What are some alternatives?
When comparing Kodon and A-Painter, you can also consider the following products
Oculus Medium - Sculpt, model and paint in virtual reality on a 3D canvas.
Tilt Brush by Google - Paint in spaces around you with Virtual Reality
MasterpieceVR - Powerful VR sculpting & painting tool
SprayPrinter - Convert digital designs into wall art from your smartphone
Quill by Story Studio - Paint in virtual reality on an infinitely scalable canvas
VR Sketch - A tool for designers to draw inside virtual reality