I'm trying to learn how to set up materials using nodes in Cycles. What I want to do is to have a base material over which some other texture is overlaid, with the distribution of that texture being controlled by another texture. For example dirt patches on some concrete that appears only in a few places.
I've got this working, but only in one file. Here's a screenshot of my node setup in the working file :
And here's the .blend file :
Play with the the "scale" parameter in the dirt distribution setting and you can watch the size of the areas populated with "dirt" patches change as you'd expect.
But here's the weird thing. I tried to re-create this in another file, and it doesn't work. As far as I can tell the settings are identical. Here's a screenshot of the nodes :
And the .blend :
This time if you play with the scale parameter, nothing much happens.
I'm at a loss as to what's different about the two files. Maybe a fresh pair of eyes can spot something obvious.