#version 400
uniform vec4 color;
uniform sampler2D tex;
in vec2 texCoord;
out vec4 FragColor;
uniform bool modulate;
void main() {
	// Cf = color from fragment, Ct = color from texture
	// Cc = color from texture environment -- not set, defaults to (0,0,0,0)
	// Af = alpha from fragment, At = alpha from texture
	// C = output color, A = output alpha
	float f = texture(tex, texCoord).r;
	if (modulate) { 
		// GL_MODULATE: C
		// C = Cf * Ct
		// A = Af * At				
		FragColor = color * f;
	} else {
		// GL_BLEND:
		// C = Cf * (1-Ct) + Cc * Ct
		// A = Af * At
		vec3 C = color.rgb * (1 - f);
		float A = color.a * f;
		FragColor = vec4(C, A);
	}
}