Abstract
The difference between orthogonaly projected cube which is valuntaly located in space, and the perceived cube which is drawingly constructed by using the same angle relation of the projected three axes and with one point given on one of these axis, is studied experimentaly. The main results are as follows. 1 Perceived scale ratio is always larger than theoretical one. 2 Perceived scale ratio show the constancy tendency in comparison to the changing charactor of the projectional ratios. 3 The difference between these are independently determined by theoretical angle of each axis to the projecting plane. 4 Perceived scale on vertical axis is larger than the scale on the other two axes.
