varying float X, Y;
varying vec4 Color;
varying float LightIntensity; 

uniform float A;
uniform float P;
uniform float Tol;

void
main( void )
{
	vec4 WHITE = vec4( 1., 1., 1., 1. );

	float f = fract( A*X );
	
	float t = smoothstep( 0.5-P-Tol, 0.5-P+Tol, f )  -  smoothstep( 0.5+P-Tol, 0.5+P+Tol, f );
	gl_FragColor = mix( WHITE, Color, t );
	gl_FragColor.rgb *= LightIntensity;
}