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Captain Obvious
08-21-2008, 04:05 AM
I've been working on converting an old layer-based surface to a node shader network. It's not primarily about moving the layers into nodes, as such, but rather about modifying the output of the layers. I've got it working rather well, but the Bump Layer profoundly confuses me. With a single layer in it (a Crumble procedural, in this case), the old layer stack produces the same exact output as a Layer node with the same layer in it. When I turn off the procedural and turn on an image map layer instead, the output is again exactly the same. However, when they're BOTH turned on and the upper layer is set to additive mode, they produce different outputs, almost as if the "Add" mode in the Layer node does its addition in a different way than the old Layer system.

I don't doubt that I can massage the texture into something better than it was, even if it does end up looking different, but it would be nice to know why it produces different output. I can't really post any images at this stage, unfortunately, but it should be easy to verify with experimentation:

Add two layers in an old layer stack in the bump channel (set to additive), and do a render. Copy the layers into a Bump Layer node, and turn off the old layer stack. Now do another render -- output isn't the same. However, when only you're using BOTH layers. With just one layer, the output matches.

Is this something else can verify/refute, or has noticed in the past?

I'm using LW9.3.1, by the way.

Thanks

dpont
08-21-2008, 06:38 AM
I tried a classic addition layer in Bump,
a (addition)Turbulence on top of a Crumple,

9.3.1/9.5 Classic matches the 8.5 (Classic of course)version
9.3.1/9.5 Nodal Layer Bump node doesnt match 8.5 version.

Subsidiary note:
9.2 Classic and Nodal match the 9.3.1/9.5 Nodal...

Haven't tested the other Blending mode but
I think the nodal layer blending formulae should match
the classic one.
Fog it.

Denis.