Cycles: add Principled Hair BSDF.

This is a physically-based, easy-to-use shader for rendering hair and fur,
with controls for melanin, roughness and randomization.

Based on the paper "A Practical and Controllable Hair and Fur Model for
Production Path Tracing".

Implemented by Leonardo E. Segovia and Lukas Stockner, part of Google
Summer of Code 2018.

1 files changed, 133 insertions, 0 deletions

diff --git a/source/blender/nodes/shader/nodes/node_shader_bsdf_hair_principled.c b/source/blender/nodes/shader/nodes/node_shader_bsdf_hair_principled.c
new file mode 100644
index 00000000000..c5029852033
--- /dev/null
+++ b/source/blender/nodes/shader/nodes/node_shader_bsdf_hair_principled.c
@@ -0,0 +1,133 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2018 Blender Foundation.
+ * All rights reserved.
+ *
+ * The Original Code is: all of this file.
+ *
+ * Contributor(s): Lukas Stockner, L. E. Segovia
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#include "../node_shader_util.h"
+
+/* **************** OUTPUT ******************** */
+
+/* Color, melanin and absorption coefficient default to approximately same brownish hair. */
+static bNodeSocketTemplate sh_node_bsdf_hair_principled_in[] = {
+	{	SOCK_RGBA,		1, N_("Color"),						0.017513f, 0.005763f, 0.002059f, 1.0f, 0.0f, 1.0f},
+	{	SOCK_FLOAT,		1, N_("Melanin"),					0.8f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT,		1, N_("Melanin Redness"),			1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_RGBA,		1, N_("Tint"),						1.0f, 1.0f, 1.0f, 1.0f, 0.0f, 1.0f},
+	{	SOCK_VECTOR,	1, N_("Absorption Coefficient"),	0.245531f, 0.52f, 1.365f, 0.0f, 0.0f, 1000.0f},
+	{	SOCK_FLOAT,		1, N_("Roughness"),					0.3f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT,		1, N_("Radial Roughness"),			0.3f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT,		1, N_("Coat"),						0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT,		1, N_("IOR"),						1.55f, 0.0f, 0.0f, 0.0f, 0.0f, 1000.0f},
+	{	SOCK_FLOAT,		1, N_("Offset"),					2.f*((float)M_PI)/180.f, 0.0f, 0.0f, 0.0f, -M_PI_2, M_PI_2, PROP_ANGLE},
+	{	SOCK_FLOAT, 	1, N_("Random Color"),				0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT, 	1, N_("Random Roughness"),			0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+	{	SOCK_FLOAT,		1, N_("Random"),					0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_NONE, SOCK_HIDE_VALUE},
+	{	-1, 0, ""	},
+};
+
+static bNodeSocketTemplate sh_node_bsdf_hair_principled_out[] = {
+	{	SOCK_SHADER, 0, N_("BSDF")},
+	{	-1, 0, ""	}
+};
+
+/* Initialize the custom Parametrization property to Color. */
+static void node_shader_init_hair_principled(bNodeTree *UNUSED(ntree), bNode *node)
+{
+	node->custom1 = SHD_PRINCIPLED_HAIR_REFLECTANCE;
+}
+
+/* Triggers (in)visibility of some sockets when changing Parametrization. */
+static void node_shader_update_hair_principled(bNodeTree *UNUSED(ntree), bNode *node)
+{
+	bNodeSocket *sock;
+	int parametrization = node->custom1;
+
+	for (sock = node->inputs.first; sock; sock = sock->next) {
+		if (STREQ(sock->name, "Color")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_REFLECTANCE) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+		else if (STREQ(sock->name, "Melanin")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_PIGMENT_CONCENTRATION) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+		else if (STREQ(sock->name, "Melanin Redness")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_PIGMENT_CONCENTRATION) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+		else if (STREQ(sock->name, "Tint")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_PIGMENT_CONCENTRATION) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+		else if (STREQ(sock->name, "Absorption Coefficient")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_DIRECT_ABSORPTION) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+		else if (STREQ(sock->name, "Random Color")) {
+			if (parametrization == SHD_PRINCIPLED_HAIR_PIGMENT_CONCENTRATION) {
+				sock->flag &= ~SOCK_UNAVAIL;
+			}
+			else {
+				sock->flag |= SOCK_UNAVAIL;
+			}
+		}
+	}
+}
+
+/* node type definition */
+void register_node_type_sh_bsdf_hair_principled(void)
+{
+	static bNodeType ntype;
+
+	sh_node_type_base(&ntype, SH_NODE_BSDF_HAIR_PRINCIPLED, "Principled Hair BSDF", NODE_CLASS_SHADER, 0);
+	node_type_compatibility(&ntype, NODE_NEW_SHADING);
+	node_type_socket_templates(&ntype, sh_node_bsdf_hair_principled_in, sh_node_bsdf_hair_principled_out);
+	node_type_size_preset(&ntype, NODE_SIZE_LARGE);
+	node_type_init(&ntype, node_shader_init_hair_principled);
+	node_type_storage(&ntype, "", NULL, NULL);
+	node_type_update(&ntype, node_shader_update_hair_principled, NULL);
+
+	nodeRegisterType(&ntype);
+}