 const float EFFECT_GAIN = 4.0;
 const float DIFFUSE_GAIN = 0.25;
 
+const float FRESNEL_BIAS = 0.0;
+const float FRESNEL_SCALE = 0.5;
+const float FRESNEL_POWER = 3.0;
+
 void main() {
 	vec4 kd = vec4(0.2, 0.2, 0.2, 1.0);
     vec4 ks = vec4(1.0, 1.0, 1.0, 1.0);

		if (lambert >= 0.0) {
			//	Blinn-Phong:
			vec3 lightDir = light_to_point_normal.xyz;
			vec3 viewDir = vec3(0.0, 0.0, 1.0); // ortho, normalize(-v_In.Position.xyz); perspective
			vec3 halfDir = normalize(lightDir + viewDir); // can be done in vertex shader
			float specAngle = max(dot(halfDir, normal), 0.0);
			specular = pow(vec4(specAngle), kp);

		color_specular += light_intensity * ks * specular;
	}

	vec4 solid_color = color_diffuse + color_lambert + color_specular + vec4(fresnel);

	//o_Color.rgb = color_lambert.rgb;
	o_Color.rgb = r_mask * (h_mask * highlight_color.rgb + solid_color.rgb);
	//o_Color.rgb = vec3(fresnel);
	o_Color.a = r_mask * color_diffuse.a;
}
