#version 120

/*
	Cathode Ray Tube (CRT) Display Effect
	
	made by xcvb85 for HHS81's do328 (https://github.com/HHS81/do328)
	huge thanks to them!
	
	adapted slightly to the Cessna 208B's Weather Radar (RDR-2000)
*/

varying vec3 VNormal;
varying vec3 vViewVec;
varying	vec3 reflVec;

uniform float osg_SimulationTime;

uniform sampler2D BaseTex;
uniform sampler2D DirtTex;
uniform sampler2D Scanlines;
uniform samplerCube Environment;

uniform int display_enabled;
uniform float frame_factor;
uniform float test_value;
uniform float distortion;
uniform float flicker_factor;
uniform float view_y;

float SCANTHICK = 2.0;
float INTENSITY = 0.15;
float BRIGHTBOOST = 0.15;
//float DISTORTION = 0.03;
float THRESHOLD = 0.05;

vec2 TextureSize = vec2(800, 950);

vec4 bloomTexture2D(sampler2D texture, vec2 texCoords)
{
	vec4 texel = vec4(0, 0, 0, 0);
	float blur = 0.4;
	int size = 3;

	for(int x = -size; x <= size; x++)
	{
		for(int y = -size; y <= size; y++)
		{
			texel += texture2D(texture, texCoords + vec2(x/TextureSize.x, y/TextureSize.y));
		}
	}
	return (blur*texel/pow((2*size)+1, 2) + (1.0-blur)*texture2D(texture, texCoords));
}

vec2 distort(vec2 position)
{
	position = vec2(2.0 * position - 1.0);
	position = position /(1.0 - distortion * length(position));
	position =(position + 1.0) * 0.5;
	return position;
}

vec3 frame(vec2 position, vec3 color)
{
	// intersection between two ellipses and four circles
	position -= vec2(0.5);
	position *= vec2(2.0);

	float x2 = position.x * position.x;
	float y2 = position.y * position.y;

	if((x2/frame_factor) +(y2/20) > 1 || (x2/40) +(y2/frame_factor+0.03) > 1) {
		color = vec3(0.0, 0.0, 0.0);
	}

	// && length(abs(position)-vec2(frame_factor-0.08, frame_factor-0.06)) > 0.1
	float val = 0.6293*frame_factor + 0.2869;
	if( length(position) > frame_factor + 0.4 && length(abs(position)-vec2(val,val)) > 0.1 ) {
		color = vec3(0.0, 0.0, 0.0);
	}
	return color;
}

vec3 scanline(vec3 texel)
{
	vec3 scanlines = texture2D(Scanlines, vec2(150, 300)*gl_TexCoord[0].xy).rgb;
	texel *= 1.5*scanlines;
	return texel;
}

vec3 backlight(vec3 color)
{
	if(color.r < THRESHOLD && color.g < THRESHOLD && color.b < THRESHOLD) {
		color = vec3(THRESHOLD, THRESHOLD, THRESHOLD);
	}
	return color;
}

vec3 flickering(vec2 position, vec3 texel)
{
	texel *= 0.95+flicker_factor*(1-mod(5*osg_SimulationTime+position.y, 1.0));
	return texel;
}

vec3 reflection()
{
	vec3 coords;
	coords.x = reflVec.x; // distance
	coords.y = 1.5*reflVec.y + 0.5*view_y;
	coords.z = 1.5*reflVec.z - 0.25;
	vec3 reflection = 0.1*textureCube(Environment, coords).rgb;
	float NdotL;
	vec3 n = normalize(VNormal);
	vec3 lightDir = gl_LightSource[0].position.xyz;
	NdotL = max(dot(n, lightDir), 0.0);
	return NdotL*reflection;
}

void main()
{
	vec3 texel = vec3(0.0, 0.0, 0.0);
	vec3 dirt = 0.1*texture2D(DirtTex, gl_TexCoord[0].xy).rgb;

	// crt-effect
	if(display_enabled > 0) {
		vec2 position = distort(gl_TexCoord[0].xy);

		if(position.x > 0.0 && position.y > 0.0 && position.x < 1.0 && position.y < 1.0) {
//			texel = texture2D(BaseTex, position).rgb;
			texel = bloomTexture2D(BaseTex, position).rgb;
			texel = backlight(texel);
			texel = scanline(texel);
			texel = flickering(position, texel);
		}
		texel = frame(position, texel);
	}

	texel += dirt;
	texel += reflection();
	texel = clamp(texel, 0.0, 1.0);

	gl_FragColor = vec4(texel, 1.0);
}
