Hi!
I am from Russia (sorry for my English)!
Please help me with render calculations of distance between camera and point on animated surface. We need in sequence. On russian forum say that exist “I vector” which is local variable, but nothing more. I am novice in houdini and don't understand where I'm find this and how use this in my task. Please help!

If you wanna render distance between camera and all of the points from objects ,you should use depth map :
Add “Pz (position-z)” Extra Image Plane in the Mantra node.

But If you just wanna render distance between camera and specify point(or Points) in the custom Image Plane ,You should compute distance between camera and your specify point(or Points) and save this value in the specify attribute (for example Distance) ,and export this attribute from your material and finaly add custom Extra Image Plane for this attribute (Distance).

Check attached file 8)

If you wanna another idea please explain more clearly