Cycles: Add Support for IES files as textures for light strength

This patch adds support for IES files, a file format that is commonly used to store the directional intensity distribution of light sources.
The new IES node is supposed to be plugged into the Strength input of the Emission node of the lamp.

Since people generating IES files do not really seem to care about the standard, the parser is flexible enough to accept all test files I have tried.
Some common weirdnesses are distributing values over multiple lines that should go into one line, using commas instead of spaces as delimiters and adding various useless stuff at the end of the file.

The user interface of the node is similar to the script node, the user can either select an internal Text or load a file.
Internally, IES files are handled similar to Image textures: They are stored in slots by the LightManager and each unique IES is assigned to one slot.

The local coordinate system of the lamp is used, so that the direction of the light can be changed. For UI reasons, it's usually best to add an area light,
rotate it and then change its type, since especially the point light does not immediately show its local coordinate system in the viewport.

Reviewers: #cycles, dingto, sergey, brecht

Reviewed By: #cycles, dingto, brecht

Subscribers: OgDEV, crazyrobinhood, secundar, cardboard, pisuke, intrah, swerner, micah_denn, harvester, gottfried, disnel, campbellbarton, duarteframos, Lapineige, brecht, juicyfruit, dingto, marek, rickyblender, bliblubli, lockal, sergey

Differential Revision: https://developer.blender.org/D1543

2 files changed, 57 insertions, 0 deletions

diff --git a/source/blender/makesrna/RNA_access.h b/source/blender/makesrna/RNA_access.h
index e512aebfa71..73beee51a8b 100644
--- a/source/blender/makesrna/RNA_access.h
+++ b/source/blender/makesrna/RNA_access.h
@@ -529,6 +529,7 @@ extern StructRNA RNA_ShaderNodeCombineRGB;
 extern StructRNA RNA_ShaderNodeExtendedMaterial;
 extern StructRNA RNA_ShaderNodeGeometry;
 extern StructRNA RNA_ShaderNodeHueSaturation;
+extern StructRNA RNA_ShaderNodeIESLight;
 extern StructRNA RNA_ShaderNodeInvert;
 extern StructRNA RNA_ShaderNodeLampData;
 extern StructRNA RNA_ShaderNodeMapping;
diff --git a/source/blender/makesrna/intern/rna_nodetree.c b/source/blender/makesrna/intern/rna_nodetree.c
index f5c464c0758..8dbb133a8ac 100644
--- a/source/blender/makesrna/intern/rna_nodetree.c
+++ b/source/blender/makesrna/intern/rna_nodetree.c
@@ -2946,6 +2946,30 @@ static bNodeSocket *rna_NodeOutputFile_slots_new(ID *id, bNode *node, bContext *
 	return sock;
 }
 
+static void rna_ShaderNodeTexIES_mode_set(PointerRNA *ptr, int value)
+{
+	bNode *node = (bNode *)ptr->data;
+	NodeShaderTexIES *nss = node->storage;
+
+	if (nss->mode != value) {
+		nss->mode = value;
+		nss->filepath[0] = '\0';
+
+		/* replace text datablock by filepath */
+		if (node->id) {
+			Text *text = (Text *)node->id;
+
+			if (value == NODE_IES_EXTERNAL && text->name) {
+				BLI_strncpy(nss->filepath, text->name, sizeof(nss->filepath));
+				BLI_path_rel(nss->filepath, G.main->name);
+			}
+
+			id_us_min(node->id);
+			node->id = NULL;
+		}
+	}
+}
+
 static void rna_ShaderNodeScript_mode_set(PointerRNA *ptr, int value)
 {
 	bNode *node = (bNode *)ptr->data;
@@ -3293,6 +3317,12 @@ static const EnumPropertyItem node_script_mode_items[] = {
 	{0, NULL, 0, NULL, NULL}
 };
 
+static EnumPropertyItem node_ies_mode_items[] = {
+	{NODE_IES_INTERNAL, "INTERNAL", 0, "Internal", "Use internal text datablock"},
+	{NODE_IES_EXTERNAL, "EXTERNAL", 0, "External", "Use external .ies file"},
+	{0, NULL, 0, NULL, NULL}
+};
+
 static const EnumPropertyItem node_principled_distribution_items[] = {
 	{SHD_GLOSSY_GGX, "GGX", 0, "GGX", ""},
 	{SHD_GLOSSY_MULTI_GGX, "MULTI_GGX", 0, "Multiscatter GGX", ""},
@@ -4471,6 +4501,32 @@ static void def_sh_subsurface(StructRNA *srna)
 	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_ShaderNodeSubsurface_update");
 }
 
+static void def_sh_tex_ies(StructRNA *srna)
+{
+	PropertyRNA *prop;
+
+	prop = RNA_def_property(srna, "ies", PROP_POINTER, PROP_NONE);
+	RNA_def_property_pointer_sdna(prop, NULL, "id");
+	RNA_def_property_struct_type(prop, "Text");
+	RNA_def_property_flag(prop, PROP_EDITABLE | PROP_ID_REFCOUNT);
+	RNA_def_property_ui_text(prop, "IES Text", "Internal IES file");
+	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+	RNA_def_struct_sdna_from(srna, "NodeShaderTexIES", "storage");
+
+	prop = RNA_def_property(srna, "filepath", PROP_STRING, PROP_FILEPATH);
+	RNA_def_property_ui_text(prop, "File Path", "IES light path");
+	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+	prop = RNA_def_property(srna, "mode", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_funcs(prop, NULL, "rna_ShaderNodeTexIES_mode_set", NULL);
+	RNA_def_property_enum_items(prop, node_ies_mode_items);
+	RNA_def_property_ui_text(prop, "Source", "Whether the IES file is loaded from disk or from a Text datablock");
+	RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+	RNA_def_struct_sdna_from(srna, "bNode", NULL);
+}
+
 static void def_sh_script(StructRNA *srna)
 {
 	PropertyRNA *prop;