When I draw a billboard sprite, and pass the xsacle to -1 for draw_sprite_3d, the result distorted.
How can I get this effect normal？
Got that, I should calculate the Angle between the player's direction with camera
var cdir = abs(Camera.Angle) % 360;
if ( Camera.Angle < 0 ){ cdir = 360-cdir; }
var dAng = cdir+direction-90;
if ( dAng <0 ){ dAng += 360; }
if ( dAng >=360 ){ dAng -= 360; }
if( moving ){
if( dAng>100 && dAng<260 ){ sprite_index = sprGroup[$ "moveL"]; }
if( dAng>280 || dAng<80 ){ sprite_index = sprGroup[$ "moveR"]; }
}