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Thread: Volume Render in 2.5...

  1. #1
    Member NRK's Avatar
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    Volume Render in 2.5...

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    CLOUD SCRIPT THREAD



    See my vimeo tutorial on the Script here:



    Dark Scarab did a nice tutorial on how to use the cloud generator(it's somewhat sparse, but for those that do not like my vimeo tuts here's a written one):

    http://www.darkscarab.com/tutorials/...ticle%20Clouds

    Also another tutorial on the script here making a tornado:



    Here are some clouds animated:



    Here is a Billboard Animateable Cloud Tutorial:










    Notes about the script:

    Be aware that some things are created in memory that I cannot delete. I tried to use commands like main.materials.remove to clean up memory after degenerate, but it only crashes blender so degenerate leaves lots of junk in the memory of your file that will eat into your file size, so degenerate sparingly.


    Cloud Script:


    As of 28315 Script now included with BLENDER!
    No more installing etc.
    Just go to preferences AddOns and enable the script! The version included is my latest and degenerate now works properly so have fun!

    OK, so I've spent quite a few hours working volumetrics because I REALLY want clouds and thought I'd post what I have.

    Here's a tutorial I made on somewhat how to do it with nodes....



    And here is the fairly old volume point density tutorial



    And here is a quick flythrough:



    Notes about how to do volumes:
    Here are some general notes about volumes from Matt Ebb (the creator of volumes)
    Anyway, the main thing to realise with this stuff is that it's 'physically based'. That is, it works internally based on physical principles of how light works in reality. So, it's important to remember that in rendering, it's all about light, and the final picture you get (just like in a real world camera) is just the resulting light that's made its way through the scene and into the lens. That light can be emitted from a light source like a lamp, or coming through/from the sky, or being reflected off a solid object. In physical terms, there's no difference between light that has reflected off an object (eg. the resulting color coming to the camera after a solid object has been shaded) vs the light being emitted from a lamp, it's all just light.


    When you think about it like this, there's not really such a thing as 'transparency', its more like 'how much light is transmitted through the volume' - i.e if lots of light passes through from behind, its transparent, but if the volume blocks out lots of light from behind, it becomes opaque. But to keep this physically consistent, this doesn't just govern 'the light coming from behind' (i.e. transparency) but also the way that the volume reacts to light that's coming into the volume from light sources. This must be treated consistently in order to get realistic results.


    One other disclaimer I should add is that (i regret) that the system has some problems atm that may not be fixed soon. When I merged this code into blender 2.5, the plan was that we would have a new shading system, implemented during durian, for the 2.5 release. The current shading system in blender is really nasty ancient code, and it's not very well set up for more sophisticated stuff like volumes, so there are several issues such as volumes interacting with refracting/reflecting solid objects that can have problems, among other things too.


    Some of this i was able to hack around with dodgy workarounds, but some of it is just really difficult in the current architecture. I didn't think (and still don't) it was worth my time and frustration spending a lot of time making even more dirty hacks to try and get it to 'kind of work' especially with a new shading system around the corner (bmesh syndrome!), so I've ignored some of those things. But now it seems we have no new shading system, and are a bit stuck with what we have for the time being. So unfortunately the volume rendering isn't up to the standard of quality that I really hoped it would be, which i'm unhappy about, but there's not a lot I can do about it right now from a practical standpoint :/


    So, with all that said and in mind, this page might be a bit more understandable: http://wiki.blender.org/index.php/Us...olumeRendering
    and also for some more background, you can read here too: http://mke3.net/weblog/volume-shading-updates

    In blender now, 'transmission' is a kind of inverse. Transmission defines the colour (and intensity) of the remaining light after it has entered, and then been absorbed or scattered out of the volume. So in a sense you're indirectly controlling how much light gets lost, by defining what the remainder should be. The reason it's done like this is mainly because it's more intuitive - you're controlling how the end result should look (eg. 'blue') rather than specifying the colour of light that gets lost (orange) that would leave your final result that is blue.


