Potetiometer and Scale texture in Cycles

Hello Everyone,

Potentiometer is an instrument used in physics experiments to determine the potential difference of an instruments.

Screw Details

Measuring Scale

Final Render in Cycles 300 Sample

Originally done Blender 2.4

Metallic textures are easy enough to do with using mix shadder with difuse and glossy shader.

The real problem comes in Measuring Scale while doing scale markings.
Generally after getting glass right any material should sound easy enough to do, but my team mates would say differently, after glass there is UV mapping.
So UV mapping in this one I would say was quite different from the others which I had done so far.

Unwrap process in simple enough to select the upper face of the measuring scale and select unwrap option.
The problem begins after you unwrap and apply image texture. For scale marking we need a good transparent image texture in .png format and alpha mapping should do the trick right? wrong...
For this texture to make happen I tried all the possible mapping technique I knew alpha mapping, tried all the forms of unwrapping, cube projection etc.
Like Glass Jar earlier where problem was with mesh rather than material, but in this mesh was as simple as it can be a CUBE!.
I could only see scale marking as the mixture of both scale texture and wood material, depending upon the factor value in mix shader, and after using invert node i got the scale marking in white color rather than black.

Node setup and aftter invert node.

So I thought problem is in texture itself and my team mate Bhavya Balakrishanan prepared a new texture.
But with new texture the problem was in render it didn't show any texture.

Add caption

But than alpha mapping did the trick.. I connected alpha of the image texture to invert node and output of invert node to factor value of mix shader and finally it is done.

The Final Node setup.

UV mapping is not that difficult as it sounds it is but there is a method and particular steps to follow and a definite way to unwrap your mesh and not just the hit U key and Unwrap.