The problem of lighting 3D scenes in hardware accelerated rasterized rendering is really hard to solve. There are no 100% solutions, and what seems perfectly obvious to the uninitiated (light just bounces around) is extremely hard to do in practise. The following blog post is about one such method that I wanted to try out for a long time.
A while ago I finished playing From Dust which I enjoyed a lot. What impressed me about that game was the application of landscape changes by erosion. One drawback of the tool Lithosphere I wrote earlier is that it can't do any form of hydraulic erosion. I decided to write a test in WebGL to see if a few simple algorithms could be used to shape a landscape according to hydraulic erosion.
The grass demo I did earlier used some Screenspace Ambient Occlusion. I thought it was a cool effect, and decided to research the topic futher. Scren-Space Ambient Occlusion is an incorrect aproximation to true ambient occlusion, and it has a couple problems, but it can be a useful technique.
In the book Game Engine Gems 2: Chapter 13 author Rémi Arnaud examines different browser based 3d rendering techniques. According to Rémi, many 3D web rendering technologies failed because they could not get game developers on board. An example is VRML, which was pronounced dead on arrival by John Carmack.
In part 2 of this series I explained about how to get the sky. This entry is about how to compute an irradiance environment map from this cubemap.
In Part 1 of this howto, I introduced my demo. In this part I'm going to talk about how to make the sky. The demo also computes an irradiance map and applies it to the cube. I'm going to talk about this in Part 3.
WebGL is now enabled by default in both Firefox 4.0 and Chrome 10.0, so I thought I give it a try and see what I can get out of it. The goal was to render some simple terrain, nice looking sky and waving grass. In this part of the description I will give the overview of how that works.
Since all the excitement about Minecraft I wondered what nice rendering effects could be done in such a restricted environment. I have decided to pursue that avenue of research and a variety of techniques will be presented in the following article.
A common approach to UV mapping terrain is to use planar mapping. This works well except with steep faces where the texture gets stretched. Solutions like tri-planar mapping can remedy this, but introduce other artefacts and are hard to get seamless. The picture below illustrates stretching artefacts with planar UV mapping.
In order to light terrain, it is not enough just to cast self shadows. It is also important to light it according to sky/sun occlusion and bounced secondary light. Lumiscape allows you to compute a lightmap for use in interactive applications. The lightmap is rendered using a GPU accelerated variant of radiosity. However, it is still exceedingly slow for large terrain textures.