lab/lmapper/shaders/utils.h

/*
	Copyright (c) 2006 soho vfx inc.
	Copyright (c) 2006 The 3Delight Team.
*/


#ifndef _utils_h
#define _utils_h

#define LOG05 -0.693147180559945  /* log(0.5) */
#ifndef UNDEFINED_UV
#define UNDEFINED_UV -10000000
#endif

#define ISUVDEFINED(U, V) ( abs(U) < 100000 && abs(V) < 100000 )

#define WRAPMAX (1.000001)
#define EPSILON 1e-6

float
luminance( color i_color )
{
	return
		0.3 * comp(i_color, 0) + 
		0.59 * comp(i_color, 1) + 
		0.11 * comp(i_color, 2);
}

// Compute the CIE luminance (Rec. 709) of a given color.
float CIEluminance(color c)
{
	return
	      comp(c, 0) * 0.212671
	    + comp(c, 1) * 0.715160
	    + comp(c, 2) * 0.072169;
}

// Compute the square of a given value.
float sq(float x)
{
	return x * x;
}

color
cabs( color i_color )
{
	return color(
		abs(comp(i_color, 0)), abs(comp(i_color,1)), abs(comp(i_color,2)) );
}

/* Taken from ARMAN */
float filteredpulse (float edge0, edge1, x, dx)
{
    float x0 = x - dx/2;
    float x1 = x0 + dx;
    return max (0, (min(x1,edge1)-max(x0,edge0)) / dx);
}

/* Taken from ARMAN and improved. */
float filteredpulsetrain (float edge, period, x, dx)
{
	/* First, normalize so period == 1 and our domain of interest is > 0 */
    float w = dx/period;
    float x0 = x/period - w/2;
    float x1 = x0+w;
    float nedge = edge / period;

	/* Definite integral of normalized pulsetrain from 0 to t */
    float integral (float t) { 
        extern float nedge;
        return ((1-nedge)*floor(t) + max(0,t-floor(t)-nedge));
    }

	float result;
	if( x0 == x1 )
	{
		/* Trap the unfiltered case so it doesn't return 0 (when dx << x). */
		result = (x0 - floor(x0) < nedge) ? 0 : 1;
	}
	else
	{
    	result = (integral(x1) - integral(x0)) / w;

		/*
			The above integral is subject to its own aliasing as we go beyond
			where the pattern should be extinct. We try to avoid that by
			switching to a constant value.
		*/
		float extinct = smoothstep( 0.4, 0.5, w );
		result = result + extinct * (1 - nedge - result);
	}

	return result;
}

/*
	Perlin's bias function
*/
float bias(float b, x)
{
    return pow(x, log(b)/LOG05);
}
	
void
colorBalance(
	output color io_outColor;
	output float io_outAlpha;
	uniform float i_alphaIsLuminance;
	float i_alphaGain;
	float i_alphaOffset;
	color i_colorGain;
	color i_colorOffset;
	uniform float i_invert; )
{
	if(i_invert != 0.0)
	{
		io_outColor = 1 - io_outColor;
		io_outAlpha = 1 - io_outAlpha;
	}

	if(i_alphaIsLuminance != 0.0)
	{
		io_outAlpha = luminance( io_outColor );
	}

	io_outColor *= i_colorGain;
	io_outColor += i_colorOffset;

	io_outAlpha *= i_alphaGain;
	io_outAlpha += i_alphaOffset;
}	

float srgbToLinear(float i_value)
{
	float linear;

	if(i_value <= 0.04045)
	{
		linear = (1.0/12.92) * i_value;
	}
	else
	{
		linear = pow((i_value + 0.055) * (1.0 / 1.055), 2.4);
	}

	return linear;
}

float rec709ToLinear(float i_value)
{
	float linear;

	if(i_value <= 0.081)
	{
		linear = (1.0 / 4.5) * i_value;
	}
	else
	{
		linear = pow((i_value + 0.099) * (1.0 / 1.099), (1.0 / 0.45));
	}

	return linear;
}

color getLinearizedColor(color i_color)
{
	color result = i_color;

	float profile;
	if( option( "user:defaultinputcolorprofile", profile ) != 0 )
	{
		if( profile == 3 )
		{
			result =
				color(
					srgbToLinear(result[0]),
					srgbToLinear(result[1]),
					srgbToLinear(result[2]) );
		}
		else if( profile == 5 )
		{
			result =
				color(
					rec709ToLinear(result[0]),
					rec709ToLinear(result[1]),
					rec709ToLinear(result[2]) );
		}
	}

	return result;
}

#endif