# VR as a 3D Modelling Tool in Engineering Design Applications
## 3 Results
### Preliminary Study: Desktop Modelling  
The results of the tasks indicate that most participants chose a similar approach of importing the drawings, creating sketches and projected curves, creating surfaces, and then creating a solid body with details. All of them used the strategy of creating half of the model and then mirroring it. However, correct surface transitions need to be used between the mirrored surfaces because the joined union need to be blended without any visible edges.  
The average total time of task completion was 75 min, with eight of 14 participants reaching the time limit. The fastest one took 63 min. All except one participant managed to import and set the drawings and it took them an average of 15 min. All but two participants managed to create sketches and projected sketches that would later be used for creating the surfaces. It took them an average of 19 min for this step. All but two participants managed to create the base surfaces. It took them an average of 25 min for this step. The geometry matching and surface transitions are included in the time for creating surfaces. Only six participants managed to create a solid body. This step took them an average of 4 min. Seven participants managed to detail the body. This step took an average of 20 min. Values displayed in Table 2 specify the percentage of participants completing each task. A  
Figure 6: Still from a video showing the creation of an example model in a VR environment.  
single task is divided into three levels of achievement which are: achieved, not achieved and partially achieved.  
Most participants managed to import the images. There were only 7% of participants that did not import images into the CAD software. Figure 7 shows participants' models of diverse levels of achievement.  
Commonly the difficulties started when they had to project and scale sketches in the layout of the software. Only 57% of participants arranged the sketches in the correct order. Next, half (50%) of participants have partially achieved creating the surface model. This means that the quality of the surface was not sufficient and would probably result in a zero-thickness geometry in the next steps (Figure 7,e). Still, 36% managed to create a surface model. In the geometry matching, visual similarity between the picture of a mouse and the surface model was observed. This task was successfully achieved by 36% of participants (Figure 7,c). The quality of a surface is essential for creating a smooth surface transition. If continuity is not established at a merging point between two surface models, an edge or hole will appear at the joining end. Again, only 29% of participants achieved a satisfactory surface transition. If every step in a process of CAD modelling was made at a sufficient level so far, this would lead to a solid body. A solid body with varying surface quality was achieved by 43% of participants. Furthermore, a high number (43%) of participants didn't create details on a solid body. The participants which faced difficulties during CAD modelling dedicated too much time to steps trying to complete a particular task and lost the motivation to make details or didn't know how to achieve it (lack of knowledge).