using UnityEngine;
using System.Collections;

public class PlanetInit : MonoBehaviour 
{
	public GameObject m_sun;
	public Material m_groundMaterial;
	public Material m_skyMaterial;
	
	public float m_hdrExposure = 0.8f;
	public Vector3 m_waveLength = new Vector3(0.65f,0.57f,0.475f); // Wave length of sun light
	public float m_ESun = 20.0f; 			// Sun brightness constant
	public float m_kr = 0.0025f; 			// Rayleigh scattering constant
	public float m_km = 0.0010f; 			// Mie scattering constant
	public float m_g = -0.990f;				// The Mie phase asymmetry factor, must be between 0.999 to -0.999
	
	//Dont change these
	private const float m_outerScaleFactor = 1.025f; // Difference between inner and ounter radius. Must be 2.5%
	private float m_innerRadius;		 	// Radius of the ground sphere
	private float m_outerRadius;		 	// Radius of the sky sphere
	private float m_scaleDepth = 0.25f; 	// The scale depth (i.e. the altitude at which the atmosphere's average density is found)
				
	void Start () 
	{
		//Get the radius of the sphere. This presumes that the sphere mesh is a unit sphere (radius of 1)
		//that has been scaled uniformly on the x, y and z axis
		float radius = transform.lossyScale.x;
		
		m_innerRadius = radius;
		//The outer sphere must be 2.5% larger that the inner sphere
		m_outerRadius = m_outerScaleFactor * radius;
		
		InitMaterial(m_groundMaterial);
		InitMaterial(m_skyMaterial);
	}
	
	void Update () 
	{
		InitMaterial(m_groundMaterial);
		InitMaterial(m_skyMaterial);
	}
	
	void InitMaterial(Material mat)
	{
		Vector3 invWaveLength4 = new Vector3(1.0f / Mathf.Pow(m_waveLength.x, 4.0f), 1.0f / Mathf.Pow(m_waveLength.y, 4.0f), 1.0f / Mathf.Pow(m_waveLength.z, 4.0f));
		float scale = 1.0f / (m_outerRadius - m_innerRadius);

		mat.SetVector("v3LightPos", m_sun.transform.forward*-1.0f);
		mat.SetVector("v3InvWavelength", invWaveLength4);
		mat.SetFloat("fOuterRadius", m_outerRadius);
		mat.SetFloat("fOuterRadius2", m_outerRadius*m_outerRadius);
		mat.SetFloat("fInnerRadius", m_innerRadius);
		mat.SetFloat("fInnerRadius2", m_innerRadius*m_innerRadius);
		mat.SetFloat("fKrESun", m_kr*m_ESun);
		mat.SetFloat("fKmESun", m_km*m_ESun);
		mat.SetFloat("fKr4PI", m_kr*4.0f*Mathf.PI);
		mat.SetFloat("fKm4PI", m_km*4.0f*Mathf.PI);
		mat.SetFloat("fScale", scale);
		mat.SetFloat("fScaleDepth", m_scaleDepth);
		mat.SetFloat("fScaleOverScaleDepth", scale/m_scaleDepth);
		mat.SetFloat("fHdrExposure", m_hdrExposure);
		mat.SetFloat("g", m_g);
		mat.SetFloat("g2", m_g*m_g);
		mat.SetVector("v3LightPos", m_sun.transform.forward*-1.0f);
		mat.SetVector("v3Translate", transform.position);

	}
}