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-rw-r--r--basegfx/source/polygon/b2dpolygonclipper.cxx887
1 files changed, 887 insertions, 0 deletions
diff --git a/basegfx/source/polygon/b2dpolygonclipper.cxx b/basegfx/source/polygon/b2dpolygonclipper.cxx
new file mode 100644
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+++ b/basegfx/source/polygon/b2dpolygonclipper.cxx
@@ -0,0 +1,887 @@
+/*************************************************************************
+ *
+ * OpenOffice.org - a multi-platform office productivity suite
+ *
+ * $RCSfile: b2dpolygonclipper.cxx,v $
+ *
+ * $Revision: 1.2 $
+ *
+ * last change: $Author: kz $ $Date: 2005-11-02 13:57:47 $
+ *
+ * The Contents of this file are made available subject to
+ * the terms of GNU Lesser General Public License Version 2.1.
+ *
+ *
+ * GNU Lesser General Public License Version 2.1
+ * =============================================
+ * Copyright 2005 by Sun Microsystems, Inc.
+ * 901 San Antonio Road, Palo Alto, CA 94303, USA
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ *
+ ************************************************************************/
+
+#ifndef _BGFX_POLYPOLYGON_B2DPOLYGONCLIPPER_HXX
+#include <basegfx/polygon/b2dpolygonclipper.hxx>
+#endif
+
+#ifndef _OSL_DIAGNOSE_H_
+#include <osl/diagnose.h>
+#endif
+
+#ifndef _BGFX_POLYGON_B2DPOLYGONTOOLS_HXX
+#include <basegfx/polygon/b2dpolygontools.hxx>
+#endif
+
+#ifndef _BGFX_NUMERIC_FTOOLS_HXX
+#include <basegfx/numeric/ftools.hxx>
+#endif
+
+#ifndef _BGFX_MATRIX_B2DHOMMATRIX_HXX
+#include <basegfx/matrix/b2dhommatrix.hxx>
+#endif
+
+#ifndef _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX
+#include <basegfx/polygon/b2dpolypolygoncutter.hxx>
+#endif
+
+#ifndef _BGFX_POLYGON_CUTANDTOUCH_HXX
+#include <basegfx/polygon/b2dpolygoncutandtouch.hxx>
+#endif
+
+#ifndef _BGFX_POLYPOLYGON_B2DPOLYGONTOOLS_HXX
+#include <basegfx/polygon/b2dpolypolygontools.hxx>
+#endif
+
+#ifndef _BGFX_CURVE_B2DCUBICBEZIER_HXX
+#include <basegfx/curve/b2dcubicbezier.hxx>
+#endif
+
+//////////////////////////////////////////////////////////////////////////////
+
+namespace basegfx
+{
+ namespace tools
+ {
+ B2DPolyPolygon clipPolygonOnParallelAxis(const B2DPolygon& rCandidate, bool bParallelToXAxis, bool bAboveAxis, double fValueOnOtherAxis, bool bStroke)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rCandidate.count())
+ {
+ const B2DRange aCandidateRange(getRange(rCandidate));
+
+ if(bParallelToXAxis && fTools::moreOrEqual(aCandidateRange.getMinY(), fValueOnOtherAxis))
+ {
+ // completely above and on the clip line. also true for curves.
+ if(bAboveAxis)
+ {
+ // add completely
+ aRetval.append(rCandidate);
+ }
+ }
+ else if(bParallelToXAxis && fTools::lessOrEqual(aCandidateRange.getMaxY(), fValueOnOtherAxis))
+ {
+ // completely below and on the clip line. also true for curves.
+ if(!bAboveAxis)
+ {
+ // add completely
+ aRetval.append(rCandidate);
+ }
+ }
+ else if(!bParallelToXAxis && fTools::moreOrEqual(aCandidateRange.getMinX(), fValueOnOtherAxis))
+ {
+ // completely right of and on the clip line. also true for curves.
+ if(bAboveAxis)
+ {
+ // add completely
+ aRetval.append(rCandidate);
+ }
+ }
+ else if(!bParallelToXAxis && fTools::lessOrEqual(aCandidateRange.getMaxX(), fValueOnOtherAxis))
+ {
+ // completely left of and on the clip line. also true for curves.
