Recenty, I was making a plasma-like forcefield, and I found this material, which is almost what I wanted. So I copied the node setup, and I tried a test render, but it looked nothing like the render preview.
Render preview with correct material:
Final render, but the material is wrong:
I am using Cycles BTW.
Strange things happen here, I suppose this is buried somewhere in Color Management or somehow the way Alpha is treated. If you turn off 'Transparent' in the 'Film' Section, the renders become identical.
left: Viewport Render, right: Final Render, with Transparent turned off
The thing is that the ViewPort Render seems to Comp the Alpha against a different Color Value than the Final Render. If you render the image with Transparent Background, and Comp it using an Alpha Over node, you get these results here:
The Split Viewer Node shows you (with a percentage slider) in this setup the raw render on the left, the comped image on the right. The darker you make the background, the more you see the texture. If the background becomes white, the texture disappears. So I have the suspicion the Render View node comps the Alpha values against white background, the Preview render against the checkerboard background.
See these tests of the very same render for comparison:
