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slow/retime RBD sim

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Hey Guys, I know this has been asked a few times, and I did some searching, but I'm still unclear on a few things.

I need to retime a large RBD sim, with many objects. The time scale parm on the dop network doesn't seem to be much use (?), and I've tried messing around with using a dop import to fetch my sim, and send that into a timeshift sop, but then how do I go about caching everything out?

Is there a better way to do this? with more control? less iterations?

Thanks!

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also, how do I blend between time scales in the timeshift sop? I can easily set the time to 1 * .25 or whatever, and slow the entire sim, but how to go from 100% to 25% say over 10 frames?

I tried adding an additional float parm, multiplying the time, and keying that float parm, but that didnt work for me either. it caused the sim to jump

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I suppose you using Voronoi Fracture inside your simulation. That will cause to new points to be created and the timeshift don't have constant information to slow down the simulation.

Can you post your file or a simple version of it so we tests it?

Cheers

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well the timeshift sop works if I set the time to "$T * 0.1". However, I can't seem to figure out how to ramp this up or down. If I create a multiplier and key that, My sim jumps backwards when it starts the blend. I must be doing something wrong, but if at frame 10, the time is $T * 1, then at frame 11, it's $T * 0.1 It makes sense that it jumps backwards. so how to avoid that.

also, I'm unable to use explicit cache with this. although I have a feeling if I turn off integer frame playback, and cache substep data, it may work, but will be limited to the substep data...?

I think I could just use some advice on a good workflow for all this. I suppose if I did get the timeshift sop working as I want, I could just copy it into every object, then cache those out,..? what would someone with a brain do?

Edited by substep

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If you cache your geometry to disk you need to drop down a timeblend afterwards, so it will make substeps for you.

Also a simple way to manipulate the timeshift without math would be, for example, keyframe a value 1 in the frame 1 and a value 72 in the frame 72. Then you just add other key frames in between or just move your key frame 72 to frame 50. That curve can never go slope down, if you do that, then you're reversing time.

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ahh, ok, that's what I was missing. keying it makes a lot more sense. it's working swimmingly. many thanks!

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well I don't think the timeshift sop is gonna cut it. for some things, I could see it being really useful. however, I have objects hitting some glass, and it looks slightly strange with glass shattering before something actually hits it. I know this is due to the linear interpolation of the timeshift sop, but how could I avoid that? different approach?

edit: I think cowboy swapping the objects when they're hit will alleviate this. It causes a little jump, but feels more like impact than anything else.

for something that I couldn't swap out, how best to retime without timeshift sop? Also, anyway to make the switch automatic with impact data?

Edited by substep

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You can raise your substeps and save those as well. Just use $FF in your file name.

By the way, decreasing timescale works really well. Actually it will gave you the same result as increasing substeps.

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ok, I'll give that a go with $FF in the cache name. I did notice that "scale time" on the dopnet works really well. actually, it's exactly what I need for accuracy, but I can't figure out a way to animate it.

edit: well, feeding it substeps doesn't really help, as I would need to give it quite a few to more accurate collisions. I'm at 5-6 right now on the dopnet. I guess right now I'm kinda relying on getting the dopnet's time scale animated and not use interpolated frames or substep data.

Edited by substep

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okay, I think I'm getting this figured out. I'm testing it right now, so it will take some time to compare the results. But I think substepping wasn't helping just cause there wasn't enough steps to make a noticeable difference.

I'm taking 5 sim frames, and slowing them down to be 180 frames. If my math is correct, I'll need 36 substeps to get perfect motion - no interpolation. So If I substep at 18, I'm getting half interpolated frames. so obviously 5-6 substeps was giving me poor accuracy.

I'm simming right now with 20 substeps, so we'll see how it goes.

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well I don't think the timeshift sop is gonna cut it. for some things, I could see it being really useful. however, I have objects hitting some glass, and it looks slightly strange with glass shattering before something actually hits it. I know this is due to the linear interpolation of the timeshift sop, but how could I avoid that? different approach?

edit: I think cowboy swapping the objects when they're hit will alleviate this. It causes a little jump, but feels more like impact than anything else.

for something that I couldn't swap out, how best to retime without timeshift sop? Also, anyway to make the switch automatic with impact data?

could you upload some example file?

do you have your glass prefractured?

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yes, I can throw together an example file. I've been figuring this out with a test file, but it's still probably too big to up, i'll simplify it, and send it off.

yes, the glass is prefractured.

I just want to animate the "scale time" on the dop net, sob, sob, grrrrrrrr

standby...

Edited by substep

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