Rendering IPR in VFB: strange behaviour when using render button in Houdini render view (nightly build)

[sebastian_orosz]

Hi,

since I updated my installation to a nightly build, I get strange render results, varying from missing objects to complete black renders. This seems to happen when

- VFB is closed and I
- Start an IPR render in VFB by using the 'Render' button on the Houdini 'Render View' (which I always do, because I permanently close the VFB after I'm done with it).

What happens after starting an IPR session: VFB opens and sometimes there are objects missing in the scene, sometimes the scene is rendered completely black. Then I stop the rendering (stop button in VFB) and start again (start button in VFB). This solves the issue in moste cases until I close the VFB again.

I'm using:

Houdini 18.5.596
V-Ray for Houdini number:18261 hash:7f8ebba from 08 Nov 2021 04:54 (build number:18261)
V-Ray Core 5.10.20 [ca680a00] from 3 Nov 2021

I managed to replicate this issue with a few simple steps:

- Start Houdini (empty project)
- Add V-Ray ShaderBall to obj level
- In the ROP enable 'Use V-Ray Frame Buffer' (it is disabled by default)
- Hit the 'Render' button on the Houdini 'Render View'
--> Everything seems ok
- Hit stop button in VFB
- Close VFB
- Hit the 'Render' button on the Houdini 'Render View' again
--> The shader ball is missing, and I'm sure he was there just a moment ago.
- Hit stop button in VFB
- Hit start button in VFB
--> Now the shader ball is visible again.
- Sometimes it does not help to hit stop and start in VFB, in this case it helps to switch one of the lights on and off, or off and on and then hit start in VFB again ...

Cheers

[bdancer]

Will it work better if you'll use V-Ray's toolbar "IPR (VFB)" button instead of "Render View" button?
"Use V-Ray Frame Buffer" option should be removed actually, VFB should not be used with Render View workflow anymore...

[sebastian_orosz]

Hi,

when I manually open the VFB there seem to be no issues, at least I could not replicate the behaviour anymore.

I didn't ever use the Houdini Render View for V-Ray rendering, just the 'Render' button for bringing up VFB and starting IPR, which in my case is very comfortable, because I'm permanently switching between Mantra IPR and V-Ray IPR (dual scene setup). Would be great, if this could be fixed just for the sake of bringing up VFB automatically and starting IPR. You know: One Button to render them all!

[bdancer]

> You know: One Button to render them all!

Well, "IPR (VFB)" is exactly this button...
"Render View" IPR is pretty Mantra specific... I could make this button to do the same as "IPR (VFB)" but this may break some other SOHO things so this may take some time.

Could you at least confirm that toolbar button works as expected? Or there are issues as well? Could you send me the hip file?

[sebastian_orosz]

Yes sir, opening VFB from the toolbar and then rendering the scene works without problems.

The thing is, I used the Render View Render button for a long time to bring up VFB and start rendering. This worked without problems for as long as I used the official V-Ray 5 update 1 release (June 17th 2021) from the Houdini download page. But yesterday I had to switch to a current nightly build, because there were problems downloading the material library with the official release. With the current release I suddenly got these problems as mentioned above. So it used to work in the past, but now it doesn't anymore, or at least buggy.

[sebastian_orosz]

How do you switch between different ROPs in the VFB? I can find different options for cams, but ... Only way I see is using the render view, switching the ROP and hit the infamous render button, which results in the aforementioned problems.

[bdancer]

> How do you switch between different ROPs in the VFB?

Well, you don't, each ROP has its own VFB...
You could Shift+LMB on the "Render" toolbar button and it'll show you a menu of available V-Ray ROPs.