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Thread: Controlling the size and falloff of Volumetric Fog

  1. #1

    Controlling the size and falloff of Volumetric Fog

    Ive posted on this subject before... I make a lot of use of the fog settings under the Render Properties > Volumetrics tab.

    I like it because its simple to use and more importantly it renders really fast compared to using Hypervoxels or primitive volumetrics.

    From what my layman brain can tell, with standard fog under the Volumetrics tab, Lightwave is adding fog according to a kind of distance form camera formula.

    Ive always wanted a way to control how "large" this fog field is. Specifically for me, control in the Y axis would be great - when doing landscapes I want the fog to be infinite in the X and Z plane, but I only want it to extend a smaller amount into the Y axis, so that it hugs the ground plane.

    I submitted a feature request for this, and got the following respnse:


    "Nodes should allow this control.

    Thank you for your report.
    --
    LightWave 3D Group Support"


    Does anybody out there have any idea how I would set this up? I cant find any node button under the Render Properties > Volumetrics tab.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  2. #2
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    Ask him to clarify
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  3. #3
    Medical Animator mummyman's Avatar
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    Are you in 2019? or 2015? In 2019 there is an edit node graph for "use volumetric scattering" which may get the look you are after. I haven't had time to check into it yet.

  4. #4
    Quote Originally Posted by Asticles View Post
    Ask him to clarify
    Haha

    i did!

    - - - Updated - - -

    Quote Originally Posted by mummyman View Post
    Are you in 2019? or 2015? In 2019 there is an edit node graph for "use volumetric scattering" which may get the look you are after. I haven't had time to check into it yet.
    Thanks mummyman, Im in 2019

    I found the node editor for scattering, but I assume thats to control the nature of the volumetric scattering effect. I dont see any node controls in there for distance/falloff/type etc....
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  5. #5
    Medical Animator mummyman's Avatar
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    hmm.. I was only thinking if it was on a light or something, it could be piped in with a falloff to a null or something. Not exactly the same I guess.

  6. #6
    most likely 'Fog Volume' controlled by a null, that is a volume attached to a null that allows for nodal control, not a volumetric fog from the BG options window or the one in the volumetric section of the properties window, either of which do not

  7. #7
    Quote Originally Posted by gerry_g View Post
    most likely 'Fog Volume' controlled by a null, that is a volume attached to a null that allows for nodal control, not a volumetric fog from the BG options window or the one in the volumetric section of the properties window, either of which do not
    Thanks for the reply gerry_g, but I am not understanding you...

    Are you suggesting I use a Null as a Volumetric Primitive? I want to avoid that approach as it pushes up render times massively. The simple fog option in the Render Properties is the kind of "fast fog" I am wanting.

    Where would one find this Fog Volume controlled by a null that you are mentioning?
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  8. #8
    skeptic lertola2's Avatar
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    Instead of using volumetrics you could just add an opaque ground plane object and move it up over one frame. If you render with motion blur you get a fog effect. Set the blur length to be 100% for the fog to cover the whole distance of the move:

    Click image for larger version. 

Name:	ground_fog.jpg 
Views:	67 
Size:	425.6 KB 
ID:	146629
    Last edited by lertola2; 01-14-2020 at 09:42 PM.

  9. #9
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    Great possibility for faking the fog with the ground plane motion blur!

    Since you don't want / need textured fog, you may also get OK results by using a very large Step Size on the Volumetric null to significanly speed up the render.

    A sample scene is attached:

    Click image for larger version. 

Name:	VolumetricNull_NoTexture_LargeStepSize_0000_1280x720.jpg 
Views:	73 
Size:	565.8 KB 
ID:	146634 1280x720 render took 34.4 seconds on my laptop

    Here's the Volumetric Null setup:

    Click image for larger version. 

Name:	VolumetricFog_NoTexture_LargeStepSize.jpg 
Views:	67 
Size:	1.39 MB 
ID:	146632

    The Volumetric Null is not only stretched to (50x,4x,50x) from a 1-meter radius, but it's also moved toward the camera and down to show the top edge of the Cube-type volume.

