C++ Vector2D::LengthSqr方法代码示例

		// Get the distance from this vector to the other one squared.
		// NJS: note, VC wasn't inlining it correctly in several deeply nested inlines due to being an 'out of line' .  
		// may be able to tidy this up after switching to VC7
		vec_t DistToSqr( const Vector2D &vOther ) const {
			Vector2D delta;

			delta.x = x - vOther.x;
			delta.y = y - vOther.y;

			return delta.LengthSqr();
		}

//-----------------------------------------------------------------------------
// Computes error between two texcoords; returns false if the error is too great
//-----------------------------------------------------------------------------
bool CompareTexCoordsFuzzy( const Vector2D &t1, const Vector2D &t2, float &flError )
{
	Vector2D vecError;
	vecError[0] = fabs( t2[0] - t1[0] );
	vecError[1] = fabs( t2[1] - t1[1] );
	flError = vecError.LengthSqr();
	return ( flError <= (TEXCOORD_EPSILON * TEXCOORD_EPSILON) );
}

//-----------------------------------------------------------------------------
// Computes the closest point to vecTarget no farther than flMaxDist from vecStart
//-----------------------------------------------------------------------------
void ComputeClosestPoint2D(const Vector2D& vecStart, float flMaxDist, const Vector2D& vecTarget, Vector2D *pResult)
{
	Vector2D vecDelta;
	Vector2DSubtract(vecTarget, vecStart, vecDelta);
	float flDistSqr = vecDelta.LengthSqr();
	if (flDistSqr <= flMaxDist * flMaxDist) {
		*pResult = vecTarget;
	}
	else {
		vecDelta /= sqrt(flDistSqr);
		Vector2DMA(vecStart, flMaxDist, vecDelta, *pResult);
	}
}

// Build a 2D convex hull of the set of points.
// This essentially giftwraps the points as it walks around the perimeter.
int Convex2D( Vector2D const *pPoints, int nPoints, int *indices, int nMaxIndices )
{
	int nIndices = 0;
	bool touched[512];
	int indexMap[512];

	if( nPoints == 0 )
		return 0;


	// If we don't collapse the points into a unique set, we can loop around forever
	// and max out nMaxIndices.
	nPoints = FindUniquePoints( pPoints, nPoints, indexMap, ARRAYSIZE( indexMap ), 0.1f );
	memset( touched, 0, nPoints*sizeof(touched[0]) );

	// Find the (lower) left side.
	int i;
	int iBest = 0;
	for( i=1; i < nPoints; i++ )
	{
		if( pPoints[indexMap[i]].x < pPoints[indexMap[iBest]].x ||
			(pPoints[indexMap[i]].x == pPoints[indexMap[iBest]].x && pPoints[indexMap[i]].y < pPoints[indexMap[iBest]].y) )
		{
			iBest = i;
		}
	}

	touched[iBest] = true;
	indices[0] = indexMap[iBest];
	nIndices = 1;

	Vector2D curEdge( 0, 1 );

	// Wind around clockwise.
	while( 1 )
	{
		Vector2D const *pStartPoint = &pPoints[ indices[nIndices-1] ];

		float flEdgeAngle = atan2( curEdge.y, curEdge.x );
		
		int iMinAngle = -1;
		float flMinAngle = 5000;

		for( i=0; i < nPoints; i++ )
		{
			Vector2D vTo = pPoints[indexMap[i]] - *pStartPoint;
			float flDistToSqr = vTo.LengthSqr();
			if ( flDistToSqr <= 0.1f )
				continue;

			// Get the angle from the edge to this point.
			float flAngle = atan2( vTo.y, vTo.x );
			flAngle = AngleOffset( flEdgeAngle, flAngle );

			if( fabs( flAngle - flMinAngle ) < 0.00001f )
			{
				float flDistToTestSqr = pStartPoint->DistToSqr( pPoints[iMinAngle] );

				// If the angle is the same, pick the point farthest away.
				// unless the current one is closing the face loop
				if ( iMinAngle != indices[0] && flDistToSqr > flDistToTestSqr )
				{
					flMinAngle = flAngle;
					iMinAngle = indexMap[i];
				}
			}
			else if( flAngle < flMinAngle )
			{
				flMinAngle = flAngle;
				iMinAngle = indexMap[i];
			}
		}

		if( iMinAngle == -1 )
		{
			// Couldn't find a point?
			Assert( false );
			break;
		}
		else if( iMinAngle == indices[0] )
		{
			// Finished.
			break;
		}
		else
		{
			// Add this point.
			if( nIndices >= nMaxIndices )
				break;

			for ( int jj = 0; jj < nIndices; jj++ )
			{
				// if this assert hits, this routine is broken and is generating a spiral
				// rather than a closed polygon - basically an edge overlap of some kind
				Assert(indices[jj] != iMinAngle );
			}

			indices[nIndices] = iMinAngle;
//.........这里部分代码省略.........