Hi all,

A nearly up-to-date detailed manual is available here.

Aim is to make you understand the fundamental concepts: this can take a bit more time than applying a tutorial, but at least you know then precisely the reason behind a setting: So after its reading, you will have much much more clouds/smoke in your blender scene than in your head 😉

PS: This would be very cool if somebody could update the blenderwiki accordingly. Indeed, with a few more optimizations and additions, chances are really high that volumetrics make their way toward an official release: As Ton can not integrate a new feature if there is no decent documentation (have you ever seen an empty release log?), we have to make a full-feature wiki. Matt Ebb has told:

Anyone would be very welcome to help fleshing this out straight in the wiki, if there any mistakes I can clean them up afterwards – just getting stuck into it would be great because I don’t have a huge amount of time for it these days. There’s a lot of people here following this progress and offering thanks, which is great to see, but this is one way you can make a considerable concrete difference and I’d very much appreciate any help here.

He has encouraged to use his commit logs as support, so feel free to reuse Matt’s pictures and movies.

So if you want to support this project (better documentation -> more users -> more interest for the project -> more motivation for the coders -> more features/optimizations -> users go nuts), this is the right time to do it

Thank you in advance



35 thoughts on “Documentation

  1. Dennis Fassbaender says:

    Thank you very much!

    Would love to see some good PointDensity-Presets.
    I tryed different things but never got any good result.

    I whant to use the particleSystem- because so i have the most control over the smokes/fires motion.

    So some good settings would be great :)!


  2. Dennis Fassbaender says:

    Thank you! Im missing an emiterobject in this file.
    I added one.
    There is one thing i have in my tests:
    PointDensity only renders smokeparticles near the emitter object.
    Particles that are away from the emitter can´t be seen.
    It looks like a very bad resolution.
    Ill try to upload images for you!


  3. Ruddy says:

    Hi Dennis:
    – Is there enough light away from the emitter? Although the dots emit some light, this may be hardly visible.. About this, you should have noticed that the orange color near the emitter is given by a lamp (dots have no color variation): this easily fakes the irradiations generated by standard combustion
    – More probable: do you particles live long enough? go back to particle system menu, and increase their life, and refresh the baking (if you can not edit it, you must first click on a “free bake” button) with CTRL+A or “bake” button: if you use CTRL+A, you will have to wait some frame before the baking start (if you have a 100 frame animation, CTRL+A will first pass these frame without baking, before passing them again and doing the baking (you should heard hard disk sounds this time)

    Finally, there were already a particle system on the file (you have missed it), but very scale down, near the lamp: select it and click F7, then increase the “Life” parameter, then go back to the point density texture and play with the turbulence button

    take care


  4. Ruddy says:

    – a last possibility was a bug due to the old file version: Matt Ebb has done this with an old sim-physics version, and some files make newer sim-physics crashed… I advise you to create a fresh new file if you are going to invest a lot of time in this effect with the newest sim-physics build.

    However, this is not very probable, because blender structures for storage (sdna) allow a lot of compatibility between various blender forks: if a blender version finds by loading a file an unknown structure, it simply skips it; on the other hand if you load your current file with a newer version, blender will simply adds newer variables when you will save the file. As a example, this file might have been created when turbulences were not implemented, but newer sim-physics build do not prevent you from adding turbulences…

    I am telling that in order that people understand that they don’t have to wait for future builds before doing projects; this would only be the case if the build was very buggy and the same settings were being modified over and over, leading to a lot of differences/corruptions between each version with the same file.
    This already kind of production proven (Promotion Studio), and the setting are more or less “frozen” for a future integration in blender official build, except perhaps the light cache structure, which has to be optimized (or modified?) for animations…

    For next additions, Farsthary will wait for Matt Ebb analysis about the external shading (Matt would like to have a more quicker way to generate the external shadows) and he has told me that he will try to re-implement (like in his old build) an adaptative Size Step, so that you can create huge domains without being bothered by rendering time if you want as an example to fill most of your scene with smoke (parts far ray from the camera (details less necessary) will use big slices while near the camera they will be thiny). This should also dramatically decrease render time of cloudy sky (because we have to use huge parallelepiped for these ones)

    do not hesitate to ask me questions…


  5. Ruddy says:

    ray button in the render menu (F10), you can uncheck the other button except shadow to save some render time

    If this is indeed the problem, this must come from the version change (between the old volumetric build where Matt created this file, and the current one): perhaps if blender do not find all the parameters he expects in a blender file, he loads its factory setting?


