Notation used in Ruby API documentation
Module: db
Description: A generic polygon filter adaptor
Polygon filters are an efficient way to filter polygons from a Region. To apply a filter, derive your own filter class and pass an instance to the Region#filter or Region#filtered method.
Conceptually, these methods take each polygon from the region and present it to the filter's 'selected' method. Based on the result of this evaluation, the polygon is kept or discarded.
The magic happens when deep mode regions are involved. In that case, the filter will use as few calls as possible and exploit the hierarchical compression if possible. It needs to know however, how the filter behaves. You need to configure the filter by calling is_isotropic, is_scale_invariant or is_isotropic_and_scale_invariant before using the filter.
You can skip this step, but the filter algorithm will assume the worst case then. This usually leads to cell variant formation which is not always desired and blows up the hierarchy.
Here is some example that filters triangles:
class TriangleFilter < RBA::PolygonFilter
# Constructor
def initialize
self.is_isotropic_and_scale_invariant # the triangle nature is not dependent on the scale or orientation
end
# Select only triangles
def selected(polygon)
return polygon.holes == 0 && polygon.num_points == 3
end
end
region = ... # some Region
triangles_only = region.filtered(TriangleFilter::new)
This class has been introduced in version 0.29.
| new PolygonFilter ptr | new | Creates a new object of this class |
| [const] | PolygonFilter ptr | _const_cast | Returns a non-const reference to self. | |
| void | _create | Ensures the C++ object is created | ||
| void | _destroy | Explicitly destroys the object | ||
| [const] | bool | _destroyed? | Returns a value indicating whether the object was already destroyed | |
| [const] | bool | _is_const_object? | Returns a value indicating whether the reference is a const reference | |
| void | _manage | Marks the object as managed by the script side. | ||
| void | _unmanage | Marks the object as no longer owned by the script side. | ||
| void | is_isotropic | Indicates that the filter has isotropic properties | ||
| void | is_isotropic_and_scale_invariant | Indicates that the filter is isotropic and scale invariant | ||
| void | is_scale_invariant | Indicates that the filter is scale invariant | ||
| void | requires_raw_input= | (bool flag) | Sets a value indicating whether the filter needs raw (unmerged) input | |
| [const] | bool | requires_raw_input? | Gets a value indicating whether the filter needs raw (unmerged) input | |
| [virtual,const] | bool | selected | (const Polygon polygon) | Selects a polygon |
| void | wants_variants= | (bool flag) | Sets a value indicating whether the filter prefers cell variants | |
| [const] | bool | wants_variants? | Gets a value indicating whether the filter prefers cell variants |
| void | create | Use of this method is deprecated. Use _create instead | ||
| void | destroy | Use of this method is deprecated. Use _destroy instead | ||
| [const] | bool | destroyed? | Use of this method is deprecated. Use _destroyed? instead | |
| [const] | bool | is_const_object? | Use of this method is deprecated. Use _is_const_object? instead |
_const_cast | Signature: [const] PolygonFilter ptr _const_cast Description: Returns a non-const reference to self. Basically, this method allows turning a const object reference to a non-const one. This method is provided as last resort to remove the constness from an object. Usually there is a good reason for a const object reference, so using this method may have undesired side effects. This method has been introduced in version 0.29.6. |
_create | Signature: void _create Description: Ensures the C++ object is created Use this method to ensure the C++ object is created, for example to ensure that resources are allocated. Usually C++ objects are created on demand and not necessarily when the script object is created. |
_destroy | Signature: void _destroy Description: Explicitly destroys the object Explicitly destroys the object on C++ side if it was owned by the script interpreter. Subsequent access to this object will throw an exception. If the object is not owned by the script, this method will do nothing. |
_destroyed? | Signature: [const] bool _destroyed? Description: Returns a value indicating whether the object was already destroyed This method returns true, if the object was destroyed, either explicitly or by the C++ side. The latter may happen, if the object is owned by a C++ object which got destroyed itself. |
_is_const_object? | Signature: [const] bool _is_const_object? Description: Returns a value indicating whether the reference is a const reference This method returns true, if self is a const reference. In that case, only const methods may be called on self. |
_manage | Signature: void _manage Description: Marks the object as managed by the script side. After calling this method on an object, the script side will be responsible for the management of the object. This method may be called if an object is returned from a C++ function and the object is known not to be owned by any C++ instance. If necessary, the script side may delete the object if the script's reference is no longer required. Usually it's not required to call this method. It has been introduced in version 0.24. |
