uniform vec4 U_AmbientMaterial;
uniform vec4 U_AmbientLight;
uniform vec4 U_DiffuseMaterial;
uniform vec4 U_DiffuseLight;
uniform vec4 U_SpecularMaterial;
uniform vec4 U_SpecularLight;
uniform vec4 U_LightPos;
uniform vec4 U_CameraPos;
uniform vec4 U_LightDirection;
uniform vec4 U_LightOption;
varying vec4 V_Normal;
varying vec4 V_WorldPos;

void main(){
	//ambient
	vec4 ambientColor = U_AmbientMaterial * U_AmbientLight;

	//diffuse
	vec3 n = normalize(V_Normal.xyz);
	vec3 l = normalize(U_LightPos.xyz - V_WorldPos.xyz);
	float duffuseIntensity = max(0.0, dot(l,n));
	
	//¾Û¹â¼ÆËã
	float attenuation = 1.0;
	float distance = 0;
	float constantFactor = 0.5;
	float linearFactor = 0.3;
	float expFactor = 0.1;

	distance =length(U_LightPos.xyz - V_WorldPos.xyz);
	attenuation = 1.0 / (constantFactor + linearFactor*distance + expFactor*distance*distance);

	if(duffuseIntensity > 0){
		vec3 spot_direction = normalize(U_LightDirection.xyz);
		float currentCosThta = max(0.0, dot(-l, spot_direction)); 
		float radianCutoff = U_LightDirection.w * 3.14 / 180;
		float cosThta = cos(radianCutoff);
		if(currentCosThta > cosThta) {
			duffuseIntensity = pow(currentCosThta, U_LightOption.x)*U_LightOption.y;
		} else {
			duffuseIntensity = 0.0;
		}
	}

	vec4 duffuseColor = U_DiffuseMaterial * U_DiffuseLight * duffuseIntensity * attenuation;

	//specular
	vec4 specularColor = vec4(0);
	if(duffuseIntensity > 0){
		vec3 rd = normalize(reflect(-l,n));
		vec3 vd = normalize((U_CameraPos - V_WorldPos).xyz);
		float specularIntensity = pow(max(0.0,dot(vd,rd)), 128);
		specularColor = U_SpecularMaterial * U_SpecularLight * specularIntensity;
	}

	gl_FragColor = ambientColor + duffuseColor + specularColor;
}