Guide To High Dynamic Range Imagery In Image-Based Lighting

This downloadable document is a general guide to high-dynamic range image-based lighting.  Maxwell Render is used to describe various mechanics of image-based lighting because of its simplicity of operation. Howver, the basic concepts and observations apply to any rendering application and situation. This document was originally prepared to help people trained only in studio lighting to better understand image-based lighting.  I don't suppose any "guide" is truely "comprehensive," but this document does attempt to cover the subject in a reasonably complete fashion.

The Guide is organized into four sections.

Part 1- Basic Concepts
The first part explains some very basic things, such as the nature of an HDRI image and how it is made, how it is deployed in a rendering engine and where you can obtain good quality HDRI images. The first part ends with some observations about building a library for yourself so that you can easily draw from a collection of HDRI images.

Part 2 – The Mechanics Of Image-Based Lighting In Maxwell Render
The second part also is elementary. This section outlines the simple mechanics of image-based lighting in Maxwell Render. For those who might be curious, some key features of other rendering applications are described that represent changes taking place in the technology of image-based rendering.

Part 3 – Selection Of An Appropriate High Dynamic Range Image
This part of the document presents the core of the subject. This section goes into the technical properties of the various kinds of HDR image file formats in a little more depth. It describes how to select an HDR image based on the amount of light required for the render, and requirements for color, light direction, degree of light softness and light variability. One sub-section explains how to locate key orientation points in an HDR image so that you can precisely control light direction in a render. Other sub-sections describe Filestar, HDRI Light Studio and Real HDR – applications that are important tools for regular work in image-based lighting. One purpose of this part is to help you become familiar with the most versatile and well-known of the HDR images in the marketplace.

Part 4- Background Images – “Backplates”
Some people use image-based lighting in a rendering application primarily for, ... or only for the purpose of putting 3D objects into a context, ...a scene suggested by a background of some type. All rendering engines support the use of background images (increasingly known as “backplates”) in image-based lighting. This section describes the use of backplates, mechanisms for their use and ways to create your own. This part ends with a short section on “starscape” backgrounds and lighting as this particular subject is not well covered elsewhere.

While this document is lengthy and full of many small “facts,” “tips” and image comparisons, it is not necessary that you read it in its entirety. Nor is it necessary to read it in order. For example, you really don’t need to know how an HDR image is made to be able to use it well. If Maxwell Render is not your primary rendering application, you can skip Part 2. Part 4 deals with a subject important to only some users. To be able to use image-based lighting with some expertise, all that is really necessary is to read and understand the concepts and information presented in Part 3.