    Reflectance is a non-physical parameter i added, which is an exception to all that previous stuff i wrote above It's a bit of a multiplier/tweak to let you control the colour/intensity of the reflected light (i.e. the light heading out of the volume and towards the camera) easily. it lets you do unphysical things like if your turn it up high, it will mean that more light is heading out of the volume than what entered it (since it's scaling up the amount of light that gets reflected). This is un-physical, but can be useful if needed, though it's better to use the non-physical stuff as a last resort after working with the other settings.
    /
    The texture stack is how you control volumes, the graphic below maps how the texture parameters to the actual material paramters:

    These are my definitions from trial and error (not correct! but possibly useful)
    Density:Where the volume is.
    Scattering: How whispy the volume is 0=really faint, 10 = absorbs a ton of light
    Asymmetry: How effective the Scattering is (0=scattering is really whispy even all the way to 10) as you go higher material gets really black and scattering gets more potent. Also effects how much volumes glow when backlit.
    Emission:Make the material not black anymore.
    Reflection: Leave at one because dropping it lower makes material black and higher is warned against. (haven't played with this one too much)
    Resolution: How accurate the shadows are. Lower resolution puts the shadows in the wrong areas and looks weird.

    Step Size: How Pixelated the volume is. If this number is too large you will get weird star shaped spots in the volume.

    Ok, I'm sure Matt Ebb is going to shoot me for the above definitions, but I don't have all his technical knowledge and I want to make pretty pictures and these help me do it. Please comment and Correct me... Anybody?

    Happy Voluming!

    Here's more renders........
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    Last edited by NRK; 26-Dec-10 at 01:25. Reason: Made video links interactive
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  2. #2
    Member NRK's Avatar
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    Ok Here's another try.

    Ok, I've updated to the latest SVN and tried another cloud. I've noticed a few artifacts here and there, but not bad so far. I must say I am REALLY enjoying 2.5's interface! It is awesome, WAY more intuitive. Thanks Devs. I've attached the .blend for the latest if anyone is interested.... anybody.....anybody........?

    Also I made a video tutorial on what I'm doing if you're interested:


    http://www.vimeo.com/6450820
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    Last edited by NRK; 08-Sep-09 at 23:51. Reason: added tutorial link
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  3. #3
    Member NRK's Avatar
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    Another Attempt

    I made another attempt using the latest SVN. I think I'm getting closer. Also note I've got the .blend files attached if you want it.
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  4. #4
    You should turn town the alpha, right now they look like dirty sleet.
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  5. #5
    Agree that the alpha values need work -- these are way too hard-edged to be clouds as I know them (and I fly gliders, so I know CU pretty well :P ) Still neat to see this in Blender! I should try it.



  6. #6
    Member Ace Dragon's Avatar
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    Have you tried to use a volume filled with particles and using the point density texture? That could give you softer clouds, also use a clouds texture to subtract from the density to make it look a little softer.
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  7. #7
    Member NRK's Avatar
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    Thanks for the comments! I agree about the edges. I would love to have a texture node that tells me how far away the closest face is so I could make the center of the clouds denser than the outside. The alpha is easy to do, but it won't help with the hard edges, I'll try it tonight and post it for you. I will continue down the path of trying point density with particles, but I haven't figured them out in 2.5 yet. I am using a cloud texture for density with nodes subtraction to get the interior volume, that's what gave me the first post above, but obviously it has it's drawbacks. Just an FYI.... I found I have to light the coulds from below to simulate reflected light from the earth.
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  8. #8
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    Implementing your suggestions... moving on to particles.

    I think I have maxed out node textures. I gave them more 'alpha' per your suggestions, (in volume speak I reduced the density). The thing I have always struggled with making cloud textures is you want wispy low densities on the edges, but then you want the cloud to be opaque in the middle. With no way in nodes to determine how close you are to the edge of a cloud you have to apply it to an entire cloud and making the edges wispy enough you make the whole thing see through. Anyway, I'm moving on from nodes and trying particles..... wish me luck!
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  9. #9
    Member NRK's Avatar
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    So who says 2.5 doesn't ROCK!

