Creating Puddles and Wet Surfaces
Even in a game engine that's over a decade old, you can still pull off some snazzy visual effects with a bit of shader magic. One of these eye-candy examples is the creation of puddles and wet surfaces. This tutorial will show you how to do both, (as they are closely related in their functionality) and assumes you have a basic knowledge of id tech 3 level design, the shader system, and an advanced image-editing software. (In this tutorial, we will use GIMP)
Let's start with puddles. To begin, you'll need three different textures; we'll list them in the order they'll appear later on in the actual shader. The first texture will be a transparent texture with the shape of puddle you want to design. You need not apply any special colors, decorations or patterns to it - that's where the second texture comes in. Here we'll apply the special effects that make the puddle shine, (in many cases literally) such as environment mapping and turbulence, along with the texture map that will determine the overall appearance of the puddle. Note that the effects will vary depending on what type of substance you want to produce - in this tutorial we'll stick to a classic water puddle. The third and final required texture is an opaque version of the first texture, with the puddle shape being exactly the same but all transparent areas being white instead.