Jump to content
Unai

Chromakey and Lumakey not generating alpha

Recommended Posts

Hi there,

I was trying the composite features in H16, and found out that no matter what I do, the Chromakey and Lumakey nodes don’t output any alpha.

I thought the problem was due to my File nodes not having any alpha plane on them, but even after creating one with the Color node, the alpha doesn’t get modified, just the colour plane —keyed out areas are black as expected. Is this normal behaviour, am I doing something wrong?

Not attaching any example file since the only thing I’m doing is File > Chromakey or Lumakey, check the A plane, and it either doesn’t exist or it’s unmodified by the keyer.

Thanks in advance!

Share this post


Link to post
Share on other sites

Thanks Szymon, that would definitely be enough for a Luma key, since you can crush the alpha afterwards, but what about a Chroma key though?

I forgot to mention, I’m using 16.0.504.20 on OSX 10.12.3 with an unsupported GPU (Intel Iris Pro). Do you think the GPU might be the issue? I thought COPs didn’t use it…

Share this post


Link to post
Share on other sites

hmm... In 15.0 they both work as expected. I would assume it's a bug rather than deliberate change.  I will submit a bug. Thanks!

Share this post


Link to post
Share on other sites

Cheers! Were you able to try it in 16 in your system though? Did it fail too?

Share this post


Link to post
Share on other sites

It seems they don't work in 16.0.547 (don't produce any Alpha as you discovered). Only LumaMatte works. Bug submitted.

  • Like 1

Share this post


Link to post
Share on other sites

In H16 we finally dropped the requirement that C and A must exist regardless of the actual file contents. This is good in a lot of cases (why create C and A when an EXR contains only Pz) and was pushed by the Terrain project. It was also the original intent of COPs, so I'm glad that this change finally happened.

Unfortunately, due to the fact that this restriction has been in place for a dozen versions or so, a few cases that expect A to exist have now broken, the lumakey and chromakey among them.

  • Like 2

Share this post


Link to post
Share on other sites

Thanks Mark, happy to hear I’m not the only one with the problem. Hope it gets fixed!

Share this post


Link to post
Share on other sites

From the journal:

Houdini 16.0.563: The Chromakey and Lumakey COPs now have a toggle to generate an Alpha plane if it is missing in the input. It is on by default for 15.5 compatibility.

 

  • Like 1

Share this post


Link to post
Share on other sites

Wow, that was quick! I’ve tried it and it works as long as your input doesn’t already have an A plane. Not really sure if that’s the intended behaviour (pre-16), but hey, it’s easy to fix anyway with a Delete node. Awesome! :D

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×