Hello everyone,

I have a quick question regarding the Mantra Surface shader and Metal/Roughness workflow.

Is the Mantra Surface shader Metallic Map intended to act the same way as the Metallic Map in the Principled Shader, allowing a Metal/Roughness workflow?

From what I can see in the Mantra Surface, the metallic setting is reflecting the specular colour not the diffuse colour, resulting in the need for a specular map.

Compared to the Principled shader where the metallic setting it reflecting the diffuse colour. (which is what I expect for a metal/roughness workflow)

It's most likely user error so I appreciate any help I can get from more experienced users. Apologies if this has already been answered elsewhere.

Thanks
Rob

Hi,

I probably wasn't clear enough in my description so I've added some visual information and corresponding Houdini file.

I've shown that using a base/diffuse colour of red and setting the Squares.jpg texture as the Metallic map produces different results between the two shaders.

Ideally, I'd like to either;
a) Modify the Mantra Surface Shader metallic setting to behave like the Principled Shader.
b) Modify the Principled Shader to include Opacity Maps.

I am new to Houdini so although I am aware that I could dive in and modify them myself, I would appreciate any help that would make that process a little easier for me.

Thanks
Rob

The Surface Model seems to be a general shader that users can umm pretty much break! It's a bit of a bugbear of mine, I don't need to be spending hours pushing and pulling sliders trying to get a shader to look right.

I'm hoping the SideFX implements the extended Disney shader in the next version, so I can stop using the Surface model!

http://blog.selfshadow.com/publications/s2015-shading-course/burley/s2015_pbs_disney_bsdf_slides.pdf [blog.selfshadow.com]

So for now, if your doing something like a Metallic surface I would use the Principled Shader.

Thanks for the reply and the link.

Part of the issue is that I needed to use opacity maps for holes in the metal. (ie. old rusty metal)

I use Substance Painter for texturing which allows me to work in either metal/roughness or spec/gloss. So, to work with opacity and metal/roughness… In Photoshop, I needed to invert the metallic map, apply it as a mask on a white layer with the diffuse underneath so I can apply it as specular map in Houdini. (for multiple textures)

I love Houdini for it's non-destructive workflow. The Principled shader works perfectly with Substance Painter export, allowing me to quickly update textures and test results but it lacks opacity maps. The Mantra Surface shader works as expected, apart from the need to create a specular map for a metal/roughness workflow. (which is where I'm confused)

I assumed that there must be a better method of using the Mantra Surface shader in a metal/roughness workflow so I guess my questions are (in order);

1) Is the Mantra Surface shader meant to work in a Metal/Roughness workflow or not?
2) If so, should I send a bug report for the metallic setting to be fixed?
3) If not, is it possible for me to modify it so it will work?
4) If not, is it possible to modify the Principled Shader to include opacity maps?

Thanks
Rob

Here is a quick and dirty setup to get opacity on a principled shader

Thank you very much, I appreciate the help.

Seems so simple when I look at it. I had looked inside before but totally missed that the “Of” opacity was already in the Principled Shader's Compute Lighting and it basically just needed a texture node plugged into it.

thanks
Rob

Glad to help!

Apologies for the necro but I have a further question that I'd like to ask.

What is the correct procedure for editing the Principled Shader (or any digital asset shader) and saving a separate version from the original.

ie.
1. In SHOP, add a Principled Shader.
2. Allow editing of contents
3. Edit (ie. add opacity map, edit parameter interface)
4. This is where I get confused - Last time I managed to overwrite the principled shader and I would like to avoid doing this again.

From what I know, in it's current “allow editing” state, it's slower. (not cached) I can save to gallery but if I remember, when I match definition, it will overwrite the Principled. So I need to create a new digital asset from it (so it's cached again) but can't find any info/tutorials regarding editing shaders as digital assets.

“New digital asset from selection” looked like a solution but it doesn't seem to work with shaders.

I'm sure it's something simple (again) but I'd appreciate any help.

thanks
Rob

The way I do it is to not unlock the original asset at all but make my own copy first with the Operator Type Manager and put either in my sandbox directory (any directory that you do test stuff in or desktop which is the new /tmp ), add that and edit that.

1. RMB on node and choose “Operator Type Manager…”.

This opens up the Operator Type Manager with the given node highlighted.

2. RMB on the selected operator definition in the Operator Type Manger and choose the “Copy…” option.

This opens up the create new asset definition pop up widget to give your asset a new name and label. Definitely give it a unique new name and unique new label. In tab menus, it's the label that determines the sorting so I add suffix (after name) to identify uniqueness but still shows up with the original version.

3. Give your asset a new name and label along with a directory location and file name with a .hda extension. Then press Accept.

Now add your new node to the same network. MMB on the node to verify that it is your new defined node in the directory that you saved it in with the correct file name.

Unlock and edit away.


I do this so often that I want it to be a RMB menu option to “Create Asset Copy” and it immediately pops up a dialog where you change name and label and save directory.

Please RFE this to support.

Thanks for your help, it's most appreciated as this opens up a lot of customisation that I was wary of trying before.

Kinda related and you guys probably knew about this already, but just in case you didn't…
http://archive.sidefx.com/docs/houdini15.5/nodes/vop/pxrdisney [archive.sidefx.com]

Thanks for the link, unfortunately I'm still fairly new to Houdini so I don't understand the relation. I remember seeing information regarding Disney shaders before you released the Principled Shader but I'm not sure if it's the same as that link mentions it's for RIS rendering (which is Renderman right?)

I tried finding the node itself but it only seems to show up in locked shader assests. ie. tab menu inside locked shader, can see it but can't place it. tab inside same shader, unlocked, can't see it.

Related to my earlier post, I'm getting a warning message when matching definition on my edited Principled Shader. (attached) I've not included a hip file/shader as this also happens if you just click “allow editing” immediately followed by “match definition” on the original Principled Shader. Is this warning message pointing to a problem that I can fix myself (with help) or a candidate for a bug report?

thanks
Rob

I believe you have to enable the RenderMan option in the Houdini > Preferences > Rendering to see the PRMan nodes…

Okay, I don't use Renderman so I'll just stick with the Principled shader. My main goal was to be able to use a metal/roughness workflow in Houdini and thanks to the help on this thread, I've achieved that. (albeit with a pesky error message)