specular channel in VFB question

[vanhage]

Hi all,

I've been browsing a few compositing tutorials online and many seem to use the specular channel (and others) from the vfb channels list. When I output the specular channel it comes out black every time.

So my questions are:

1. Am I doing something wrong?

2. Does the specular channel not work properly? If so, does anyone know an alternative method with similar results to get the specular information isolated?

Thanks!

[frip51]

Re: specular channel in VFB question

Vanhage,
welcome aboard!

Well, you might find your Specular channel empty for different reasons.
The most important thing is to understand what Specularity stands for. Here's a few links that underline its meaning:

http://en.wikipedia.org/wiki/Specularity
http://en.wikipedia.org/wiki/Specular_reflection
http://en.wikipedia.org/wiki/Specular_highlight

So, what you need is a light source with a single point of origin in order to bounce single rays of light into the camera.
GI or rectangular lights won't do it.

You also need a material with a certain gloss level. No or too much reflexion will both result in a black Specular map.
Generally speaking: the lower the Highlight Glossiness value of the material, the more Specularity.

Hope this helps


Cheers,
Matthias

If you set up a test scene using a spotlight