Pyro slow motion with animated object

[angadrana]

So I have a missile animated with a smoke trail made by using the Flame shelf tool.

 

I want to make the enitre scene slow motion from a particular frame till a particular frame. 2 ways come in my mind but I want to know what's the best way to do it since I'm new to houdini.

 

1. Use timescale setting in DOP? (But how will the missile get slowed down in accordance with the smoke since the missile animation is done with a transform node at the SOP level?)

 

2. Cache the simulation with 10+ substeps and use timeshift to slow the enitre scene down?

3. Your way (the best way).

[StepbyStepVFX]

Never tried, but I would indeed animate the timescale of the DOP.

No problem with the speed of the missile : it's already slowed down in SOP, right ? I think the timescale of DOP is more to be seen as the scaling factor of the time applied to the forces during inegration of motion/fluids equations. So it should be consistent with the factor you applied to the speed of your missile in SOP, but this is a different thing. Just think the speed of the missile itself only impact where will be your fluid source, but the timescale of DOP will impact the speed at which smoke dissipate, how intense is the buoyancy between timesteps, etc. If you slow only the missile, the physics of fluids will remain the same (same speed) andthere will be a discrepency, but if you slow the physics of fluids, the swirls will appear more slowly, and accordingly to the way the missile is slowed down.

Well... that's my opinion :-)

[Midasssilver]

Or, you can just sim the entire thing at the slower timescale, then control the animation post sim by animating a timeshift. Then you don't need to worry about the physics not lining up as the timescale animates.