Exemplo n.º 1
0
	//-----------------------------------------------------------------------
	bool ConvexBody::findAndEraseEdgePair(const Vector3& vec, 
		Polygon::EdgeMap& intersectionEdges, Vector3& vNext ) const
	{
		for (Polygon::EdgeMap::iterator it = intersectionEdges.begin(); 
			it != intersectionEdges.end(); ++it)
		{
			if (it->first.positionEquals(vec))
			{
				vNext = it->second;

				// erase found edge
				intersectionEdges.erase( it );

				return true; // found!
			}
			else if (it->second.positionEquals(vec))
			{
				vNext = it->first;

				// erase found edge
				intersectionEdges.erase( it );

				return true; // found!
			}
		}

		return false; // not found!
	}
Exemplo n.º 2
0
	//-----------------------------------------------------------------------
	Polygon::EdgeMap ConvexBody::getSingleEdges() const
	{
		Polygon::EdgeMap edgeMap;

		// put all edges of all polygons into a list every edge has to be
		// walked in each direction once	
		for ( size_t i = 0; i < getPolygonCount(); ++i )
		{
			const Polygon& p = getPolygon( i );

			for ( size_t j = 0; j < p.getVertexCount(); ++j )
			{
				const Vector3& a = p.getVertex( j );
				const Vector3& b = p.getVertex( ( j + 1 ) % p.getVertexCount() );

				edgeMap.insert( Polygon::Edge( a, b ) );
			}
		}

		// search corresponding parts
		Polygon::EdgeMap::iterator it;
		Polygon::EdgeMap::iterator itStart;
		Polygon::EdgeMap::const_iterator itEnd;
		while( !edgeMap.empty() )
		{
			it = edgeMap.begin(); ++it;	// start one element after itStart
			itStart = edgeMap.begin();	// the element to be compared with the others
			itEnd = edgeMap.end();		// beyond the last element
			
			bool bFound = false;

			for ( ; it != itEnd; ++it )
			{
				if (itStart->first.positionEquals(it->second) &&
					 itStart->second.positionEquals(it->first))
				{
					// erase itStart and it
					edgeMap.erase( it );
					edgeMap.erase( itStart );

					bFound = true;

					break; // found
				}
			}

			if ( bFound == false )
			{
				break;	// not all edges could be matched
						// body is not closed
			}
		}

		return edgeMap;
	}
Exemplo n.º 3
0
	//-----------------------------------------------------------------------
	void ConvexBody::clip( const Plane& pl, bool keepNegative )
	{
		if ( getPolygonCount() == 0 )
			return;

		// current will be used as the reference body
		ConvexBody current;
		current.moveDataFromBody(*this);
		
		OgreAssert( this->getPolygonCount() == 0, "Body not empty!" );
		OgreAssert( current.getPolygonCount() != 0, "Body empty!" );

		// holds all intersection edges for the different polygons
		Polygon::EdgeMap intersectionEdges;

		// clip all polygons by the intersection plane
		// add only valid or intersected polygons to *this
		for ( size_t iPoly = 0; iPoly < current.getPolygonCount(); ++iPoly )
		{

			// fetch vertex count and ignore polygons with less than three vertices
			// the polygon is not valid and won't be added
			const size_t vertexCount = current.getVertexCount( iPoly );
			if ( vertexCount < 3 )
				continue;

			// current polygon
			const Polygon& p = current.getPolygon( iPoly );

			// the polygon to assemble
			Polygon *pNew = allocatePolygon();

			// the intersection polygon (indeed it's an edge or it's empty)
			Polygon *pIntersect = allocatePolygon();
			
			// check if polygons lie inside or outside (or on the plane)
			// for each vertex check where it is situated in regard to the plane
			// three possibilities appear:
			Plane::Side clipSide = keepNegative ? Plane::POSITIVE_SIDE : Plane::NEGATIVE_SIDE;
			// - side is clipSide: vertex will be clipped
			// - side is !clipSide: vertex will be untouched
			// - side is NOSIDE:   vertex will be untouched
			Plane::Side *side = OGRE_ALLOC_T(Plane::Side, vertexCount, MEMCATEGORY_SCENE_CONTROL);
			for ( size_t iVertex = 0; iVertex < vertexCount; ++iVertex )
			{
				side[ iVertex ] = pl.getSide( p.getVertex( iVertex ) );
			}

			// now we check the side combinations for the current and the next vertex
			// four different combinations exist:
			// - both points inside (or on the plane): keep the second (add it to the body)
			// - both points outside: discard both (don't add them to the body)
			// - first vertex is inside, second is outside: add the intersection point
			// - first vertex is outside, second is inside: add the intersection point, then the second
			for ( size_t iVertex = 0; iVertex < vertexCount; ++iVertex )
			{
				// determine the next vertex
				size_t iNextVertex = ( iVertex + 1 ) % vertexCount;

				const Vector3& vCurrent = p.getVertex( iVertex );
				const Vector3& vNext    = p.getVertex( iNextVertex );

