Hey all, I've only been learning Houdini for a short time, so any help would be massively appreciated for something that I think should be fairly simple but is proving to be a bit difficult.

So I'm working solely in Solaris/Karma right at the moment.
All I want to do is to project an EXR, that has an alpha channel onto a vertical grid.
I've tried to look at the coordsys, which I think is the 'correct' way but I'm still not quite getting what I was hoping for.
https://www.sidefx.com/docs/houdini/nodes/lop/coordsys.html [www.sidefx.com]

I did load this example up, and tried to copy what I was seeing but applied to my scene, it was kind of working but I can't control the size of the projection.
And I don't quite get if things need to be in 'World' (I guess it can be named anything?).
I presume the projection camera, material and mesh\geo just need to be within something (ie 'World') in the scene graph path.

What I tried to do with the alpha, which seems to be working is from my mtlximage, I went into a mtlxseparate4, XYZ into a mtlxcombine (1,2,3), then the W I piped into the opacity slot of a mtlxstandard_surface.
That seemed to get my alpha at least.

From what I've seen it looked a lot easier if you were using Arnold (I'm not, just learning), so I'm not really quite sure if I'm on the right track.
I tried using cGTP/Copilot, it was sort of helping but really made a huge mad shader tree.

If you can share a file, or screen shots etc that would be handy to help understand this a bit more.

It`s not that hard there is a library that someone uploaded on the forum that has a wrapper that makes this a 1 node solution.

Here`s the pack. some of it is a bit outdated needing you to go in and flip some switches so it`s not ideal but it shows what you need.

also i think in just karma there is a 1 node solution to this.

https://www.sidefx.com/forum/topic/89089/ [www.sidefx.com]
https://github.com/Faitel/MaterialXEssentials [github.com]

Hey Nic, thank you for suggesting this.
I'm going to take a look tonight, the main problem (unless it's REALLY obvious) is that it's all new to me, so may need breaking down like you're talking to a child

If you can share a hip file with your progress thus far, we can probably advise further.