animating particles in slow motion

[Morne]

Hi Guys

I had a problem a while back and today I though about it again. I had a particle system of explosions and rocket exhaust etc that I needed to animate. You will see it normal speed, but halfway through the animation (same shot) I needed to show things happening in slow motion. I had VRay mtl assigned with gradient ramp oppacity map.

The problem was that I could not figure out to "stretch time" to simulate slow motion, without messing up the particle birth. There were either too many particles, too little, going of at the wrong angle, or all of the above. Man I'm struggling to put my thoughts into words today. I hope you guys understand what I'm trying to ask.

Any thoughts on this particle issue?

[instinct]

do you need to slow down (=nonlinear retime) or just have a cut to a different speed ?
If you can cut then simply upping the framerate to render might be an option to simply render inbetween frames.

Kind Regards,
Thorsten

[Neilg]

If you do need to blend into the slow motion, you can up the fps as instinct said, render the entire section in slow motion to a degree you can work out easily (say, 1/10the original), and timestretch it in post to get it back to original speed.

Its wasteful, but if your render times are only a couple of minutes it is a reliable option.

[Shimakaze]

This is how I would do it as well, but you only need to render out the section that should be slowed down (including the blend sections) that way. The rest of the animation can be rendered out normally (or you can use the "render every---" setting to render only every 10'th picture for the normal speed parts)
Sucks that Max can't render out sub-frames...

Vlado, there isn't any way this can be added to Vray is it?
Imagine being able to control sub frame rendering internally in Vray with a bezier curve... woooh! Instant smooth bullet time!

[instinct]

Well you can render ticks cant you ? by setting your timeline to "Frames:Ticks" you also get ticks in the renderdialogue. Never tried that tho as increasing fps seemed to do the trick usually.

Regards,
Thorsten