Cycles / Blackbody to RGB node:

* Added a node to convert a temperature in Kelvin to an RGB color. This can be used e.g. for lights, to easily find the right color temperature. 
= Some common temperatures =
Candle light: 1500 Kelvin
Sunset/Sunrise: 1850 Kelvin
Studio lamps: 3200 Kelvin
Horizon daylight: 5000 Kelvin

Documentation: http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/More#Blackbody

Thanks to Philipp Oeser (lichtwerk), who essentially contributed to this with a patch! :)

This is part of my GSoC 2013 project. SVN merge of r57424, r57487, r57507, r57525, r58253 and r58774

1 files changed, 84 insertions, 0 deletions

diff --git a/intern/cycles/kernel/svm/svm_blackbody.h b/intern/cycles/kernel/svm/svm_blackbody.h
new file mode 100644
index 00000000000..3c6e11ca683
--- /dev/null
+++ b/intern/cycles/kernel/svm/svm_blackbody.h
@@ -0,0 +1,84 @@
+/*
+ * 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
+
+/* Blackbody Node */
+
+__device void svm_node_blackbody(KernelGlobals *kg, ShaderData *sd, float *stack, uint temperature_offset, uint col_offset)
+{
+	/* Output */
+	float3 color_rgb = make_float3(0.0f, 0.0f, 0.0f);
+
+	/* Input */
+	float temperature = stack_load_float(stack, temperature_offset);
+
+	if (temperature < BB_DRAPPER) {
+		/* just return very very dim red */
+		color_rgb = make_float3(1.0e-6f,0.0f,0.0f);
+	}
+	else if (temperature <= BB_MAX_TABLE_RANGE) {
+		/* This is the overall size of the table */
+		const int lookuptablesize = 956;
+		const float lookuptablenormalize = 1.0f/956.0f;
+
+		/* reconstruct a proper index for the table lookup, compared to OSL we don't look up two colors
+		just one (the OSL-lerp is also automatically done for us by "lookup_table_read") */
+		float t = powf((temperature - BB_DRAPPER) * (1.0f / BB_TABLE_SPACING), 1.0f/BB_TABLE_XPOWER);
+
+		int blackbody_table_offset = kernel_data.blackbody.table_offset;
+
+		/* Retrieve colors from the lookup table */
+		float lutval = t*lookuptablenormalize;
+		float R = lookup_table_read(kg, lutval, blackbody_table_offset, lookuptablesize);
+		lutval = (t + 319.0f*1.0f)*lookuptablenormalize;
+		float G = lookup_table_read(kg, lutval, blackbody_table_offset, lookuptablesize);
+		lutval = (t + 319.0f*2.0f)*lookuptablenormalize;
+		float B = lookup_table_read(kg, lutval, blackbody_table_offset, lookuptablesize);
+
+		R = powf(R, BB_TABLE_YPOWER);
+		G = powf(G, BB_TABLE_YPOWER);
+		B = powf(B, BB_TABLE_YPOWER);
+
+		color_rgb = make_float3(R, G, B);
+	}
+
+	/* Luminance */
+	float l = linear_rgb_to_gray(color_rgb);
+	if (l != 0.0f)
+		color_rgb /= l;
+
+	if (stack_valid(col_offset))
+		stack_store_float3(stack, col_offset, color_rgb);
+}
+
+CCL_NAMESPACE_END