The Volumetric Lighting Filter

I try to use some volumetric lighting in common filter. But It not same the picture of Nvidia Page. … _ch13.html
I check all input param and read that topic Volumetric Lighting .It’s same. But

this is mine:

This is sample :

And this is warning :

Have any way to make it right ?!
My video Card is AMD 4650. And I try it in AMD 5470. It’s same.
I’m using Version 1.8.1

Try making the number of iterations in the for loop of the shader a constant.