+ if(!bAboveAxis)
+ {
+ // add completely
+ aRetval.append(rCandidate);
+ }
+ }
+ else
+ {
+ // prepare loop(s)
+ OSL_ENSURE(!rCandidate.areControlPointsUsed(), "clipPolygonOnParallelAxis: ATM works not for curves (!)");
+ B2DPolygon aNewPolygon;
+ B2DPoint aCurrent(rCandidate.getB2DPoint(0L));
+ bool bCurrentInside(bParallelToXAxis ?
+ fTools::moreOrEqual(aCurrent.getY(), fValueOnOtherAxis) == bAboveAxis :
+ fTools::moreOrEqual(aCurrent.getX(), fValueOnOtherAxis) == bAboveAxis);
+ const sal_uInt32 nPointCount(rCandidate.count());
+ const sal_uInt32 nEdgeCount(rCandidate.isClosed() ? nPointCount : nPointCount - 1L);
+
+ if(bCurrentInside)
+ {
+ aNewPolygon.append(aCurrent);
+ }
+
+ if(bStroke)
+ {
+ // open polygon, create clipped line snippets.
+ for(sal_uInt32 a(0L); a < nEdgeCount; a++)
+ {
+ // get next point data
+ const sal_uInt32 nNextIndex((a + 1L == nPointCount) ? 0L : a + 1L);
+ const B2DPoint aNext(rCandidate.getB2DPoint(nNextIndex));
+ const bool bNextInside(bParallelToXAxis ?
+ fTools::moreOrEqual(aNext.getY(), fValueOnOtherAxis) == bAboveAxis :
+ fTools::moreOrEqual(aNext.getX(), fValueOnOtherAxis) == bAboveAxis);
+
+ if(bCurrentInside != bNextInside)
+ {
+ // change inside/outside
+ if(bNextInside)
+ {
+ // entering, finish existing and start new line polygon
+ if(aNewPolygon.count() > 1L)
+ {
+ aRetval.append(aNewPolygon);
+ }
+
+ aNewPolygon.clear();
+ }
+
+ // calculate and add cut point
+ if(bParallelToXAxis)
+ {
+ const double fNewX(aCurrent.getX() - (((aCurrent.getY() - fValueOnOtherAxis) * (aNext.getX() - aCurrent.getX()) / (aNext.getY() - aCurrent.getY()))));
+ aNewPolygon.append(B2DPoint(fNewX, fValueOnOtherAxis));
+ }
+ else
+ {
+ const double fNewY(aCurrent.getY() - (((aCurrent.getX() - fValueOnOtherAxis) * (aNext.getY() - aCurrent.getY()) / (aNext.getX() - aCurrent.getX()))));
+ aNewPolygon.append(B2DPoint(fValueOnOtherAxis, fNewY));
+ }
+
+ // pepare next step
+ bCurrentInside = bNextInside;
+ }
+
+ if(bNextInside)
+ {
+ aNewPolygon.append(aNext);
+ }
+
+ // pepare next step
+ aCurrent = aNext;
+ }
+
+ if(aNewPolygon.count() > 1L)
+ {
+ aRetval.append(aNewPolygon);
+ }
+ }
+ else
+ {
+ // closed polygon, create single clipped closed polygon
+ for(sal_uInt32 a(0L); a < nEdgeCount; a++)
+ {
+ // get next point data, use offset
+ const sal_uInt32 nNextIndex((a + 1L == nPointCount) ? 0L : a + 1L);
+ const B2DPoint aNext(rCandidate.getB2DPoint(nNextIndex));
+ const bool bNextInside(bParallelToXAxis ?
