uniform vec4 U_AmbientLightColor;
uniform vec4 U_AmbientMaterial;
uniform vec4 U_LightPos;
uniform vec4 U_LightDirection;
uniform float U_Cutoff;
uniform vec4 U_DiffuseLightColor;
uniform vec4 U_DiffuseMaterial;
uniform vec3 U_EyePos;
uniform vec4 U_SpecularLightColor;
uniform vec4 U_SpecularMaterial;


varying vec3 V_Normal;
varying vec3 V_WorldPos;

void main()
{
	//角度转弧度
	float radianCutoff = U_Cutoff * 3.14 / 180;
	float cosThta = cos(radianCutoff);
	vec3 spotLightDirection = normalize(U_LightDirection.xyz);

	//ambient
	vec4 ambientColor = U_AmbientLightColor * U_AmbientMaterial;

	//diffuse
	vec3 L = vec3(0.0);
	float distance = 0.0;
	float attenuation = 1.0;

	//light attribute
	float constantFactor=0.5;
	float linearFactor=0.3;
	float expFactor=0.1;

	if(U_LightPos.w==0.0){
		//这是方向光
		L = normalize(U_LightPos.xyz);
	} else {
		//这是点光源
		//model point -> light pos
		L = normalize(U_LightPos.xyz - V_WorldPos);
		distance = length(U_LightPos.xyz - V_WorldPos);
		attenuation = 1.0 / (constantFactor + linearFactor * distance + expFactor * distance * distance);
	}


	L = normalize(-L);

	vec3 N = normalize(V_Normal);


	float currentCosThta = max(0.0, dot(L,spotLightDirection));

	float diffuseIntensity = 0.0;
	
	if(currentCosThta > cosThta){
		diffuseIntensity = pow(currentCosThta, U_LightDirection.w);
	}
	
	vec4 diffuseColor = U_DiffuseLightColor * U_DiffuseMaterial * diffuseIntensity * attenuation *4.0;

	gl_FragColor = ambientColor + diffuseColor;
}