Joris, about the layer underneath as second texture. Can you explain a little bit how the fx clips works?
I mean, when you load an fx as clip gives you the ability of setting up what will be affected (comp, layer1, layers 2, etc). I'm aware that in certain comps-sittuations have an unexpected behaviour (think about the usual settings with a matrox and asigned layers to slices). Is that selector just a jump in the fx pipeline's order?
I think the approuch of 2 layers for feeding a shader is not possible in the way Lynn is sugesting.
At least in my undestanding, a simple shader will not see Layer1 as iChannel1.
I don't know if we can sample an external image file either, right now I'm just feeding iChannel1 with perling noise, and inside shader stuff.
Remember, I don't know if my words have any sense, but I like to see life in this threath