摘要
提出一种基于PC图形卡W Buffer的交互光线投射算法,这是一种面绘制与体绘制结合的快速体绘制方法.首先用3D分割等方法提取边界体素或用MarchingCubes等算法提取等值面,然后利用图形硬件预先投影这些边界体素或等值面以产生深度信息,最后由光线投射模块根据W Buffer中的深度信息快速找到实际等值面的位置,进行采样、着色、不透明度与颜色合成等渲染工作.这一方法不仅显著地加快了成像速度,而且不降低图像质量.实验结果表明,用该算法在PC机上以200×200分辨率渲染时,能达到10帧/秒的速度,基本满足虚拟内窥镜系统的动态导航和高质量图像要求,具有较大实用价值.
A new interactive ray casting algorithm based on WBuffering of PC graphic adaptor and combining surface rendering and volume rendering is presented. The first operation is to extract the boundary voxels using a fast 3D segmentation algorithm, or to extract the isosurfaces triangles by Marching Cubes algorithm. Then the boundary voxels or isosurface triangles are transferred to graphic adaptor for producing depths information in WBuffer. At last, the ray casting module utilizes the depths information to find the exact positions of isosurfaces and perform the rendering operations of sampling, shading, composing color and opacity. By using hardwareaccelerated technology provided by modern PCs, the rendering speed is greatly improved without degrading image quality. Experimental results show that the rendering speed of 10 frames per second is obtained on PC with an image resolution of 200×200 pixels. This rendering speed will satisfy the needs of the clinincal operation of Virtual Endoscope, which requires interactive navigation speed and high quality image.
基金
安徽省自然科学基金(01042202)
