Blending Textures
Often we need to blend color values together, in this case to composite two images together, but it could be for any number of other reasons too.
Example Links
How to composite one texture over another
First we need to assign our two textures to two channels.
The first texture is a solid background, but the second is some foreground layer with transparency, i.e. an alpha value that varies between 0.0 and 1.0.
val channel0: Option[AssetPath] = Option(AssetPath("assets/fire-background.png"))
val channel1: Option[AssetPath] = Option(AssetPath("assets/campfire.png"))We can access the color of each texture by using the channel reference.
The mix function is then used to blend the two textures together, putting the foreground on
top of the background, based on the alpha value of the foreground.
All quite straightforward, but what is this mix function? mix is a GLSL term that is also
known as lerp, or linear interpolation. The arguments are: a) The value to interpolated from,
b) The value to interpolate to, c) The interpolation factor.
In this example we've used mix to blend the two textures together based on the alpha value
of the foreground texture, for example when the alpha value is 0.0 the result will be the
background texture, when the alpha value is 1.0 the result will be the foreground texture.
It is important to note that mix is just a mathematical function that will work with many
numeric and vector types, we're using it for textures here, but you can use it to interpolate
between any values you like.
inline def fragment: Shader[FragmentEnv, Unit] =
Shader[FragmentEnv] { env =>
def fragment(color: vec4): vec4 =
val background: vec4 = env.CHANNEL_0
val foreground: vec4 = env.CHANNEL_1
mix(background, foreground, foreground.a)
}