Lighting Effects

So in my last blog I mentioned that I would be focuses on a few lighting effects that can make your games, 2D art and even your maya scenes look awesome! So basically in this blog I'm going to explain what a few of these lighting effects are and teach you how to create a few, in Maya and photoshop (more than likely I'm just going to end up teaching you how to create bloom in both Maya and Photoshop and potential curl in a dark corner and cry when the others don't turn out right). Also if I'm nice i might teach something else that's really cool, but not necessarily a lighting effect although it does use some of the topics talked about in my last blog (so who knows I may teach it).

 Lighting Effects

• Radiosity
• Global Illumination
• HDR/Bloom 

Radiosity

Radiosity is a method of rendering used in 3D computer graphics rendering that is based on a detailed analysis of light off diffuse surfaces. The images that result from a radiosity renderer are characterized by soft gradual shadows. Generally it is used to render images of the interior of building and for photo-realism in scenes comprised of diffuse reflecting surfaces. There are 4 major procedures that a radiosity renderer would take in when computing the scene:

1. Generate Model
2. Compute Form Factors
3. Solve Radiosity Matrix
4. Render

For more indepth information on how Radiosity works, check out the following links:

• Radiosity
• Radiosity Overview

 Global Illumination 

   

 Global Illumination is the general term given to a group of computer graphics algorithms that are designed to add realistic lighting ti a 3D scene, where these algorithms take into consideration both the light coming directly from the source and the light rays from the source that are reflected off other surfaces.  Some of the algoritms taken into consideration when doing Global Illumination are:

• Ambient Occlusion
• Radiosity
• Ray Tracing
• Photon Mapping
• Among others

 Global Illumination is often used to bring realistic lighting and photo-realism into video games since images rendered using the global illumination algorithms are often more realistic than images rendered with direct illumination.

	Advantages	Disadvantages
Radiosity:	- Very realistic lighting for diffuse surfaces - Conceptually simple and easy to implement - Easy to optimise with 3D hardware	- Slow - Does not handle point sources well - nor shiny surfaces - Always over complicated and poorly explained in books
Monte Carlo Method:	- Very, very good results. - Can simulate pretty well any optical phenomenon	- Slow - Slightly difficult - Requires some cleverness to optimise - Always over complicated and poorly explained in books

Direct Illumination

 Direct Illumination is a term that covers the principle lighting methods used by old school rendering engines in which a scene consists of two types of entities: Objects and Lights. Lights cast light on objects and create shadows when other objects are in front.

	Advantages	Disadvantages
Ray Tracing:	- Can render both mathematically described  objects and polygons - Allows you to do some cool volumetric effects	- Slow - Very sharp shadows and reflections
Shadow Volumes:	- Can be modified to render soft shadows (very tricky)	- Tricky to implement - Very sharp shadows - Polygons only
Z-Buffer:	- Easy to implement - Fast (real-time)

HDR/Bloom 

Bloom( often refered to as light bloom or glow) is an effect in computer graphics used in video games, HDR and demos to recreate an effect of real-world cameras. The Bloom effect creates a type of fringe of light that extends from the borders of bright areas in an image or scene, that is used to contribute to the illusion of an extremely bright light that overwhelms the camera or eye.

BASIC THEORY

The basic theory behind Bloom is that lenses can never focus perfectly and no matter what will convolve the incoming image. Normally this distortion is unnoticeable however an intensely bright light source draws attention to these imperfections. This results in the bright light in the image will appear to bleed into the surrounding areas.

To create Bloom you need to remember that it is a multi-pass rendering algorithm that first has to render the original scene, then find all the bright points, blurs them and then adds them back to the original scene.

4 Stages of Bloom:

   (1)         (2)         (3)          (4)
 _______                                            ______
|       |       ____        ____                    |      |
| scene | --> |Tone| ---> |Blur| ----> ((+)) --->  | BLOOM |
|_______|     |____|      |____|         ^         |______|
    |        downsize    downsize        |
    |                                    |
    |____________________________________|

1. Render 3D scene to  off-scene Framebuffer (FBO)
2. Highlight Bright Areas (tone-mapping) (FBO_BP)
3. Apply a Gaussian Blur to FBO_BP (FBO_BLUR)
4. Final Image = FBO_BLUR + FBO

Tutorial:
So since this blog post ended up longer than I thought it would I'm going to do my lighting and effects tutorial in my next blog. Which you will be able to find Here, when its done.