Monochromatic texture based on one of the image channels [✨ feature request]

[nmichiels]

Adding support for a monochromatic texture based on one of the image channels (e.g. r, g, b, a, x, y, z etc.) would be nice. Lots of my material textures use channel-packing where monochromatic textures (for example roughness or metallic map) are packed in rgb channels of one texture. This feature was available in Mitsuba 0.6 as a 'channel' parameter of a bitmap texture.

[Speierers]

Hi @nmichiels ,

Indeed it would be a great feature to have! This isn't currently on our roadmap and other projects will keep us busy for the next months at least.

If you would like to give this a try and open a PR, I will be happy to help you.

Let's keep this issue open as a reminder.