Atmospheric Fog

To those who joined the Wed session,
check out the Thursday session since the "simulated Zdepth" issue was covered.
(Watch from 1h16m38s)

Download Wed Session

Download Thu Session  <---Check this one out!

Download (Nuke file, images)

<Atmospheric Effect>
1. Why is the sky blue?
The sun ray scatters in the atmosphere.
The blue scatters first and becomes dominant in the sky.

2.
-Rayleigh scattering:
When the particle is extremely small as air molecule.
Scattering in all directions (omni)
The scattering color is blue (the sky)

-Mie scattering:
When the particle is larger than air molecule.
The scattering direction is more directional(forward).
Depending up on the size of the particle, the color is different. . (The larger the particle, the whiter the scattering )
The fog / the cloud

3. When you render something really large or something really far, you need to take "Distance" into account.
You can just use zdepth information.

4. To add atmospheric effect,
-Add grade to scale the brightness toward black.
(The fog can block the background pixel)
-Add another grade node to add Fog color
-Use the Zdepth image as a mask to manipulate the above grade nodes.

5. Make sure to use unpremult and premult to avoid
edge artifacts and unwanted extra color to the BG.

6. Pick the fog color from the background.
Any color from the background is gonna work.
But the color near the horizon is recommended.

7. Using  regular Zdepth may create some edge artifacts. Since it is not anti-aliased.
I recommend using  Atmospheric fog ( environmental fog ) in Maya.

Motion Blur lecture resources

Here you can download the recordings of the two sessions on Wed/Thu.

Download Wed Session

Download Thu Session

Download (Maya scene, Nuke file)


<Motion blur>
1. Pixel-analysis based motion blur
Pros:
-Easy to use, cheap, fast
-can even work for stop-motion animation
-Just try and see if it works

Cons:
-Works well for linear motion but not adequte for curved motion. (rotation)
-Can generate artifacts
when lack of pixel info. . ( when things are entering the frame or exiting the frame)
with Reflection/Refraction.
when Lighting changes

Best when passes are seperate ( character against black background)



2. Motion-vector based motion blur

What to check?
- How long the motion trail
(duration of the motion blur - half frame is usually good )
- Deformation and Camera must be on.
-To have clean beauty AOV and working motionBlur AOV
go to the renderable camera and turn off Use Global Shutter option and use 0 and 0 for Shutter start/End.
- Red is for horizontal motion. Green is for vertical motion.
Negative value can be used.

- In Redshift, just by adding MotionBlur AOV takes care of setup. But make sure to use Output Raw Vectors option and turn ON Filtering.

-In Nuke, sometimes R and G need to be swapped.
It can flip back again even with Shuffle node (just strange).

Best when passes are seperate ( character against black background)