Layering Multiple Bitmaps on a Shader

[todd21st]

Looking to get some help with 3ds Max and Arnold. I'm still relatively new to Arnold and am slowly making the transition from Mental Ray. One thing that I can not seem to be able to figure out is how to map more than one image on to a base surface like you see below;

The above image was generated using Mental Ray. A simple shader using the Composite map and a Bitmap loader with "Show Map on Back" unchecked. On the object itself I just stacked two UVW maps each with their own channel to position the maps on the object. Simple enough.

But in Arnold I can't seem to figure out how to do this. I can get one map to show up layered on top of a base material but the map shows on the back side of the object as well, which I do not want. And when I go to add a second map on top, this just doesn't work at all.

I know I could turn on the "Legacy" option in the render settings and keep using the old Composite Map but I'd really like to get away from using legacy features and embrace Arnold and what it can do. I'm just stumped by something that should be super simple.

Any help you could advise would greatly be appreciated.

[Anonymous]

I use a multi/sub-object and different material IDs + different map channels per texture.

[Anonymous]

Use This video its the exact same idea

https://www.youtube.com/watch?v=GESiRlLGF6Y

[Anonymous]

Use This video its the exact same idea

https://www.youtube.com/watch?v=GESiRlLGF6Y

[todd21st]

True, for the above example a a multi/sub-object and different material IDs would do the trick. Thanks Michiel!

But what I am more looking for is to pull off an effect of layering bitmaps like you see below...

This is also what the guy demonstrates in the video in the comment above. Problem is I don't know how he is positioning those bitmaps? In 3ds Max I would always stack each UVW Map on top of one another and give each a different channel corresponding to the different maps;

The guy in the video is positioning them in some other fashion which I can not figure out?

[lee_griggs]

Have you tried the Layer RGBA shader?

[todd21st]

Yes. The Layer RGBA shader was recommended to me but I still keep coming up with the issue that when I set up an object with that shader and put a UVW map on it, it will map the bitmap on the object but the map shows on the backside too. When I go to add another bitmap and place it with a 2nd UVW map then all of them disappear. I must be missing something big or else Arnold does not use 3ds Max's UVW maps to place bitmaps.

[Anonymous]

Screenshot from previous comment was wrong.(don't use composite)

It should look something like this:

Stacking different uvw maps with different map channels should work.

Yes the backside will always show, I use a different Id/ material on that.

You can also use UV transform to tweak the position, scaling, …

[todd21st]

Michiel, I tried your example from the screen shot above. Stacking different uvw maps with different map channels does seem to do the trick with one exception; as soon as I connect the first bitmap into input 1 of the Layer RGBA map it replaces the base color of the standard surface material. Where I need the bitmap (which has an alpha) to overlay on top of the material.

[Anonymous]

Put the base color into input3.

[todd21st]

lol...of course! That did the trick. Thank again for all your help! So as of now there is no way to get the textures to not show up on the back side of the object? I suppose Arnold does not respect 3ds Max's General Bitmap setting "Show Map on Back" when it's unchecked?

[Anonymous]

I don't get "Show map on back" to work in any way. I would use material ID + user data. Explained here by Mads Drøschler:

https://www.youtube.com/watch?v=bjYgHcLjkG0