Kling-Petersen T, Rydmark M
Mednet, Goteborg, Sweden.
Stud Health Technol Inform. 2000;70:162-7.
The Computer Laboratory of the medical faculty in Goteborg (Mednet) has since the end of 1998 been one of a limited numbers of participants in the development of a new modeling tool together with SensAble Technologies Inc [http:¿www.sensable.com/]. The software called SensAble FreeForm was officially released at Siggraph September 1999. Briefly, the software mimics the modeling techniques traditionally used by clay artists. An imported model or a user defined block of "clay" can be modified using different tools such as a ball, square block, scrape etc via the use of a SensAble Technologies PHANToM haptic arm. The model will deform in 3D as a result of touching the "clay" with any selected tool and the amount of deformation is linear to the force applied. By getting instantaneous haptic as well as visual feedback, precise and intuitive changes are easily made. While SensAble FreeForm lacks several of the features normally associated with a 3D modeling program (such as text handling, application of surface and bumpmaps, high-end rendering engines, etc) it's strength lies in the ability to rapidly create non-geometric 3D models. For medical use, very few anatomically correct models are created from scratch. However, FreeForm features tools enable advanced modification of reconstructed or 3D scanned models. One of the main problems with 3D laserscanning of medical specimens is that the technique usually leaves holes or gaps in the dataset corresponding to areas in shadows such as orifices, deep grooves etc. By using FreeForms different tools, these defects are easily corrected and gaps are filled out. Similarly, traditional 3D reconstruction (based on serial sections etc) often shows artifacts as a result of the triangulation and/or tessellation processes. These artifacts usually manifest as unnatural ridges or uneven areas ("the accordion effect"). FreeForm contains a smoothing algorithm that enables the user to select an area to be modified and subsequently apply any given amount of smoothing to the object. While the final objects need to be exported for further 3D graphic manipulation, FreeForm addresses one of the most time consuming problems of 3D modeling: modification and creation of non-geometric 3D objects.
自1998年底以来，哥德堡医学院的计算机实验室（Mednet）一直是与SensAble Technologies Inc[http://www.sensable.com/]共同开发一种新型建模工具的少数参与者之一。名为SensAble FreeForm的软件于1999年9月在Siggraph上正式发布。简而言之，该软件模仿了传统上陶艺家使用的建模技术。通过使用SensAble Technologies PHANToM触觉臂，可以使用不同的工具（如球、方块、刮刀等）对导入的模型或用户定义的“黏土”块进行修改。由于用任何选定的工具触摸“黏土”，模型将在三维空间中变形，并且变形量与所施加的力成线性关系。通过获得即时的触觉和视觉反馈，可以轻松进行精确而直观的更改。虽然SensAble FreeForm缺乏一些通常与三维建模程序相关的功能（如文本处理、表面和凹凸贴图的应用、高端渲染引擎等），但其优势在于能够快速创建非几何三维模型。对于医学用途，很少有从头创建的解剖学正确的模型。然而，FreeForm的功能工具能够对重建或三维扫描的模型进行高级修改。医学标本三维激光扫描的主要问题之一是，该技术通常会在数据集中留下与阴影区域（如孔口、深槽等）相对应的孔洞或间隙。通过使用FreeForm的不同工具，可以轻松纠正这些缺陷并填补间隙。同样，传统的三维重建（基于连续切片等）由于三角测量和/或镶嵌过程，经常会出现伪影。这些伪影通常表现为不自然的脊或不均匀区域（“手风琴效应”）。FreeForm包含一种平滑算法，用户可以选择要修改的区域，然后对对象应用任何给定数量的平滑处理。虽然最终对象需要导出以进行进一步的三维图形操作，但FreeForm解决了三维建模中最耗时的问题之一：非几何三维对象的修改和创建。
