Animated slow motion

[Lummers]

Hi,

I have a fire simulation travelling towards camera which is working fine.
What i want to be able to do is have the fire play full speed to a certain frame and then go into slow motion for a few frames, then re ramp it back to normal speed!
Whats the best work flow for this, i have had a play with the time blend controls, and play speed which is fine for just making the whole sim go slow mo, but how do i animate this as i believe you cant animate the play speed, is this correct?
Any pointers would be most appreciated

[slavina.nikolova]

Hey,


In our Tips and Tricks section has a part called "Slowing Down a Simulation, Animating the Time-Scale, etc." - https://docs.chaosgroup.com/display/...ips+and+Tricks, where you can find an explanation of how to animate slow motion.

In your case the setup will be:

1. Enable Velocity export in the Output rollout. This channel is necessary for resimulation.

2. Simulate your base simulation.

3. When the simulation finishes, you can adjust your Time bend controls to use Cashe Index and animate the Direct Cache Index - that option tells you which cache answers to the selected frame.

4. From the Resimulation rollout, enable Grid Resimulation and enable Use Time Bend Controls.

5. Choose the General-Purpose method and resimulate.


Hope that helps!

[Lummers]

can you explain the cache index and direct cache index, as i played with this and couldn't quite fathom how to do it.

Lets say i wanted normal speed up to frame 50 and then into slow down till frame 80, then back to normal speed.

[slavina.nikolova]

Hey,

If you need the speed to be normal till the 50th frame - the Direct Cache Index should have a value of 0 at frame 0 and a value of 50 at frame 50, since at this frames, with normal speed, these are the caches.

After that at frame 80 pick a cache which gives you the desired slow motion speed - for example 60 or so. Add a keyframe at your last frame with a value of the Direct Cache Index answering to your final cache - for example at frame 100 set the value at 100.

At the attached scene for the simulation I had 100 frames, but since for the resimulation in this setup are added 20 more frames (80-60 = 20) - the animation length should be extended to 120 frames.

Hope that helps!

[Lummers]

Ah ok great thanks for this!