Fig. 2

The establishment of the mid-sagittal plane according to the orthogonal lasers projected on T0 scan a. Take the intersection of the horizontal and vertical lasers as the Origin; b. Select any two points except the Origin in the horizontal laser (the distance between the two points should be as far as possible), and build the horizontal plane (Plane 1) with three points; Construct a line (Line 1) that passes through the Origin and is perpendicular to the horizontal plane; Construct a line (Line 2) passing through the Origin and any point in the vertical laser; c. Construct the mid-sagittal plane (Plane 2) with Line 1 and Line 2; Construct a line (Line 3) that passes through the Origin and is perpendicular to the mid-sagittal plane, which features the direction of the projection method