Graphic Painting

[TimeSpaceLightForce]

The artist in the market is giving this painting for free (the last one on his rack). I asked him if I can take it but he replied "Why should I give it to you?" The frame could be useful but I don't want to tell him that so I ask him why should he give it for free. He answered "because I miss to paint something into it". It looks like straight edge drawing to me but Im curious so I asked him what is missing in his painting. He told me that I can take it if I figured it out. I offer to buy it if he would tell me but he just refused while people are now gathering around the painting. What is missing?

[Thalia]

Not sure why all the axes are labeled X along with the origin. The painting seems to be called "4th Dimension." No clue how you'd represent that but I'm not seeing that in the picture.

[TimeSpaceLightForce]

Spoiler

time is the 4th dimension .

 

[Thalia]

Still not sure how that would be represented here. I assume what's shown is X, Y, and Z despite all being labeled X...

[TimeSpaceLightForce]

Spoiler

count the letters

 

[Thalia]

If the X at the origin is indicating a dimension, does that mean the dimension comes straight at the screen?  If that's the case, it looks like the arrow is missing. Unless it's hiding in the origin dot.

[TimeSpaceLightForce]

 

Spoiler

The dot is a cone of paint when looked at closer.. but maybe its not about the 4 dimensions. Just the 4th dimension.