My fault, pardon me for using the wrong terminology. Texture and bump maps are 3D speak. In Piranesi they use the terms “texture” and “grains”. Texture can be color, grains is always greyscale. When I mention texture in Photoshop I mean an image that is under the original image shining through because of the (partial) transparency of the layer above. “Grain” I understand as a greyscale image added to a brush. I never need to export a “bump map to Poser or any other 3D program because the workflow is always going the other way, from 3D to Photoshop. In short, I want to render the 3D image in Photoshop.

 

So with the information I have now the workflow for a fictive house house will be thus,

 

1)      In My 3D program I colour all the different parts of the house, wall, front side, and so on with different  (temporary) colours. The colours are only for so it will be easier to pick out the selections with the magic wand in Photoshop.

 

2)      Then in Photoshop, I cut-out all the different parts to separate layers, using dreamer101 and Quests method Layer via Cut, collect all in a group. (+ and backup I actually made a mistake in 1983...), Now the original image is no more, all shopped up.

 

3)      Then I can go through all the parts in turn, put a texture map under and a clipping mask over (thank you I didn’t know about that.:) over each object.

 

The advantage of this is that I am the whole time seeing the whole finished image + any texture or “grains” added to it. And I can easily correct mistakes or try a different approach.