The problem is “print” node in Mat could not return the value(the console will not pop up).

Here I have 2 file which have exactly the same nodes.

The file A is from the Internet where other people have “print” node and it works well. I delete all his nodes and create some other nodes to make things easier to understand.
The “print” node could return the right value in console while rendering.

So I create a file B and do exactly the same thing. But the console just won't pop up when I start render.

By the way, the console will not pop up either if I use non-commercial houdini to open file A.

I really have no idea about why that happens.

Thanks for any clue.

Not sure how you are doing it, but here's how I do it. Because I always forget, we have put this on our internal wiki here at Lost boys. I am quoting from the wiki:

• Wire the output you want to print into a print VOP.
  
• Wire the same output into a null and into the second output of the null, wire the print.
  
• In the print vop, put in “%” and check “output text to console” - this will print the text to the shell you launched Houdini from
  NOTE: It looks like there is a bug in the print VOP, where it won't print a vector. If you want to print a vector, pipe it into a vector to float and then pipe this into the print VOP.
  
• TIP: Draw a render region in your render view to speed interaction. This is also useful if you are wondering what the exact value of something is at a very specific location in your image. (EX: is a geo attribute coming through to my shader?)
  

Thx mrCatfish

I did link the print to a null node and check the “output text to console”.

But it still doesn't work.

And in another topic I posted(it's my first time posting topic…so I posted the same topic twice…), someone told me the file that doesn't work for me works fine with him…

So…I don't know…