Fix my own stupidity with the Intro.
Models weren't being paired with shields due to the random shuffling of meshes etc.
Added a default shield strength in the material if no shield params set.
Added a shield cooldown, set to 1 second for testing.
Only render the if the cooldown is above 0.0 and only set it to 1.0 when we get hit.
Modify the fragment shader to have a base colour which linearly interpolates from red to blue, and a fresnel highlight as before.