Hello,

I am desperately looking for a basic scene or tutorial to better understand the relationship between composting and 3D.

Practically I would like:
- to apply basic filters on an image and to be able to use it as a background image when rendering a 3D scene
- to be able to use this filtered image as a texture

In the other way I would like to get the output of a camera (the real output, not a generated images sequence) into the compositor and to apply some filters on it.

It may sound basic but I have a hard time to find tutorials on that.

Thank you very much for any help

Hi,

I am not aware of a tutorial about these topics.
But, the docs should help you getting started:

op-syntax
It can be used for referencing the output of a cop-node.
http://www.sidefx.com/docs/houdini12.0/io/op_syntax [sidefx.com]

render-cop
Can be used to pipe the render output directly into cops.
http://www.sidefx.com/docs/houdini12.0/nodes/cop2/render [sidefx.com]

Cheers

Thanks a lot, Bollili, those topics really help!

By browsing in the documentation from them i aslo found this interesting page: Mantra render node (http://www.sidefx.com/docs/houdini12.0/nodes/out/ifd [sidefx.com]), with several examples including one called Rop_Fetch_Example1 (Fetch example), which is quite simple and nice to start with.

Things are still a bit tricking though and I still have troubles to understand with I sometimes don't get a visual result.
I'll play some more and come back with a scene if I still have some troubles.


Best

Hi again Bollili,

In spite of many tries I still have troubles with the nodes you suggested

- I failed to make the Render COP node work:

• Whatever I do the node says that it cannot read the input files.
  
  Here is a basic scene. Could you please have a look at it and tell me if I do something wrong?
  
  As the documentation says: “This node currently only works with output drivers that produce .pic format files.”
  I start wondering if it supports .picnc files…
  
  
  - Unfortunately I also failed to make the ‘op’ function work. (I know it sounds a lot at the same time, but honestly I would have expected Houdini to be more intuitive and documented sometimes…).
  I used a File node in the Img network to get the 3D renderings (with the expression opout/mantra1 to get the output) and plugged it into a composite. Here the File node says 'Cannot find file opout/mantra1.
  … Although I followed the documentation samples. :?
  
  I also provided a sample file here.
  
  
  
  Thank you very much for your help.
  
  
  Best

Hm.

Guess, you're right. I suppose, your first approch doesn't work, because you're on a non-commercial license. Just double-checked it with Hmaster - no problem here…

You're second approch doesn't work. The op-syntax doesn't trigger renders. Use it instead to access eg. the cop-out from SHOPs or SOPs.

Could be, that you have to render files to disk first, when you're on apprentice. I didn't know that. But, documentation on what's supported and what not with non-commercial licenses always seemed to be not very comprehensive in my eyes.

So I fear, you have to hit ‘render’, first.