ID 359045 - Layer masks with black edge pixels incorrectly apply backface masking.

Problem summary

Layer masks with transparent edge pixels incorrectly apply backface masking.

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Customer reported version
modo.12.1v1

Customer reported platform
windows10

Steps to reproduce

1) Open Modo.

2) Load the attached scene.
3) Press "F9" to render.

Result: the entire cone will be grey, with green lines. The cone should instead be half green, with green lines on the positive X side.

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:

12.1v2 - Windows 10, OSX 10.13.5

12.1v1 - Windows 10

12.0v1 - Windows 10

11.2v3 - Windows 10

11.2v1 - Windows 10, OSX 10.13.5

Unable to reproduce bug in:
11.1v1 - Windows 10 - Backface masking is not respected at all using the same steps.

11.0v3 - Windows 10 - Backface masking is not respected at all using the same steps.

10.2v4 - Windows 10 - Backface masking is not respected at all using the same steps.

Earliest version tested
11.2v1 - Windows 10, OSX 10.13.5 - This feature did not exist in a working form before this version.

Expected behaviour
A texture used as a layer or group mask should respect backface culling if the edge pixels are black or transparent.

Actual behaviour
If the edges of the texture used as a mask is black, the backface masking option will incorrectly mask the underlying layers.