+ fTools::moreOrEqual(aNext.getY(), fValueOnOtherAxis) == bAboveAxis :
+ fTools::moreOrEqual(aNext.getX(), fValueOnOtherAxis) == bAboveAxis);
+
+ if(bCurrentInside != bNextInside)
+ {
+ // change inside/outside, calculate and add cut point
+ if(bParallelToXAxis)
+ {
+ const double fNewX(aCurrent.getX() - (((aCurrent.getY() - fValueOnOtherAxis) * (aNext.getX() - aCurrent.getX()) / (aNext.getY() - aCurrent.getY()))));
+ aNewPolygon.append(B2DPoint(fNewX, fValueOnOtherAxis));
+ }
+ else
+ {
+ const double fNewY(aCurrent.getY() - (((aCurrent.getX() - fValueOnOtherAxis) * (aNext.getY() - aCurrent.getY()) / (aNext.getX() - aCurrent.getX()))));
+ aNewPolygon.append(B2DPoint(fValueOnOtherAxis, fNewY));
+ }
+
+ // pepare next step
+ bCurrentInside = bNextInside;
+ }
+
+ if(bNextInside && nNextIndex)
+ {
+ aNewPolygon.append(aNext);
+ }
+
+ // pepare next step
+ aCurrent = aNext;
+ }
+
+ if(aNewPolygon.count() > 2L)
+ {
+ aNewPolygon.setClosed(true);
+ aRetval.append(aNewPolygon);
+ }
+ }
+ }
+ }
+
+ return aRetval;
+ }
+
+ B2DPolyPolygon clipPolyPolygonOnParallelAxis(const B2DPolyPolygon& rCandidate, bool bParallelToXAxis, bool bAboveAxis, double fValueOnOtherAxis, bool bStroke)
+ {
+ const sal_uInt32 nPolygonCount(rCandidate.count());
+ B2DPolyPolygon aRetval;
+
+ for(sal_uInt32 a(0L); a < nPolygonCount; a++)
+ {
+ B2DPolygon aCandidate(rCandidate.getB2DPolygon(a));
+
+ aRetval.append(clipPolygonOnParallelAxis(aCandidate, bParallelToXAxis, bAboveAxis, fValueOnOtherAxis, bStroke));
+ }
+
+ return aRetval;
+ }
+
+ B2DPolyPolygon clipPolygonOnRange(const B2DPolygon& rCandidate, const B2DRange& rRange, bool bInside, bool bStroke)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rRange.isEmpty())
+ {
+ // clipping against an empty range. Nothing is inside an empty range, so the polygon
+ // is outside the range. So only return if not inside is wanted
+ if(!bInside && rCandidate.count())
+ {
+ aRetval.append(rCandidate);
+ }
+ }
+ if(rCandidate.count())
+ {
+ const B2DRange aCandidateRange(getRange(rCandidate));
+
+ if(rRange.isInside(aCandidateRange))
+ {
+ // candidate is completely inside given range, nothing to do. Is also true with curves.
+ if(bInside)
+ {
+ aRetval.append(rCandidate);
+ }
+ }
+ else
+ {
+ // clip against the four axes of the range
+ // against X-Axis, lower value
+ aRetval = clipPolygonOnParallelAxis(rCandidate, true, bInside, rRange.getMinY(), bStroke);
+
+ if(aRetval.count())
+ {
+ // against Y-Axis, lower value
+ if(1L == aRetval.count())
+ {
+ aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0L), false, bInside, rRange.getMinX(), bStroke);
+ }
+ else
+ {
+ aRetval = clipPolyPolygonOnParallelAxis(aRetval, false, bInside, rRange.getMinX(), bStroke);
+ }
+
+ if(aRetval.count())
+ {
+ // against X-Axis, higher value
+ if(1L == aRetval.count())
+ {
+ aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0L), true, !bInside, rRange.getMaxY(), bStroke);
+ }
+ else
+ {
+ aRetval = clipPolyPolygonOnParallelAxis(aRetval, true, !bInside, rRange.getMaxY(), bStroke);
+ }
+
+ if(aRetval.count())
+ {
+ // against Y-Axis, higher value
+ if(1L == aRetval.count())
+ {
+ aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0L), false, !bInside, rRange.getMaxX(), bStroke);
+ }
+ else
+ {
