Taper textures do not render correctly when using the same texture

[mphe]

See #156 (comment) and #156 (comment).

the issue only seems to occur if and only if the taper left and right textures reference the same texture resource.

Workaround:

If, for whatever reason, someone is using the same texture for left and right taper textures, they can disable the taper_sharp_corners option and it will behave as expected.

[Technostalgic]

I feel it's important to note that this only occurs when using the taper_sharp_corners feature. If you use multiple edge material metadatas with different angles, and use taper textures normally (even with the same taper texture for left and right), this issue does not seem to occur.

Also, posting an example image of the issue here for ease of access: