Hey all,
Its probably a beginner/noob question but does anyone have a tutorial or place of reference I can use to convert an older shader I
made from a Maya Blinn shader rendered with Mental ray to a Principle shader that can be rendered with mantra?

the answer lies at the fundamental question: what is material?

it is a jasper polished stone

not THE material but material. What I was saying is that in a physically based ray tracer, material is a set of algorithm that defines a physical surface/volume's behavior of reflecting/absorbing/scattering light. As far as I know, mental ray is an outdated renderer that's not physically based, and mantra, like arnold is a physically based physical renderer. I hope this answers your question.

Oo I gotcha, Thankyou I answered too quickly before without thinking

If it is a standard Maya blinn shader it should be very easy to convert it to a similar Mantra shader, parameters are different but the blinn has very few and “old style” controls like specular, eccentricity, spec rolloff, you can substitute them playing with reflectivity parameters …