Iridescence shader + UV lightmap concerns

[FONT=Times New Roman] I would like to create a dynamic material (more specifically, hair on alpha cards) which iridesces between the tones of dark blue, dark purple and black-- switching colours as a reaction to light in a similar manner to corvine feathers. How would I be able to implement this?

Also, many tutorials have recently said that every mesh needs to be imported with its respective lightmap in order to receive proper lighting. How much space does each UV lightmap take up, and should it be a cause for concern in terms of project size? If so, is there a way to feed a UV lightmap to the given object using a RGB or Alpha channel within a material instance?

Thanks in advance :cool:

Meshes only need lightmaps if you’re going to be baking lighting onto them with Lightmass. You’d only do that for things like architecture and static props. Since you’re doing hair (presumably for a character), you don’t need to worry about that. No idea how to do the iridescence shader though!

[FONT=Times New Roman] Apologies. I forgot to clarify that I meant UV lightmaps for static floor- and wall-meshes. How much space do general UV lightmaps take up? A concerning amount, or…? :confused:

Generally, lightmap resolutions are kept pretty low, like around 64 or 128, unless you are trying to get that crazy smooth archviz quality. 128x128 lightmaps aren’t very big compared to 4k, or even 2k or 1k PBR texture maps…