[Paraview] Transparency based on scalar

[Tim Gallagher]

Hi,

I would like to set the transparency of something based on a scalar. For example, if I took a Slice of a dataset, I would like to make it transparent based on, say, density gradient such that zero-gradient is transparent and some value indicates opaque. 

I haven't seen any existing filters to indicate this is possible. Is there a filter that does it? Is it something that's even possible to do through, say, a programmable filter? 

We're just getting into scripting with Paraview and it takes us a long time to figure out how to even do simple things, so before I spin my wheels on this one, I'd like to get some expert opinions on if it's even feasible. 

Thanks,

Tim