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32 
33 /*! \file SbClip.h */
34 #include <Inventor/SbClip.h>
35 #include <Inventor/SbVec2f.h>
36 #include <Inventor/SbPlane.h>
37 #include <cstdio>
38 #include <cassert>
39 
40 /*!
41   \class SbClip SbClip.h include/Inventor/base/SbClip.h
42   \brief The SbClip class is a generic polygon clipper class.
43 
44   \ingroup base
45 
46   It is used by first adding all vertices in the polygon, and then
47   clipping against any number of planes. If you need to supply
48   additional information per vertex (e.g. texture coordinates), you
49   should supply a callback in the constructor, and a pointer to your
50   vertex structure in addVertex(). For every new vertex created, the
51   callback is called with the line being clipped, including the
52   pointers to your vertex structures and the position of the new
53   (clipped against some plane) vertex. You should then create a new
54   vertex structure, calculate your data (e.g. a new texture
55   coordinate) and return a pointer to this structure.
56 
57   \COIN_CLASS_EXTENSION
58 
59   \since Coin 2.0
60 */
61 // FIXME: a small usage example would do wonders for the class
62 // doc. 20020120 mortene.
63 
64 /*!
65   \typedef void * SbClipCallback(const SbVec3f & v0, void * vdata0,
66                               const SbVec3f & v1, void * vdata1,
67                               const SbVec3f & newvertex,
68                               void * userdata)
69 
70   The type definition for the callback function when additional data handling per vertex
71   is required.
72 */
73 
74 /*!
75   A constructor. Supply a callback if you need to handle additional
76   data per vertex.
77 */
SbClip(SbClipCallback * callback,void * userdata)78 SbClip::SbClip(SbClipCallback * callback, void * userdata)
79   : callback(callback),
80     cbdata(userdata),
81     curr(0)
82 {
83 }
84 
85 /*!
86   Adds a polygon vertex. \a vdata could be a pointer to your
87   vertex structure.
88 */
89 void
addVertex(const SbVec3f & v,void * vdata)90 SbClip::addVertex(const SbVec3f &v, void * vdata)
91 {
92   this->array[this->curr].append(SbClipData(v, vdata));
93 }
94 
95 /*!
96   Resets the clipper. This should be called before adding any vertices
97   when reusing an SbClip instance.
98 */
99 void
reset(void)100 SbClip::reset(void)
101 {
102   this->array[0].truncate(0);
103   this->array[1].truncate(0);
104 }
105 
106 //
107 // private method, inline only inside this class
108 //
109 inline void
outputVertex(const SbVec3f & v,void * data)110 SbClip::outputVertex(const SbVec3f & v, void * data)
111 {
112   this->array[this->curr ^ 1].append(SbClipData(v, data));
113 }
114 
115 /*!
116   Clip polygon against \a plane. This might change the number of
117   vertices in the polygon. For each time a new vertex is created, the
118   callback supplied in the constructor (if != NULL) is called with the
119   line being clipped and the new vertex calculated. The callback
120   should return a new void pointer to be stored by the clipper.
121 */
122 void
clip(const SbPlane & plane)123 SbClip::clip(const SbPlane & plane)
124 {
125   int n = this->array[this->curr].getLength();
126 
127   if (n == 0) return;
128 
129   // create loop
130   SbClipData dummy = this->array[this->curr][0];
131   this->array[this->curr].append(dummy);
132 
133   const SbVec3f & planeN = plane.getNormal();
134 
135   for (int i = 0; i < n; i++) {
136     SbVec3f v0, v1;
137     void * data0, *data1;
138     this->array[this->curr][i].get(v0, data0);
139     this->array[this->curr][i+1].get(v1, data1);
140 
141     float d0 = plane.getDistance(v0);
142     float d1 = plane.getDistance(v1);
143 
144     if (d0 >= 0.0f && d1 < 0.0f) { // exit plane
145       SbVec3f dir = v1-v0;
146       // we know that v0 != v1 since we got here
147       (void) dir.normalize();
148       float dot = dir.dot(planeN);
149       SbVec3f newvertex = v0 - dir * (d0/dot);
150       void * newdata = NULL;
151       if (this->callback) {
152         newdata = this->callback(v0, data0, v1, data1, newvertex, this->cbdata);
153       }
154       outputVertex(newvertex, newdata);
155     }
156     else if (d0 < 0.0f && d1 >= 0.0f) { // enter plane
157       SbVec3f dir = v1-v0;
158       // we know that v0 != v1 since we got here
159       (void) dir.normalize();
160       float dot = dir.dot(planeN);
161       SbVec3f newvertex = v0 - dir * (d0/dot);
162       void * newdata = NULL;
163       if (this->callback) {
164         newdata = this->callback(v0, data0, v1, data1, newvertex, this->cbdata);
165       }
166       outputVertex(newvertex, newdata);
167       outputVertex(v1, data1);
168     }
169     else if (d0 >= 0.0f && d1 >= 0.0f) { // in plane
170       outputVertex(v1, data1);
171     }
172   }
173   this->array[this->curr].truncate(0);
174   this->curr ^= 1;
175 }
176 
177 /*!
178   Returns the number of vertices in the polygon.
179   \sa SbClip::getVertex()
180 */
181 int
getNumVertices(void) const182 SbClip::getNumVertices(void) const
183 {
184   return this->array[this->curr].getLength();
185 }
186 
187 /*!
188   Returns the vertex at index \a idx.
189   \sa SbClip::getNumVertices()
190 */
191 void
getVertex(const int idx,SbVec3f & v,void ** vdata) const192 SbClip::getVertex(const int idx, SbVec3f & v, void ** vdata) const
193 {
194   v = this->array[this->curr][idx].vertex;
195   if (vdata) *vdata = this->array[this->curr][idx].data;
196 }
197 
198 /*!
199   Return the vertex data at index \a idx.
200 */
201 void *
getVertexData(const int idx) const202 SbClip::getVertexData(const int idx) const
203 {
204   return this->array[this->curr][idx].data;
205 }
206