    Good luck!
    mTp
    Attached Files Attached Files
    Last edited by MonroePoteet; 01-14-2020 at 10:43 PM. Reason: Reference motion-blur ground plane; add 1280x720 render, time

  10. #10
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    Ive posted on this subject before... I make a lot of use of the fog settings under the Render Properties > Volumetrics tab.

    I like it because its simple to use and more importantly it renders really fast compared to using Hypervoxels or primitive volumetrics.

    From what my layman brain can tell, with standard fog under the Volumetrics tab, Lightwave is adding fog according to a kind of distance form camera formula.

    Ive always wanted a way to control how "large" this fog field is. Specifically for me, control in the Y axis would be great - when doing landscapes I want the fog to be infinite in the X and Z plane, but I only want it to extend a smaller amount into the Y axis, so that it hugs the ground plane.

    I submitted a feature request for this, and got the following respnse:


    "Nodes should allow this control.

    Thank you for your report.
    --
    LightWave 3D Group Support"


    Does anybody out there have any idea how I would set this up? I cant find any node button under the Render Properties > Volumetrics tab.
    I think they ment nodes should allow for this control, within the newer global scattering system, I think Chuck mentioned that a tutorial was on the way for setting it up, but I think it may have been forgotten, or not having time to do it.

    Not sure if Janti is still with them, he did some nodal tricks with atmospheres, so I think he would the one to do it.

    I havenīt looked in to it properly either, I prefer to add volumetric items and stretch and move as i want, but it can also be slow to render.

    such as this..which took to long to render..



  11. #11
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by MonroePoteet View Post
    Great possibility for faking the fog with the ground plane motion blur!

    Since you don't want / need textured fog, you may also get OK results by using a very large Step Size on the Volumetric null to significanly speed up the render.

    A sample scene is attached:

    Click image for larger version. 

Name:	VolumetricNull_NoTexture_LargeStepSize_0000_1280x720.jpg 
Views:	73 
Size:	565.8 KB 
ID:	146634 1280x720 render took 34.4 seconds on my laptop

    Here's the Volumetric Null setup:

    Click image for larger version. 

Name:	VolumetricFog_NoTexture_LargeStepSize.jpg 
Views:	67 
Size:	1.39 MB 
ID:	146632

    The Volumetric Null is not only stretched to (50x,4x,50x) from a 1-meter radius, but it's also moved toward the camera and down to show the top edge of the Cube-type volume.

    Good luck!
    mTp


    Good setup there MoroePoteet,
    I got 7,2 second in render, but that was on desktop Asus Rog G20CB
    Changed to have non texture mode as opposed to non-pyroclastic and got only a speed increasement to 7.1 seconds, so not worth it...you would also have to drop down absorption and chance emission scale to something like 0,02 to get close to the
    original.

    One thing to be careful about is the emission, normally I donīt think you should need to use that, since it actually emitts light particles, you can instead just either correct the absorbtion amount and color, etc, or set a scattering value and do the same there for the color.

  12. #12
    MonroePoteet, Prometheus and lertola2 - thanks so much for the help with this, you guys are awesome.

    Monroe, that volume setup is great and the step size adjustment seems to make a big difference to render times.

    lertola2, the moton blur trick is really interesting but I gave it a try and it didnt quite work out for what Im trying to do in my scene.

    Prometheus - as always those clouds are looking epic. They seem to be getting better and better everytime you post something.

    So here are some renders showing different techniques and the looks (and render times) I am getting from each.

    Click image for larger version. 

Name:	15sec_Fog_single_colour.jpg 
Views:	59 
Size:	415.7 KB 
ID:	146635 15sec, one colour fog from Volumetrics tab in Render Properties
    Click image for larger version. 

Name:	18sec_Fog_Backdrop.jpg 
Views:	61 
Size:	510.9 KB 
ID:	146636 18sec, "Use Backdrop" fog from Volumetrics tab in Render Properties
    Click image for larger version. 

Name:	39sec_Volumetric_Null.jpg 
Views:	61 
Size:	467.8 KB 
ID:	146637 39sec, Volumetric Primitive Null with step size set to 25m
    Click image for larger version. 

