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Thread: Limiting a Fog's Height on the Y axis?

  1. #16
    Curmudgeon in Training Ma3rk's Avatar
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    Since the volumetric objects are separate & have their own settings, sure, why couldn't your simply have both?

    Here's a W.I.P. that I always intended to have in heavy atmosphere, so a Before & After if you will:

    Click image for larger version. 

Name:	TramLine_NoVolumet_12m30s.jpg 
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ID:	145315

    And with volum cube:

    Click image for larger version. 

Name:	TramLine+Volumetrics_63m47s.jpg 
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ID:	145316

    Just a tad different feeling to be sure.

    Something to note though are the settings. Mine are all on the right hand side of the decimal point in the tenths and thousandths, whereas Prometheus's are in the low single digits. I suspect that's due to the scale & camera distance, etc. but have you tested with foreground & distant objects P.?

    Click image for larger version. 

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ID:	145317
    "Never be a cat in a cartoon. Never." Chief Wiggum

  2. #17
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by Ma3rk View Post
    Since the volumetric objects are separate & have their own settings, sure, why couldn't your simply have both?

    Here's a W.I.P. that I always intended to have in heavy atmosphere, so a Before & After if you will:

    Click image for larger version. 

Name:	TramLine_NoVolumet_12m30s.jpg 
Views:	56 
Size:	621.9 KB 
ID:	145315

    And with volum cube:

    Click image for larger version. 

Name:	TramLine+Volumetrics_63m47s.jpg 
Views:	59 
Size:	354.5 KB 
ID:	145316

    Just a tad different feeling to be sure.

    Something to note though are the settings. Mine are all on the right hand side of the decimal point in the tenths and thousandths, whereas Prometheus's are in the low single digits. I suspect that's due to the scale & camera distance, etc. but have you tested with foreground & distant objects P.?

    Click image for larger version. 

Name:	VoluFogSets.jpg 
Views:	66 
Size:	433.5 KB 
ID:	145317
    yes I have, but not in this particular scene above, I think using this method you and I use.. is good for foggy/misty days, like a boat on the sea etc.
    Sure you can get similar look with global scattering as well, though I think it requires more nodal work...I am not that versed in them both to give a proper opinion on what is best in terms of realism, and speed in rendering.

  3. #18
    pass:sword OFF's Avatar
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    You can always use gradient (distance to object or Y distance to object) adjusting Scattering Weight.

  4. #19
    Not so newbie member lardbros's Avatar
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    Quote Originally Posted by Ma3rk View Post
    Since the volumetric objects are separate & have their own settings, sure, why couldn't your simply have both?

    Here's a W.I.P. that I always intended to have in heavy atmosphere, so a Before & After if you will:

    Click image for larger version. 

Name:	TramLine_NoVolumet_12m30s.jpg 
Views:	56 
Size:	621.9 KB 
ID:	145315

    And with volum cube:

    Click image for larger version. 

Name:	TramLine+Volumetrics_63m47s.jpg 
Views:	59 
Size:	354.5 KB 
ID:	145316

    Just a tad different feeling to be sure.

    Something to note though are the settings. Mine are all on the right hand side of the decimal point in the tenths and thousandths, whereas Prometheus's are in the low single digits. I suspect that's due to the scale & camera distance, etc. but have you tested with foreground & distant objects P.?

    Click image for larger version. 

Name:	VoluFogSets.jpg 
Views:	66 
Size:	433.5 KB 
ID:	145317
    These are nice examples BTW...
    I think the new volume stuff in LW is awesome and not too slow either, on a half-decent PC.
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  5. #20
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by OFF View Post
    You can always use gradient (distance to object or Y distance to object) adjusting Scattering Weight.
    You need depth too..so another gradient or node to adjust thickness/density closer to the camera

  6. #21
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by lardbros View Post
    These are nice examples BTW...
    I think the new volume stuff in LW is awesome and not too slow either, on a half-decent PC.
    The speed and quality is pretty decent for volumetric lights, but as soon as you add several layers of volumetrics, such as overlaying global scattering on top of volumetric clouds, rendertimes and interactivity speed decreases rapidly, and you can expect similar rendering times as when using vue and terragen for godrays etc..45 minutes and above per frame at maybe 1280x700 resolution.
    in 2019 lightwave, they implemented the new physical sunlight, the distant light previously didnīt work with the global volumetric scattering, it now does so that is one improvement.

    However..that new implementation is tricky to get physical correct for acheiving godrays, hard to set up due to the volumetric distance option and knowing how to set it right in relation to a clouds distance and scale..and I can see it yields sharp cut off in the volumetric ray casting some distance away from the clouds, that doesnīt look good...extremely hard to set right...that is when you look at the rays just behind the cloud edges.

  7. #22
    I gotta say Lee - Ive wanted this exact feature so many times! It would be great to have it as a simple control in the volumetrics tab, seeing as though Fog type, min and max distance are already there. Personally i would love to have a "Y fog height control" that quickly allows you to create a sort of ground haze or fog for landscape scenes.

