hi guys
im dying here trying to modefie the first frame for starting simulate exploison on object using pyro fx
any one know how i specifie the first frame for starting simulation because i want my object to start smoke and fire after a 50 frame of animation
any help guys and thank you

The PyroFX Explosion and FireBall shelf tool presets all assume that the start frame is 1.
If you want to choose a different start frame, do the three steps:

1. Adjust the Start Frame parameter on the top level Dopnet node.

2. Change the Creation Frame parameter on the Pyro Object DOP.

3. Look for all the animated channels that adjust the initial behaviour and shift them over so that they align with the start of the explosion.

In the Explosion tool preset, I believe there are only two animated channels. One on the Scale Source Volume parameter in the Source Volume DOP adding the fuel and temperature. The other is on the Pyro Solver's Gas Released parameter. Just open up the channel editor on each of these parameters and select then drag all the keys over 50 frames.

That should do it.


Note: If you want the animation to be automatically shifted procedurally, you can use Motion Effects (CHOPs) to shift the existing animation. For each animation channel you wish to shift, just RMB on that parameter and choose from the “Motion Effects” menu, select the “Shift” option. This adds a Shift CHOP to the key framed animation. Just put your value in the shift start range.

You can have everything driven by a single start frame value. Use either the Pyro Object's Creation Frame parameter or the Dopnet node's Start Frame parameter and channel reference everywhere including the Shift start range parameter to automate it all.

you are a genius man
it will be nice from side effects to make a controler change all this paramiteres because it very important to get something define the start and the end of the effects
i do every thing you said and i shift the animation the problem still is when i change the start frame in dop network to 50 frame all my object disappear and every thing messed up so i keep it at 0 frame
i dont know why but that mean the animation still start at 0 frmae for that i get the source volume appear on my object
any suggestion to make the source volume start just at 50 frame
thanks you

made21
you are a genius man
it will be nice from side effects to make a controler change all this paramiteres because it very important to get something define the start and the end of the effects

All the controls are there, otherwise you'd see a lot more posts about this issue than you usually see…
You must be forgetting to do step 2 on Jeff's answer. You'll find that once you do it, things will work as you want.

Cheers

thank you man for reply
im new to Houdini and i think he is a piece of diamond it just i get losted because im new to it

that's normal, I'm still overwhelmed sometimes, even though I've been using it for a while now

cheers

Here's the file I created when I was making sure I covered all the steps.

I added some notes to make it very clear what you need to do to get this all working. It takes longer to find the two animated channels than it does to rig this all up once you know how.

Be great if the tools created a single entry point to this… nothing ever really starts on frame 1

Yep Peter.
I was thinking the very same thing when I was sussing this out this morning. Yes in production, not often do sims start at frame 1.

We are already creating CHOP networks for many sim Tool presets and would be straight forward to add Shift CHOP offsets for any key framed animation and drive the offset by the Creation Time from the Smoke Object.

thank you jeff for the file that demonstrate every step perfectly
lets talk about ending the effect
i try to make a shift for end and i put the last frame for scale volum source to 0 and for gas release also 0
the animation fade out but not totally
am i missing something ???

So you set the last keyframe for Scale Source Volume parameter to 0 in the Source Apply DOP. That will stop the low level fuel emission after the explosion. That channel also goes on for a long time. Just delete all the keys after the initial start peak emission.

To get rid of all the remaining smoke, you can create a sink field using the Sink tool and use a box encompassing the entire simulation and keyframe animate this on to sink everything away. The value of the sink can be set to below 1 to gradually erode everything away. That's brute force.

You can try the Dissipate settings on the Pyro Solver but internally that is just eroding the “soot” scalar field and won't extinguish the entire effect but if you are not adding fuel at that time just key frame this value to say 1 or higher at the frame you want to dissipate the soot (secondary combustion and expansion). The explosion will play itself out in a more natural way.

thank you jeff i will try it

Awesome information everyone.

Many thanks

old_school
Here's the file I created when I was making sure I covered all the steps.

I added some notes to make it very clear what you need to do to get this all working. It takes longer to find the two animated channels than it does to rig this all up once you know how.

Thank you so much! My first week in Houdini and I tried this for hours before I found your post.