Direct-touch interaction is receiving an increasing amount of attention in the HCI domain and has recently been applied to some problems in information visualization. However, the field of scientific visualization has not seen much work on how direct-touch interaction could benefit the interactive visualization process. One reason may be that scientific visualization typically deals with datasets that are defined in 3D space, while touch input is two-dimensional. Therefore, to control scientific datasets in interactive visualizations one has to define intuitive mappings from 2D input to 3D manipulations for a variety of data types and exploration techniques. In this position paper we discuss some of the challenges of using direct-touch interaction in the field of scientific visualization that arise from the specific constraints of scientific visualization and argue for the development of integrated techniques to overcome these problems.