Blender/addons/Mesh Outline Projector/README.md

@@ -0,0 +1,219 @@
+# Mesh Outline Projector
+
+A Blender addon that projects the vertical outline of selected objects onto a target mesh and transfers materials, perfect for architectural visualization and terrain mapping.
+
+## Overview
+
+Mesh Outline Projector takes the 2D silhouette of objects (when viewed from above) and "stamps" them onto a mesh below, automatically cutting the mesh and applying the source object's material to the projected area. Think of it as a cookie-cutter that works vertically through 3D space.
+
+### Key Features
+
+- **Vertical Projection**: Projects object outlines straight down (Z-axis) onto target surfaces
+- **Material Transfer**: Automatically applies source object materials to projected regions
+- **Clean Cutting**: Uses Blender's knife project for precise edge creation
+- **Smart Material Assignment**: Point-in-polygon detection with edge tolerance for accurate coverage
+- **Mesh Cleanup**: Automatically removes previous cuts with Limit Dissolve
+- **Intersection Detection**: Validates that objects actually overlap before processing
+- **Multiple Objects**: Process multiple source objects in a single operation
+
+## Installation
+
+1. Download `mesh_outline_projector.py`
+2. Open Blender → Edit → Preferences → Add-ons
+3. Click "Install..." and select the downloaded file
+4. Enable "Mesh: Mesh Outline Projector" in the add-ons list
+5. The panel appears in the 3D Viewport sidebar under the "Outline Projector" tab
+
+## Quick Start
+
+### Basic Workflow
+
+1. **Setup Scene**
+   - Position your source objects (e.g., building footprints) above your target mesh (e.g., terrain)
+   - Objects can be at any height - only horizontal (XY) overlap matters
+
+2. **Select Objects**
+   - Select one or more source objects (the objects whose outlines you want to project)
+   - Select the target mesh **last** (it becomes the active object - shown in orange)
+
+3. **Set View**
+   - Press **Numpad 7** to switch to top orthographic view
+   - This is required for knife project to work correctly
+
+4. **Run Operator**
+   - Open the sidebar (N key) → "Outline Projector" tab
+   - Adjust settings if needed (see below)
+   - Click "Project Outline"
+
+### What Happens
+
+The addon performs these steps automatically:
+
+1. **Validates** that source objects overlap with target in XY plane
+2. **Cleans up** the target mesh (Limit Dissolve + Quads to Tris)
+3. **Resets materials** to the first material slot
+4. **For each source object**:
+   - Extracts the horizontal perimeter edges (2D outline)
+   - Creates a temporary curve from these edges
+   - Uses knife project to cut the target mesh
+   - Assigns the source material to faces within the projected area
+5. **Reports** results with detailed console output
+
+## Settings
+
+### Dissolve Angle
+
+- **Default**: 0.04 degrees
+- **Range**: 0.0 - 5.0 degrees
+- **Purpose**: Controls how aggressively Limit Dissolve removes edges from previous operations
+
+**When to adjust:**
+- **Increase** (0.5-2.0°) if working with curved or organic surfaces
+- **Keep low** (0.01-0.1°) for architectural/flat surfaces
+- Higher values = more aggressive cleanup, fewer edges
+
+### Edge Tolerance
+
+- **Default**: 0.05 units
+- **Range**: 0.0 - 1.0 units
+- **Purpose**: How close a vertex must be to a polygon edge to be considered "on the edge"
+
+**When to adjust:**
+- **Increase** (0.1-0.5) if missing faces at the boundaries
+- **Decrease** (0.01-0.03) if getting material bleeding outside the outline
+- Affects the precision of material assignment at polygon boundaries
+
+## Use Cases
+
+### Architectural Site Plans
+
+Project building footprints onto terrain meshes:
+- Import IFC building models
+- Create terrain mesh from topography data
+- Project building outlines to create material zones
+
+### Terrain Texturing
+
+Stamp different material zones onto landscapes:
