add angle angle2 angledVector angleTo angleTo2 crossProduct distanceToVector dotProduct get isCodirectionalTo isCodirectionalTo isDegenerate isEqualTo isLeftOf isOppositeTo isOppositeTo isParallelTo isParallelTo isPerpendicularTo isPerpendicularTo isRightOf isUnitVector isZeroVector kIdentity kXAxis kYAxis length lengthSquare negate normalize operator!= operator* operator* operator* operator* operator* operator*= operator*= operator+ operator+= operator- operator- operator-= operator/ operator/ operator/= operator== perpVector projectResolveVector projectScaleToVector resolveVector resolveVector scaleBy scaleBy scaledVector set set setAngleLength setLength subtract transform unitVector Vector2d Vector2d Vector2d x y

projectScaleToVector() float Vector2d::projectScaleToVector ( const Vector2d &  xAxis ) const 求本矢量在矢量xAxis上的投影比例 投影矢量 = xAxis * 投影比例 投影比例在0到1之间时表示投影矢量是xAxis内的一部分 参数 [in] xAxis 投影到的矢量 返回 投影比例，有正负 函数调用图: 这是这个函数的调用关系图: