CUGL 2.3
Cornell University Game Library

#include <CUComplexExtruder.h>
Public Member Functions  
ComplexExtruder ()  
ComplexExtruder (const std::vector< Vec2 > &points, bool closed)  
ComplexExtruder (const Path2 &path)  
~ComplexExtruder ()  
void  setJoint (poly2::Joint joint) 
poly2::Joint  getJoint () const 
void  setEndCap (poly2::EndCap endcap) 
poly2::EndCap  getEndCap () const 
void  setMitreLimit (float limit) 
float  getMitreLimit () const 
void  setResolution (Uint32 resolution) 
Uint32  getResolution () const 
void  set (const std::vector< Vec2 > &points, bool closed) 
void  set (const Vec2 *points, size_t size, bool closed) 
void  set (const Path2 &path) 
void  reset () 
void  clear () 
void  calculate (float stroke) 
Poly2  getPolygon () const 
Poly2 *  getPolygon (Poly2 *buffer) const 
std::vector< Path2 >  getBorder () const 
size_t  getBorder (std::vector< Path2 > &buffer) const 
This class is a factory for extruding wireframe paths into a solid path.
An extrusion of a path is a polygon that follows the path but gives it width. Hence it takes a path and turns it into a solid shape. This is more complicated than simply triangulating the original path. The new polygon has more vertices, depending on the choice of joint (shape at the corners) and cap (shape at the end).
This class is significantly more accurate than SimpleExtruder
. The extruded shape has no overlapping triangles and is safe to use with transparency. However, this comes at massive cost in speed. Even a simple line can take a full millisecond to compute, and more complicated paths will significantly affect frame rate. If you need to extrude a path at framerate, you should use SimpleExtruder
instead, and prerender to a texture if you need transparency.
As with all factories, the methods are broken up into three phases: initialization, calculation, and materialization. To use the factory, you first set the data (in this case a set of vertices or Path2
object) with the initialization methods. You then call the calculation method. Finally, you use the materialization methods to access the data in several different ways.
This division allows us to support multithreaded calculation if the data generation takes too long. However, note that this factory is not thread safe in that you cannot access data while it is still in midcalculation.
cugl::ComplexExtruder::ComplexExtruder  (  ) 
Creates an extruder with no vertex data.
cugl::ComplexExtruder::ComplexExtruder  (  const std::vector< Vec2 > &  points, 
bool  closed  
) 
Creates an extruder with the given vertex data.
The vertex data is copied. The extruder does not retain any references to the original data.
points  The vertices to extrude 
closed  Whether the path is closed 
cugl::ComplexExtruder::ComplexExtruder  (  const Path2 &  path  ) 
Creates an extruder with the given vertex data.
The path data is copied. The extruder does not retain any references to the original data.
path  The vertices to extrude 

inline 
Deletes this extruder, releasing all resources.
void cugl::ComplexExtruder::calculate  (  float  stroke  ) 
Performs a extrusion of the current vertex data.
An extrusion of a polygon is a second polygon that follows the path of the first one, but gives it width. Hence it takes a path and turns it into a solid shape. This is more complicated than simply triangulating the original polygon. The new polygon has more vertices, depending on the choice of joint (shape at the corners) and cap (shape at the end).
This method uses the Clipper library to perform the extrusion. While accurate and the preferred for static shapes, it is not ideal to call this method at framerate. Furthermore, while Clipper produces the boundary path of the extrusion, it does not triangulate it. This class uses a DelaunayTriangulator
to complete the calculation, as that triangulator produces the best triangles for geometric purposes.
stroke  The stroke width of the extrusion 
void cugl::ComplexExtruder::clear  (  ) 
Clears all internal data, including initial vertex data.
When this method is called, you will need to set a new vertices before calling calculate
. However, the joint, cap, and precision settings are preserved.
std::vector< Path2 > cugl::ComplexExtruder::getBorder  (  )  const 
Returns a (closed) path representing the extrusion border(s)
So long as the calculation is complete, the vector is guaranteed to contain at least one path. Counterclockwise paths correspond to the exterior boundary of the stroke. Clockwise paths are potential holes in the extrusion. There is no guarantee on the order of the returned paths.
If the calculation is not yet performed, this method will return the empty path.
size_t cugl::ComplexExtruder::getBorder  (  std::vector< Path2 > &  buffer  )  const 
Stores a (closed) path representing the extrusion border in the buffer
So long as the calculation is complete, the vector is guaranteed to contain at least one path. Counterclockwise paths correspond to the exterior boundary of the stroke. Clockwise paths are potential holes in the extrusion. There is no guarantee on the order of the returned paths.
This method will append append its results to the provided buffer. It will not erase any existing data. You should clear the buffer first if you do not want to preserve the original data.
If the calculation is not yet performed, this method will do nothing.
buffer  The buffer to store the path around the extrusion 
poly2::EndCap cugl::ComplexExtruder::getEndCap  (  )  const 
Returns the end cap value for the extrusion.
The end cap type determines how the extrusion draws the ends of the line segments at the start and end of the path. See poly2::EndCap
for the description of the types.
poly2::Joint cugl::ComplexExtruder::getJoint  (  )  const 
Returns the joint value for the extrusion.
The joint type determines how the extrusion joins the extruded line segments together. See poly2::Joint
for the description of the types.

