Stair Modifier : You can now set a total length target that will update individual tread runs automatically. You can lock the total length target and modify tread run or number of treads to keep the same global dimensions.

src/bonsai/bonsai/bim/module/model/prop.py

@@ -250,6 +250,24 @@ class BIMArrayProperties(PropertyGroup):
     )
 
 
+def update_total_length_target(self, context):
+    self["tread_run"] = self.total_length_target / (self.number_of_treads + 1)
+
+
+def update_tread_run(self, context):
+    if self.total_length_lock:
+        self["number_of_treads"] = int((self.total_length_target / self.tread_run) - 1)
+    else:
+        self["total_length_target"] = (self.number_of_treads + 1) * self.tread_run
+
+
+def update_number_of_treads(self, context):
+    if self.total_length_lock:
+        self["tread_run"] = self.total_length_target / (self.number_of_treads + 1)
+    else:
+        self["total_length_target"] = (self.number_of_treads + 1) * self.tread_run
+
+
 class BIMStairProperties(PropertyGroup):
     def validate_nosing_value(self, context):
         if self.stair_type != "WOOD/STEEL" and self.nosing_length < 0:
@@ -265,9 +283,26 @@ class BIMStairProperties(PropertyGroup):
     is_editing: bpy.props.BoolProperty(default=False)
     width: bpy.props.FloatProperty(name="Width", default=1.2, soft_min=0.01, subtype="DISTANCE")
     height: bpy.props.FloatProperty(name="Height", default=1.0, soft_min=0.01, subtype="DISTANCE")
-    number_of_treads: bpy.props.IntProperty(name="Number of Treads", default=6, soft_min=1)
+    number_of_treads: bpy.props.IntProperty(
+        name="Number of Treads", default=6, soft_min=1, update=update_number_of_treads
+    )
+    total_length_target: bpy.props.FloatProperty(
+        name="Total Length Target",
+        default=3.0,
+        soft_min=0.01,
+        subtype="DISTANCE",
+        update=update_total_length_target,
+        description="Total Length Target, might not be exactly respected depending on the parameters",
+    )
+    total_length_lock: bpy.props.BoolProperty(
+        default=False,
+        name="Lock Total Length",
+        description="Lock Total Length when changing number of treads or tread run",
+    )
     tread_depth: bpy.props.FloatProperty(name="Tread Depth", default=0.25, soft_min=0.01, subtype="DISTANCE")
-    tread_run: bpy.props.FloatProperty(name="Tread Run", default=0.3, soft_min=0.01, subtype="DISTANCE")
+    tread_run: bpy.props.FloatProperty(
+        name="Tread Run", default=0.3, soft_min=0.01, subtype="DISTANCE", update=update_tread_run
+    )
     base_slab_depth: bpy.props.FloatProperty(name="Base Slab Depth", default=0.25, soft_min=0, subtype="DISTANCE")
     top_slab_depth: bpy.props.FloatProperty(name="Top Slab Depth", default=0.25, soft_min=0, subtype="DISTANCE")
     has_top_nib: bpy.props.BoolProperty(name="Has Top Nib", default=True)

src/bonsai/bonsai/bim/module/model/ui.py

@@ -311,6 +311,15 @@ class BIM_PT_stair(bpy.types.Panel):
                         self.layout.prop(props, prop_name, text="")
                     else:
                         self.layout.prop(props, prop_name)
+                    if prop_name == "height":  # Weak but we just want to insert this inside props drawing
+                        row_length = self.layout.row(align=True)
+                        row_length.prop(props, "total_length_target")
+                        row_length.prop(
+                            props,
+                            "total_length_lock",
+                            text="",
+                            icon="LOCKED" if props.total_length_lock else "UNLOCKED",
+                        )
                 regenerate_stair_mesh(obj)
             else:
                 calculated_params = StairData.data["calculated_params"]