Chapter 6.1 Lighting and Shadows

Overview of Unreal Lighting And Shadow Techniques
When it comes to creating believable environments, the way the geometry within the level is lit plays an extremely important role. The human eye and brain expect light to interact with surfaces, fill a room, or cast shadows in a particular way. Anything that deviates from this can break up the immersive experience for the user. Unreal Engine 3's lighting system is very flexible, allowing for different types of lights and shadows to all be used in harmony to create just the right look for any game. The Lightmass static global illumination lighting system makes setting up entire environments extremely easy as most of the leg-work is done by the lighting build process and dominant lights provide for detailed shadows without sacrificing performance.
Lightmass static global illumination system creates lightmaps with complex light interactions like area shadowing and diffuse interreflection. It is orthogonal to the rest of the rendering pipeline (dynamic lighting and shadowing), it just replaces the lightmaps and static shadow maps with higher quality ones.

Lightmass Tools
There are many useful tools for getting the most out of Lightmass, including Debugging and Troubleshooting tools to optimize

Dominant Lights ( supported only in levels using Lightmass )
Existing level and character lighting in UE3 is very general and flexible, for example there's no code limit to the number of dynamic lights or shadows affecting a primitive, and you can use many shadowing types (shadow volumes, precomputed shadow maps per vertex or texture, different types of shadow map filtering) with different light types. Unfortunately this generality has a performance and quality cost when a very specific lighting scenario is desired, for example outdoor lighting where the sun is the most significant light, followed by its indirect lighting and the influence of the sky. Dominant lights exist to special case lighting setups with few significant lights and gain back the lost quality and performance.

Light Environments
Light environments provide Level Designers with an automated way of controlling dynamic lighting by approximating the effect of relevant static lights. Together with modulated shadows, light environments were used on all characters & vehicles and most other dynamic objects in Gears of War and Unreal Tournament 3.

Light Functions
Lights functions are mathematical representations of how lights should illuminate the scene in Unreal Engine 3. By default, lights will use a constant value based on the various inputs defined by the light component; such as brightness and color. Light functions allow you to define more interesting set ups to achieve flicking lights, masked lights and strobing lights, textured lights. Light functions use the material system in Unreal Engine 3, making it really easy for artist and level designers to create and modify. Also, because light functions uses the material system, these light functions can be instanced for variations.

Lighting Reference ( Legacy )
In Unreal Engine 3, we place light actors in the world to illuminate our scenes and characters. To manage the behavior of these lights we have created a number of different classes of lights and options to control them. These options give us a very broad spectrum of usage cases ranging from very simple baked lighting to very complex dynamic lighting. The kind of lighting you choose may vary based on the requirements of your project. This guide will serve to explain the various options so that you can understand the limitations and tradeoffs between different lighting options and make the most appropriate choices. We will also attempt to give rough estimates of the performance cost associated with enabling certain options.

Shadowing Reference
The four distinct shadowing solutions use by UDK:
  • Whole-scene dynamic shadows - Movable lights use whole-scene dynamic shadows.
  • Per-object dynamic shadows - Immovable lights illuminating movable or dynamic objects use per-object dynamic shadows.
  • Precomputed shadows - Immovable lights illuminating static objects use precomputed shadow maps.
  • Precomputed lighting - Static lights illuminating static objects use precomputed light maps.

Modulated Shadows
Modulated shadows were introduced to solve some of the performance problems with normal shadows, and to give artists more control over shadow appearances. Throughout this doc, 'normal shadows' simply means non-modulated shadows, and does not imply anything about the filtering technique.
Note that modulated shadows work with both projected shadow buffers as well as shadow volumes.

Distance Field Shadows ( supported only in levels using Dominate Lights )
Distance field shadows are a different approach to encoding precomputed shadows with improved quality and memory optimization. 

    • UDK Lightmass: A Basic Setup
    • Lightmass / Global Illumination

    • UDK: Adding Dominant Directional Lights & Point Lights

    No comments:

    Post a Comment