+- Roads, paths, and sidewalks
+- Water bodies and wetlands
+- Vegetation zones
+- Building pads
+
+### Urban Planning
+
+Visualize zoning and land use:
+- Different materials for residential/commercial/industrial zones
+- Overlay multiple boundary shapes
+- Iterate quickly as plans change
+
+## Tips & Best Practices
+
+### Before Running
+
+✅ **Do:**
+- Ensure source objects are above or at the same level as target mesh
+- Use simple, clean geometry for source objects
+- Press Numpad 7 (top view) before running
+- Save your work before first use
+
+❌ **Don't:**
+- Use extremely complex source meshes (simplify first)
+- Forget to set top view
+- Run on unsaved files (though Undo works)
+
+### Iteration Workflow
+
+The addon is designed for iteration:
+
+1. Run projection with objects A and B
+2. Adjust position/scale of object A
+3. Run projection again - mesh is automatically cleaned up
+4. Materials from both objects are preserved
+
+**The mesh reset happens automatically** - you can run the operator multiple times without manual cleanup.
+
+### Material Management
+
+- The addon preserves the **first material slot** as the "base" material
+- Source materials are added as new slots (slot 1, 2, 3, etc.)
+- Each run resets everything to the base material before applying projections
+- If you want a different base material, assign it to slot 0 before running
+
+## Troubleshooting
+
+### "No source objects intersect with target mesh"
+
+**Problem**: Objects don't overlap in the XY plane (when viewed from above)
+
+**Solutions**:
+- Check bounding boxes in debug output
+- Move objects horizontally to overlap
+- Objects can be at different Z heights - that's fine
+- Ensure you're not selecting the target as a source object
+
+### Materials not appearing correctly
+
+**Problem**: Materials bleeding outside boundaries or missing at edges
+
+**Solutions**:
+- Adjust **Edge Tolerance** setting
+- Increase if missing edge faces (try 0.1-0.2)
+- Decrease if bleeding outside (try 0.02-0.03)
+- Check that source objects have materials assigned
+
+### Blender crashes
+
+**Problem**: Crash during operation (rare)
+
+**Solutions**:
+- Ensure you're in **top orthographic view** (Numpad 7)
+- Simplify source mesh geometry
+- Update to latest Blender version
+- Check console for error messages
+
+### Unexpected results after multiple runs
+
+**Problem**: Results look different on subsequent runs
+
+**Solutions**:
+- This is normal - each run subdivides the mesh differently
+- Knife project creates new edges each time
+- Undo (Ctrl+Z) to return to previous state
+- The dissolve/cleanup helps but won't make mesh identical
+
+## Technical Details
+
+### How Outline Detection Works
+
+The addon uses three methods to find outline edges:
+
+1. **Boundary edges**: Edges with only one connected face
+2. **Silhouette edges**: Edges where connected faces have different vertical orientations
+3. **Perimeter edges**: Vertical edges at the outer boundary
+
+These are combined to form the complete 2D outline when viewed from above.
+
+### Material Assignment Algorithm
+
+1. **Extract horizontal edges** from the 3D outline
+2. **Build a 2D polygon** from these edges (in world XY space)
+3. **For each face** in the target mesh:
+   - Check if **all vertices** are inside the polygon OR near an edge
+   - Uses ray-casting for point-in-polygon test
+   - Uses perpendicular distance for edge proximity
+4. **Assign material** only if all vertices pass
+
+This ensures clean boundaries without bleeding.
+
+
+## Known Limitations
+
+- Requires **top orthographic view** (Numpad 7) to work correctly
+- Works best with **relatively flat** target meshes
+- Very **dense meshes** may slow down processing
+- **Complex source geometry** may produce unexpected outlines
+- Knife project can create **overlapping edges** in some cases
+- **Z-axis projection only** - cannot project at angles
+
+

