'is_data'
since the move from 'cycles_shader_compat' (2.79) to
'PrincipledBSDFWrapper' (2.8) we lost the ability to (automatically) set
this colorspace setting for imported textures. This was useful for e.g.
normalmaps to always assume 'Non-Color' data.
This adds the possibility to overide and uses this for normalmaps...
Fixes T66368
Reviewers: mont29, brecht
Maniphest Tasks: T66368
Differential Revision: https://developer.blender.org/D5176
711960b3c2