在体绘制中，传递函数将3维数据场的采样点映射成光学参数，直接决定了绘制的效果，成为体绘制研究的关键。然而传递函数的设计存在盲目性、用户界面不直观、参数调节复杂等问题，针对这些问题，提出了许多解决方法。首先介绍传递函数的定义，总结各种设计传递函数的定义域、值域、映射规则的方法，然后从不同的角度对传递函数的设计方法作全面的概述，重点介绍图像中心法、数据中心法和对象中心法，既分析了这些方法的特点，又比较了它们之间的内在联系，并探讨了新的设计思路，展望了该领域未来的研究方向。

Volume rendering has proven to be an effective and flexible visualization method for large three dimensional data sets from scientific or medical applications perspective. Transfer functions are particularly important to the quality of volume rendered images because their role is essentially to make the data visible by assigning optical properties like color and opacity to the original values of the data set being visualized. Good transfer functions reveal the important structures in the data without obscuring them with unimportant regions. Unfortunately, specifying a good transfer function can be a difficult and tedious task due to the lack of intuitive interface and guiding information. Recent research has focused on automatic and semiautomatic techniques for creating transfer functions. A comprehensive survey of the up to date design approaches and strategies for transfer function is presented. After introducing the mathematical definition of the transfer function, different data and optical properties that can be used in the domain of transfer function are discussed. The proposed approaches of designing transfer functions can be classified into three categories;image centric, data centric and object centric methods according to the extent of automation and interaction. Their characteristics and relationship also are analyzed and reviewed in detail. Along existing methods, some potential directions for future research are predicted finally.