Units: Support for fixed units

Users can select the main unit they want to use now.
Previously the displayed unit always depended on the magnitude of the value.
The old behavior can be restored by switching to the "Adaptive" mode for length, mass and time units.

Meters, kilograms and seconds are the default units for new and old scenes.

The selected unit is also the default unit for user input.
E.g. if cm is selected, whenever the user inputs a unitless number into a field of type length, it will be interpreted as cm.

Reviewer: brecht

Differential: https://developer.blender.org/D3740

1 files changed, 86 insertions, 3 deletions

diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 81e144925be..11d56206d6e 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -515,6 +515,7 @@ const EnumPropertyItem rna_enum_transform_orientation_items[] = {
 #include "BKE_animsys.h"
 #include "BKE_freestyle.h"
 #include "BKE_gpencil.h"
+#include "BKE_unit.h"
 
 #include "ED_info.h"
 #include "ED_node.h"
@@ -2015,6 +2016,68 @@ const EnumPropertyItem *rna_TransformOrientation_itemf(
 	return item;
 }
 
+static const EnumPropertyItem *get_unit_enum_items(int system, int type, bool *r_free)
+{
+	const void *usys;
+	int len;
+	bUnit_GetSystem(system, type, &usys, &len);
+
+	EnumPropertyItem *items = NULL;
+	int totitem = 0;
+
+	EnumPropertyItem adaptive = { 0 };
+	adaptive.identifier = "ADAPTIVE";
+	adaptive.name = "Adaptive";
+	adaptive.value = USER_UNIT_ADAPTIVE;
+	RNA_enum_item_add(&items, &totitem, &adaptive);
+
+	for (int i = 0; i < len; i++) {
+		if (!bUnit_IsSuppressed(usys, i)) {
+			EnumPropertyItem tmp = { 0 };
+			tmp.identifier = bUnit_GetName(usys, i);
+			tmp.name = bUnit_GetNameDisplay(usys, i);
+			tmp.value = i;
+			RNA_enum_item_add(&items, &totitem, &tmp);
+		}
+	}
+
+	*r_free = true;
+	return items;
+}
+
+const EnumPropertyItem *rna_get_length_unit_items(
+        bContext *UNUSED(C), PointerRNA *ptr, PropertyRNA *UNUSED(prop), bool *r_free)
+{
+	UnitSettings *units = ptr->data;
+	return get_unit_enum_items(units->system, B_UNIT_LENGTH, r_free);
+}
+
+const EnumPropertyItem *rna_get_mass_unit_items(
+        bContext *UNUSED(C), PointerRNA *ptr, PropertyRNA *UNUSED(prop), bool *r_free)
+{
+	UnitSettings *units = ptr->data;
+	return get_unit_enum_items(units->system, B_UNIT_MASS, r_free);
+}
+
+const EnumPropertyItem *rna_get_time_unit_items(
+        bContext *UNUSED(C), PointerRNA *ptr, PropertyRNA *UNUSED(prop), bool *r_free)
+{
+	UnitSettings *units = ptr->data;
+	return get_unit_enum_items(units->system, B_UNIT_TIME, r_free);
+}
+
+static void rna_unit_system_update(Main *UNUSED(bmain), Scene *scene, PointerRNA *UNUSED(ptr))
+{
+	UnitSettings *unit = &scene->unit;
+	if (unit->system == USER_UNIT_NONE) {
+		unit->length_unit = USER_UNIT_ADAPTIVE;
+		unit->mass_unit = USER_UNIT_ADAPTIVE;
+	}
+	else {
+		unit->length_unit = bUnit_GetBaseUnitOfType(unit->system, B_UNIT_LENGTH);
+		unit->mass_unit = bUnit_GetBaseUnitOfType(unit->system, B_UNIT_MASS);
+	}
+}
 
 #else
 
@@ -2915,7 +2978,7 @@ static void rna_def_statvis(BlenderRNA  *brna)
 	RNA_def_property_update(prop, 0, "rna_EditMesh_update");
 }
 
-static void rna_def_unit_settings(BlenderRNA  *brna)
+static void rna_def_unit_settings(BlenderRNA *brna)
 {
 	StructRNA *srna;
 	PropertyRNA *prop;
@@ -2940,7 +3003,7 @@ static void rna_def_unit_settings(BlenderRNA  *brna)
 	prop = RNA_def_property(srna, "system", PROP_ENUM, PROP_NONE);
 	RNA_def_property_enum_items(prop, unit_systems);
 	RNA_def_property_ui_text(prop, "Unit System", "The unit system to use for button display");
-	RNA_def_property_update(prop, NC_WINDOW, NULL);
+	RNA_def_property_update(prop, NC_WINDOW, "rna_unit_system_update");
 
 	prop = RNA_def_property(srna, "system_rotation", PROP_ENUM, PROP_NONE);
 	RNA_def_property_enum_items(prop, rotation_units);
@@ -2948,7 +3011,9 @@ static void rna_def_unit_settings(BlenderRNA  *brna)
 	RNA_def_property_update(prop, NC_WINDOW, NULL);
 
 	prop = RNA_def_property(srna, "scale_length", PROP_FLOAT, PROP_UNSIGNED);
-	RNA_def_property_ui_text(prop, "Unit Scale", "Scale to use when converting between blender units and dimensions");
+	RNA_def_property_ui_text(prop, "Unit Scale", "Scale to use when converting between blender units and dimensions."
+	                         " When working at microscopic or astronomical scale, a small or large unit scale"
+	                         " respectively can be used to avoid numerical precision problems");
 	RNA_def_property_range(prop, 0.00001, 100000.0);
 	RNA_def_property_ui_range(prop, 0.001, 100.0, 0.1, 6);
 	RNA_def_property_update(prop, NC_WINDOW, NULL);
@@ -2957,6 +3022,24 @@ static void rna_def_unit_settings(BlenderRNA  *brna)
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", USER_UNIT_OPT_SPLIT);
 	RNA_def_property_ui_text(prop, "Separate Units", "Display units in pairs (e.g. 1m 0cm)");
 	RNA_def_property_update(prop, NC_WINDOW, NULL);
+
+	prop = RNA_def_property(srna, "length_unit", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_items(prop, DummyRNA_DEFAULT_items);
+	RNA_def_property_enum_funcs(prop, NULL, NULL, "rna_get_length_unit_items");
+	RNA_def_property_ui_text(prop, "Length Unit", "Unit that will be used to display length values");
+	RNA_def_property_update(prop, NC_WINDOW, NULL);
+
+	prop = RNA_def_property(srna, "mass_unit", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_items(prop, DummyRNA_DEFAULT_items);
+	RNA_def_property_enum_funcs(prop, NULL, NULL, "rna_get_mass_unit_items");
+	RNA_def_property_ui_text(prop, "Mass Unit", "Unit that will be used to display mass values");
+	RNA_def_property_update(prop, NC_WINDOW, NULL);
+
+	prop = RNA_def_property(srna, "time_unit", PROP_ENUM, PROP_NONE);
+	RNA_def_property_enum_items(prop, DummyRNA_DEFAULT_items);
+	RNA_def_property_enum_funcs(prop, NULL, NULL, "rna_get_time_unit_items");
+	RNA_def_property_ui_text(prop, "Time Unit", "Unit that will be used to display time values");
+	RNA_def_property_update(prop, NC_WINDOW, NULL);
 }
 
 void rna_def_view_layer_common(StructRNA *srna, int scene)