#version 150

in vec2 vertTexCoord;

out vec4 fragColor;
uniform vec4 color1;
uniform vec4 color2;
uniform vec4 color3;
uniform vec2 color2Spacing;
uniform vec2 color3Spacing;

float gridStep(float texCoord, float unitSize) {
	float width = fwidth(texCoord) / unitSize;
	float fraction = mod(texCoord, unitSize) / unitSize;
	return min(smoothstep(width * 0.875, width * 1.125, fraction), 1.0 - smoothstep(1.0 - width * 1.125, 1.0 - width * 0.875, fraction));
}

void main() {
	float colorMix3X = gridStep(vertTexCoord.x, color3Spacing.x);
	float colorMix3Y = gridStep(vertTexCoord.y, color3Spacing.y);
	float colorMix3 = 1.0 - min(colorMix3X, colorMix3Y);
	float colorMix2X = gridStep(vertTexCoord.x, color2Spacing.x);
	float colorMix2Y = gridStep(vertTexCoord.y, color2Spacing.y);
	float colorMix2 = min(1.0 - min(colorMix2X, colorMix2Y), 1.0 - colorMix3);
	float colorMix1X = gridStep(vertTexCoord.x, 1);
	float colorMix1Y = gridStep(vertTexCoord.y, 1);
	float colorMix1 = min(min(1.0 - min(colorMix1X, colorMix1Y), 1.0 - colorMix3), 1.0 - colorMix2);
	fragColor = (color1 * colorMix1 + color2 * colorMix2 + color3 * colorMix3);
}