  Interactive volume visualization using a mixed reality (MR) system helps
provide users with an intuitive spatial perception of volumetric data. Due to
sophisticated requirements of user interaction and vision when using MR
head-mounted display (HMD) devices, the conflict between the realisticness and
efficiency of direct volume rendering (DVR) is yet to be resolved. In this
paper, a new MR visualization framework that supports interactive realistic DVR
is proposed. An efficient illumination estimation method is used to identify
the high dynamic range (HDR) environment illumination captured using a panorama
camera. To improve the visual quality of Monte Carlo-based DVR, a new
spatio-temporal denoising algorithm is designed. Based on a reprojection
strategy, it makes full use of temporal coherence between adjacent frames and
spatial coherence between the two screens of an HMD to optimize MR rendering
quality. Several MR development modules are also developed for related devices
to efficiently and stably display the DVR results in an MR HMD. Experimental
results demonstrate that our framework can better support immersive and
intuitive user perception during MR viewing than existing MR solutions.
