Visualization of AutoCAD Model Cell Structures in CAVE Immersive Environments

          The modern technology of the new millennia allows one to enjoy the reality of the virtual world. The CAVE, a trademark of the Electronic Visualization Laboratory of the University of Illinois, actually stands for CAVE Automatic Virtual Environments (Pape, 1997). But what exactly is virtual reality? Virtual reality is a computer simulation of a system that allows a user to perform operations and shows the effects in real time. For example, a system for surgeons might allow the user to “operate” on a “virtual patient” for experimentation before carrying out the risky procedure on an actual person.
          The objective of this project was to explore visualization in the CAVE virtual environment to gain a better understanding of the different components in the created model and also to see how these immersive environments provide an infinite opportunity for the better scope and experimentation of sophisticated technology. For this purpose the fundamental techniques of computer graphics software, AutoCAD and NuGraf, were investigated. The model was first completely drawn and rendered in AutoCAD. After the model had been converted into CAVE format through NuGraf, it was ready for CAVE simulation. After simulation, the model was brought up in the CAVE using special interactive software.
          The CAVE helped bring out the model to life, and the user in the CAVE was able to explore the different parts of the model by simply walking through it. The main AutoCAD model for this project was an animal cell containing a nucleus, nucleolus, chromatin material, ribosomes, endoplasmic reticulum, golgi apparatus and mitochondrion. Moreover, the model and the movement of the user inside the CAVE were recorded on video. Finally, the project concluded with the different types of applications the CAVE could be used for, the description of other AutoCAD models made, such as, the structure of a chloroplast containing double membranes, thylakoids and stroma, and how virtual environments give the vast opportunity for exploration and visualization of various different structures and components.
           The most important item required for this project was the CAVE itself. The CAVE located at Virginia Tech was used for this project. Further, numerous computers are necessary to operate the CAVE. The primary CAVE computer, named cave, was a Silicon Graphics International (SGI) Onyx system with three Infinite Reality Engines (Kriz, 2001). Another computer, named tensor, was a desktop support computer for the cave computer. The tensor is very similar to the cave computer and is used for CAVE simulation. These computers were used to execute the complex interactive software (ex: Pfnav, Saranav, DIVERSE).
          Four Electrohome Marquis 8000 projectors surround the CAVE and project imagery (Kriz, 2001). When one enters the CAVE, shutter glasses are required to see images in 3-D (NADP Proceedings, 2001). The tracking system was yet another important item required for viewing. The person that wore tracked glasses controlled the perspective, while the CAVE wand allowed the experimenter to walk and interact with the environment. The interactive software on the computers aided in evaluating the position of tracked glasses and the CAVE wand (NADP Proceedings, 2001). For this project, additional software was required. For drawing and rendering the model, AutoCAD 2002 was used. Next, for converting the file format from .3ds to .flt, NuGraf was used. AutoCAD and NuGraf were used on a Windows workstation (NT and 2000).

Methods

          Primarily, the animal cell was drawn in AutoCAD 2002. By using special commands like “elev”, “extrude” and “subtract” the cell was made into a 3-Dimensional solid. Once the outer membranes were drawn, the various inner structures were constructed in a similar way. The height at which an organelle was drawn was adjusted using “elev”. Once, the cell was completed, the various structures were given their specific colors. The “materials” and “materials library” commands helped in adding color to the object. Once, the different colors, textures and background were added, the object was rendered using the command “render.” Two view ports could be selected for the object to be viewed in 2D, as well as, in 3D as shown in Figure A.1 on page 15 in the appendix. This drawing was drawn as a .dwg file. Since, the CAVE does not recognize this format, it was necessary to convert .dwg files into flight (.flt) files.
          Next, as shown in Figure A.2, the File menu pull-down was clicked, followed by the selection of the Export command. When the export data window appeared (Figure A.3), the 3D Studio (*.3ds) file type was chosen and the Save button was clicked. Once, the Save button was clicked on, the initial drawing of the animal cell re-appeared and the user was prompted by AutoCAD to select objects. With the help of the mouse, a box was drawn around the model of the animal cell, and everything was selected as shown in Figure A.4. After, the selection of the objects, the return key was hit, and another dialog box called 3D Studio File Export Options appeared on the screen. Everything was set as shown in Figure A.5 and then the OK button was clicked. Figure A.6 shows the command toolbar when AutoCAD finished saving the file as a .3ds file.
          AutoCAD was minimized and the NuGraf application was brought up. As illustrated in Figure A.7 the File menu was clicked, followed by the selection of Import 3D Geometry command and finally the selection of 3D Studio .3ds file pull-down. The user was then prompted by NuGraf to either Merge or Replace (Figure A.8). Figure A.9 shows how the desired file was selected. The clicking of the OK button was followed by the appearance of the 3D Studio Geometry Import Plug-In (Figure A.10). Everything was set as shown and then the OK button was clicked. Another dialog box called Info Request was brought up by NuGraf (Figure A.11). The No button was clicked.
          The drawing of the animal cell was brought up by NuGraf (Figure A.12). The drawing appeared black because NuGraf does not recognize glass and other transparent textures recognized by AutoCAD 2002. The animal cell was almost completely rendered with glass and transparent textures in order for the user to look through and see the different parts of the cell. Followed by the appearance of the drawing on the screen, the File menu was clicked and the Export 3D Geometry command was selected (Figure A.13). The CAVE recognized flight (.flt) files and therefore the OpenFlight file command was selected. Following the selection of OpenFlight file, NuGraf brought up another dialog box called OpenFlight Export Filter (Figure A.14). Everything was set as shown, and the OK button was clicked. The user then had to save the file as an OpenFlight file (Figure A.15) and the Save button was clicked.
          After the drawing was saved as an OpenFlight file, the drawing was ready for transfer from Windows NT workstation to the tensor computer for the purpose of CAVE simulation. The File Transfer Protocol (FTP) box was brought up (Figure A.16). Once, the password was entered, the desired file was chosen (Figure A.17) and with the use of the special arrow icons (Figure A.18) the file was transferred into the tensor computer (Figure A.19).
          Once the user logged on into the tensor computer, the file was brought up using special interactive software (Pfnav, Saranav, Diverse) for simulation (Figure A.20). Finally, the animal cell was brought up by tensor and Figure A.21 shows the different components of the cell with a viewpoint higher than the surface of the cell.
          After it was simulated and the origins were set using tensor, the animal cell was ready to be brought up in the CAVE. The cave computer was also a Linux system, and the animal cell was brought up in the same way as it was brought up in tensor. With the help of the special stereo glasses and the wand, the user was able to walk through and explore the different parts of the cell. Visualization was done and the movement was recorded on video. The position of the head and the wand with respect to the CAVE were also shown in the video.