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geometryspec.md

@@ -78,3 +78,52 @@ The Geometry library incorporates the 3 parts:
   - shape groups (a set of shapes treated as a single solid shape) and
     indexes.
 
+### Basic classes
+
+  - **template<typename T> VECTOR2**  
+    Numerically stable (explicit specialization for T == int to avoid
+    overflow on multiplication) 2D vector class.  
+    Provides standard vector arithmentic, product, and distance
+    operators. Replacement of all wxPoints in the code that is not
+    related to the GUI.
+  - **template<class Vec> class BOX2**  
+    Bounding box class, based on EDA\_RECT. Intended to replace
+    EDA\_RECT, GAL's BOUNDING\_BOX and wxRects in the parts of code that
+    are not UI-specific.
+  - **class ANGLE**, implementing a restricted set of angles. Provides
+    accurate point rotation  
+    and vector-\>magnitude operators (in certain cases, without floating
+    point trigonometry and rounding errors  
+    associated with it). For example an ANGLE45 class could be derived  
+    from ANGLE and provide float-less (n \* 45 degree) directions for
+    all other geometry operations.
+  - **template<class Vec> class SEG**  
+    Class defining a line segment. Provides segment/line intersection,
+    point-to-segment and segment-to-segment operators.
+
+### Supported shapes
+
+Shapes mandatory for the P\&S router:
+
+  - **class SHAPE** : abstract interface for all **SHAPE\_** classes.
+  - **class SHAPE\_RECT**: axis-aligned rectangle
+  - **class SHAPE\_ORIENTED\_RECT**: rectangle with rotation
+  - **class SHAPE\_CIRCLE**: full circle 
+  - **class SHAPE\_LINE\_STRING**: string of line segments (a polyline)
+
+More complex shapes (for DRC)
+
+  - **class SHAPE\_POLYGON**: polygon with holes. Cleaned-up version of
+    CPolyLine.
+  - **class SHAPE\_ARC**: circular arc
+  - \*class SHAPE\_BEZIER: quadratic bezier curve.
+
+### Shape groups and indexes
+
+  - class SHAPE\_GROUP: group of shapes, behaving as a single body. Each
+    shape can have an individual offset (a vector) wrs to the group
+    origin.
+  - class SHAPE\_INDEX: class for spatial indexing of shapes. Internally
+    implements an R/R\*/Bounding Volume/Bounding Interval Tree. Provides
+    fast distance/collision query operator.
+