+ aRetval = clipPolyPolygonOnParallelAxis(aRetval, false, !bInside, rRange.getMaxX(), bStroke);
+ }
+ }
+ }
+ }
+ }
+ }
+
+ return aRetval;
+ }
+
+ B2DPolyPolygon clipPolyPolygonOnRange(const B2DPolyPolygon& rCandidate, const B2DRange& rRange, bool bInside, bool bStroke)
+ {
+ const sal_uInt32 nPolygonCount(rCandidate.count());
+ B2DPolyPolygon aRetval;
+
+ for(sal_uInt32 a(0L); a < nPolygonCount; a++)
+ {
+ B2DPolygon aCandidate(rCandidate.getB2DPolygon(a));
+
+ aRetval.append(clipPolygonOnRange(aCandidate, rRange, bInside, bStroke));
+ }
+
+ return aRetval;
+ }
+
+ B2DPolyPolygon clipPolygonOnEdge(const B2DPolygon& rCandidate, const B2DPoint& rPointA, const B2DPoint& rPointB, bool bAbove, bool bStroke)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rPointA.equal(rPointB))
+ {
+ // edge has no length, return polygon
+ aRetval.append(rCandidate);
+ }
+ else if(rCandidate.count())
+ {
+ const B2DVector aEdge(rPointB - rPointA);
+ B2DHomMatrix aMatrixTransform;
+ B2DPolygon aCandidate(rCandidate);
+
+ // translate and rotate polygon so that given edge is on x axis
+ aMatrixTransform.translate(-rPointA.getX(), -rPointA.getY());
+ aMatrixTransform.rotate(-atan2(aEdge.getY(), aEdge.getX()));
+ aCandidate.transform(aMatrixTransform);
+
+ // call clip method on X-Axis
+ aRetval = clipPolygonOnParallelAxis(aCandidate, true, bAbove, 0.0, bStroke);
+
+ if(aRetval.count())
+ {
+ // if there is a result, it needs to be transformed back
+ aMatrixTransform.invert();
+ aRetval.transform(aMatrixTransform);
+ }
+ }
+
+ return aRetval;
+ }
+
+ B2DPolyPolygon clipPolyPolygonOnEdge(const B2DPolyPolygon& rCandidate, const B2DPoint& rPointA, const B2DPoint& rPointB, bool bAbove, bool bStroke)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rPointA.equal(rPointB))
+ {
+ // edge has no length, return polygon
+ aRetval = rCandidate;
+ }
+ else if(rCandidate.count())
+ {
+ const B2DVector aEdge(rPointB - rPointA);
+ B2DHomMatrix aMatrixTransform;
+ B2DPolyPolygon aCandidate(rCandidate);
+
+ // translate and rotate polygon so that given edge is on x axis
+ aMatrixTransform.translate(-rPointA.getX(), -rPointA.getY());
+ aMatrixTransform.rotate(-atan2(aEdge.getY(), aEdge.getX()));
+ aCandidate.transform(aMatrixTransform);
+
+ // call clip method on X-Axis
+ aRetval = clipPolyPolygonOnParallelAxis(aCandidate, true, bAbove, 0.0, bStroke);
+
+ if(aRetval.count())
+ {
+ // if there is a result, it needs to be transformed back
+ aMatrixTransform.invert();
+ aRetval.transform(aMatrixTransform);
+ }
+ }
+
+ return aRetval;
+ }
+
+ //////////////////////////////////////////////////////////////////////////////
+
+ B2DPolyPolygon clipPolyPolygonOnPolyPolygon(const B2DPolyPolygon& rCandidate, const B2DPolyPolygon& rClip, bool bStroke, bool bInvert)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rCandidate.count() && rClip.count())
+ {
+ if(bStroke)
+ {
+ // line clipping, create line snippets
+ for(sal_uInt32 a(0L); a < rCandidate.count(); a++)
+ {
+ // get candidate and add cuts and touches with rClip to aCandidate
+ const B2DPolygon aCandidate(addPointsAtCutsAndTouches(rClip, rCandidate.getB2DPolygon(a)));
+ const sal_uInt32 nPointCount(aCandidate.count());
+
+ if(nPointCount)
+ {
+ const sal_uInt32 nEdgeCount(aCandidate.isClosed() ? nPointCount : nPointCount - 1L);
