delellis@gmail.com]

hi Izo,

i never got it! but managed to sort it out by offsetting the animation and making the particle size bigger

[LuisMiguel]

Hi Octavio,

I don't know why I thought I had sent you the graph long time ago. Sorry for that.

Here is the graph to add particles so you can simulate with less resolution and applying the graph to avoid gaps. Please, put it into Simulation Flow>FramePost.



luisM.

[izo]

I for some reason don't have the permission to see that file. Luis? Help?

[izo]

hi Izo,

i never got it! but managed to sort it out by offsetting the animation and making the particle size bigger

Hey Octavio,
That's cool.

Which offset are you setting to negative values? The surface offset or the domain offset?

/Dave

[o.delellis@gmail.com]

surface offset, but watch it cos its not offcially really working..

i was using -0.04