uniform vec4 U_AmbientLightColor;
uniform vec4 U_AmbientMaterial;
uniform vec3 U_LightPos;
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()
{
	//ambient
	vec4 ambientColor = U_AmbientLightColor * U_AmbientMaterial;

	//diffuse
	vec3 N = normalize(V_Normal);
	vec3 L = normalize(U_LightPos);
	float diffuseIntensity = max(0.0, dot(L,N));
	vec4 diffuseColor = U_DiffuseLightColor * U_DiffuseMaterial * diffuseIntensity;

	//specular
	vec3 reflectDir = normalize(reflect(-L,N));//-L是入射光向量，通过reflect函数求到反射光方向
	vec3 viewDir = normalize(U_EyePos - V_WorldPos);
	vec4 specularColor = U_SpecularLightColor * U_SpecularMaterial * pow(max(0.0, dot(viewDir,reflectDir)), 64.0);


	gl_FragColor = ambientColor + diffuseColor + specularColor;
}