_unmanage | Signature: void _unmanage Description: Marks the object as no longer owned by the script side. Calling this method will make this object no longer owned by the script's memory management. Instead, the object must be managed in some other way. Usually this method may be called if it is known that some C++ object holds and manages this object. Technically speaking, this method will turn the script's reference into a weak reference. After the script engine decides to delete the reference, the object itself will still exist. If the object is not managed otherwise, memory leaks will occur. Usually it's not required to call this method. It has been introduced in version 0.24. |
create | Signature: void create Description: Ensures the C++ object is created Use of this method is deprecated. Use _create instead Use this method to ensure the C++ object is created, for example to ensure that resources are allocated. Usually C++ objects are created on demand and not necessarily when the script object is created. |
destroy | Signature: void destroy Description: Explicitly destroys the object Use of this method is deprecated. Use _destroy instead Explicitly destroys the object on C++ side if it was owned by the script interpreter. Subsequent access to this object will throw an exception. If the object is not owned by the script, this method will do nothing. |
destroyed? | Signature: [const] bool destroyed? Description: Returns a value indicating whether the object was already destroyed Use of this method is deprecated. Use _destroyed? instead This method returns true, if the object was destroyed, either explicitly or by the C++ side. The latter may happen, if the object is owned by a C++ object which got destroyed itself. |
is_const_object? | Signature: [const] bool is_const_object? Description: Returns a value indicating whether the reference is a const reference Use of this method is deprecated. Use _is_const_object? instead This method returns true, if self is a const reference. In that case, only const methods may be called on self. |
is_isotropic | Signature: void is_isotropic Description: Indicates that the filter has isotropic properties Call this method before using the filter to indicate that the selection is independent of the orientation of the shape. This helps the filter algorithm optimizing the filter run, specifically in hierarchical mode. Examples for isotropic (polygon) filters are area or perimeter filters. The area or perimeter of a polygon depends on the scale, but not on the orientation of the polygon. |
is_isotropic_and_scale_invariant | Signature: void is_isotropic_and_scale_invariant Description: Indicates that the filter is isotropic and scale invariant Call this method before using the filter to indicate that the selection is independent of the scale and orientation of the shape. This helps the filter algorithm optimizing the filter run, specifically in hierarchical mode. An example for such a (polygon) filter is the square selector. Whether a polygon is a square or not does not depend on the polygon's orientation nor scale. |
is_scale_invariant | Signature: void is_scale_invariant Description: Indicates that the filter is scale invariant Call this method before using the filter to indicate that the selection is independent of the scale of the shape. This helps the filter algorithm optimizing the filter run, specifically in hierarchical mode. An example for a scale invariant (polygon) filter is the bounding box aspect ratio (height/width) filter. The definition of heigh and width depends on the orientation, but the ratio is independent on scale. |
new | Signature: [static] new PolygonFilter ptr new Description: Creates a new object of this class Python specific notes: |
requires_raw_input= | Signature: void requires_raw_input= (bool flag) Description: Sets a value indicating whether the filter needs raw (unmerged) input This flag must be set before using this filter. It tells the filter implementation whether the filter wants to have raw input (unmerged). The default value is 'false', meaning that the filter will receive merged polygons ('merged semantics'). Setting this value to false potentially saves some CPU time needed for merging the polygons. Also, raw input means that strange shapes such as dot-like edges, self-overlapping polygons, empty or degenerated polygons are preserved. Python specific notes: |
requires_raw_input? | Signature: [const] bool requires_raw_input? Description: Gets a value indicating whether the filter needs raw (unmerged) input See requires_raw_input= for details. Python specific notes: |
selected | Signature: [virtual,const] bool selected (const Polygon polygon) Description: Selects a polygon This method is the actual payload. It needs to be reimplemented in a derived class. It needs to analyze the polygon and return 'true' if it should be kept and 'false' if it should be discarded. |
wants_variants= | Signature: void wants_variants= (bool flag) Description: Sets a value indicating whether the filter prefers cell variants This flag must be set before using this filter for hierarchical applications (deep mode). It tells the filter implementation whether cell variants should be created (true, the default) or shape propagation will be applied (false). This decision needs to be made, if the filter indicates that it will deliver different results for scaled or rotated versions of the shape (see is_isotropic and the other hints). If a cell is present with different qualities - as seen from the top cell - the respective instances need to be differentiated. Cell variant formation is one way, shape propagation the other way. Typically, cell variant formation is less expensive, but the hierarchy will be modified. Python specific notes: |
wants_variants? | Signature: [const] bool wants_variants? Description: Gets a value indicating whether the filter prefers cell variants See wants_variants= for details. Python specific notes: |