Why won't my object react to a displacement?

[SteveR]

Hi all, I wonder if anyone can help me at all.

I am learning to surface an imported object, in this case an alienesque zbrush head. For some reason I am unable to fathom, why my fractal noise node which outputs into the displacement node of the objects default shader is having precisley zero effect. I wondered if I had the scale screwed up but I don't think so. If anybody fancies taking a look the render and the tgd file can be downloaded from here...

image of the head:   https://dl.dropboxusercontent.com/u/72065240/terragen/head.bmp
the tgd file itself:      https://dl.dropboxusercontent.com/u/72065240/terragen/Head.tgd

Thanks.

And can I also ask a couple of related q's....

Is there a way to add several texture layers to the same object? ie several 'default shaders'?

And, what does the parts shader do, it replaces the multishader node according to the wiki but I don't understad it's primary purpose / use.

Many many thanks
Steve

[Oshyan]

When rendering with Ray trace Objects, which is the default (for speed and quality reasons), displacement is rendered as bump mapping only. If you need displacement on your object, you will need to turn off Ray trace Objects (in the Renderer node settings). This can have a negative affect on population rendering speed and quality, but unfortunately displacement is not available for ray traced object rendering yet.

- Oshyan

[SteveR]

Thanks Oshyan, that explains that I think

With ray trace objects off I get a bump map effect which is really what I was after to be honest anyway so that's great - but I hear what you are saying re other objects and impact on quality if there are a lot of objects in a scene which are therfore not ray traced. From what you say can I assume you cannot turn ray trace on/off per object?

Presumably one answer here is to model the bumps, high poly count maybe but probably achievable in Zbrush and TG is designed to handle a lot of ploys it seems so that might be a way to go in some situations.

Thanks

[Oshyan]

Yes, using real geometry is generally preferable wherever possible. TG does handle high geometry counts well. Per-object raytracing is not an option yet but will be in the future.

- Oshyan