体绘制中显示隐含分界面的一种方法及其实现

A Method of Display Hide Interfaces in Volume Rendering and Its Realization

在普通的体光照模型下,使用直接体绘制显示对象内部的隐含分界面(内部不同介质之间的分界面),需要改变传递函数,确定体素的颜色值和不透明度.虽然能够看到对象内部的结构,但是在这种模型下,要透过物体的表面清晰地看到其内部的隐含分界面是不可能的.这一方面是由于普通体光照模型中的粒子不具有选择透光性,即不能透过波长在一定范围内的可见光而吸收另一部分波长不同的可见光,只能同等地吸收各种波长的光;另一方面是因为普通体光照模型缺乏表面信息部分.该算法使用一种具有选择透光性的体光照模型,在这种模型中加入表面散射部分,这一部分与视线、光源位置无关,同时采用非真实感绘制技术来加大隐含分界面的显示效果.在这种光照模型下,可以清晰地显示出隐含分界面具体的细节部分.

The colors and the opacity of voxels in transfer function should be assigned in order to display hide interfaces (the interface of inner different mediums) in objects by direct volume rendering based on the general volume light model. Although the inner structure of objects is seen, it is not clear to see inner hide interfaces from the surface based on this model. One reason is that the general volume light model does not have the attribute of select transparency. The particles in 3D space are not penetrated by visible lights with one wavelength and absorb visible lights with another different wavelength. They can only absorb all kinds of visible light in the same extent. Another reason is that it is short of surface information. A light model with the attribute of select transparency is used in the new algorithm, and the surface scatter which has nothing to do with the line of sight and the position of light source is put up into it. Meanwhile, the non-photorealistic rendering techniques are used to advance effects of inner hide interfaces. The hide interfaces and details are clearly displayed based on the new light model.