    Ok, so I pulled down the latest 2.5 and nodes are broken, but regular old materials work just fine! Here's a render I did messing around in one evening. I really had to monkey around with lighting because volumetric shadows aren't there yet.... but hey WHAT FUN IS THIS!
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  10. #10
    Member NRK's Avatar
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    One More Just for Fun

    I feel the need to go flying.... Don't you?

    I am using 23617 for these renders... Fly Mode is now enabled... Thanks Guys!
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  11. #11
    Member JayDez's Avatar
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    The last one look the best. The first ones looked a bit to much like foam. But good work can't wait till the final release of 2.5 when EVERYTHING is done!



  12. #12
    Member NRK's Avatar
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    Volume Materials?

    So are we going to start being able to submit volumes materials for inclusion in Blender?
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  13. #13
    Member NRK's Avatar
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    ParticleClouds

    Ok, so I did this with 23890 which is quite crashy, and doesn't save the Particle Name in the point density texture so if you open the file you have to go to the point density textures and select the correct ones because they don't save.... but man what FUN! Particles are going to make clouds ROCK! I just wish editable particle systems allowed you to sculpt static particles, but oh well.... Enjoy!
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  14. #14
    Member NRK's Avatar
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    Ok so I posted my latest render at the top because this one is worth keeping. It uses nodes and particles... man what a fun learning process! If you don't like blender now.... just wait ... you will!
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  15. #15
    Member NRK's Avatar
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    I just added the new tutorial link to the top:

    http://www.vimeo.com/7177831
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  16. #16
    You're definatly getting there. Just keep making that stuff over and over again and you'll get better. Sorry, don't have any advice.



  17. #17
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    In case you thought I wasn't working on it anymore...

    So every couple of weekends I make another stab. Below is a picture I took from an airplane that is my goal and at the left is where I'm at. I have played and played with the features and I am pretty much at a standstil until Jahka gets texture effecting emission of particles which looks like is going to wait until he gets through finals.
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  18. #18
    Member JayDez's Avatar
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    Looking nice! I got to the bottom post and for a moment thought the picture on the right was from blender. It would be amazing if we could achieve that realistic a quality with just volume rendering..



  19. #19
    Member NRK's Avatar
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    Ok figured out a way to fake Particle textures.

    Ok, so even though we can't control emissions of particles with a texture yet I figured out a way to do it. And I may even like this way better than textured emission because it allows me to control the look more.

    Take a plane and subdivide it a bunch of times. Then apply a displace modifier using a good nodes based cloud texture for plenty of variation. Then apply the modifier and looking at it from the side, in edit mode delete all verts in the lower 1/3 of the displaced plane. This gives you the picture below. Then use this object as a particle emitter. Emit particles up applying a whispy texture with a point density, then emit particles down using a more solid point density texture... voila!

    Let me know if anyone is interested in a tutorial on how to do this or want me to post a .blend with textures (I'm hesitant because this one is 18 meg and has a weird bug where the camera seems to have a weird offset from where it actually renders).... anyway, I'm getting closer!

    P.S.
    for this render:
    all textures applied to density
    Density Scale: 1.14
    Scattering: 3.17
    Emision: .28
    Asymmetry:. 252
    Reflection: 1.00
    Resolution: 60
    Step Size: .05
    Depth Cutoff: .01
    Sun Energy: 5.71
    Version: 2.5 alpha 0
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    Last edited by NRK; 15-Dec-09 at 08:47. Reason: added settings
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  20. #20
    Member UglyMike's Avatar
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    Nicely done. I would suggest you lose the 'background clouds' as they are now pretty much spoiling the effect.
    I wonder, does a flythru work with this setup?
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