package main

// Uniform variables.
var Time float
var Cursor vec2
var ScreenSize vec2

// Fragment is the entry point of the fragment shader.
// Fragment returns the color value for the current position.
func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
	// You can define variables with a short variable declaration like Go.
	lightpos := vec3(Cursor, 50)
	lightdir := normalize(lightpos - position.xyz)
	normal := normalize(imageSrc1UnsafeAt(texCoord) - 0.5)
	ambient := 0.25
	diffuse := 0.75 * max(0.0, dot(normal.xyz, lightdir))

	// You can treat multiple source images by
	// imageSrc[N]At or imageSrc[N]UnsafeAt.
	return imageSrc0UnsafeAt(texCoord) * (ambient + diffuse)
}