Image-Based Lighting Workflows

This article is currently a work in process

Originally written by Spooks on the TDM forum:
https://forums.thedarkmod.com/index.php?/topic/19803-tutorial-image-based-lighting-workflows-for-tdm/
I (datiswous) copied over the original formatting, but it might change somewhat because of (possibly better) organizational features of the wiki.

Hello, everyone! In this multi-part, comprehensive tutorial I will introduce you to a new light type that has been available in The Dark Mod since version 2.06, what it does, why you would want to use it and how to implement it in your Fan Missions.

This tutorial is aimed at the intermediate mapper. Explanations of how to use DarkRadiant, write material files, etc. are outside of its scope. I will, however, aim to be thorough and explain the relevant concepts comprehensively. Let us begin by delineating the sections of the tutorial:

Part 1 will walk you through four, distinct ways to add ambient light to a scene, the last way using irradiance environment maps (or IEMs). Lighting a scene with an IEM is considered image-based lighting. Explaining this concept is not in the scope of this tutorial; rather, we will compare and contrast our currently available methods with this new one. If you already understand the benefits IBL confers, you may consider this introductory section superfluous.

Part 2 will review the current state of cubemap lights in TDM, brief you on capturing an environment cubemap inside TDM and note limitations you may run into. Three cubemap filtering applications will be introduced and reviewed.

Part 3 will go into further detail of the types of inputs and outputs required by each program and give a walkthrough of the simplest way to get an irradiance map working in-game.

Part 4 will guide you through two additional, different workflows of how to convert your cubemap to an irradiance map and unstitch it back to the six separate image files that the engine needs.

Part 5 will conclude the tutorial with some considerations as to the scalability of the methods hitherto explained and will enumerate some good practices in creating IEMs. Typical scenes will be considered. Essential links and resources will be posted here and a succinct list of the steps and tools needed for each workflow will be summarized, for quick reference.

Without further ado, let us begin.

Part 1

Imagine the scene. You’ve just made a great environment for your map, you’ve got your geometry exactly how you want it… but there’s a problem. Nobody can appreciate your efforts if they can’t see anything!