al_draw_spline - Allegro 5 API
  
  - 
    #include <allegro5/allegro_primitives.h>
void al_draw_spline(float points[8], ALLEGRO_COLOR color, float thickness)
    
Draws a Bézier spline given 4 control points.
Parameters:
  - points - An array of 4 pairs of coordinates of the 4 control points
- color - Color of the spline
- thickness - Thickness of the spline, pass <= 0
      to draw a hairline spline