Texture placement node input not evaluated on rendertime

[mschreck]

Hi

I have a problem with rendering animated texture placement nodes that have inputs driven by a custom attributes output connection.

custom attribute>uv transform
custom attribute>uv coverage

our characters pupil size is driven by these custom values connected to the uv placement and coverage u v values.
this is working in mayas viewport but when I render vray ignores the input.
i managed to fix the problem by connecting the values via an expression.but i was wondering if there is any other way of forcing the evaluation of this connection.

i assume it is related to the way vray gets these values handed over from maya before rendering?
I can reproduce the problem in a simple sphere test scene.
Vray 5.1 maya 2022.3

[hermit.crab]

Mind if you attach the simple scene? I may be misunderstanding the issue.

[mschreck]

Hi, so i have attached a simple test scene TestScene.zip showing the difference between Node and Expression connection.
The pupils are connected to a custom attribute called.


Top left: Pupil vray render with node input (doesnt work, pupil is squashed)
Top right: Pupil connected via expression (works)
Bottom: Pupils Viewport

[hermit.crab]

Thanks for the provided scene.

Not sure if you got confused by this, but I certainly was. Even though an "animCurveUU" (Float input / Float output) is used for the Coverage/Translate Frame slot with the idea of the attribute's value acting as an input to the evaluated at render time value of the curve, the Coverage/Translate Frame slot still defaults to its "animCurveTU" (taking Time as input / Float as output). In other words, what the custom attribute value controls is the frame number of the key, which is going to be evaluated. F.e. you chose a value of 0.5 for the "Fk Ctrl Eye R Size". This value is interpreted by the Coverage/Translate Frame as Time. The output result is a float based on the animCurve's position at frame 0.5.

That being said, the yielded float values for the Coverage/ Translate Frame are indeed correct and display as expected in the viewport. V-Ray seems to render only the keyed frames (0,1,2) and their corresponding values correctly. Interpolations produce wrong results (compared with the same Coverage/Translate Frame values without any drivers).

I'll log an issue asap. For now, use the expression method.

EDIT: Logged (internal bug-tracker id: VMAYA-13182).

[mschreck]

Hi,

thanks for checking this out. I wasn´t able to make sense on whats going on. Thanks for the detailed explanation.
I assume a fix won´t be quickly possible and not provided for our old version of vray.
We can start changing our assets to use expressions for the placement nodes