在onTouchesBegan中，touches.size()一直是1。这对多点缩放图片，三维模型来说，挺郁闷的。本文把初始值放在onTouchesMoved 中，基本解决问题，但有一小点问题，就是第一次触摸时有小范围的缩放，因为只有移动才可以得出新的距离，但是此时的距离一定不等于之前的距离。对我的项目够了，不知道其它人能不能用。

void CocaineLayer::onTouchesMoved(const std::vector<Touch*>& touches,cocos2d::Event *event) {
	
	
		if (touches.size() >= 2) {
			if (mulTouchesFlag) {
				auto t0 = touches[0];
				auto t1 = touches[1];
				auto location0 = t0->getLocation();
				auto location1 = t1->getLocation();
				_oldDis = (float) sqrt((location0.x - location1.x) * (location0.x - location1.x) + (location0.y - location1.y) * (location0.y - location1.y));

				mulTouchesFlag = false;
			} else {
				auto t0 = touches[0];
				auto t1 = touches[1];
				auto location0 = t0->getLocation();
				auto location1 = t1->getLocation();
				float newDis = (float) sqrt((location0.x - location1.x) * (location0.x - location1.x) + (location0.y - location1.y) * (location0.y - location1.y));
				_scale *= newDis / _oldDis;
				_model->setScale(_scale * 0.01f);
				if (_scale > 10.0f) {
					_scale = 10.0f;
				}
				if (_scale < 0.7f) {
					_scale = 0.7f;
				}
				_oldDis = newDis;
			}

		}
}

void CocaineLayer::onTouchesEnded(const std::vector<Touch*>& touches,cocos2d::Event *event) {

	mulTouchesFlag = true;
}