Long story short, I found that there is only a "Special - Grayscale" shader that is outside SkeletonGraphic folder under the Shader directory but no such shader inside the SkeletonGraphic folder. Thus, I tried to port that shader to SkeletonGraphic. Well, it works most of the time but for a particular spine export, I found that a piece of supposedly invisible attachment get drawn incorrectly.
The huge Rect is the attachment that is not suppose to be visible. As you can see, its only dawn on the grayscale shader.
Sample Unity Project:
https://1drv.ms/u/s!AtvZrOJIVJhLykQ-3G8iKrGMle0M?e=hWNFJ3
I uploaded the sample project to OneDrive as the forum now seems cannot upload zip / 7zip file anymore.
Thanks.
