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Bobby Ushiro avatar image
Bobby Ushiro asked ·

Custom LPE AOV's in Cinema 4D not working

I believe I found a bug and will continue to believe so until someone can point out a user-error on my part.


I work with MPC and the Mill often and they use Arnold 5.0.2.1 (v2.2.1) in C4D r18. Yes it is not the most up to date but I checked the release notes to make sure this wasn't fixed in the newest version of Arnold C4DtoA.

The problem has to do with custom LPE's. If I'm writing a custom AOV, c4dtoA simply does not recognize the LPE or render it.


I've tested the SAME LPE's in Maya and it works perfectly. Why does c4dtoA does not support custom LPE's? Yes the UI is all there and is seems that it should be working but simply put, the same LPE's the work in Maya, do NOT work in C4DtoA.


I know it's not different as Arnold LPE's are the same regardless of what 3D platform you're working on.

If you happen to have Maya + C4D, try out this LPE:

C<TS>*<TD>L

Make sure to place an object within a tranmissive container, and you'll see exactly the issue.

Maya's renderview will indeed show the custom AOV, C4DtoA will not. Just in case this might be an issue affecting IPR, I've tried rendering but c4dtoA definitely needs to be updated so LPE's can work in Arnold.

Let me know if I am wrong about this, I'd much rather prefer to be wrong than wait on Arnold to update c4dtoA so it can support custom LPE AOV's for more intense projects.


Very disappointed,

Bobby

c4dtoaaovaovsosl
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tomas land answered ·

Hi everyone. Thanks for the information.

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Bobby Ushiro avatar image
Bobby Ushiro answered ·

Thanks Stephen, I'll get this checked out as soon as I can, we'll even try testing this in R20 in case there happens to be something odd happening with R18. Will get back to you on Monday with our results.

Much appreciated and hopefully we'll be able to setup some proper AOV's instead of having to split our renders!

Bobby

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Stephen Blair answered ·

lpe-test.ass

Here's the ass file I'm using as a procedural in CINEMA 4D. Just a sphere, plane, and box.

The box is transmissive.

The sphere is the car paint preset, with some SSS so that it shows up in the custom LPE.

On your side, with your own scene, what I would do is export your scene to ASS from both Maya and CINEMA 4D, and compare them. What's the diff?


custom-lpe.jpg (197.1 KiB)
lpe-test.ass (30.3 KiB)
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Bobby Ushiro avatar image
Bobby Ushiro answered ·

Very interesting. I'm also working in 2.2.1. The upgrade cycles at the larger VFX studios are a bit slower since we have propriety plugins and scripts that take awhile to port to the newer versions of C4D, but I'm not really thinking that there should be a difference between R18 and R20...

I don't understand how the LPE's managed to work for you.. is there possibly ANY chance you could share your basic C4D scene so we can take a look and figure out what's going on?

Again.. thank you for your time, it is much appreciated.

Bobby

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Stephen Blair answered ·

I got the right setup now, and C<TS>*<TD>L works in my Maya test scene.

I exported my shapes and shaders to ASS, loaded them into CINEMA 4D, and C<TS>*<TD>L worked there too. Both in R18 with C4DtoA 2.2.1 and in R20 with 2.4.5

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Bobby Ushiro answered ·

Hey Stephen,


Yeah C<TS>*L would work as it's essentially the default LPE for the Transmission Direct AOV:

You can read more here:

https://docs.arnoldrenderer.com/display/A5ARP/Light+Path+Expression+AOVs

The issue I'm having is working with custom LPE's that are not default LPE's specifically in C4DtoA- which I believe is not working with any custom LPE's.


C<TS>*<TD>L would give us a different AOV from C<TS>*L that's being used since it would only output the transmission direct pass. What I'm trying to get a diffuse pass that bypasses the transmission of a material. Essentially an object within a glass object (this would be extremely useful for example when creating individual object masks within a scene).

For an example of proof that this LPE works in Maya please watch 14:10 of this LPE Arnold tutorial:

https://www.youtube.com/watch?v=7mRxUuqI5Fc&t=1336s

I had my colleagues try this in Maya and it works for them. Doesn't work in C4DtoA. Perhaps this is something that Autodesk needs to fix in the next update?

I appreciate your attention and time, thanks!

Bobby


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Stephen Blair answered ·

C<TS>*L works in CINEMA 4D R18 with C4DtoA 2.2.1

For C<TS>*<TD>L, can you post an ASS file from Maya where that LPE works?

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Bobby Ushiro answered ·

Cool, looking forward to what you find out.

I've been attempting custom LPE's to be able to bypass the Transmission of the container to grab the diffuse color of the inner object to no avail. Maya seems to do this with no issue very strange.

C<TS>*<TD>L

= Camera rays (C) hits the Refraction event (TS) followed by (*) the diffuse transmission event (TD), where all light emissions should be calculated (L)


Should work but it doesn't.

Also might be worth trying '.*' instead of 'L'

So:

C<TS>*<TD>'.*'

(remove the ' characters, the HTML code in this forum messes up the string)

I wish I could test these out further in C4DtoA but again, LPE's just don't seem to work except for the standard default LPE's.


Very curious to see where you net out with this.


Bobby

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Stephen Blair answered ·

C<TS>*L works in CINEMA 4D R20 with C4DtoA 2.4.5

I'll test with the old stuff in a bit...

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Stephen Blair answered ·

"...place an object within a tranmissive container...."

Here's a sphere inside a cube. The cube has the glass standard surface preset. The sphere has the car paint preset. Skydome light.

For now I'll use C<TS>*L to test


test.jpg (114.1 KiB)
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