Simulate fire as low res and then render as high res

Phoenix General
1

Hi,
is there anyway to simulate fire as low resolution just to get a general direction and then quickly simulate again using data from low res sim to have sharp flames?

Thanks

2

Yup, this is basically what resimulation does.

3

I really like the result from @hammerbchen 's setup shown here: https://docs.chaosgroup.com/display/…/Burning+Chair
3ds Max setup is here:

It’s exactly the type of sim you’re looking for. Cheers!

4

Hi I just tried and it is slower.
Simulating 100 mil grid cells is around 24 sec per frame.

If we sim 10 mil grid cells 7 sec per frame and then resimulate as 100 mil it goes to 38 sec. So total time here is 45 sec vs reg sim 24 sec. So it is not efficient. I am not sure why is it slower to resim. Would be nice to have a better method to make low res flames sharper.

5

This might be caused by several factors - if your simulation is very quick and lightweight, having for example low steps per frame or low conservation quality, it would take longer to read the original cache files and upres them. It would also depend on what storage you read the caches from. It’s very interesting why you are getting such slowdown - our tests here do not behave in this way, and resimulation in higher resolution should generally be quicker. Do you have an example scene of that?

6

Hi, can you try the one I send you with barn fire. If you sim at 10 mil with velocity channel enabled and then resim as 80 mil cells you get longer times overall vs just simming as 80 mil

Also any plans to reintroduce procedural fire like you had in phoenix 1. It would be nice to sim as low res grid but during rendering system create procedural fire. I think Pixar Planes forest fire was done procedurally and it look not bad. i’d rather have this option too with a bit low quality fire that waiting 10 min per frame and you need 1000s of frames to be simmed. Unless network GPU simmulation is coming or like new Houdini sparse volume pyro solver :wink:

7

Would it be possible to fake more detail with just a texture in the modulation slot of the flames (and smoke)? Of course this would require some kind of texture that at least reacts to the motion of the sim, and doesn’t just act independent from it (like a regular noise map). Is there a way to do that?

8

Hey,

You could use the TexUVW channel we have added in Phoenix 4 to achieve that. You can find more about it here - Phoenix for 3ds Max

Cheers,