fisheye.shader

shader_type canvas_item;

uniform float PI = 3.1415926535;
uniform float aperture = 178.0; 

void fragment(){ 
	float apertureHalf = 0.5 * aperture * (PI / 180.0); 
	float maxFactor = sin(apertureHalf);

	vec2 uv; 
	vec2 xy = 2.0 * UV.xy - vec2(1.0, 1.0);
	float d = length(xy);
	if (d < (2.0-maxFactor)) {
		d = length(xy * maxFactor);
		float z = sqrt(1.0 - d * d); float r = atan(d, z) / PI; 
		float phi = atan(xy.y, xy.x);
		uv.x = r * cos(phi) + 0.5;
		uv.y = r * sin(phi) + 0.5;
	} else { 
		uv = SCREEN_UV.xy;
	}
	vec4 c = vec4(texture(SCREEN_TEXTURE, vec2(uv.x, 1.0 - uv.y)));
	
	COLOR = c; 
}