2 files changed, 81 insertions, 2 deletions

diff --git a/source/blender/makesrna/intern/rna_mesh.c b/source/blender/makesrna/intern/rna_mesh.c
index fe6f33abc8c..cf634f9c7d4 100644
--- a/source/blender/makesrna/intern/rna_mesh.c
+++ b/source/blender/makesrna/intern/rna_mesh.c
@@ -338,6 +338,29 @@ static void rna_MeshLoop_normal_get(PointerRNA *ptr, float *values)
 	}
 }
 
+static void rna_MeshLoop_tangent_get(PointerRNA *ptr, float *values)
+{
+	Mesh *me = rna_mesh(ptr);
+	MLoop *ml = (MLoop *)ptr->data;
+	const float (*vec)[4] = CustomData_get(&me->ldata, (int)(ml - me->mloop), CD_MLOOPTANGENT);
+
+	if (!vec) {
+		zero_v3(values);
+	}
+	else {
+		copy_v3_v3(values, (const float *)vec);
+	}
+}
+
+static float rna_MeshLoop_bitangent_sign_get(PointerRNA *ptr)
+{
+	Mesh *me = rna_mesh(ptr);
+	MLoop *ml = (MLoop *)ptr->data;
+	const float (*vec)[4] = CustomData_get(&me->ldata, (int)(ml - me->mloop), CD_MLOOPTANGENT);
+
+	return (vec) ? (*vec)[3] : 0.0f;
+}
+
 static void rna_MeshPolygon_normal_get(PointerRNA *ptr, float *values)
 {
 	Mesh *me = rna_mesh(ptr);
@@ -1870,10 +1893,26 @@ static void rna_def_mloop(BlenderRNA *brna)
 	RNA_def_property_range(prop, -1.0f, 1.0f);
 	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
 	RNA_def_property_float_funcs(prop, "rna_MeshLoop_normal_get", NULL, NULL);
-	RNA_def_property_ui_text(prop, "Loop Normal",
+	RNA_def_property_ui_text(prop, "Normal",
 	                         "Local space unit length split normal vector of this vertex for this polygon "
-	                         "(only computed on demand!)");
+	                         "(must be computed beforehand using calc_normals_split or calc_tangents)");
 
+	prop = RNA_def_property(srna, "tangent", PROP_FLOAT, PROP_DIRECTION);
+	RNA_def_property_array(prop, 3);
+	RNA_def_property_range(prop, -1.0f, 1.0f);
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_float_funcs(prop, "rna_MeshLoop_tangent_get", NULL, NULL);
+	RNA_def_property_ui_text(prop, "Tangent",
+	                         "Local space unit length tangent vector of this vertex for this polygon "
+	                         "(must be computed beforehand using calc_tangents)");
+
+	prop = RNA_def_property(srna, "bitangent_sign", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_range(prop, -1.0f, 1.0f);
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_float_funcs(prop, "rna_MeshLoop_bitangent_sign_get", NULL, NULL);
+	RNA_def_property_ui_text(prop, "Bitangent Sign",
+	                         "Sign of the bitangent vector of this vertex for this polygon (must be computed "
+	                         "beforehand using calc_tangents, bitangent = bitangent_sign * cross(normal, tangent))");
 }
 
 static void rna_def_mpolygon(BlenderRNA *brna)
diff --git a/source/blender/makesrna/intern/rna_mesh_api.c b/source/blender/makesrna/intern/rna_mesh_api.c
index 34f21046a92..76097b04c99 100644
--- a/source/blender/makesrna/intern/rna_mesh_api.c
+++ b/source/blender/makesrna/intern/rna_mesh_api.c
@@ -34,6 +34,8 @@
 
 #include "RNA_define.h"
 
+#include "DNA_customdata_types.h"
+
 #include "BLI_sys_types.h"
 
 #include "BLI_utildefines.h"
@@ -100,6 +102,32 @@ static void rna_Mesh_free_normals_split(Mesh *mesh)
 	CustomData_free_layers(&mesh->ldata, CD_NORMAL, mesh->totloop);
 }
 
+static void rna_Mesh_calc_tangents(Mesh *mesh, ReportList *reports, const char *uvmap)
+{
+	float (*r_looptangents)[4];
+
+	if (CustomData_has_layer(&mesh->ldata, CD_MLOOPTANGENT)) {
+		r_looptangents = CustomData_get_layer(&mesh->ldata, CD_MLOOPTANGENT);
+		memset(r_looptangents, 0, sizeof(float[4]) * mesh->totloop);
+	}
+	else {
+		r_looptangents = CustomData_add_layer(&mesh->ldata, CD_MLOOPTANGENT, CD_CALLOC, NULL, mesh->totloop);
+		CustomData_set_layer_flag(&mesh->ldata, CD_MLOOPTANGENT, CD_FLAG_TEMPORARY);
+	}
+
+	/* Compute loop normals if needed. */
+	if (!CustomData_has_layer(&mesh->ldata, CD_NORMAL)) {
+		rna_Mesh_calc_normals_split(mesh, (float)M_PI);
+	}
+
+	BKE_mesh_loop_tangents(mesh, uvmap, r_looptangents, reports);
+}
+
+static void rna_Mesh_free_tangents(Mesh *mesh)
+{
+	CustomData_free_layers(&mesh->ldata, CD_MLOOPTANGENT, mesh->totloop);
+}
+
 static void rna_Mesh_calc_smooth_groups(Mesh *mesh, int use_bitflags, int *r_poly_group_len,
                                         int **r_poly_group, int *r_group_total)
 {
@@ -141,6 +169,18 @@ void RNA_api_mesh(StructRNA *srna)
 	func = RNA_def_function(srna, "free_normals_split", "rna_Mesh_free_normals_split");
 	RNA_def_function_ui_description(func, "Free split vertex normals");
 
+	func = RNA_def_function(srna, "calc_tangents", "rna_Mesh_calc_tangents");
+	RNA_def_function_flag(func, FUNC_USE_REPORTS);
+	RNA_def_function_ui_description(func,
+	                                "Compute tangents and bitangent signs, to be used together with the split normals "
+	                                "to get a complete tangent space for normal mapping "
+	                                "(split normals are also computed if not yet present)");
+	parm = RNA_def_string(func, "uvmap", "", MAX_CUSTOMDATA_LAYER_NAME, "",
+	                      "Name of the UV map to use for tangent space computation");
+
+	func = RNA_def_function(srna, "free_tangents", "rna_Mesh_free_tangents");
+	RNA_def_function_ui_description(func, "Free tangents");
+
 	func = RNA_def_function(srna, "calc_tessface", "ED_mesh_calc_tessface");
 	RNA_def_function_ui_description(func, "Calculate face tessellation (supports editmode too)");