Week 7 - Thursday: Lighting Experimentation

Lighting in Unreal Engine is an area that I have little confidence in. Whilst I understand the basic functions of the different types of lights and the other elements such as the skydome, there are some nebulous attributes that I am still struggling to understand. There are numerous values which can be edited within Unreal Engine and each one has a knock on effect that will determine how the final light bake will render. To make matters worse, I am stuck using an outdated version of the software so I am somewhat limited in how I approach lighting my environment. I am aware that later versions of the software have made improvements on the lighting aspect but for now I have to make do with what I've got.

To help me better understand the technical side of lighting scenes, I have been watching a series of video tutorials entitled "The Unreal Engine Lighting Academy". The author covers a variety of topics but one series I am particularly interested in, involves creating the lighting for a real time architectural visualisation scene:

This is the eleventh video in a series on lighting environments within Unreal Engine. This video focuses on a lighting setup for an architectural visualisation scene.

The video strips out the default lighting of the engine and rebuilds all the elements again from scratch. Because of this I was able to gain a better understanding of what everything does in the engine as I put them back into the scene one at a time. Below you can see a new scene I created in Unreal Engine so that I could quickly test different lighting settings without waiting for lengthy bake times.

This is a new scene that I created with my own custom lighting setup.

I wanted to see the effects of an HDRI lit skydome within an environment. I stripped out all the lighting elements and created a giant sphere within the scene. Following the video tutorial I found a good HDRI image and applied it to the sphere within the scene. What you see in the images here is the baked lighting from the HDRI skydome.

This image shows only the results of the skylight I created. Take note of the soft shadows I was able to achieve.

I like the subtle lighting the HDRI image is giving the environment. I think this will prove quite helpful for my main scene as the image itself would work as a nice backdrop for my mansion environment.

The HDRI skysphere works as a nice background for the environment.

In the video tutorial, the author mentions that he is using a multi-bounce skylight plugin. The effect of which is to more accurately bake the lighting. Below you can see the effect of a single bounce compared to multiple bounces.

A lighting bake created in Unreal Engine that demonstrates the difference in lighting quality between a single bounce and multiple bounces from a skylight. On the left is the default value and on the right is the multi-bounced skylight.

I have cropped the image below to give a better look at the effect the multiple bounces is having on the scene.

Multiple bounces from the skylight cause indirect lighting to be reflected on surfaces.

Originally Unreal Engine only allowed a single bounce for the skylight and I fear this may be true for the version I am using. I want the lighting bake to appear as realistic as I possibly can and may need to simulate these effects if need be, as I can't install custom plugins on the school machines.

51DAEDALUS. (2017) Unreal 4 Lighting Academy - Session 3.1 [Online Video]. 13th May. Available from: https://www.youtube.com/watch?v=pIbpHCtmDjo. [Accessed: 05/07/2018].

LUOSHUANG. (2015), Lightmass: multi-bounced sky lighting. [Online Image]. Available at: https://forums.unrealengine.com/development-discussion/rendering/112827-lightmass-multi-bounced-sky-lighting?140006-Lightmass-multi-bounced-sky-lighting=. [Accessed: 05/07/2018].