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Bump Node Outputting Pure Black
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System Information
Windows 7
EVGA GeForce GTX 770 Classified 4GB GPU
2x Intel Xeon E5-2670 8-cre 2.6 Ghz
8 GB ADATA RAM @1833Mhz

Blender Version
Broken: Blender 2.79a (Hash: 5bd8ac9) and Blender 2.79.1 (Hash: 2ae6a93)
Worked: N/A

Short description of error
In short, I don't know for sure if it's a bug, or an intended limitation of Cycles nodes. I have over like 450 nodes, and the bump no longer works when certain ones are plugged into it, and instead acts as if it's a black emission node, as does the Principled BSDF if the Bump node is connected.
It's worth noting I had a friend test on his rig, and his own blender version, and it didn't work for him either.

Exact steps for others to reproduce the error
Just download the .blend, and it's already done for you. To "fix" it, simply delete the Reroute marked "REMOVE ME" or the Reroutes labelled "OR REMOVE US".



Event Timeline

Change this node from Multiply to Mix.
See if that fixes it for you. Everything else besides Mix, makes it black.
In the meantime, I'll see if I can recreate with a simpler set up.

@Joey Bennett (Joey_Blendhead) Joey, I started reducing this bug, but it's a massive node layout, can you do that? Delete things until you get to the minimum node setup where that still is outputting black?

For me this prints an error in the console: Cycles: out of SVM stack space, shader "Steel" too big.

Sergey Sharybin (sergey) closed this task as Archived.Dec 11 2017, 4:47 PM
Sergey Sharybin (sergey) claimed this task.

Thanks for the report, but it is a known limitation. Your shader requires too many stack variables for the shader machine. While re-route nodes doesn't necessarily require extra stack space, having them in shader graph changes the way how graph is being travesred.

There is some ongoing development to optimize stack usage, but is not all finished yet. See D1676.