Can someone please explain this Fragment Shader? It is a Chroma Key Filter (Green screen effect)

Question

I\'m trying to understand how this chroma key filter works. Chroma Key, if you don\'t know, is a green screen effect. Would someone be able to explain how some of these func

Answer 1

The smoothstep function in GLSL evaluates a smooth cubic curve over an interval (specified by the first two parameters). As compared to GLSL's mix function, which linearly blends its parameters as:

smoothstep uses a Hermite cubic polynomial to determine the value

In your shader, blendValue is a smooth interpolation of your smoothing value based on the distance between the red and blue chrominance values.

Finally, gl_FragColor specifies the final fragment color (before blending, which occurs after completion of the fragment shader). In your case, it's the modulated value read from the input image, and a modulated alpha value for translucency.