#version 330 core

// Input
in vec4 LightColor;

// Output
out vec4 PixelColor;

// Uniforms
uniform vec4 TintColor;

// Functions
float InterpolateDecelerate(float Min, float Max, float t, float Factor)
{
	float Alpha = (1.0 - pow(1.0 - t, Factor));
	return mix(Min, Max, Alpha);
}

// Main
void main()
{
	const float kMaxDepth = 75.0;		// Controls the max depth range that kDepthTintNear and kDepthTintFar are interpolated between
	const float kDepthTintNear = 0.0;	// Sets the pixel color offset for pixels close to the screen
	const float kDepthTintFar = -0.2;	// Sets the pixel color offset for pixels far from the screen
	const float kDepthCurveFactor = 2;	// Controls the strength of the interpolation curve (higher = color chabges faster from up close and slower from further away)
	
	// Apply some fake fog so pixels closer to the camera appear slightly brighter
	float Depth = ( (2.0 * gl_FragCoord.z - gl_DepthRange.near - gl_DepthRange.far) / (gl_DepthRange.far - gl_DepthRange.near) ) / gl_FragCoord.w;
	float DepthAlpha = min(Depth, kMaxDepth) / kMaxDepth;
	DepthAlpha = clamp(DepthAlpha, 0.0, 1.0);
	float DepthTint = InterpolateDecelerate(kDepthTintNear, kDepthTintFar, DepthAlpha, kDepthCurveFactor);
	PixelColor = (LightColor + vec4(DepthTint, DepthTint, DepthTint, 1.0)) * TintColor;
}