				// case 1: both points inside (store next)
				if ( side[ iVertex ]     != clipSide &&		// NEGATIVE or NONE
					 side[ iNextVertex ] != clipSide )		// NEGATIVE or NONE
				{
					// keep the second
					pNew->insertVertex( vNext );
				}

				// case 3: inside -> outside (store intersection)
				else if ( side[ iVertex ]		!= clipSide &&
						  side[ iNextVertex ]	== clipSide )
				{
					// Do an intersection with the plane. We use a ray with a start point and a direction.
					// The ray is forced to hit the plane with any option available (eigher current or next
					// is the starting point)

					// intersect from the outside vertex towards the inside one
					Vector3 vDirection = vCurrent - vNext;
					vDirection.normalise();
					Ray ray( vNext, vDirection );
					std::pair< bool, Real > intersect = ray.intersects( pl );

					// store intersection
					if ( intersect.first )
					{
						// convert distance to vector
						Vector3 vIntersect = ray.getPoint( intersect.second );	

						// store intersection
						pNew->insertVertex( vIntersect );
						pIntersect->insertVertex( vIntersect );
					}
				}

				// case 4: outside -> inside (store intersection, store next)
				else if ( side[ iVertex ]		== clipSide &&
					side[ iNextVertex ]			!= clipSide )
				{
					// Do an intersection with the plane. We use a ray with a start point and a direction.
					// The ray is forced to hit the plane with any option available (eigher current or next
					// is the starting point)

					// intersect from the outside vertex towards the inside one
					Vector3 vDirection = vNext - vCurrent;
					vDirection.normalise();
					Ray ray( vCurrent, vDirection );
					std::pair< bool, Real > intersect = ray.intersects( pl );

					// store intersection
					if ( intersect.first )
					{
						// convert distance to vector
						Vector3 vIntersect = ray.getPoint( intersect.second );

						// store intersection
						pNew->insertVertex( vIntersect );
						pIntersect->insertVertex( vIntersect );
					}

					pNew->insertVertex( vNext );

				}
				// else:
				// case 2: both outside (do nothing)
					
			}

			// insert the polygon only, if at least three vertices are present
			if ( pNew->getVertexCount() >= 3 )
			{
				// in case there are double vertices, remove them
				pNew->removeDuplicates();

				// in case there are still at least three vertices, insert the polygon
				if ( pNew->getVertexCount() >= 3 )
				{
					this->insertPolygon( pNew );
				}
				else
				{
					// delete pNew because it's empty or invalid
					freePolygon(pNew);
					pNew = 0;
				}
			}
			else
			{
				// delete pNew because it's empty or invalid
				freePolygon(pNew);
				pNew = 0;
			}

			// insert intersection polygon only, if there are two vertices present
			if ( pIntersect->getVertexCount() == 2 )
			{
				intersectionEdges.insert( Polygon::Edge( pIntersect->getVertex( 0 ),
														  pIntersect->getVertex( 1 ) ) );
			}

			// delete intersection polygon
			// vertices were copied (if there were any)
			freePolygon(pIntersect);
			pIntersect = 0;

			// delete side info
			OGRE_FREE(side, MEMCATEGORY_SCENE_CONTROL);
			side = 0;
		}

		// if the polygon was partially clipped, close it
		// at least three edges are needed for a polygon
		if ( intersectionEdges.size() >= 3 )
		{
			Polygon *pClosing = allocatePolygon();

			// Analyze the intersection list and insert the intersection points in ccw order
			// Each point is twice in the list because of the fact that we have a convex body
			// with convex polygons. All we have to do is order the edges (an even-odd pair)
			// in a ccw order. The plane normal shows us the direction.
			Polygon::EdgeMap::iterator it = intersectionEdges.begin();

			// check the cross product of the first two edges
			Vector3 vFirst  = it->first;
			Vector3 vSecond = it->second;

			// remove inserted edge
			intersectionEdges.erase( it );

			Vector3 vNext;

			// find mating edge
			if (findAndEraseEdgePair(vSecond, intersectionEdges, vNext))
			{
				// detect the orientation
				// the polygon must have the same normal direction as the plane and then n
				Vector3 vCross = ( vFirst - vSecond ).crossProduct( vNext - vSecond );
				bool frontside = ( pl.normal ).directionEquals( vCross, Degree( 1 ) );

				// first inserted vertex
				Vector3 firstVertex;
				// currently inserted vertex
				Vector3 currentVertex;
				// direction equals -> front side (walk ccw)
				if ( frontside )
				{
					// start with next as first vertex, then second, then first and continue with first to walk ccw
					pClosing->insertVertex( vNext );
					pClosing->insertVertex( vSecond );
					pClosing->insertVertex( vFirst );
					firstVertex		= vNext;
					currentVertex	= vFirst;