Blender/addons/Mesh Outline Projector/__init__.py

@@ -69,6 +69,50 @@ def point_near_polygon_edge(point, polygon_verts, tolerance=0.05):
     return False
 
 
+def check_bounding_box_intersection(obj1, obj2):
+    """Check if two objects' bounding boxes intersect in the XY plane (horizontal)
+    
+    Note: Only checks X and Y overlap, not Z, because this is a vertical projection.
+    The source objects are expected to be above or below the target.
+    """
+    # Get world space bounding box corners
+    bbox1 = [obj1.matrix_world @ Vector(corner) for corner in obj1.bound_box]
+    bbox2 = [obj2.matrix_world @ Vector(corner) for corner in obj2.bound_box]
+    
+    # Get min/max for each axis
+    min1 = Vector((min(v.x for v in bbox1), min(v.y for v in bbox1), min(v.z for v in bbox1)))
+    max1 = Vector((max(v.x for v in bbox1), max(v.y for v in bbox1), max(v.z for v in bbox1)))
+    
+    min2 = Vector((min(v.x for v in bbox2), min(v.y for v in bbox2), min(v.z for v in bbox2)))
+    max2 = Vector((max(v.x for v in bbox2), max(v.y for v in bbox2), max(v.z for v in bbox2)))
+    
+    # Debug output
+    print(f"\n    Bounding Box Check: {obj1.name} vs {obj2.name}")
+    print(f"      {obj1.name} bounds:")
+    print(f"        X: [{min1.x:.2f}, {max1.x:.2f}]")
+    print(f"        Y: [{min1.y:.2f}, {max1.y:.2f}]")
+    print(f"        Z: [{min1.z:.2f}, {max1.z:.2f}]")
+    print(f"      {obj2.name} bounds:")
+    print(f"        X: [{min2.x:.2f}, {max2.x:.2f}]")
+    print(f"        Y: [{min2.y:.2f}, {max2.y:.2f}]")
+    print(f"        Z: [{min2.z:.2f}, {max2.z:.2f}]")
+    
+    # Check for overlap on X and Y axes only (horizontal plane)
+    # Z is ignored because we're projecting vertically
+    x_overlap = max1.x >= min2.x and max2.x >= min1.x
+    y_overlap = max1.y >= min2.y and max2.y >= min1.y
+    
+    print(f"      Overlap check (XY plane only - vertical projection):")
+    print(f"        X overlap: {x_overlap} (max1:{max1.x:.2f} >= min2:{min2.x:.2f} and max2:{max2.x:.2f} >= min1:{min1.x:.2f})")
+    print(f"        Y overlap: {y_overlap} (max1:{max1.y:.2f} >= min2:{min2.y:.2f} and max2:{max2.y:.2f} >= min1:{min1.y:.2f})")
+    print(f"        Z check: SKIPPED (vertical projection - objects can be above/below each other)")
+    
+    result = x_overlap and y_overlap
+    print(f"      Result: {'INTERSECTS (XY)' if result else 'NO INTERSECTION'}")
+    
+    return result
+
+
 def get_object_outline_edges_2d(obj, context):
     """Get the outline edges of an object when viewed from above (Z-axis)"""
     print(f"\n=== Getting outline edges for: {obj.name} ===")
@@ -230,7 +274,7 @@ def get_object_outline_edges_2d(obj, context):
 
 # View manipulation functions removed - now using direct bisect projection
 
-def project_outline_to_mesh(context, source_obj, target_obj, outline_edges):
+def project_outline_to_mesh(context, source_obj, target_obj, outline_edges, edge_tolerance=0.05):
     """Project outline edges vertically (Z-axis) onto target mesh using direct cutting"""
     
     print(f"\n=== Projecting outline from {source_obj.name} to {target_obj.name} ===")
@@ -418,7 +462,7 @@ def project_outline_to_mesh(context, source_obj, target_obj, outline_edges):
         source_max_z_local = (target_matrix_inv @ Vector((0, 0, source_max_z_world))).z
         
         print(f"  Source Z max: {source_max_z_world:.2f} (world), {source_max_z_local:.2f} (target local)")
-        print(f"  Material assignment: ALL vertices inside or on edge (tolerance: 0.05)")
+        print(f"  Material assignment: ALL vertices inside or on edge (tolerance: {edge_tolerance})")
         
         faces_assigned = 0
         faces_rejected_outside_polygon = 0
@@ -447,7 +491,7 @@ def project_outline_to_mesh(context, source_obj, target_obj, outline_edges):
                 
                 # Check if vertex is inside polygon OR on/near the edge (with tolerance)
                 inside = point_in_polygon_2d((vert_world.x, vert_world.y), polygon_2d_world)
-                on_edge = point_near_polygon_edge((vert_world.x, vert_world.y), polygon_2d_world, tolerance=0.05)
+                on_edge = point_near_polygon_edge((vert_world.x, vert_world.y), polygon_2d_world, tolerance=edge_tolerance)
                 
                 if not (inside or on_edge):
                     all_verts_inside = False
@@ -509,6 +553,16 @@ class MESH_OT_outline_project(bpy.types.Operator):
         precision=3
     )
     
+    edge_tolerance: bpy.props.FloatProperty(
+        name="Edge Tolerance",
+        description="Distance tolerance for vertices near polygon edges (world units)",
+        default=0.05,
+        min=0.0,
+        max=1.0,
+        step=0.01,
+        precision=3
+    )
+    
     @classmethod
     def poll(cls, context):
         return (context.active_object is not None and 
@@ -534,6 +588,38 @@ class MESH_OT_outline_project(bpy.types.Operator):
             self.report({'WARNING'}, "No source mesh objects selected")
             return {'CANCELLED'}
         
