/*
 * Adapted from Open Shading Language with this license:
 *
 * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
 * All Rights Reserved.
 *
 * Modifications Copyright 2013, Blender Foundation.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * * Redistributions of source code must retain the above copyright
 *	 notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *	 notice, this list of conditions and the following disclaimer in the
 *	 documentation and/or other materials provided with the distribution.
 * * Neither the name of Sony Pictures Imageworks nor the names of its
 *	 contributors may be used to endorse or promote products derived from
 *	 this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

CCL_NAMESPACE_BEGIN

/* Wavelength to RGB */

ccl_device void svm_node_wavelength(ShaderData *sd, float *stack, uint wavelength, uint color_out)
{	
	// CIE colour matching functions xBar, yBar, and zBar for
	//	 wavelengths from 380 through 780 nanometers, every 5
	//	 nanometers.  For a wavelength lambda in this range:
	//		  cie_colour_match[(lambda - 380) / 5][0] = xBar
	//		  cie_colour_match[(lambda - 380) / 5][1] = yBar
	//		  cie_colour_match[(lambda - 380) / 5][2] = zBar
	const float cie_colour_match[81][3] = {
		{0.0014f,0.0000f,0.0065f}, {0.0022f,0.0001f,0.0105f}, {0.0042f,0.0001f,0.0201f},
		{0.0076f,0.0002f,0.0362f}, {0.0143f,0.0004f,0.0679f}, {0.0232f,0.0006f,0.1102f},
		{0.0435f,0.0012f,0.2074f}, {0.0776f,0.0022f,0.3713f}, {0.1344f,0.0040f,0.6456f},
		{0.2148f,0.0073f,1.0391f}, {0.2839f,0.0116f,1.3856f}, {0.3285f,0.0168f,1.6230f},
		{0.3483f,0.0230f,1.7471f}, {0.3481f,0.0298f,1.7826f}, {0.3362f,0.0380f,1.7721f},
		{0.3187f,0.0480f,1.7441f}, {0.2908f,0.0600f,1.6692f}, {0.2511f,0.0739f,1.5281f},
		{0.1954f,0.0910f,1.2876f}, {0.1421f,0.1126f,1.0419f}, {0.0956f,0.1390f,0.8130f},
		{0.0580f,0.1693f,0.6162f}, {0.0320f,0.2080f,0.4652f}, {0.0147f,0.2586f,0.3533f},
		{0.0049f,0.3230f,0.2720f}, {0.0024f,0.4073f,0.2123f}, {0.0093f,0.5030f,0.1582f},
		{0.0291f,0.6082f,0.1117f}, {0.0633f,0.7100f,0.0782f}, {0.1096f,0.7932f,0.0573f},
		{0.1655f,0.8620f,0.0422f}, {0.2257f,0.9149f,0.0298f}, {0.2904f,0.9540f,0.0203f},
		{0.3597f,0.9803f,0.0134f}, {0.4334f,0.9950f,0.0087f}, {0.5121f,1.0000f,0.0057f},
		{0.5945f,0.9950f,0.0039f}, {0.6784f,0.9786f,0.0027f}, {0.7621f,0.9520f,0.0021f},
		{0.8425f,0.9154f,0.0018f}, {0.9163f,0.8700f,0.0017f}, {0.9786f,0.8163f,0.0014f},
		{1.0263f,0.7570f,0.0011f}, {1.0567f,0.6949f,0.0010f}, {1.0622f,0.6310f,0.0008f},
		{1.0456f,0.5668f,0.0006f}, {1.0026f,0.5030f,0.0003f}, {0.9384f,0.4412f,0.0002f},
		{0.8544f,0.3810f,0.0002f}, {0.7514f,0.3210f,0.0001f}, {0.6424f,0.2650f,0.0000f},
		{0.5419f,0.2170f,0.0000f}, {0.4479f,0.1750f,0.0000f}, {0.3608f,0.1382f,0.0000f},
		{0.2835f,0.1070f,0.0000f}, {0.2187f,0.0816f,0.0000f}, {0.1649f,0.0610f,0.0000f},
		{0.1212f,0.0446f,0.0000f}, {0.0874f,0.0320f,0.0000f}, {0.0636f,0.0232f,0.0000f},
		{0.0468f,0.0170f,0.0000f}, {0.0329f,0.0119f,0.0000f}, {0.0227f,0.0082f,0.0000f},
		{0.0158f,0.0057f,0.0000f}, {0.0114f,0.0041f,0.0000f}, {0.0081f,0.0029f,0.0000f},
		{0.0058f,0.0021f,0.0000f}, {0.0041f,0.0015f,0.0000f}, {0.0029f,0.0010f,0.0000f},
		{0.0020f,0.0007f,0.0000f}, {0.0014f,0.0005f,0.0000f}, {0.0010f,0.0004f,0.0000f},
		{0.0007f,0.0002f,0.0000f}, {0.0005f,0.0002f,0.0000f}, {0.0003f,0.0001f,0.0000f},
		{0.0002f,0.0001f,0.0000f}, {0.0002f,0.0001f,0.0000f}, {0.0001f,0.0000f,0.0000f},
		{0.0001f,0.0000f,0.0000f}, {0.0001f,0.0000f,0.0000f}, {0.0000f,0.0000f,0.0000f}
	};

	float lambda_nm = stack_load_float(stack, wavelength);
	float ii = (lambda_nm-380.0f) * (1.0f/5.0f);  // scaled 0..80
	int i = float_to_int(ii);
	float3 color;
	
	if(i < 0 || i >= 80) {
		color = make_float3(0.0f, 0.0f, 0.0f);
	}
	else {
		ii -= i;
		const float *c = cie_colour_match[i];
		color = interp(make_float3(c[0], c[1], c[2]), make_float3(c[3], c[4], c[5]), ii);
	}
	
	color = xyz_to_rgb(color.x, color.y, color.z);
	color *= 1.0f/2.52f;	// Empirical scale from lg to make all comps <= 1
	
	/* Clamp to zero if values are smaller */
	color = max(color, make_float3(0.0f, 0.0f, 0.0f));

	if(stack_valid(color_out))
		stack_store_float3(stack, color_out, color);
}

CCL_NAMESPACE_END