+ B2DPolygon aRun;
+ B2DPoint aCurrent(aCandidate.getB2DPoint(0L));
+
+ for(sal_uInt32 b(0L); b < nEdgeCount; b++)
+ {
+ B2DVector aControlVectorA;
+ B2DVector aControlVectorB;
+ bool bCurveEdge(false);
+
+ if(aCandidate.areControlPointsUsed())
+ {
+ aControlVectorA = aCandidate.getControlVectorA(b);
+ aControlVectorB = aCandidate.getControlVectorB(b);
+ bCurveEdge = !(aControlVectorA.equalZero() && aControlVectorB.equalZero());
+ }
+
+ const sal_uInt32 nNextIndex((b + 1L == nPointCount) ? 0L : b + 1L);
+ const B2DPoint aNext(aCandidate.getB2DPoint(nNextIndex));
+ B2DPoint aComparePoint;
+
+ if(bCurveEdge)
+ {
+ B2DCubicBezier aCubicBezier(aCurrent, aControlVectorA, aControlVectorB, aNext);
+ aComparePoint = aCubicBezier.interpolatePoint(0.5);
+ }
+ else
+ {
+ aComparePoint = average(aCurrent, aNext);
+ }
+
+ const bool bInside(isInside(rClip, aComparePoint) != bInvert);
+
+ if(bInside)
+ {
+ if(!aRun.count())
+ {
+ aRun.append(aCurrent);
+
+ if(bCurveEdge)
+ {
+ const sal_uInt32 nNextRunIndex(aRun.count() - 1L);
+ aRun.setControlVectorA(nNextRunIndex, aControlVectorA);
+ aRun.setControlVectorB(nNextRunIndex, aControlVectorB);
+ }
+ }
+
+ aRun.append(aNext);
+
+ if(bCurveEdge)
+ {
+ const sal_uInt32 nNextRunIndex(aRun.count() - 1L);
+ aRun.setControlVectorA(nNextRunIndex, aCandidate.getControlVectorA(nNextIndex));
+ aRun.setControlVectorB(nNextRunIndex, aCandidate.getControlVectorB(nNextIndex));
+ }
+ }
+ else
+ {
+ if(aRun.count())
+ {
+ aRetval.append(aRun);
+ aRun.clear();
+ }
+ }
+
+ // prepare next step
+ aCurrent = aNext;
+ }
+
+ if(aRun.count())
+ {
+ aRetval.append(aRun);
+ }
+ }
+ }
+ }
+ else
+ {
+ // area clipping
+ B2DPolyPolygon aMergePolyPolygonA(rClip);
+ aMergePolyPolygonA = SolveCrossovers(aMergePolyPolygonA);
+ aMergePolyPolygonA = StripNeutralPolygons(aMergePolyPolygonA);
+ aMergePolyPolygonA = StripDispensablePolygons(aMergePolyPolygonA);
+
+ if(bInvert)
+ {
+ aMergePolyPolygonA.flip();
+ }
+
+ B2DPolyPolygon aMergePolyPolygonB(rCandidate);
+ aMergePolyPolygonB = SolveCrossovers(aMergePolyPolygonB);
+ aMergePolyPolygonB = StripNeutralPolygons(aMergePolyPolygonB);
+ aMergePolyPolygonB = StripDispensablePolygons(aMergePolyPolygonB);
+
+ aRetval.append(aMergePolyPolygonA);
+ aRetval.append(aMergePolyPolygonB);
+ aRetval = SolveCrossovers(aRetval, false);
+ aRetval = StripNeutralPolygons(aRetval);
+ aRetval = StripDispensablePolygons(aRetval, !bInvert);
+ }
+ }
+
+ return aRetval;
+ }
+
+ //////////////////////////////////////////////////////////////////////////////
+
+ B2DPolyPolygon clipPolygonOnPolyPolygon(const B2DPolygon& rCandidate, const B2DPolyPolygon& rClip, bool bStroke, bool bInvert)
+ {
+ B2DPolyPolygon aRetval;
+
+ if(rCandidate.count() && rClip.count())
+ {
+ aRetval = clipPolyPolygonOnPolyPolygon(B2DPolyPolygon(rCandidate), rClip, bStroke, bInvert);
+ }
+
+ return aRetval;
+ }
+
+ //////////////////////////////////////////////////////////////////////////////
+
+ /*
+ * let a plane be defined as
+ *
+ * v.n+d=0
+ *
+ * and a ray be defined as
+ *
+ * a+(b-a)*t=0
+ *
+ * substitute and rearranging yields
+ *
+ * t = -(a.n+d)/(n.(b-a))
+ *
+ * if the denominator is zero, the line is either
+ * contained in the plane or parallel to the plane.
