GLSL Debugging Continues!

So, I made SOME progress on debugging GLSL using Apple's Shader Builder, which you can download from, with a free Apple Developer's account.

I'm doing most of my prototyping work in threeJS because the javascript environment is far more familiar to me.  Here, I'm trying to "plug in" a threeJS shader into libGDX.  I've synced up a few variables without errors so far, the shader compiles and runs on the device.  BUT, the screen is black..... still working.

Though, this morning I'm reevaluating this approach.  While, I often find doing such exercises are massively educational, they are often a exercise in futility. 

I'm thinking, now, that I might best find my time productive if I target libGDX's Default Shader.  It's set up nice, in a largely modular way, lots of #includes, etc. When I finish, I can commit the result to source, so others might benefit from my labor.