Hi - is there a way to change the speed of a simulation without changing its overall evolution and appearance?
When changing the Timestep in the Simulation-Time Control settings, often the simulation itself changes drastically. For example, the volcano preset (009-Volcano.ember) doesn’t create a massive explosion cloud when the Timestep is changed from 60 to 960.
The appearance I am after is something more like filming the simulation at a higher frame so that it can be slowed down in post production.
I’m guessing changing the Timestep doesn’t work as it impacts all the evolutions that happen per second so I’m hoping its possible at the Render or Camera stage but I can’t see anything related to time in those nodes.
Or is Timestep the only way to do this meaning that other parameters will then need to also be scaled accordingly?
No way to do this yet. We have plans for retiming in our big update early next year. I’d not recommend using timescale as it breaks everything you had. If you want a faster sim, do it in post. If you want a slower sim, use optical flow in post.
Thanks for your reply, that’s good to know - I’ll look into the post methods for now.
Do you think it would be possible (with enough knowledge how the physics of EmberGen simulations work) to build a super slow sim from the ground up? That is - start with a much larger timestep and scale all the variables based on that from the outset?
Does that require expert level physics knowledge or is it just not possible because of how the underlying equations work?
Just an update to this question. I tried the optical flow methods and for complex simulations like fire, the estimation algorithm doesn’t work nearly as well as adjusting the timestep which really does produce the look of high frame rate photography.
In some sims, it’s possible to tweak the settings to re-create something like its original appearance so it seems technically possible but once the timestep goes paste 240, they generally break.
Are there any further resources to study to help get a sense of how to build simulations from the ground up?
The documentation is great but it I’m wondering whether its essential to study the underlying physics in order to produce new custom simulations from scratch.
So the problem with adjusting timestep is that it introduces significant issues with the simulation and you often will not get much detail at all.
As for resources for building simulations from scratch, you can either watch some of the live streams on our youtube channel where I do things live, or just mess with the settings in the simulation node.
Want the smoke/fire to raise faster? Use buoyancy. Need heavy smoke? Increase the smoke weight. Want fuel to burn faster? Increase oxygen amount, maybe reduce smoke production, and increase fuel consumption.
Honestly, best learning resource besides our live streams is just playing with parameters. The great thing about EmberGen is that it instantly responds to inputs.
Thanks for your reply Nick. I’ve been going through the live streams and they’ve been very helpful
One suggestion though - the live streams seem to cover alot of different tutorial info but in no particular order and without a way to know what content is in what stream. I’m currently having to keep a separate document with timestamps grouped into content areas.
It would be great if the streamed tutorials could focus on single topics for longer in a such a way that they really that cover specific content area in depth in a single video. For example - a video that just looks at how to get the best results for a certain kind of simulation (e.g. fire explosions). Watching the streams, it always feels like there is a huge chunk of information left out as it’s always a quick summary of a particular preset or technique.
Perhaps a walk through of building some of the more complicated presets from the ground up would help us understand what we need to in order get better at building our own custom sims.
I have plans for a serious tutorial series vs having people rely on live streams like they do now. Live streams are typically for going over new features and how to use them. We haven’t done a serious string of tutorials due to us knowing the UI was going to change drastically throughout the beta. After January, you’ll see our in-depth series of tutorials start to come out.
I have a similar question: Is there a way to globally slow down the animation of an EmberGen project file, like the Smoke Shockwave preset, e.g., make it evolve over 128 frames rather than 64? I would like it to take approximately twice as long as it does now. I’ve reviewed tutorials, but so far no joy.
Sounds like from this thread there is no way to do this (yet), but this thread is nearly three years old. Has anything changed since? Thanks.
Hi all,
This is exactly my problem, too. More specifically, I need more vdb files from an explosion to drop them into a 300 frame video, but the explosion is only 64 frames long.
I have been playing with settings, but all I achieved was prolong smoke generation. The fireball always dies at frame 64. Is there any way to make the actual explosion last longer?
Thank you, guys
Not all input changes responds directly while doing it in the continuous simulation, most stuff do however, there are some parameter changes you will have to reset the simulation in order for it to take effect.
Always have your index finger on the “r” shortcut, the thumb on the spacebar so you can reset and play fast, set a repeat frame that isn´t too long so you can more easy tweak parameters.
I often just cut down every channel I can for the forces, anyway, so I start with the simples fluid flow upwards without any forces, even turn off bouyance, all other stuff for wind, pressure and vortices I set to zero and then going throgh all parameters and increase them to see where the effect takes place.
Of course, there are so many forces that is dependet on eachother, so you will not get a full cover of testing it this way.
I Love Embergen, I haven´t touched any 3D tool for many many months now, including embergen, but I am soon back at it again for this year.
Depends on what is triggering the explosion, for basic surface emitting you can extend the flame intensity, also the combustion settings you can go in to advanced mode and have more controls to play with fuel, oxygene, In the emission tab of the emitter, you can also increase fuel rate wich will let the amount of heat/fire continue to prolong the explosion sort of.
Also…the pressure rate may help to extend the explosion.
For any particle emitter driven explosion, you have to increase age lifespan of particles or set continuous birth rate.
Increasing time rate to give it a bit of longer simulation as well as smoother, but increasing other fuel rate settings, flame intensity may also be a way.
Also…setting fuel rate to replace may give you a longer initial explosion.
So many ways to do it, the combustion settings to advanced allows you to turn down flames loss, increase temp gain and much more.
So try turn down smoke settings, rate and let fire/temp/flames and fuel run as long as you need, and then turn up smoke settings.
There should probably be some free samples you can study that has explosions lasting longer than 64 frames.
An explosion isn´t long, unless it is triggering other fuel to explode, so you would need several burst, or more fuel to have it last longer.
And…if you see that the smoke fluid is going on longer in the timerange for the fluids, you may also adress the actual shading and not the fluid generation itself, you can balance smoke and fire so that the fire propagetes through more within the smoke as it lasts longer.
And always, always check all Scene content/presets, in my older version there is at least 100.
And you can always check the VDB assets, some of those laters also include the actual presets for you do load in to Embergen to check how it is set up.
There could be issues loading perhaps depending on Embergen versions…
