#include "material.h"
#include "locillum.h"
#include "noises.h"
#include "filterwidth.h"
//! The Bark_Colour Shader
/**
* This file contains the Bark_Colour surface shader. 
* @author Hannes Ricklefs - NCCA 2005
*/

//! A Function
/**
* Small helper function if color values are expressed in 0 - 255. 
* \param i - number to be devided by 255
* \return - the equivalent value i space 0 - 1 
*/
float photo_prman(float i) {
	return i/255;
}

//! The surface Shader
/**
* This surface shader applies the colour to a surface in order to create
* a Photorealistic tree bark image. 
* Inputs:
* \param Kd 				- the diffuse component
* \param Ka 				- the ambient component
* \param crack_moss_height 	- the hight up to which the moss in the crack should grow
* \param top_moss_height 	- the hight from which the moss should grow on top of the surface
* \param grain 				- the amount of grain to mix the overall color of the surface
* \param roughness			- the roughness parameter of the surface
* \param baseColor 			- the color for the bottom of the cracks
* \param middleColor 		- the color between the cracks and the top of the surface
* \param topColor			- the color for the top of the surface
* \param topMoss			- the color of the Moss to grow on top of the surface
* \param crackMoss 			- the color of the Moss to grow in the cracks
* \param space 				- the space in which to apply the shader.
*/
surface Bark_Colour(float Kd = 0.7,
						 Ka = 1,
						crack_moss_height = 3.0,
						top_moss_height = 6.0,
						grain = 0.5,
						roughness = 0.5;
						varying color baseColor = color (photo_prman(194), photo_prman(206), photo_prman(104)),
						middleColor = color (photo_prman(119), photo_prman(92), photo_prman(25)),
						topColor = color (photo_prman(206), photo_prman(175), photo_prman(95)),
						topMoss = color (photo_prman(174), photo_prman(200), photo_prman(73)),
						crackMoss = color (0.3,0.3,0.2);
						string space="shader";
                        )
{
	//standard shader initialisation
	normal n = normalize(N);
	normal Nf = faceforward(n, I);
	
	point PP = transform(space, P);

	float height = 0;
	color finalColor = 0;
	
	//get the displacment
	if(displacement("hump",height) == 1) {
		//generate a variation of colours-
		color darkColor = baseColor - 0.025;
		color lowBaseColor =  baseColor + 0.025;
		color lowerMiddleColor = middleColor - 0.0125;
		color higherMiddleColor = middleColor + 0.0125;
		color lowTopColor = topColor - 0.025;
		color higherTopColor = topColor + 0.025;
		//interpolate the color
		finalColor = spline ( height, darkColor, 
										baseColor, 
										lowBaseColor,
										lowerMiddleColor, 
										middleColor, 
										higherMiddleColor,
										topColor,
										lowTopColor,
										higherTopColor);
     
		
		//apply a more organic look to the surface
		float mixvalue = fBm(2*PP,filterwidthp(PP),6,2,grain);
		
		//check if we grow moss in the cracks
		if(height < crack_moss_height) {
			//push the value more towards the Moss value
			finalColor = mix(finalColor,crackMoss,mixvalue+0.5);
			
   		}
		
		//check if we grow moss on the surface
		if(height > top_moss_height) {
			//push the value more towards the Moss value
			finalColor = mix(finalColor,topMoss,mixvalue+0.5);
		}	
		
	
	}


	//assigne the final color based on the clay material
	Ci = finalColor * (Ka*ambient() + Kd*LocIllumOrenNayar(Nf,-normalize(I),roughness));
	Oi = Os;
}