+ * in either case, there is no intersection.
+ * if numerator and denominator are both zero, the
+ * ray is contained in the plane.
+ *
+ */
+ struct scissor_plane {
+ double nx,ny; // plane normal
+ double d; // [-] minimum distance from origin
+ sal_uInt32 clipmask; // clipping mask, e.g. 1000 1000
+ };
+
+ inline sal_uInt32 getClipFlags( const ::basegfx::B2DPoint& rV,
+ const ::basegfx::B2DRectangle& rR )
+ {
+ // maxY | minY | maxX | minX
+ sal_uInt32 clip = (rV.getX() < rR.getMinX()) << 0;
+ clip |= (rV.getX() > rR.getMaxX()) << 1;
+ clip |= (rV.getY() < rR.getMinY()) << 2;
+ clip |= (rV.getY() > rR.getMaxY()) << 3;
+ return clip;
+ }
+
+ /*
+ *
+ * polygon clipping rules (straight out of Foley and Van Dam)
+ * ===========================================================
+ * current |next |emit
+ * ____________________________________
+ * inside |inside |next
+ * inside |outside |intersect with clip plane
+ * outside |outside |nothing
+ * outside |inside |intersect with clip plane follwed by next
+ *
+ */
+ sal_uInt32 scissorLineSegment( ::basegfx::B2DPoint *in_vertex, // input buffer
+ sal_uInt32 in_count, // number of verts in input buffer
+ ::basegfx::B2DPoint *out_vertex, // output buffer
+ scissor_plane *pPlane, // scissoring plane
+ const ::basegfx::B2DRectangle &rR ) // clipping rectangle
+ {
+ ::basegfx::B2DPoint *curr;
+ ::basegfx::B2DPoint *next;
+
+ sal_uInt32 out_count=0;
+
+ // process all the verts
+ for(sal_uInt32 i=0; i<in_count; i++) {
+
+ // vertices are relative to the coordinate
+ // system defined by the rectangle.
+ curr = &in_vertex[i];
+ next = &in_vertex[(i+1)%in_count];
+
+ // perform clipping judgement & mask against current plane.
+ sal_uInt32 clip = pPlane->clipmask & ((getClipFlags(*curr,rR)<<4)|getClipFlags(*next,rR));
+
+ if(clip==0) { // both verts are inside
+ out_vertex[out_count++] = *next;
+ }
+ else if((clip&0x0f) && (clip&0xf0)) { // both verts are outside
+ }
+ else if((clip&0x0f) && (clip&0xf0)==0) { // curr is inside, next is outside
+
+ // direction vector from 'current' to 'next', *not* normalized
+ // to bring 't' into the [0<=x<=1] intervall.
+ ::basegfx::B2DPoint dir((*next)-(*curr));
+
+ double denominator = ( pPlane->nx*dir.getX() +
+ pPlane->ny*dir.getY() );
+ double numerator = ( pPlane->nx*curr->getX() +
+ pPlane->ny*curr->getY() +
+ pPlane->d );
+ double t = -numerator/denominator;
+
+ // calculate the actual point of intersection
+ ::basegfx::B2DPoint intersection( curr->getX()+t*dir.getX(),
+ curr->getY()+t*dir.getY() );
+
+ out_vertex[out_count++] = intersection;
+ }
+ else if((clip&0x0f)==0 && (clip&0xf0)) { // curr is outside, next is inside
+
+ // direction vector from 'current' to 'next', *not* normalized
+ // to bring 't' into the [0<=x<=1] intervall.