Name:	469sec_Hypervoxels_sprites.jpg 
Views:	58 
Size:	464.0 KB 
ID:	146638 469sec using Hypervoxels sprites

    The Hypervoxels one was a total render killer even though it was only using sprites. Overall, I think I like the "Use Backdrop" fog one the most - thats using the fog from the Volumetrics tab under Render Properties
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  13. #13
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    MonroePoteet, Prometheus and lertola2 - thanks so much for the help with this, you guys are awesome.

    Monroe, that volume setup is great and the step size adjustment seems to make a big difference to render times.

    lertola2, the moton blur trick is really interesting but I gave it a try and it didnt quite work out for what Im trying to do in my scene.

    Prometheus - as always those clouds are looking epic. They seem to be getting better and better everytime you post something.

    So here are some renders showing different techniques and the looks (and render times) I am getting from each.

    Click image for larger version. 

Name:	15sec_Fog_single_colour.jpg 
Views:	59 
Size:	415.7 KB 
ID:	146635 15sec, one colour fog from Volumetrics tab in Render Properties
    Click image for larger version. 

Name:	18sec_Fog_Backdrop.jpg 
Views:	61 
Size:	510.9 KB 
ID:	146636 18sec, "Use Backdrop" fog from Volumetrics tab in Render Properties
    Click image for larger version. 

Name:	39sec_Volumetric_Null.jpg 
Views:	61 
Size:	467.8 KB 
ID:	146637 39sec, Volumetric Primitive Null with step size set to 25m
    Click image for larger version. 

Name:	469sec_Hypervoxels_sprites.jpg 
Views:	58 
Size:	464.0 KB 
ID:	146638 469sec using Hypervoxels sprites

    The Hypervoxels one was a total render killer even though it was only using sprites. Overall, I think I like the "Use Backdrop" fog one the most - thats using the fog from the Volumetrics tab under Render Properties
    good look there with sprites, but I can not for the life of me understand how you can get even worse rendertimes with that, when testing in 2019..it is faster than the other methods, or did you go back to 2015? or did you have a texture on the sprite?

  14. #14
    Thanks Prometheus

    Im glad you mentioned the long render time for the sprites - it pushed me to relook the scene and by bringing down the particle count and increasing the particle size Ive managed to bring it down significantly with a similar look.

    This frame took 65 seconds to render and has 2000 particles. The previous 469 sec version had 10000 particles I think. There isnt any texture on the sprites and there wasnt in the longer render version either.

    Click image for larger version. 

Name:	65sec_Hypervoxels_2000_particles.jpg 
Views:	48 
Size:	471.5 KB 
ID:	146639
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  15. #15
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    Thanks Prometheus

    Im glad you mentioned the long render time for the sprites - it pushed me to relook the scene and by bringing down the particle count and increasing the particle size Ive managed to bring it down significantly with a similar look.

    This frame took 65 seconds to render and has 2000 particles. The previous 469 sec version had 10000 particles I think. There isnt any texture on the sprites and there wasnt in the longer render version either.

    Click image for larger version. 

Name:	65sec_Hypervoxels_2000_particles.jpg 
Views:	48 
Size:	471.5 KB 
ID:	146639
    Ahh..particles, thought you used one single null, sort of stretched..you have to be careful with sprites though since there can be clipping artifacts.

    It just struck me, the fog (legacy system) doesnīt have the texture button as in 2015, it had an option to use the gradient and camera gradient...but not anymore it seems.

    But, what you also can do, check use backdrop in the fog panel, and simply use textured environment, you can use a pitch gradient, or just use a procedural gradient, and lowering texture effect so it will be so subtle it hardly is seen, by using falloff, and minus plus position, One may get good effects there.

    Not sure if I am able to set it up and post it today.

    There is also and option to use that fog item posted, but adding a color layer, and in that color layer use the value procedural, and just use the falloff and postion settings there.

    But as the support team told you, you should be able to use nodes, is all wrong..at least for backdrop fog, there is no options for that...only if they ment using global scattering.

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