V-Ray proxy and Alembic channels

[jonathandeblok]

Hi I'm working on some Houdini/Max interop contraption and ran into a few issues regarding the V-Ray Proxy object that I'm using to load Alembic data.

I can get Houdini's point color (Cd) into a mapchannel, but in houdini I have to promote the color attribute for 'Point' to the vertices first, would be nice if the proxy loader could handle that by itself. (A 'point' in houdini is a collection of vertices from a mesh where multiple polygons meet). Not a big problem but took me a while to figure out.

And I can get any data into a mapchannel just fine only not directly into the vertexcolor channel. I can copy the mapchannel data into the VC-channel using maxscript but that is a bit awkward with baked animated meshes and such.

Second, max becomes unstable when you repetitively update/change the filename property of a vrayproxy object using maxscript while it's selected (in up to data max2017, latest public V-Ray, haven't tried any other), it's fine when it's non selected.

And last I came across some info about remapping channels from a proxy using the 'user defined properties' of a node with entries like 'mapchannel:1=uv' etc.. I seems to do something but not sure if/how that is working..

[kagemaru]

I think i'm missing something from your explanation: i travel from houdini to max all the time with alembic with tons of point attributes directly that get read in max with the vertex color map.
Tested with meshes and particles.
What i'm doing wrong?

[jonathandeblok]

Yeah, that's in a mapchannel, not the vertexcolorchannel. Technically it's the same, but vertexcolor = channel 0 and I'm not seeing any way of feeding Cd directly into that. Not a biggie but I got a few tools that expect data in vertexcolor, not in higher mapchannel

I forgot to mention.. houdini's point data comes in fine indeed initially, but as soon as you put a modifier on the proxy it will drop all point data and leave only vertex data. Add a 'bend' modifier for example and render your test scene again.. will probably be all black. Adn if you use a 'promote attribute' in houdini to get Cd from points to vertex it will work again.. I think that should be considered a bug, or at least unexpected behavior.

[kagemaru]

Ahhh ok, i see what you mean now.
I'm not used to fiddle with vertexcolorchannel, so i never came across this issue but i see your point. It does make sense that, since in max the difference between points and vertex isn't a matter, vrayproxy would put that information in both channels.