|Errors in Line Estimation
Figure 1: You can change the orientation of the diagonal line by clicking on the diagonal line and moving your cursor up and down.
In this illusion the two ends of the straight diagonal line passing behind the rectangle appear to be offset. This effect is predicted by the bias in the estimation of the intersection points between the diagonal line segments and the lines at the border of the rectangle. The model also predicts the increase in the illusory effect with a decrease in the acute angle. In the figure above the green dots show the actual intersection points and the red dots denote the estimated intersection points.