float control_x = (x1 - half_track_w) * projector_z + projector_x;
float control_y = (y1 - half_track_h) * projector_z + projector_y;
float distance = line_dist(control_x,control_y, mask_cursor_x,mask_cursor_y);
float control_x = (x1 - half_track_w) * projector_z + projector_x;
float control_y = (y1 - half_track_h) * projector_z + projector_y;
float distance = line_dist(control_x,control_y, mask_cursor_x,mask_cursor_y);