+ ::basegfx::B2DPoint dir((*next)-(*curr));
+
+ double denominator = ( pPlane->nx*dir.getX() +
+ pPlane->ny*dir.getY() );
+ double numerator = ( pPlane->nx*curr->getX() +
+ pPlane->ny*curr->getY() +
+ pPlane->d );
+ double t = -numerator/denominator;
+
+ // calculate the actual point of intersection
+ ::basegfx::B2DPoint intersection( curr->getX()+t*dir.getX(),
+ curr->getY()+t*dir.getY() );
+
+ out_vertex[out_count++] = intersection;
+ out_vertex[out_count++] = *next;
+ }
+ }
+
+ return out_count;
+ }
+
+ B2DPolygon clipTriangleListOnRange( const B2DPolygon& rCandidate,
+ const B2DRange& rRange )
+ {
+ B2DPolygon aResult;
+
+ if( !(rCandidate.count()%3) )
+ {
+ const int scissor_plane_count = 4;
+
+ scissor_plane sp[scissor_plane_count];
+
+ sp[0].nx = +1.0;
+ sp[0].ny = +0.0;
+ sp[0].d = -(rRange.getMinX());
+ sp[0].clipmask = 0x11; // 0001 0001
+ sp[1].nx = -1.0;
+ sp[1].ny = +0.0;
+ sp[1].d = +(rRange.getMaxX());
+ sp[1].clipmask = 0x22; // 0010 0010
+ sp[2].nx = +0.0;
+ sp[2].ny = +1.0;
+ sp[2].d = -(rRange.getMinY());
+ sp[2].clipmask = 0x44; // 0100 0100
+ sp[3].nx = +0.0;
+ sp[3].ny = -1.0;
+ sp[3].d = +(rRange.getMaxY());
+ sp[3].clipmask = 0x88; // 1000 1000
+
+ // retrieve the number of vertices of the triangulated polygon
+ const sal_uInt32 nVertexCount = rCandidate.count();
+
+ if(nVertexCount)
+ {
+ ////////////////////////////////////////////////////////////////////////
+ ////////////////////////////////////////////////////////////////////////
+ ////////////////////////////////////////////////////////////////////////
+ //
+ // Upper bound for the maximal number of vertices when intersecting an
+ // axis-aligned rectangle with a triangle in E2
+ //
+ // The rectangle and the triangle are in general position, and have 4 and 3
+ // vertices, respectively.
+ //
+ // Lemma: Since the rectangle is a convex polygon ( see
+ // http://mathworld.wolfram.com/ConvexPolygon.html for a definition), and
+ // has no holes, it follows that any straight line will intersect the
+ // rectangle's border line at utmost two times (with the usual
+ // tie-breaking rule, if the intersection exactly hits an already existing
+ // rectangle vertex, that this intersection is only attributed to one of
+ // the adjoining edges). Thus, having a rectangle intersected with
+ // a half-plane (one side of a straight line denotes 'inside', the
+ // other 'outside') will at utmost add _one_ vertex to the resulting
+ // intersection polygon (adding two intersection vertices, and removing at
+ // least one rectangle vertex):
+ //
+ // *
+ // +--+-----------------+
+ // | * |
+ // |* |
+ // + |
+ // *| |
+ // * | |
+ // +--------------------+
+ //
+ // Proof: If the straight line intersects the rectangle two
+ // times, it does so for distinct edges, i.e. the intersection has
+ // minimally one of the rectangle's vertices on either side of the straight
+ // line (but maybe more). Thus, the intersection with a half-plane has
+ // minimally _one_ rectangle vertex removed from the resulting clip
+ // polygon, and therefore, a clip against a half-plane has the net effect
+ // of adding at utmost _one_ vertex to the resulting clip polygon.
+ //
+ // Theorem: The intersection of a rectangle and a triangle results in a
+ // polygon with at utmost 7 vertices.
+ //
+ // Proof: The inside of the triangle can be described as the consecutive
+ // intersection with three half-planes. Together with the lemma above, this
+ // results in at utmost 3 additional vertices added to the already existing 4
+ // rectangle vertices.
