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How to simulate smoke with pre-roll in Blender

Category : Animation, Tips and Tricks · by Jun 30th, 2015

The simulation preroll

In this small tutorial we will create a smoke simulation with pre-roll, that is a cache on the negative frames in order to run the simulation for a specified number of frames prior to the beginning of the actual animation. Because of that the smoke/fire will be already initiated when the animation starts.

  no_preroll with_preroll

I’ve found those questions online and decided to write a tutorial about it, so if you are interested about the original istructions you can find them here:
http://blender.stackexchange.com/questions/18402/for-smoke-how-can-i-take-certain-frame-of-smoke-and-use-as-initial-frame

Simulation issues

Blender is a great tool but sometimes it will disappoint us, not because it lacks some functionality, but because for some features there is a functionIsThereButWorksOnlyAfterBlackMagicActivation feeling…

I’ve worked with simulations in the cloth, fluid and rigid body field and the ongoing revision of the physic system is a really great and challenging task for the Blender foundation (did you said tornado in project gooseberry?)
Well, my new kryptonite was is the smoke simulation and its parameters.

How to create a smoke simulation with pre-roll

In order to do a bake of the smoke domain with a pre-roll of 100 frames(that is sufficient for my purpose, change it for your own task) you have to follow those few simple steps:

  • Set the cache of smoke domain to “External” and starting from frame -100 (desired pre-roll) to frame x (your total simulation)
    Selection_012
  • If the smoke is particle generated set the beginning of particles also to -100 or you won’t have anything to simulate
  • Start the bake all dynamics. At the end of this process be careful because you can’t touch the timeline or scroll through time. This because if you move the time blender will rewrite (and lose) that part of the cache.
  • Now from your file system navigate into the cache folder that should be beside your blend file and delete all your negative frames (from -99 to -1)
    Selection_015
  • Into blender refresh the cache by choosing the cache folder from “File Path” in the cache settings. This process will update the frame range excluding negative frames (starting from 1)
    Selection_016
  • Save and reopen the file to confirm the reload and finally enjoy your pre rolled simulation!

 

Let me know if you encounter any issue!

This guide is tested with Blender 2.71-2.74

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(7) comments

Aclariel
2 anni ago · Rispondi

Very useful tutorial, thank you!

Anuga
2 anni ago · Rispondi

Why not just set the Scene Start Frame forward 100 frames..?

blenderprops
2 anni ago · Rispondi

Yep! It’s another workaround but works only if you start the rendering of the scene from frame 100.
Some could use the smoke simulation into an already motion tracked, composited or animated scene and e.g. the torch should have a fire from the beginning… this is just my case but I think that it could be useful to others to not change the scene start/end or cache frames

Cheers
Sparazza

Warren
2 anni ago · Rispondi

Thanks! I was wondering, do I really have to make my characters stand around and wait for the smoke to be ready, or what? Very useful tip thanks so much.

vklidu
2 anni ago · Rispondi

Thanks. Just … why you didn’t answer on stackexchange site? Would be more useful for users to find answer there.

    blenderprops
    2 anni ago · Rispondi

    Yep It’s a really good idea to answer there! I’ll post a link to this tutorial
    Thank’s for asking! I didn’t just reply there and instead I wrote this guide because from the user (and my) point of view i’ve sadly discovered that looking for “blender smoke pre roll” on Google there isn’t the stackexchange discussion on the first pages. That’s obviously because the question on that site doesn’t use the word preroll or similar ones, but that function in blender has that name, so I decided to create a guide easily searchable on the internet

    Cheers
    Sparazza

adultfrinendfinder mobile
4 settimane ago · Rispondi

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a massive amount work? I’ve virtually no expertise in programming but I had been hoping to start my own blog
soon. Anyway, should you have any ideas or tips for new blog owners
please share. I know this is off subject but I just needed to ask.
Thanks!

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