Shape Manipulation and Cleanup
Shape Component Manipulation
The following operations directly work on the components of shapes: Polygons (faces), vertices and edges. They can be used to clean up imported shapes, separate or combine shapes.
Separate FacesSelect a shape, and click Separate Faces. This creates an individual shape for every face. All new shapes are put in the layer of the original shape.
Combine ShapesSelect multiple shapes, and click Combine Shapes. This creates one shape containing all components of the selected shapes.
This tool cleans the geometry of selected shapes. It is very useful to prepare imported meshes for 3D editing. The 3D editing works best after cleanup is performed, as this ensures correct connectivity information in the mesh. If you ever encounter problems with 3D editing, try a cleanup operation with the default values.The individual operations are performed in the direction indicated by the dialog, and work as follows:
- Merge Vertices: If the distance between two vertices is lower than the threshold, they are combined into one.
- Remove Coplanar Edges: Merge connected coplanar polygons.
- No Cleanup on Discontinuous Textures: When the texture coordinates are not continuous for a vertex, the all operations are skipped for this vertex.
- Remove Collinear Vertices: Multiple vertices on one straight line are removed.
- Remove Double Faces: Faces that have identical vertices (up to shift and inversion) are removed but one is kept.
- Remove Zero Faces: Faces with zero size are removed.
- Intersect Edges: All edges are intersected, and new vertices are inserted for every intersection point.
- Split Coplanar Polygons: Overlapping polygons on the same plane are split into non-overlapping polygons. This requires the "Intersect Edges" operation.
- Conform normals: Computes consistent normals using the connectivity and a heuristic that favors the world's up direction. It may be necessary to merge vertices and remove double faces in order to be successful.
- Distance Tolerance, Angle Tolerance: Tresholds for the above operations.
Further Manipulation Operations
. This operation reverses the normals (i.e., the orientation) of all selected faces. This step is often necessary after importing shapes with reversed orientation.
. This operation sets the first edge of a face to the currently selected edge. This step is often needed to orient a face's "zero" edge towards a street (e.g. for placing the buildings front correctly). If a face is selected, the highlighted gradient line indicates the first edge (with gradient from vertex 0 to vertex 1).
comp() in CGA reference). This operation marks selected edges as street edges. More specifically, it sets the street width object attribute array to 1 for selected edge indices. When mapped to a CGA rule, the streetWidth() attribute can be used to identify edges or faces that are facing a street. (see also
. This operation automatically calculates the first and street width attributes of the selected shapes. It works as follows: First it finds the nearest street (within 100m) for every edge of a shape. The corresponding street width attribute is set to the width of the nearest street. The edge closest to a street is set as the first edge (edge 0).
. Removes all holes from the selected shapes.
. In order to manually edit CGA generated models, they have to be converted to shapes first, using this command. Note that after this conversion, changes in attributes and CGA rules do not affect the shapes anymore.
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