Convex or Concave Sphere? - Drawing Optical Illusion with Charcoal Pencils - Vamos

Is it convex or concave sphere? Drawing a convex or concave sphere. How to draw optical illusion on lined paper. Cool 3d trick art. Awesome magic realism. Artistic graphic with Vamos.
• Material used:
Paper: 250x175 mm, white coloured cardboard.
Graphite pencils STABILO HB
STABILO Pen marker.
DERWENT charcoal pencils, dark and light.
White pastel pencil.
Kneaded eraser, ruler.
Cotton material.
♪ MUSIC: Elephants - Huma-Huma,
(Youtube Music Audio Library)
http://www.youtube.com/audiolibrary
By Sandor Vamos. I'm Hungarian.
Copyright © New video 2017. Vamos. All rights reserved.