inline 
Returns the mitre limit of the extrusion.
The mitre limit sets how "pointy" a mitre joint is allowed to be before the algorithm switches it back to a bevel/square joint. Small angles can have very large mitre offsets that go way offscreen.
In the case of Clipper, the mitre limit is the maximum distance in multiples of delta that vertices can be offset from their original positions before squaring is applied. By default this value is 2 (e.g. twice delta). That is also the smallest value allowed.
Poly2 cugl::ComplexExtruder::getPolygon  (  )  const 
Returns a polygon representing the path extrusion.
The polygon contains the a completely new set of vertices together with the indices defining the extrusion path. The extruder does not maintain references to this polygon and it is safe to modify it.
If the calculation is not yet performed, this method will return the empty polygon.
Stores the path extrusion in the given buffer.
This method will add both the new vertices, and the corresponding indices to the new buffer. If the buffer is not empty, the indices will be adjusted accordingly. You should clear the buffer first if you do not want to preserve the original data.
If the calculation is not yet performed, this method will do nothing.
buffer  The buffer to store the extruded polygon 

inline 
Returns the subdivision resolution for the Clipper library.
Clipper is not only accurate, it is also computationally stable. However, it achieves this stable by only using integer coordinates. This class supports float coordinates, but it does it by scaling the points to fit on an integer grid.
The resolution is the scaling factor before rounding the points to the nearest integer. It is effectively the same as specifying the number of integer subdivisions supported. For example, if the resolution is 8 (the default), then every point will be rounded to the nearest 1/8 value.
void cugl::ComplexExtruder::reset  (  ) 
Clears all computed data, but still maintains the settings.
This method preserves all initial vertex data, as well as the joint, cap, and precision settings.
void cugl::ComplexExtruder::set  (  const Path2 &  path  ) 
Sets the path for this extruder.
The path data is copied. The extruder does not retain any references to the original data.
This method resets all interal data. You will need to reperform the calculation before accessing data.
path  The path to extrude 
void cugl::ComplexExtruder::set  (  const std::vector< Vec2 > &  points, 
bool  closed  
) 
Sets the vertex data for this extruder.
The vertex data is copied. The extruder does not retain any references to the original data.
This method resets all interal data. You will need to reperform the calculation before accessing data.
points  The vertices to extruder 
closed  Whether the path is closed 
void cugl::ComplexExtruder::set  (  const Vec2 *  points, 
size_t  size,  
bool  closed  
) 
Sets the path for this extruder.
The path data is copied. The extruder does not retain any references to the original data. All points will be considered to be corner points.
This method resets all interal data. You will need to reperform the calculation before accessing data.
points  The path to extrude 
size  The number of points 
closed  Whether the path is closed 
void cugl::ComplexExtruder::setEndCap  (  poly2::EndCap  endcap  ) 
Sets the end cap value for the extrusion.
The end cap type determines how the extrusion draws the ends of the line segments at the start and end of the path. See poly2::EndCap
for the description of the types.
endcap  The extrusion end cap type 
void cugl::ComplexExtruder::setJoint  (  poly2::Joint  joint  ) 
Sets the joint value for the extrusion.
The joint type determines how the extrusion joins the extruded line segments together. See poly2::Joint
for the description of the types.
joint  The extrusion joint type 

inline 
Sets the mitre limit of the extrusion.
The mitre limit sets how "pointy" a mitre joint is allowed to be before the algorithm switches it back to a bevel/square joint. Small angles can have very large mitre offsets that go way offscreen.
In the case of Clipper, the mitre limit is the maximum distance in multiples of delta that vertices can be offset from their original positions before squaring is applied. By default this value is 2 (e.g. twice delta). That is also the smallest value allowed.
limit  The mitre limit for joint calculations 

inline 
Sets the subdivision resolution for the Clipper library.
Clipper is not only accurate, it is also computationally stable. However, it achieves this stable by only using integer coordinates. This class supports float coordinates, but it does it by scaling the points to fit on an integer grid.
The resolution is the scaling factor before rounding the points to the nearest integer. It is effectively the same as specifying the number of integer subdivisions supported. For example, if the resolution is 8 (the default), then every point will be rounded to the nearest 1/8 value.
resolution  The subdivision resolution 