curveshader.gl

//small shader to curve the screen out torwards the edges

vec4 effect(vec4 color, Image tex, vec2 texture_coords, vec2 screen_coords) {
	const float col_divergence = 0.002;
	
	vec2 affected_coords = texture_coords;
	
	float squishstretch = 1.5;
	float squish = (texture_coords.x-0.5)/squishstretch;
	squish *= squish;
	
	//inverts the direction of the curve
	//squish *= -1;
	
	squish += 1;
	
	affected_coords.y = (affected_coords.y-0.5)*squish+0.5;
	
	squishstretch = 2.2;
	squish = (texture_coords.y-0.5)/squishstretch;
	squish *= squish;
	
	//inverts the direction of the curve
	//squish *= -1;
	
	squish += 1;
	
	affected_coords.x = (affected_coords.x-0.5)*squish+0.5;
	
	vec4 texturecolor = Texel(tex, affected_coords);
	
	//apply chromatic aberration by modifying the red and blue values
	vec2 diverged_coords = affected_coords;
	diverged_coords.x -= col_divergence;
	float divred = Texel(tex, diverged_coords).r;
	diverged_coords.x += col_divergence*2;
	float divblue = Texel(tex, diverged_coords).b;
	
	texturecolor.r = divred;
	texturecolor.b = divblue;
	
	//discard all pure black pixels; we need transparency
	if (texturecolor.r+texturecolor.g+texturecolor.b == 0) {
		texturecolor.a = 0;
	}
	
	//scanlines
	if (mod(affected_coords.y,0.01) < 0.005) {
		return texturecolor * color;
	} else {
		return (texturecolor * color) * 0.85;
	}
}