+ //
+ // This upper bound is attained with the following example configuration:
+ //
+ // *
+ // ***
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ** *
+ // ----*2--------3 *
+ // | ** |*
+ // 1* 4
+ // **| *|
+ // ** | * |
+ // **| * |
+ // 7* * |
+ // --*6-----5-----
+ // ** *
+ // **
+ //
+ // As we need to scissor all triangles against the
+ // output rectangle we employ an output buffer for the
+ // resulting vertices. the question is how large this
+ // buffer needs to be compared to the number of
+ // incoming vertices. this buffer needs to hold at
+ // most the number of original vertices times '7'. see
+ // figure above for an example. scissoring triangles
+ // with the cohen-sutherland line clipping algorithm
+ // as implemented here will result in a triangle fan
+ // which will be rendered as separate triangles to
+ // avoid pipeline stalls for each scissored
+ // triangle. creating separate triangles from a
+ // triangle fan produces (n-2)*3 vertices where n is
+ // the number of vertices of the original triangle
+ // fan. for the maximum number of 7 vertices of
+ // resulting triangle fans we therefore need 15 times
+ // the number of original vertices.
+ //
+ ////////////////////////////////////////////////////////////////////////
+ ////////////////////////////////////////////////////////////////////////
+ ////////////////////////////////////////////////////////////////////////
+
+ //const size_t nBufferSize = sizeof(vertex)*(nVertexCount*16);
+ //vertex *pVertices = (vertex*)alloca(nBufferSize);
+ //sal_uInt32 nNumOutput = 0;
+
+ // we need to clip this triangle against the output rectangle
+ // to ensure that the resulting texture coordinates are in
+ // the valid range from [0<=st<=1]. under normal circustances
+ // we could use the BORDERCOLOR renderstate but some cards
+ // seem to ignore this feature.
+ ::basegfx::B2DPoint stack[3];
+ unsigned int clipflag = 0;
+
+ for(sal_uInt32 nIndex=0; nIndex<nVertexCount; ++nIndex)
+ {
+ // rotate stack
+ stack[0] = stack[1];
+ stack[1] = stack[2];
+ stack[2] = rCandidate.getB2DPoint(nIndex);
+
+ // clipping judgement
+ clipflag |= !(rRange.isInside(stack[2]));
+
+ if(nIndex > 1)
+ {
+ // consume vertices until a single seperate triangle has been visited.
+ if(!((nIndex+1)%3))
+ {
+ // if any of the last three vertices was outside
+ // we need to scissor against the destination rectangle
+ if(clipflag & 7)
+ {
+ ::basegfx::B2DPoint buf0[16];
+ ::basegfx::B2DPoint buf1[16];
+
+ sal_uInt32 vertex_count = 3;
+
+ // clip against all 4 planes passing the result of
+ // each plane as the input to the next using a double buffer
+ vertex_count = scissorLineSegment(stack,vertex_count,buf1,&sp[0],rRange);
+ vertex_count = scissorLineSegment(buf1,vertex_count,buf0,&sp[1],rRange);
+ vertex_count = scissorLineSegment(buf0,vertex_count,buf1,&sp[2],rRange);
+ vertex_count = scissorLineSegment(buf1,vertex_count,buf0,&sp[3],rRange);
+
+ if(vertex_count >= 3)
+ {
+ // convert triangle fan back to triangle list.
+ ::basegfx::B2DPoint v0(buf0[0]);
+ ::basegfx::B2DPoint v1(buf0[1]);
+ for(sal_uInt32 i=2; i<vertex_count; ++i)
+ {
+ ::basegfx::B2DPoint v2(buf0[i]);
+ aResult.append(v0);
+ aResult.append(v1);
+ aResult.append(v2);
+ v1 = v2;
+ }
+ }
+ }
+ else
+ {
+ // the last triangle has not been altered, simply copy to result
+ for(sal_uInt32 i=0; i<3; ++i)
+ aResult.append(stack[i]);
+ }
+ }
+ }
+
+ clipflag <<= 1;
+ }
+ }
+ }
+
+ return aResult;
+ }
+
+ //////////////////////////////////////////////////////////////////////////////
+
+ } // end of namespace tools
+} // end of namespace basegfx
+
+//////////////////////////////////////////////////////////////////////////////
+
+// eof
generated by cgit (git 2.34.1) at 2025-01-16 21:52:24 +0000