  6. Ruddy says:

    I also had to rebake the particle cache. About this, the difference between CTRL+A and bake button is that the last one “secure” your parameters: perhaps this is more advice to use it with volumetric, to not loose the particles whenever we modify the emitter? (have to investigate…)


  7. Ruddy says:

    Tell me if it works…

    ..I have no issues here with the last build (self-compile)..
    Anyway, Matt has done an incredible work with the particle/volumetric integration! 🙂


  8. Dennis Fassbaender says:

    Yes oh my god that is painful for me – im sorry.
    Yes it works- and it looks realy realy good. Ive rendered that file (animation) and im happy to see that it works and it looks realy good!!!
    And im very happy that the precaching problem i had is solved :).

    Whatever- im dreaming from an integrated volumetrics in blender!
    It would be bad, if your great work never would be integrated!

    Same thing with GI- i never understood why blender uses RadioSity and AmbientOcclusion in place of GI.
    At this time i use YafARay- but its not the same as like it would when Blender had its own GI with Caustics (will it have anytime?).

    There are more things me- and some others would like in Blender. I can´t write programs (not as good as you!)- so i wish more stuff from you- much much thanks!!!


  9. Ruddy says:

    Hi Dennis,

    Really glad that you’ve solved this! 🙂
    Now just play with wind/obstacle: I assume that you already now, but just in case: select the mesh you want as an obstacle (begin with simple stuffs like a plane) and go to physics menu (same F7 key: first time physics menu, then particles, etc, (cyclic)). You will see a subpanel with field, and there is a collision panel (collision tab at the background; I mention the field subpanel, because there are plenty of collision subpanel in this menu): just click on the tab, and click “collision” in this panel. Now refresh the cache, and play with the settings….

    You can also add some wind by creating an empty object, select it and go back to the physics menu, field subpanel and select wind in the rolling menu to add a wind field to the empty.. (you can control the wind stength, variation by playing with the settings). Sadly, the wind strenght does not seem to be animatable yet..
    so you have to move the empty to modify the wind in your animation.. You can however deflect the wind with another object (

    Finally the best for the end: do you know the continuous physics options? this allows blender to dynamically refresh the baking, so that you can have an instantaneous preview (provided that your computer is not too old enough (okay with my pentium M 1.7 Ghz with Matt’ file)): this work for particles, cloths, soft-body. Here is the procedure: create a new windows (eg. split the 3d scene), and select the timeline one (click on the icon in the header, and select the one with a clock): this figure allows you to graphically select your frame, to play the animation range that you are interested in with automatic replay for tweaking..
    Now click on the Playback menu of this window and select continuous physics, then click on the play button (or CTRL+A).. and be amazed!
    Now you animation is continuously repeated, but dynamically! this means that you can work on blender as usual, change settings, and the 3D scene is directly refreshed! so you add an object with an obstacle in the meantime, and move it inside the particles, and see them being deflected in real time!!!



  10. Ruddy says:

    Do not worry about the integration, Matt Ebb (famouns blender developer) is co-developer and is very experienced (he has Ton’s trust), so as he reviews (controlled) all volumetric code, quality check is already done 😉

    This will make it for sure.. just a question of months
    For the support, this is really nice from you!!:)


  11. Dennis Fassbaender says:

    Hey much thanks! Yes- there are many things we can do now with the particle-system.
    I tryed to make a fallin bomb with smoke:

    Take a look to that blend.
    The smoke is not looking like it has to :P. The particles from the “bomb” are good, but the smoke not… please take a look and tell me what i did wrong.

    I animated the physics in an offical blender-release and recorded them to ipo :).

    I found a bug:
    Try to enable RAY MIRROR on the bomb. Blender will crash when you press the render button.

    And another thing:
    If found out, that the PointDensity will only work, when the camera is outside the DomainBox!
    This means, using PonitDensity for a volumetric-cloud-fly would not work- while flying throw them.

    Sorry for bad englisch :D.



  12. Okay, it was an issue with particles spacial reference (see the tricky part in the manual about GLobal Space, etc): you had to set Global in Map To (material menu) and select Global Space in the “cache particle in:” rolling menu of the Point Density subpanel of the texturing panel!

    great example by the way!
    Here is your file modified (just activate anew OSA and other parameters of the rendering menu that I have deactivate to decrease rendering time. I have also decrease the step size to increase smoke details (otherwise dotty artifacts))


  13. ..the particle cache has to be regenerated after you download the file: indeed, baked particles trajectory are stored in an external folder (for rendering on renderfarm, this one as to be also send with relative path activated in the blender file), otherwise you have to repeat the “free bake”, “bake” (or CTRL+A) procedure to create the cache anew


  14. One advice: volumetrics uses raytracing, which is time consuming..
    So if you want to do an animation, render in separated layers: I advice you to render smoke separately (eg. as OpenEXR file), then render your scene without smoke and with “ray” button deactivated, then stack the pictures in the node compositor: In you case, as you do not move the camera, you can use only one picture for all the scene… for shadows, you can render only the bomb one in a separate layer… This takes some time to learn these stuffs but saves dramatic amount of time…

    To decrease render time, also try to find a build with sse2/3 optimization (graphicall?): you save easily 30% of the time! 🙂


  15. Ruddy says:

    Hi Dennis,

    With your modified file, there is no camera problem: yes, it was an issue with first volumetric build, but now volumetrics rendering can also be done with the camera inside the volumetrics. Tell me if this is also okay for you


  16. Ruddy says:

    Hi again, I do not have the ray mirror issue, so there is no bug in the code (last linux build)… try on another system if available? (mac, win, linux?)


