In the medical simulation world the use of isosurfaces is a common action, as the information from some sources, e.g. CTs, is very well defined, and the isosurface can be easily set. Additionally, in any simulator shadows are a necessary addition to increase the users immersion as well as its depth perception. Unfortunately, the Visualization Toolkit does not offer these features, and so in this paper a modified vtkGPUVolumeRayCastMapper is presented. This modified version allows volumetric isosurface rendering as well as receiving shadows from polygons using the usual pipeline.