Heightfield mask into comp?

[DanFor]

Hi,

I am trying to pull height field masks from a terrain geo into a composition (to build a diffuse map as a terrain base texture), basically following the workflow in the youtube video below.

However, one thing has me stumped. Getting masks from the height field into a comp is straightforward (sop import node). However, when I set the sop import comp node to generate the custom planes (to get the mask and other geo data), the images generated are red/grey instead of grey scale. In the youtube video he does not seem to have that problem (although he skims through those parts extremely quickly, around 27 minutes in).

Am I missing some additional step to get height field mask data to work as a simple greyscale mask in a composition...?

Many thanks in advance for any pointers!

 

Edited December 6, 2017 by DanFor

[DanFor]

I should perhaps clarify.

The image in the sopimport 2 thumbnail is what I want and expect. However, when applied as a mask to the over node, the result is not as expected.

And this is why. When looking ahh the sopimport2 mask channel, it actually looks like this:

...and I cannot seem to find any option to make sure it is interpreted as a suitable mask greyscale.... :-/

Again, many thanks for any advice!

[Sepu]

I had weird results with some of the nodes like over, screen, etc. The composite node had worked for me in the past. 

[DanFor]

Thanks!

I still get the red mask image interpretation though. It is as if the imported planes are coloured. However, the thumbnails are greyscale...?

And in the composite node, I can see that the mask applied is indeed the coloured one I see in the image viewer, as areas that are supposed to be masked (with the correct mask interpretation) are bleeding through.

Any ideas?

As much as I love Houdini for its powerful procedural approach, I must say I really dislike the lack of documentation and myriad of quirks all over the place...

[Sepu]

This is a test with a roto shape, the mask should work. If you want to upload a test.hip I can have a look. 
Also, you can try the channel copy and set the target to none and set 0 to black or 1 to white depending on your source.
This is the image that I use in the comp btw.

TestComp.hipnc

Edited December 6, 2017 by Sepu

[DanFor]

Thanks!

I dug around a bit, and my problem turned out to be my confusion regarding how Houdini handles two things:

- The comp / over nodes and default alpha behaviour

- Houdini's apparent inconsistency when displaying mask images. I will explain: When looking at the my mask (the image from the sop import) the comp view displays it as black->red. However, the thumbnails in the tree view are in greyscale. This threw me for a loop and I thought I had missed some colourspace conversion step.

In the end it turned out I basically had things right, but to get the proper values I had to use a channel copy to properly bind the reds in the imported mask into mask values.

So, sorry for the ignorance and many thanks for the help. I hope this might be of help to someone else in the future.

Edited December 6, 2017 by DanFor