Redshift Volume & Fog

I finally got to messing around with the Redshift Volume node. It’s pretty straight forward for the most part. Under Render Settings, the Output tab click on the Environment – Atmosphere checker box.

redshift_volume-1

This creates the Redshift Volume Scattering node.  Now you can call this node back up through Hypershade under “Utilities” or go back to “Render settings” and click on it, if you lose track of the node while working back in your scene file.

redshift_volume-2

redshift_volume-2b

Another way to keep the “Volume scattering” attribute up is to click on the bottom right of attribute editor with it up, click the “Copy Tab”. Now you have a dedicated floating window just for the “Volume Scattering”.

redshift_volume-2c

I’ve setup a very simple file with a spot light and some cubes on a ground plane.

redshift_volume-3

Now the Volume scatterer won’t be on at first. You need to go to your scene’s light(s) and under Volume, change the contribution scale from 0 to whatever factor you want the Volume to affect. Here I changed it to a factor of 1.

redshift_volume-5

This is factor of 0.5

redshift_volume-5b

Factor of 0.25

redshift_volume-5c

Now the max value of the Contribution scale is 1. But in the Volume Scattering you can make more changes and higher parameters. So let’s put the “contribution scale” back to 1, and look at the attributes on the “volume Scattering”.

redshift_volume-6

You’ve got General, Fog, and Ray Contribution Scales settings.

General

Under General, you can change the tint of the volume. If you slide the tint bar to the left, you are lessening the brightness/saturation of the color. I’ve lowered mine to half. The render now looks like when we lowered the contribution scale. So Lighter brighter the color the more intense the volume looks, and darker less density/more transparent.

redshift_volume-7

Let’s try a color, blue. You can see by the tint, it’s a strong bright blue. The slider is all the way to the right.

redshift_volume-7b

Slide the bar over.

redshift_volume-7c

Let’s switch back to white. Now if we increase the Scattering the volume is denser and brighter. From left to right the scattering is set at 5, 2, 1, and 0.5.

redshift_volume-8

Now if we zoom out of camera a little. You’ll see I’m using a spot light. It can seem that the scene file camera was misleading. The reason I’m showing you it this way is due to the attenuation. Nothing has changed, excepted I’ve zoomed out.

redshift_volume-9

Now the attenuation is set at 1. It looks broke, but that’s because the attenuation is linked to our fog – Height, which is set at 0.1.

redshift_volume-9b

If I raise the height from 0.1 to 100. The attenuation is still set to 1.

redshift_volume-9c

Now the attenuation is set to 2.

redshift_volume-9d

Now the attenuation is set to 5.

redshift_volume-9e

So, the attenuation controls both the strength of the fog and the amount the light gets absorbed as it travels thru the fog.

redshift_volume-9f

Most of the work really is dialing in all of the setting to work together for your desired result. Here you can see scattering is 1, Attenuation is 1. The fog emission is now white. The fog height is 2.

“Phase” controls how much the lighting will bounce around inside the volume and get scattered.  This is interesting in that a positive number will create something called “forward scattering”.  This means the lighting doesn’t bounce around in the volume as much and is mostly visible when traveling toward the camera. A negative value will create something called “backward scattering”, which means the volumetric lighting will be more noticeable as it travels away from camera.

 

Here’s a mesa file I had.

mesa_scat_000_att_000

Due to the scale of my mesa, I had to reduce the numbers considerably.

mesa_scat_001_att_001

mesa_scat_01_att_001

Then I ran same numbers but with multiple mesas in distance.

mesa_scat_000_att_000

mesa_scat_001_att_001

mesa_scat_01_att_001

 

Fog Settings

Emission color allows the fog to be self-illuminating. You can apply a color to the fog.

mesa_scat_01_att_001_w_fog_color_red

You’ll want to keep “Apply Camera Exposure Compensation” on. This will allow for it to be scaled correctly.

“Height”, we’ve talked about this already, but when set to 0 the fog is omnipresent. Any non-zero value activates “height fog”.

mesa_scat_01_att_001_w_fog_color_red_height_0001

Now you can see the fog height is high enough for us to see it along the sides of the mesas.

mesa_scat_01_att_001_w_fog_color_red_height_8000

“Horizon Blur” depending on the size of your scene, there might end up being a sharp line where the fog joins the horizon. Horizon blur allows the height fog’s horizon to be faded out for a more pleasing look.

mesa_scat_01_att_001_w_fog_color_red_height_8k_hor_blur1

Or you can really increase the number, like say 100, which causes more gradation of the fog to horizon.

mesa_scat_01_att_001_w_fog_color_red_height_8k_hor_blur100

“Ground Point”, if using height fog, this determines where the fogging effect starts.

“Ground Normal”, again if using height fog, this determines the direction of the fog. You can change the fog to a “wall of fog”  instead of a “blanket of Fog”.

Adjusting fog plane, change fog normal from default (0, 1, 0) to (0, 0, 1).

Now if your Volume is looking a bit noisy. You can go to each light in your scene and increase under the Volume the Samples. Increasing this field will diminish most of the noise you are seeing in your volume.

redshift_volume-99_samples

Castle Mesas no volume

castle1_no_volume

Castle mesas with volume

castle2_w_volume_att1_

Castle mesas dialed in Volume

castle2_w_volume_dialed

castle2_w_volume_dialed2

That’s pretty much an overview on the Redshift Volume Scattering node.

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