A computational method for quantifying morphological variation in scleractinian corals

Morphological variation in marine sessile organisms is frequently related to environmental factors. Quantifying such variation is relevant in a range of ecological studies. For example, analyzing the growth form of fossil organisms may indicate the state of the physical environment in which the organism lived. A quantitative morphological comparison is important in studies where marine sessile organisms are transplanted from one environment to another. This study presents a method for the quantitative analysis of three-dimensional (3D) images of scleractinian corals obtained with X-ray Computed Tomography scanning techniques. The advantage of Computed Tomography scanning is that a full 3D image of a complex branching object, including internal structures, can be obtained with a very high precision. There are several complications in the analysis of this data set. In the analysis of a complex branching object, landmark-based methods usually do not work and different approaches are required where various artifacts (for example cavities, holes in the skeleton, scanning artifacts, etc.) in the data set have to be removed before the analysis. A method is presented, which is based on the construction of a medial axis and a combination of image-processing techniques for the analysis of a 3D image of a complex branching object where the complications mentioned above can be overcome. The method is tested on a range of 3D images of samples of the branching scleractinian coral Madracis mirabilis collected at different depths. It is demonstrated that the morphological variation of these samples can be quantified, and that biologically relevant morphological characteristics, like branch-spacing and surface/volume ratios, can be computed. Electronic supplementary material The online version of this article (doi:10.1007/s00338-007-0270-6) contains supplementary material, which is available to authorized users

Tangible Interaction for 3D Widget Manipulation in Virtual Environments

In this paper we explore the usage of tangible controllers for the manipulation of 3D widgets in scientific visualization applications. Tangible controllers can be more efficient than unrestricted 6-DOF devices, since many 3D widgets impose some restrictions on how they can be manipulated. In particular for tasks that are in essence two-dimensional, such as drawing a contour on a surface, tangible controllers have advantages over 6-DOF devices. We have conducted a user study in which subjects draw a contour on a three-dimensional curved surface using a 3D contour drawing widget. We compared four different input methods for controlling the contour drawing widget and the viewpoint of the surface: using one 2D mouse for drawing and viewpoint selection, using a 6-DOF pen for drawing and a 6-DOF cube device for viewpoint selection, using a 6-DOF pen for drawing on a tangible 6-DOF cube which implements a Magic Lens style visualization technique, and using a 2D mouse for drawing and a 6-DOF cube for viewpoint selection. We show that while the mouse outperforms 6-DOF input methods, the tangible controller is superior to unrestricted 6-DOF input

Tangible Controllers for 3D Widgets

We have used a tangible input device to control 3D widgets in a 3D VR environment. This can be a more efficient input method than unrestricted 6-DOF manipulation, since many 3D widgets impose some restrictions on how they can be manipulated. In particular for tasks that are in essence two-dimensional, such as drawing a contour on a surface, tangible controllers have advantages over unrestricted devices. This is especially useful in 3D environments which do not offer 2D input, such as the CAVE. We have combined the tangible controller with a 3D Magic Lens style visualization technique. We have conducted a small user study, in which we compare different input methods for drawing a contour on a three-dimensional curved surface using a 3D contour widget

Tangible Props for Scientific Visualization: Concept, Requirements, Application

In this paper, we explore the use of printed tangible props as input devices for scientific visualization. Three-dimensional printing technology is used to create a physical representation of data. The object is then used as a tangible input prop, which exactly matches the data. In addition, two-handed interaction with a stylus is performed on the prop without the use of buttons, instead relying on the detection of contact between the stylus and the prop through precise calibration and tracking. This allows the sense of touch to be harnessed to create a more efficient and natural interaction method for scientific visualizations in virtual and augmented reality. We explain the concept of tangible props and where it can be applied. We also consider the technical requirements of systems using such props. Finally, we present our example application, which uses printed tangible props for interactive measurement of marine coral data. The use of tangible props is found to improve the usability of the application