    The reason I say this is purely because I like using the Fog option so much, its so quick and useful for quickly creating a bit of atmosphere in a scene without complex setups.
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  8. #23
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by scott.newman.ct View Post
    I gotta say Lee - Ive wanted this exact feature so many times! It would be great to have it as a simple control in the volumetrics tab, seeing as though Fog type, min and max distance are already there. Personally i would love to have a "Y fog height control" that quickly allows you to create a sort of ground haze or fog for landscape scenes.

    The reason I say this is purely because I like using the Fog option so much, its so quick and useful for quickly creating a bit of atmosphere in a scene without complex setups.
    You could look in to this tutorial and check his node in the end when he adjust scattering in atmosphere, though that is made on the volume item and not global scattering, so I reckon one needs to do some things differently.
    You may controll this a bit with a null item, add a null..then you could for instance in global scattering node editor, add Item info( choose null as item..the plug position in to a vector scalar, and set vector scalar to length or Y-channel, then feed that vector scalar in to the scattering weigth input...but that will only make a ctrl of increasing scattering weight by moving the null, I have yet to figure out the node math to limit it on distance to the null y position.

  9. #24
    da what? daforum's Avatar
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    Quote Originally Posted by BeeVee View Post
    The tutorial is not ready, but when it is, there'll be content to go with it.

    B
    Hi BeeVee.
    Was the tutorial and scene content ever uploaded?
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  10. #25
    LightWave documentation BeeVee's Avatar
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    I got distracted by writing another tutorial about the new capabilities with OpenVDB:

    https://docs.lightwave3d.com/display...ce+Donut+Drape

    B
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  11. #26
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    If you're using the volumetric Fog in LW2019 or earlier and only want a homogenous fog (i.e. with no tendrils or other variations in density), you can use the "Sample Background" with a Pitch Gradient background to limit the fog in height. Sample scene attached.

    Click image for larger version. 

Name:	GradientFog_SimpleStreetScene_0000.jpg 
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Size:	92.0 KB 
ID:	145663

    I don't have time to write it up fully, but here's the Backdrop and Volumetric Fog setup for LW2019:

    Click image for larger version. 

Name:	GradientFog_BackdropSetup.jpg 
Views:	16 
Size:	1.17 MB 
ID:	145664 Click image for larger version. 

Name:	GradientFog_VolumetricFogSetup.jpg 
Views:	17 
Size:	1.01 MB 
ID:	145665

    Although this works OK, as Prometheus suggested earlier, using a Cubic Volumetric object with a non-pyroclastic Texture, scaled to the scene and moved down so only the top of the cube shows works much better. If I get the time I'll post a sample.

    Hope it helps!
    mTp
    Attached Files Attached Files

  12. #27
    Curmudgeon in Training Ma3rk's Avatar
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    Be mindful though when checking the Use Backdrop in the Volumetrics tab. Some lights & HDR backgrounds will show through your geometry. I had a short thread on it a few weeks ago & tracked the issue down to that.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  13. #28
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by Ma3rk View Post
    Be mindful though when checking the Use Backdrop in the Volumetrics tab. Some lights & HDR backgrounds will show through your geometry. I had a short thread on it a few weeks ago & tracked the issue down to that.
    Same issue I bellieve as in 2015 and using fog and use backdrop with dpon sunsky, it sort of projects the color image within the fog applied, so it seems it "shows through"
    I believe that using it isnīt optimal for realism ..what you try to do is add a feature of pitch gradien or retreive a color from the sky rather than being limited with old fog legacy ..and also the limits of global scattering height for 2019 version, this is pure hacks and not how it should work in more realistic ways, wich is large volume fog items, or a global scattering that can be set up with height.

  14. #29
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by MonroePoteet View Post
    If you're using the volumetric Fog in LW2019 or earlier and only want a homogenous fog (i.e. with no tendrils or other variations in density), you can use the "Sample Background" with a Pitch Gradient background to limit the fog in height. Sample scene attached.

    Click image for larger version. 

Name:	GradientFog_SimpleStreetScene_0000.jpg 
Views:	18 
Size:	92.0 KB 
ID:	145663

    I don't have time to write it up fully, but here's the Backdrop and Volumetric Fog setup for LW2019:

    Click image for larger version. 

Name:	GradientFog_BackdropSetup.jpg 
Views:	16 
Size:	1.17 MB 
ID:	145664 Click image for larger version. 

Name:	GradientFog_VolumetricFogSetup.jpg 
Views:	17 
Size:	1.01 MB 
ID:	145665

    Although this works OK, as Prometheus suggested earlier, using a Cubic Volumetric object with a non-pyroclastic Texture, scaled to the scene and moved down so only the top of the cube shows works much better. If I get the time I'll post a sample.

    Hope it helps!
    mTp
    Weird that we should define the textures as non-pyroclastic, not just plain hypertexture, we got three modes and I only use one of them...but thatīs me.
    Anway...also remember if you create a fog item cube, you could reference the density channel to a null which is located a bit above the top of the fog item, and make a gradient in the density based on the distance to that null..so it fades off more nicely.

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