To get an accurate reading of the illuminance in your level you need to measure it on a surface that’s perpendicular to the sun. We already have a couple of planes set up for this purpose so all you need to do is set r_HDRdebug 1 in the console and simply look at the surface. Keep in mind that turning this on brightens the whole scene so don’t forget to turn it off once you’re done measuring your illuminance.
Pic 89: Planes facing the sun used for measuring full sunlight/shadow illuminance.
By doing this we are now getting blue tinted shadows as opposed to pure black and our lux value also jumped up to about 100000 while keeping the shadow illuminance at around 20000. A 1/5 ratio between fully lit/shadow areas is close to real world values.
Pic 910: Top - Fully lit area lux reading, Bottom - Shadow area lux reading
Taken from the Wikipedia page on Diffuse Sky Radiation ( also known as Skylight ) we set these values at 650 (R), 550 (G), 450 (B).
Pic 1011: Screenshot from the Wikipedia page detailing Diffuse sky radiation.
Lastly we have the Shadow Darkening settings that are only used to control the appearance of the fog in shadow areas. In order to enable the effect of these values VolFogShadows needs to be enabled in the Environment Panel. This is not to be confused with the Volumetric Fog in the Environment Editor which has a global influence.
Pic 1112: The Fog parameters section inside the Environment Editor.
We start by setting the current time to 12:00 and assigning a light blue color ( 185, 251, 251 ). This value needs to stay consistent throughout the day and will start fading to almost black once we get close to sunset/sunrise. Create two more keys at 07:00 and 17:00 and assign the same color. After we’ve done that create a key at 06:00 and 18:00 and assign them a very dark grey color ( 13, 13, 13 ). Copy the same value to 00:00 and 23:59 to keep it constant for night time. We will be using this to create the illusion of light pollution on the horizon at night time.
Pic 1213: Color ( bottom ) curves setup.
If you are wondering why this is set so low for night time it is because of the way eye adaptation works making the fog way too strong in low light conditions.
Pic 1314: Color ( bottom ) multiplier curves setup.
We want the amount of fog to ramp up at sunset/sunrise. To achieve this set some keys at 06:00, 07:00, 17:00 and 18:00 wih a value of 0.3 then set 3 more keys at 00:00, 12:00 and 23:59 with a value of 0.2. As always make sure you have a smooth transition from one key to another by using editing their tangents.
Pic 15: Density ( bottom ) curves setup.
Color ( top )
This value will be very subtle as we will be setting our top density quite low. For midday assign a light blue color , slightly darker than the bottom one, let’s say 131, 183, 231. At 07:00 and 17:00 change the value to a darker blue like 51, 72, 90. With the low density we will be using this color has no impact at night time. I have created more keys at 00:00, 06:00, 18:00 and 23:59 and set the value to black, but this is entirely optional.
Pic 16: Color ( top ) curves setup.
Color ( top ) multiplier
The only key we need to create for this parameter is at 12:00 so change your current time accordingly and set the value to 1. Set the tangent to auto so it gradually transitions to 0 towards the ends of the timeline.
Height ( top )
We don’t need to change this value for this particular scenario.
Color height offset
As mentioned before this value can be used to offset the height of the transition between our top and bottom colors which is not necessary for our level.
Pic 17: The effect of Color height offset.
Color ( radial )
Between 08:00 and 16:00 set this color to a light yellow like 193, 158, 100. As we get closer to the ends of our timeline this should transition into a gradually darker orange. To get this result set two keys at 07:00 and 17:00 and assign them a dark yellow color like 192, 126, 49 and leave the 00:00 and 23:59 times to their default value of black. Provided you’ve set up the curves properly this should give you the orange color when the sun is right above the horizon.
Pic 18: Color ( radial ) curves setup.
Color ( radial ) multiplier
To start with set this to 16 for mid day. The impact of the radial fog becomes more obvious as the light intensity drops so we will have to decrease the multiplier as we go towards the ends of the timeline. Create two keys at 07:00 and 17:00 set the value to 10.
It’s probably a good time to mention that the radial fog also gets applied to the moon during night time so if we keep our multiplier at 10, as soon as the sun goes under the horizon we will get a huge orange glow for the moon. To fix this create some keys at 05:55 and 18:05 and set the value to 0. It’s possible to set this up to control the bloom for the moon but there is a dedicated section for night sky. We will go over that later on.
Pic 19: Color ( radial ) multiplier curves setup.
We only need to change this slightly to get a more pronounced effect. Set two keys with a value of 0.8 at the 07:00 and 17:00 times.
Same as the Radial size, set this to 0.8 at 07:00 and 17:00 respectively.
As mentioned previously we want our fog to be denser in the morning/evening and fade out as the sun gets higher in the sky. Set a key at 12:00 and put in a value of 0.05. To handle the smooth transition add a few more keys at 00:00, 06:00, 18:00 and 23:59 with the value of 0.1.