Help with material, oil-rubbed bronze? (mental ray)

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  05 May 2013
Help with material, oil-rubbed bronze? (mental ray)

Hello again, here I am struggling once more with creating a shader to handle oil-rubbed bronze. Here was a previous thread on the topic, but we didn't get anywhere of course. Here's the look I'm trying to get:





I'd like to do this with just one shader, as opposed to selecting faces and applying a coppery-bronze shader to those faces. So I'm hoping that there's a way to access the normals' edge somehow with facing ratio or a SamplerInfo or something, where I could rig it to the mia_material_x somehow (maybe the AO section?) to give any hard edges a different shine to them? Or perhaps use a twist on the RoundCorners mechanism to help, somehow?

It's a real pain in the ass, compared to regular metals! Every time I think I've got it, I have to do another render or angle and then it just looks black or even worse, and looks nothing like ORB...

My current bathroom project:




Any ideas would be very helpful!
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  05 May 2013
You need some sort of edge detection shader to blend between 2 different materials. in vray you can just click a checkbox on the dirt shader. in mental ray it's much more difficult and tedious. I remember you could somehow do it with the Dirtmap shader. here's the thread: http://forums.cgsociety.org/showthr...p?f=87&t=954589

cheers
/Mikael
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  05 May 2013
Thanks, Lost! I'll give it a shot, see if I can come up with anything. For now, I've just taken to isolating a few face-loops and applying another shader to 'em, but it's a short-term solution obviously. A lot of people are going with ORB for their plumbing and lighting lately, so I'll work on this shader and see if it'll do the trick.
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  05 May 2013
That edge detection set up did work for me but it was a pain in the butt. Didn't end up making anything useful with it, though. Just tested to see if I could get it to work.

This was not very much help I know, but just wanted to confirm it did work.
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  05 May 2013
Well here's what I could come up with, and hopefully it's good enough for now.



Considering the trauma of trying to deal with that edge-style shader, I think I'll just start modeling the coppery parts on a separate layer in Rhino, so that upon import into Maya I'll have two separate objects outright to quickly select and apply either shader to. Not perfect, and sometimes I don't know that my client's have chosen ORB until later, but might be a little more realistic and controllable this way.
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  05 May 2013
Was painting a mask for those copper parts not possible and using two shaders? I guess awkward as you would need some UV's but could use mudbox or mari (if you have them that is)

Final result looks nice though.

Best,

Rich
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  05 May 2013
I'm sure that would be possible too, but these fixtures I model in Rhino and then export as .obj files to Maya (my standard arch/viz workflow), and so really it was just a matter of selecting some edge loops and face areas, then assigning the coppery shader to those. It really didn't take long, the only problem with this method is of course if the client wants to see a different metal, then I need to duplicate the stuff and make a new layer for it, which is also pretty painless.

Actually, this method gives me a lot more control than an edge-based shader would. After plowing through all 15 or so fixtures in this bathroom in just a few minutes, I'll admit to just being lazy looking for a shader-based solution. Here's a quick 100dpi render with most of the fixtures shaded this way, renders in 8 minutes on 5 cores, so I'm happy with these shaders for now:



(Now I just gotta get control of those stupid lights!)
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  05 May 2013
The edge detection can be achieved with a Reverse Ambient Occlusion effect.

Assign a simple AO shader, but reverse the normals of the geo so that it is pointing inwards, then lower the far distance of the shader.

Getting that into a Mental Ray shader without reversing the normals of the geometry would require some research, my first guess is basing is using rAO on a blender node of of a two sided shader.

Otherwise, it requires baking to a texture map.
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Last edited by MasonDoran : 05 May 2013 at 08:53 AM.
 
  05 May 2013
Originally Posted by MasonDoran: Getting that into a Mental Ray shader without reversing the normals of the geometry would require some research, my first guess is basing is using rAO on a blender node of of a two sided shader.


I've been thinking down this line as well. The problem for me is getting the shading from the inside to show on the outside. Not sure how that would be possible using existing mr nodes.
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  05 May 2013
there is a post talking about this at nvidia forum
http://forum.nvidia-arc.com/showthr...-edge-detection

don't know if the solution if what you are after, you'll have to compile a shader by the looks of things.
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  05 May 2013
I found that ctrl_occlusion Shader supports reversing normals. -it has vector controls inside the shader itself.

Use the output on a blender node between 2 shaders. Keep in mind that AO is proximity based, so it will mess with anything that gets animated.
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  05 May 2013
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