VertexPaint not presenting full value (0-255) when used as a mix map?

[brittnell-cogsandmarvel]

I'm trying to use VertexPaint to drive the mix between two materials (in 3ds Max 2021), either as a general "Blend" material, or an Arnold "Mix Shader", but it doesn't seem to go to full white (255/255/255), and mixes in some of the material from the black side. 

I've found that routing the "User Data" through an "RGBA to Float" helps a bit, but still not perfect (a bit still leaks through).

I've found that if I run the whole thing through a "Color Correct", and bump contrast up to 2.0, it removes the issue, but then crunches any details and gradients.

I've made a screen-cap illustrating my process here:

Maybe I'm missing something in my process, but it seems like what I'm doing should work? 🤷‍:male_sign:

Any input or insight would be greatly appreciated, thanks!

[brittnell-cogsandmarvel]

I just did a quick test in Vray, and it seems to work as expected there (no red bleeding through the masked portion at all):

Something off in Arnold then?

[madsd]

This works fine with Arnold.

And you only neeed 1 node to do it and it also shows in the HQ viewport realtime.

Notice I source channel 3.

[brittnell-cogsandmarvel]

Hey Mads, I was actually hoping you might see this, and respond, so am super psyched that it worked out.

Your solution totally works, and I appreciate it. That said, the reason I initially posted this is because I had previously been following your Arnold VertexPaint application advice posted here, and wasn't getting the results I expected.

If you have the time, I'd be interested to know if the application I'm looking for has recently changed from UVW0 to UVW3, or if I'm totally missing some fundamental aspect of how this should work (which I definitely wouldn't present as out of the realm of expectation here).

Cheers!

[madsd · Accepted solution]

Well the thing is, stuff evolves, so more and more things gets possible to do as time progress.
I would not recommend to use that video, instead just do like the mockup using OSL map and channel 3.

If you want to use the .x channel on 3 only, use a color component node to split the signal into x,y and z. also OSL node.

Use an empty channel, there are some cases where channel 0 and channel 1 bugs out, so just make a rule to always start new data streams from 3, or 4 or something of that nature.

[brittnell-cogsandmarvel]

Right on, thanks Mads.

I appreciate both the validation that I wasn't going crazy, and that Max wasn't broken, just evolving (hopefully like all of us!). 😄

Skål!