The proposal of the technique of error visualization for a learner´s pencil drawing

In a pencil drawing class, a teacher explains often the differences between a drawing and a motif by many ways; even so, it is difficult for most learners to understand the existence of errors in his/her drawing. When a learner watches the 3D model of his/her drawing from appropriate viewpoints, he/she is immediately aware of the errors. This paper describes the technique of error visualization from a learner´s erroneous drawing. We developed a drawing advice system that consists of a 3D model converter from a 2D image and an evaluation function to estimate the effect of the 3D model. We designed a geometrical formula that expresses the relation between the geometrical feature and the error expression in the teacher´s advice.