				#ifdef _DEBUG_INTERSECTION_LIST
					std::cout << "Plane: n=" << pl.normal << ", d=" << pl.d << std::endl;
					std::cout << "First inserted vertex: " << *next << std::endl;
					std::cout << "Second inserted vertex: " << *vSecond << std::endl;
					std::cout << "Third inserted vertex: " << *vFirst << std::endl;
				#endif
				}
				// direction does not equal -> back side (walk cw)
				else
				{
					// start with first as first vertex, then second, then next and continue with next to walk ccw
					pClosing->insertVertex( vFirst );
					pClosing->insertVertex( vSecond );
					pClosing->insertVertex( vNext );
					firstVertex		= vFirst;
					currentVertex	= vNext;

					#ifdef _DEBUG_INTERSECTION_LIST
						std::cout << "Plane: n=" << pl.normal << ", d=" << pl.d << std::endl;
						std::cout << "First inserted vertex: " << *vFirst << std::endl;
						std::cout << "Second inserted vertex: " << *vSecond << std::endl;
						std::cout << "Third inserted vertex: " << *next << std::endl;
					#endif
				}

				// search mating edges that have a point in common
				// continue this operation as long as edges are present
				while ( !intersectionEdges.empty() )
				{

					if (findAndEraseEdgePair(currentVertex, intersectionEdges, vNext))
					{
						// insert only if it's not the last (which equals the first) vertex
						if ( !intersectionEdges.empty() )
						{
							currentVertex = vNext;
							pClosing->insertVertex( vNext );
						}
					}
					else
					{
						// degenerated...
						break;
					}

				} // while intersectionEdges not empty

				// insert polygon (may be degenerated!)
				this->insertPolygon( pClosing );

			}
			// mating intersection edge NOT found!
			else
			{
				freePolygon(pClosing);
			}

		} // if intersectionEdges contains more than three elements
	}
Exemplo n.º 4
0
	//-----------------------------------------------------------------------
	void ConvexBody::extend(const Vector3& pt)
	{
		// Erase all polygons facing towards the point. For all edges that
		// are not removed twice (once in AB and once BA direction) build a
		// convex polygon (triangle) with the point.
		Polygon::EdgeMap edgeMap;

		for ( size_t i = 0; i < getPolygonCount(); ++i )
		{
			const Vector3& normal = getNormal( i );
			// direction of the point in regard to the polygon
			// the polygon is planar so we can take an arbitrary vertex
			Vector3 ptDir  = pt - getVertex( i, 0 );
			ptDir.normalise();

			// remove polygon if dot product is greater or equals null.
			if ( normal.dotProduct( ptDir ) >= 0 )
			{
				// store edges (copy them because if the polygon is deleted
				// its vertices are also deleted)
				storeEdgesOfPolygon( i, &edgeMap );

				// remove polygon
				deletePolygon( i );

				// decrement iterator because of deleted polygon
				--i; 
			}
		}

		// point is already a part of the hull (point lies inside)
		if ( edgeMap.empty() )
			return;

		// remove the edges that are twice in the list (once from each side: AB,BA)

		Polygon::EdgeMap::iterator it;
		// iterate from first to the element before the last one
		for (Polygon::EdgeMap::iterator itStart = edgeMap.begin(); 
			itStart != edgeMap.end(); )
		{
			// compare with iterator + 1 to end
			// don't need to skip last entry in itStart since omitted in inner loop
			it = itStart;
			++it;

			bool erased = false;
			// iterate from itStart+1 to the element before the last one
			for ( ; it != edgeMap.end(); ++it )
			{	
				if (itStart->first.positionEquals(it->second) &&
					 itStart->second.positionEquals(it->first))
				{
					edgeMap.erase(it);
					// increment itStart before deletion (iterator invalidation)
					Polygon::EdgeMap::iterator delistart = itStart++;
					edgeMap.erase(delistart);
					erased = true;

					break; // found and erased
				}
			}
			// increment itStart if we didn't do it when erasing
			if (!erased)
				++itStart;

		}

		// use the remaining edges to build triangles with the point
		// the vertices of the edges are in ccw order (edgePtA-edgePtB-point
		// to form a ccw polygon)
		while ( !edgeMap.empty() )
		{
			Polygon::EdgeMap::iterator mapIt = edgeMap.begin();

			// build polygon it.first, it.second, point
			Polygon *p = allocatePolygon();

			p->insertVertex(mapIt->first);
			p->insertVertex(mapIt->second);

			p->insertVertex( pt );
			// attach polygon to body
			insertPolygon( p );

			// erase the vertices from the list
			// pointers are now held by the polygon
			edgeMap.erase( mapIt );
		}
	}