UE4 – Connect a Directional Light to an Atmospheric Fog effect

Software:
Unreal Engine 4.21

UE4‘s Directional Light mimics sun lighting and shadow fairly realistically,
And the Atmospheric Fog visual effect produces a realistic clear sky background that includes the sun’s disk image in the sky.
> The Atmospheric Fog produces a result similar to an implementation of a Preetham physical sky model in common rendering software.

Combined together, these two elements can produce an effective day-light system,
But inorder for this to work the sun’s direction should be controlling the time of day simulated by the Atmospheric Fog.

For the Directional light to control the Atmospheric fog:
In the Directional Light’s details, under light, expend the settings and enable:
Atmosphere / Fog Sun Light

Note:
There is a limitation to this setup’s realism because the sunlight’s color shouldn’t be pure white, but rather yellowish, to orange, depending on the time of day (you can find tables of the sunlight’s color temperature for various time of day on the web)
There is no problem setting the sun’s color, but the problem is that it causes additional coloring of the Atmospheric Fog which isn’t needed since it already is simulating the sky’s color correctly.
The result of this limitation is that we can see a sunset sky with a white sunlight which is wrong.
I didn’t find a workaround for this yet, can’t find a way to set the Atmospheric Fog‘s sun vector without connecting it to a Directional light and can’t find a way to make the Directional Light‘s color not affect the Atmospheric Fog‘s color.

Update:
It seems this limitation can be overcome by disconnecting the Atmospheric Fog from the Directional Light and using the Atmospheric Fog Object’s rotation to control it.

Directional_light_Affect_Atmo_Fog
atmo_fog.gif

Maya – Setting the V-Ray Sun direction according to location, date and time

Software:
Maya 2018 | V-Ray 3.6

To set the VRaySun photometric light source diretion according to the location in the world, the date and the time:

  1. Select the VRaySun parent node – ‘VRayGeoSun1Transform‘ and rotate it so its Z axis points to the architectural plan’s south.
  2. Select the VRaySun node – ‘VRayGeoSun1‘ and in its attributes un-check Manual Position.
    This will make the location / date / time parameters accessible.
  3. Set the GMT zone of you architectural project’s location in the world, the Date and time.
    * haven’t found how to set daylight saving time….

Untitled-1

Related:
V-Ray for Maya Physical Camera
V-Ray for Maya White Balance
Daylight system addon for Blender

Daylight system for Blender

Software:
Blender 2.78

Found a simple and effective sun positioning addon for Blender,
It can be downloaded here:
https://developer.blender.org/F20492
The addon is easy to install like all other addons in Blender,
Once installed you will find it’s controls in the World settings,
You specify a sky environment map and a sun node and it will control them acording to given latitude longitude, date, timezone ect.
Also lets you set the north direction of the system as needed.

Very simple and very effective.

Related:
Photometric daylight setup in V-Ray for Maya