Three-dimensional reconstructions come to life – interactive 3D PDF animations in functional morphology

Digital surface mesh models based on segmented datasets have become an integral part of studies on animal anatomy and functional morphology; usually, they are published as static images, movies or as interactive PDF files. We demonstrate the use of animated 3D models embedded in PDF documents, which combine the advantages of both movie and interactivity, based on the example of preserved Trigonopterus weevils. The method is particularly suitable to simulate joints with largely deterministic movements due to precise form closure. We illustrate the function of an individual screw-and-nut type hip joint and proceed to the complex movements of the entire insect attaining a defence position. This posture is achieved by a specific cascade of movements: Head and legs interlock mutually and with specific features of thorax and the first abdominal ventrite, presumably to increase the mechanical stability of the beetle and to maintain the defence position with minimal muscle activity. The deterministic interaction of accurately fitting body parts follows a defined sequence, which resembles a piece of engineering.

基于分割数据集的数字表面网格模型（digital surface mesh models）已成为动物解剖学与功能形态学研究中不可或缺的组成部分，这类模型通常以静态图像、影片或交互式PDF文件的形式发布。我们以馆藏锥象甲属（Trigonopterus）象鼻虫标本为例，展示了嵌入PDF文档的动态3D模型的应用方案——该类模型兼具影片与交互功能的双重优势。因精准形态闭合（precise form closure）可实现高度确定性运动，该方法尤其适用于模拟此类关节。我们先阐释了单一组螺杆-螺母型髋关节的运作机制，随后展示了完整昆虫个体达成防御姿态的复杂运动过程。该防御姿态通过一系列特定的连锁运动实现：头部与腿部彼此咬合，同时与胸部及第一腹腹板（abdominal ventrite）的特定结构相互卡合；此举或旨在提升甲虫的机械稳定性，并以最少的肌肉活动维持防御姿态。各精准适配的身体部件间的确定性互动遵循既定序列，其运作逻辑恰似一套精密工程装置。