+        # Check which source objects actually intersect with the target
+        print(f"\nChecking bounding box intersections...")
+        intersecting_objects = []
+        non_intersecting_objects = []
+        
+        for source_obj in source_objects:
+            intersects = check_bounding_box_intersection(source_obj, target_obj)
+            if intersects:
+                intersecting_objects.append(source_obj)
+                print(f"  ✓ {source_obj.name} intersects with target")
+            else:
+                non_intersecting_objects.append(source_obj)
+                print(f"  ✗ {source_obj.name} does NOT intersect with target")
+        
+        # Report non-intersecting objects
+        if non_intersecting_objects:
+            non_intersecting_names = ", ".join([obj.name for obj in non_intersecting_objects])
+            print(f"\nWARNING: {len(non_intersecting_objects)} object(s) do not intersect: {non_intersecting_names}")
+            self.report({'WARNING'}, f"{len(non_intersecting_objects)} object(s) do not intersect with target")
+        
+        # If no objects intersect, cancel the operation
+        if not intersecting_objects:
+            print("\nERROR: No source objects intersect with the target mesh!")
+            print("Make sure your source objects overlap with the target mesh in 3D space.")
+            self.report({'ERROR'}, "No source objects intersect with target mesh - nothing to project!")
+            return {'CANCELLED'}
+        
+        print(f"\nProceeding with {len(intersecting_objects)} intersecting object(s)")
+        
+        # Use only intersecting objects from here on
+        source_objects = intersecting_objects
+        
         # Store original mode
         original_mode = context.mode
         print(f"Original mode: {original_mode}")
@@ -541,6 +627,7 @@ class MESH_OT_outline_project(bpy.types.Operator):
         # MESH CLEANUP: Remove previous knife cuts
         print(f"\nCleaning up target mesh...")
         print(f"Dissolve angle: {self.dissolve_angle} degrees")
+        print(f"Edge tolerance: {self.edge_tolerance} units")
         
         # Switch to edit mode for cleanup operations
         bpy.context.view_layer.objects.active = target_obj
@@ -601,7 +688,7 @@ class MESH_OT_outline_project(bpy.types.Operator):
                 continue
             
             # Project onto target
-            num_verts = project_outline_to_mesh(context, source_obj, target_obj, outline_edges)
+            num_verts = project_outline_to_mesh(context, source_obj, target_obj, outline_edges, self.edge_tolerance)
             total_verts += num_verts
             
             print(f"Projected {len(outline_edges)} edges from {source_obj.name}")
@@ -622,7 +709,7 @@ class VIEW3D_PT_outline_project(bpy.types.Panel):
     bl_idname = "VIEW3D_PT_outline_project"
     bl_space_type = 'VIEW_3D'
     bl_region_type = 'UI'
-    bl_category = 'Edit'
+    bl_category = 'Outline Projector'
     
     def draw(self, context):
         layout = self.layout
@@ -636,13 +723,15 @@ class VIEW3D_PT_outline_project(bpy.types.Panel):
         box = layout.box()
         box.label(text="Settings:")
         box.prop(context.scene, 'outline_dissolve_angle', text="Dissolve Angle", slider=True)
+        box.prop(context.scene, 'outline_edge_tolerance', text="Edge Tolerance", slider=True)
         
         row = layout.row()
         row.scale_y = 1.5
         op = row.operator("mesh.outline_project", icon='MOD_UVPROJECT')
         
-        # Pass the scene value to the operator
+        # Pass the scene values to the operator
         op.dissolve_angle = context.scene.outline_dissolve_angle
+        op.edge_tolerance = context.scene.outline_edge_tolerance
 
 
 def register():
@@ -660,6 +749,16 @@ def register():
         precision=3
     )
     
+    bpy.types.Scene.outline_edge_tolerance = bpy.props.FloatProperty(
+        name="Edge Tolerance",
+        description="Distance tolerance for vertices near polygon edges (world units)",
+        default=0.05,
+        min=0.0,
+        max=1.0,
+        step=0.01,
+        precision=3
+    )
+
 
 def unregister():
     bpy.utils.unregister_class(VIEW3D_PT_outline_project)
@@ -668,6 +767,8 @@ def unregister():
     # Unregister scene property
     if hasattr(bpy.types.Scene, 'outline_dissolve_angle'):
         del bpy.types.Scene.outline_dissolve_angle
+    if hasattr(bpy.types.Scene, 'outline_edge_tolerance'):
+        del bpy.types.Scene.outline_edge_tolerance
 
 
 if __name__ == "__main__":