Making Semi-transparent textures

written by Springheel

I don't know if people already know about this, but it's news to me.

When I was working on the lantern textures, I noticed that if I used the following shader the texture turned out to be transparent.

textures/darkmod/metal/flat/lamp_glass_lit_transparent     //glass is partially transparent
{
	glass
	noshadows

	{
		blend   add 
		map	models/darkmod/props/textures/lamp_glass_lit
		rgb 1
	 }
}

Better yet, it wasn't totally transparent--you could still see the texture itself, but you could see through it. The effect was pretty neat, so I tried it on a simple brush in a map. Here's the result.

You can clearly see the texture, but you can also nicely see through it. Imagine this as a window. And no vertex shaders necessary, so it shouldn't have conflicts with water (though I haven't tested it). The only downside is that you can't apply a normalmap or specular to the texture--if you do it becomes opaque. But for glass that wouldn't be important anyway. I think this might be a cool way to provide transparent windows but still keep the warm glowy effect. You wouldn't be able to use it for all window textures (since any frame or crosspiece in the texture would also become transparent unless they were straight black) but it will be very effective for some models, and might be useful in other places I haven't thought of yet (an underwater overlay comes to mind).

An example of it in models (the two outside ones).

Pinkdot pointed out that the "blend add" effect will brighten whatever the player sees through the texture. This would work well for looking into well-lit homes or for stained glass. By using the same technique, but replacing "add" with "filter" you can get semi-transparent textures that darken what you see through them, perfect for looking outside or into unlit homes.

It's possible to put the lit texture on one side of a brush and the unlit on the other and have both work, so windows could have the proper appearance depending on whether you are looking inside or outside.