  17. Dennis F. says:

    Hi! Thank you!
    For the interested people, the link above is the rendered animation.
    Ill test other things in the next days and render some animations.

    Very great to see how helpful you are!

    Please tell me: Who is working on true volumetrics?
    I know FarstHary,Ruddy, Matt Ebb …. just interested in that ;).

    Have a nice week!

    Ahja, sorry no other system to test


  18. Ruddy says:

    Nice video! 🙂

    I am just a friend from Farsthary who manages his blog when he can not get connected 🙂 (he has no internet connection, only at his university a few hours weekly). To answer your questions:
    * Farsthary is the original developer: all the first builds are from him, and he has also written the fire/smoke simulator. He codes about 4 hours daily for the community..
    * Matt Ebb has rewritten his code in a clean way (more structure, new user interface), point density stuffs
    * Farsthary is improving this anew (MLS patch, depth cutoff, shadow)

    Thank you, I also wish you a good week and success in your VFX experiments! 🙂


  19. Ruddy says:

    Hi Falgor!:)

    Really interesting! As soon as Farsthary includes adaptative step size, this will dramatically reduce huge clouds render time. Do not hesitate to contact him if you have suggestions: despite he has little time on internet, he takes care of everybody (I often send him email and have personal answers)
    I wish you a lot of success in your VFXs researches!
    take care


  20. Dennis F. says:

    I tryed some things with the turbolence particle over age and so on … i whanted smoke that starts with blue and end with red ^^ … just testing it, but there is no effect using colors.
    Can you help me?

    And: Did i understand it right: Everytime when i change iE the camera-movement or something else i have to RE-BAKE the particleSystem?

    When i do not i have crazy effects (smoke, where no particles are) :).

    Thanks for helping :).


  21. Ruddy says:

    Hi Dennis,

    You have first to tell the texture to affect the color: go to Map To subpanel, and select also “Emit Col”: now, if you activate the color band in the Point Density subpanel, this should work; but remember: the color of your particle is a blend between the color band and the basic material, so if your basic material has a strong color, this may hide/lessen the effect (see the manual for more details)


  22. Ruddy says:

    About the cache, you do not have to bother about it as long as you do not modify the emitter: the bake button is only here to “freeze” the cache: if you use it instead of automatic caching after an animation cycle (replay of CTRL+A), this tell blender to always use the past cache and to not refresh it, so it avoids you to loose it by accident… I am not a specialist, so I advice you to make experiments (as an example, it has taken me several hour to understand subtile hair tweakings with the same particle system..)

    So you can move anything you want without thinking about the cache: it is only if you rotate/scale it or if you add a new interacting object (obstacle/wind) that the cache will disappear and be refreshed at the next animation cycle except if you use the “bake” button. (I do not know if I am clear enough)


  23. Dennis F. says:

    okay- i understand it .. was still logical, but sometimes i try so many thing that i forget the simple things 😀 … ill try it.

    Next thing is i whant a more detailed smoke. I made a scene with an obstacle (text) and thought it would look more nice, if the smoke is finer – more like the smoke from voxeldata (your simulator).

    I sent that blend to Farsthary.

    Videos from my trys will follow 🙂



  24. Ruddy says:

    Hi Dennis,

    Yeah, this is logical but not so easy to remember for me at least (it has taken me a dozen of hours to understand most of it in order to write the manual), so do not feel ashame to ask questions: the more features there are, the easier it is to get lost

    Hope that you will keep posting cool VFXs 😉


  25. ya the documentation is one of the best part of the programming i am php programmer but now i am hanging in one condition if i have a documentation of this project then i can solve it now


  26. When deodorizing walls, it is best to keep in mind a few safety measures.
    Richard Keyes at Russell Clinic, a town south of Los Angeles,
    Ca, USA. Rights of Physically Challenged Occupants – Renters with particular physiological disabilities may have other legal solutions at their
    disposal to cease drifting smoke from coming
    into their domiciles.


  27. Right here is the perfect webpage for everyone who would like to
    understand this topic. You understand so much its almost tough
    to argue with you (not that I personally will need to…HaHa).
    You definitely put a new spin on a topic that has been written about
    for decades. Wonderful stuff, just excellent!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.