Medium to create Distance Fog

[artech7]

Anyone here been able to successfully create a distance fog using Mediums?

I have a large scene that could use the touch of distance, but I don't want to use something like Vue to create it in a final render. Not when I can do it 100x faster in Octane. XD

Any advice?

[Timmaigh!]

I played around it a bit and it indeed works. You just got to add scattering medium to environment and the play around bit with the values/sliders... i think most importantly the scattering density, that "step" thing and then medium distance or whatever is it called. Luckily there are not too many of these properties, so its about finding the right combo for these few.

[bepeg4d]

Hi artech7,
the most important value is the Medium radius becouse it depends from the scale of the scene. The value is in meter, so you have to start with a much higher value than 1, based on your sene dimensions. Then start with a low Density value like 0.01 or similar, and fine tune the settings.
The Volume step lenght works only with volumes and not with medium fog.
ciao beppe

[linvanchene]

updated:
- screenshots 2x
- made distinction between short-medium term and long term possibilities
- made distinction between cylinder and dome shape
- - -

hmmm

but

To me Distance Fog is more like haze that is actually in the distance.

What the current medium node in the environment settings is doing is just adding a sphere shaped medium in a radius from the center.
-> This has the issue that now all objects in your scene are sitting in the fog.

- - -

What some might want to have is the fog only in the far away distance.

Short - medium term solution: Additional Dome or Cylinder shaped environment medium for fog / haze in the distance

-> The environment settings could be updated with an additional dome shaped medium for "Distance Fog / Haze" that has a starting and end point of the assumed dome in the far distance.

- A thick walled cylinder shaped medium also could do the trick

The advantage of the cylinder form is that it is open on top so sun rays can enter without having to cross trough the medium.

Just make sure that the cylinder with the fog / haze material is high enough so its border is not visible in your render.

- - -

A dome may be more suited to simulate an atmosphere layer.
A cylinder may be more suited for just ground level distance fog and haze.

- - -

or alternatively

Long term solution:

- > provide a completely new kernel that simulates the planetary atmosphere with different atmosphere layers and fog and haze like it is done in e-on vue.

PMC is great for product renders and indoor scenes. But for landscape outdoor scenes it is not providing many advanced options.

-> The current options of the "Daylight Environment" even in PMC mode offer only limited options similar to the "Standard model" of e-on vue that is mostly used for "preview" renders of landscapes.

What some users may still be hoping for is a "Spectral model" in GPU rendering similar like the high quality option in e-on vue that simulates light rays bouncing through several layers of atmosphere, clouds, haze, fog, the ground and then back up again lighting the clouds with bounced back rays.

Volumetric & Spectral Medium options for clouds, haze, fog shape and distribution need to be provided directly by the render engine and not some 3rd party application...

Maybe in OctaneRender 5?

[artech7]

hmmm

but

To me Distance Fog is more like haze that is actually in the distance.

What the current medium node in the environment settings is doing is just adding a medium in a radius from the center.
-> This has the issue that now all items in your scene are sitting in the fog. Not what some users may want.

What some users might want to have is the fog only in the far away distance.

-> The environment settings could be updated with an additional medium for "Distance Fog / Haze" that has a starting and end point of the assumed medium in the far distance.

or alternatively

- > provide a completely new kernel that simulates the planetary atmosphere with different atmosphere layers and fog and haze like it is done in e-on vue.

PMC is great for product renders and indoor scenes. But for landscape outdoor scenes it is not providing many advanced options.

-> The current options of the "Daylight Environment" even in PMC mode offer only limited options similar to the "Standard model" of e-on vue that is mostly used for "preview" renders of landscapes.

What some users may still be hoping for is a "Spectral model" in GPU rendering similar like the high quality option in e-on vue that simulates light rays bouncing through several layers of atmosphere, clouds, haze, fog, the ground and then back up again lighting the clouds with bounced back rays.

Volumetric & Spectral Medium options for clouds, haze, fog shape and distribution need to be provided directly by the render engine and not some 3rd party application...

Maybe in OctaneRender 5?

You hit it on the head. That is exactly what I was talking about. I know how the scattering device works, but it wasn't giving the results I thought it would, which was one of my most anticipated additions in v3. I still am in love with Octane, but I suppose, for the time being, I will just have to export the Z depth and perform some Photoshop magic to get the results I need.

Also, do you guys understand how the gradient medium works? Perhaps that can be used in some work around to create similar affects? I haven't played with it very much, but I will be testing later tonight.

[artech7]

Hi artech7,
the most important value is the Medium radius becouse it depends from the scale of the scene. The value is in meter, so you have to start with a much higher value than 1, based on your sene dimensions. Then start with a low Density value like 0.01 or similar, and fine tune the settings.
The Volume step lenght works only with volumes and not with medium fog.
ciao beppe

I wasn't aware that the value was in meters, that is good to know! Thank you! That will make guessing the amount needed a bit more easy.

[roeland]

A quick way to render a fog effect is combining absorption with emission. I attached a simple example. Unlike with proper scattering this doesn't render any god rays or shadows in the fog, but the advantage is that it produces no noise.

fake depth medium.orbx

(2.86 KiB) Downloaded 427 times

If you're rendering with daylight there's a complication though, the environment medium is currently implemented as a sphere around the camera, we haven't implemented other shapes yet. So the medium will end up blocking the sunlight. In that case, use a fog volume as follows:

• Make a flat volume, like a very flattened sphere or a cylinder.
• And leave a small open space around the camera. Your objects will indeed sit in the fog, that is expected. Fog is just usually not dense enough to absorb or scatter a significant amount of light between the objects and the camera.

The resulting volume would be a bit like the “thick walled cylinder” in the post above, but the walls would extend way further out and should cover the entire landscape. Then lower the density of the environment medium until the "fog" has the desired thickness.

The gradient medium only works with volumes loaded from VDB and is used to map the density values loaded from VDB files to color ramps.

--
Roeland