This study explored the effect of pictorial freehand sketches on CAD model building for first and second year engineering students. Thirty one students from CGT 163 Graphical Communication and Spatial Analysis course at Purdue University completed the study. Subjects were divided into two groups, one of which was required to use pictorial freehand sketches in the visualization process while the other one was not. Subjects were provided real models of physical objects of different complexity and were asked to model a part that would fit in the original one to form a rectangular prism. Outcomes were then analyzed in terms of time spent on the task, number of steps used during the process, and accuracy of the resulting model. In addition, subjects’ scores from the Purdue Spatial Visualization Test (PSVT) were recorded and used in the study as a measure of visual ability. The results showed no statistically significant effect of sketching on the construction of CAD models. At this point, we are not ready to conclude that pictorial freehand sketching directly affects CAD model construction. Subjects’ visual abilities, on the other hand, had a significant effect on model building.

Date of this Version



Computer Graphics Technology

Department Head

Dr. Marvin Sarapin

Month of Graduation


Year of Graduation



Master of Science

Head of Graduate Program

Dr. Craig Miller

Advisor 1 or Chair of Committee

Dr. Craig Miller

Committee Member 1

Dr. Patrick Connolly

Committee Member 2

Dr. Steve Visser